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Lundgren EJ, Bergman J, Trepel J, le Roux E, Monsarrat S, Kristensen JA, Pedersen RØ, Pereyra P, Tietje M, Svenning JC. Functional traits-not nativeness-shape the effects of large mammalian herbivores on plant communities. Science 2024; 383:531-537. [PMID: 38301018 DOI: 10.1126/science.adh2616] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2023] [Accepted: 11/30/2023] [Indexed: 02/03/2024]
Abstract
Large mammalian herbivores (megafauna) have experienced extinctions and declines since prehistory. Introduced megafauna have partly counteracted these losses yet are thought to have unusually negative effects on plants compared with native megafauna. Using a meta-analysis of 3995 plot-scale plant abundance and diversity responses from 221 studies, we found no evidence that megafauna impacts were shaped by nativeness, "invasiveness," "feralness," coevolutionary history, or functional and phylogenetic novelty. Nor was there evidence that introduced megafauna facilitate introduced plants more than native megafauna. Instead, we found strong evidence that functional traits shaped megafauna impacts, with larger-bodied and bulk-feeding megafauna promoting plant diversity. Our work suggests that trait-based ecology provides better insight into interactions between megafauna and plants than do concepts of nativeness.
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Affiliation(s)
- Erick J Lundgren
- Center for Ecological Dynamics in a Novel Biosphere (ECONOVO) and Center for Biodiversity Dynamics in a Changing World (BIOCHANGE), Department of Biology, Aarhus University, Aarhus, Denmark
- Section for Ecoinformatics and Biodiversity, Department of Biology, Aarhus University, Aarhus, Denmark
- School of Biology and Environmental Science, Faculty of Science, Queensland University of Technology, Brisbane City, Queensland, Australia
| | - Juraj Bergman
- Center for Ecological Dynamics in a Novel Biosphere (ECONOVO) and Center for Biodiversity Dynamics in a Changing World (BIOCHANGE), Department of Biology, Aarhus University, Aarhus, Denmark
- Section for Ecoinformatics and Biodiversity, Department of Biology, Aarhus University, Aarhus, Denmark
| | - Jonas Trepel
- Center for Ecological Dynamics in a Novel Biosphere (ECONOVO) and Center for Biodiversity Dynamics in a Changing World (BIOCHANGE), Department of Biology, Aarhus University, Aarhus, Denmark
- Section for Ecoinformatics and Biodiversity, Department of Biology, Aarhus University, Aarhus, Denmark
- Department of Conservation Biology, University of Göttingen, Göttingen, Germany
| | - Elizabeth le Roux
- Center for Ecological Dynamics in a Novel Biosphere (ECONOVO) and Center for Biodiversity Dynamics in a Changing World (BIOCHANGE), Department of Biology, Aarhus University, Aarhus, Denmark
- Section for Ecoinformatics and Biodiversity, Department of Biology, Aarhus University, Aarhus, Denmark
- Mammal Research Institute, University of Pretoria, Hatfield, South Africa
- Aarhus Institute for Advanced Studies, Aarhus University, Aarhus, Denmark
| | - Sophie Monsarrat
- Center for Ecological Dynamics in a Novel Biosphere (ECONOVO) and Center for Biodiversity Dynamics in a Changing World (BIOCHANGE), Department of Biology, Aarhus University, Aarhus, Denmark
- Section for Ecoinformatics and Biodiversity, Department of Biology, Aarhus University, Aarhus, Denmark
- Rewilding Europe, Nijmegen, Netherlands
| | - Jeppe Aagaard Kristensen
- Center for Ecological Dynamics in a Novel Biosphere (ECONOVO) and Center for Biodiversity Dynamics in a Changing World (BIOCHANGE), Department of Biology, Aarhus University, Aarhus, Denmark
- Section for Ecoinformatics and Biodiversity, Department of Biology, Aarhus University, Aarhus, Denmark
- Leverhulme Centre for Nature Recovery, School of Geography and the Environment, University of Oxford, Oxford, UK
| | - Rasmus Østergaard Pedersen
- Center for Ecological Dynamics in a Novel Biosphere (ECONOVO) and Center for Biodiversity Dynamics in a Changing World (BIOCHANGE), Department of Biology, Aarhus University, Aarhus, Denmark
- Section for Ecoinformatics and Biodiversity, Department of Biology, Aarhus University, Aarhus, Denmark
| | - Patricio Pereyra
- Consejo Nacional de Investigaciones, Científicas y Técnicas, Ciudad Autónoma de Buenos Aires, Argentina
- Centro de Investigación Aplicada y Transferencia, Tecnológica en Recursos Marinos Almirante Storni (CIMAS), San Antonio Oeste, Argentina
| | - Melanie Tietje
- Section for Ecoinformatics and Biodiversity, Department of Biology, Aarhus University, Aarhus, Denmark
| | - Jens-Christian Svenning
- Center for Ecological Dynamics in a Novel Biosphere (ECONOVO) and Center for Biodiversity Dynamics in a Changing World (BIOCHANGE), Department of Biology, Aarhus University, Aarhus, Denmark
- Section for Ecoinformatics and Biodiversity, Department of Biology, Aarhus University, Aarhus, Denmark
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2
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Pringle RM, Abraham JO, Anderson TM, Coverdale TC, Davies AB, Dutton CL, Gaylard A, Goheen JR, Holdo RM, Hutchinson MC, Kimuyu DM, Long RA, Subalusky AL, Veldhuis MP. Impacts of large herbivores on terrestrial ecosystems. Curr Biol 2023; 33:R584-R610. [PMID: 37279691 DOI: 10.1016/j.cub.2023.04.024] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Large herbivores play unique ecological roles and are disproportionately imperiled by human activity. As many wild populations dwindle towards extinction, and as interest grows in restoring lost biodiversity, research on large herbivores and their ecological impacts has intensified. Yet, results are often conflicting or contingent on local conditions, and new findings have challenged conventional wisdom, making it hard to discern general principles. Here, we review what is known about the ecosystem impacts of large herbivores globally, identify key uncertainties, and suggest priorities to guide research. Many findings are generalizable across ecosystems: large herbivores consistently exert top-down control of plant demography, species composition, and biomass, thereby suppressing fires and the abundance of smaller animals. Other general patterns do not have clearly defined impacts: large herbivores respond to predation risk but the strength of trophic cascades is variable; large herbivores move vast quantities of seeds and nutrients but with poorly understood effects on vegetation and biogeochemistry. Questions of the greatest relevance for conservation and management are among the least certain, including effects on carbon storage and other ecosystem functions and the ability to predict outcomes of extinctions and reintroductions. A unifying theme is the role of body size in regulating ecological impact. Small herbivores cannot fully substitute for large ones, and large-herbivore species are not functionally redundant - losing any, especially the largest, will alter net impact, helping to explain why livestock are poor surrogates for wild species. We advocate leveraging a broad spectrum of techniques to mechanistically explain how large-herbivore traits and environmental context interactively govern the ecological impacts of these animals.
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Affiliation(s)
- Robert M Pringle
- Department of Ecology & Evolutionary Biology, Princeton University, Princeton, NJ 08544, USA.
| | - Joel O Abraham
- Department of Ecology & Evolutionary Biology, Princeton University, Princeton, NJ 08544, USA
| | - T Michael Anderson
- Department of Biology, Wake Forest University, Winston Salem, NC 27109, USA
| | - Tyler C Coverdale
- Department of Biological Sciences, University of Notre Dame, Notre Dame, IN 46556, USA; Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, MA 02138, USA
| | - Andrew B Davies
- Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, MA 02138, USA
| | | | | | - Jacob R Goheen
- Department of Zoology & Physiology, University of Wyoming, Laramie, WY 82072, USA
| | - Ricardo M Holdo
- Odum School of Ecology, University of Georgia, Athens, GA 30602, USA
| | - Matthew C Hutchinson
- Department of Life & Environmental Sciences, University of California Merced, Merced, CA 95343, USA
| | - Duncan M Kimuyu
- Department of Natural Resources, Karatina University, Karatina, Kenya
| | - Ryan A Long
- Department of Fish and Wildlife Sciences, University of Idaho, Moscow, ID 83844, USA
| | - Amanda L Subalusky
- Department of Biology, University of Florida, Gainesville, FL 32611, USA
| | - Michiel P Veldhuis
- Institute of Environmental Sciences, Leiden University, 2333 CC Leiden, The Netherlands
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3
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Hughes LJ, Morton O, Scheffers BR, Edwards DP. The ecological drivers and consequences of wildlife trade. Biol Rev Camb Philos Soc 2022; 98:775-791. [PMID: 36572536 DOI: 10.1111/brv.12929] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2021] [Revised: 12/11/2022] [Accepted: 12/14/2022] [Indexed: 12/28/2022]
Abstract
Wildlife trade is a key driver of extinction risk, affecting at least 24% of terrestrial vertebrates. The persistent removal of species can have profound impacts on species extinction risk and selection within populations. We draw together the first review of characteristics known to drive species use - identifying species with larger body sizes, greater abundance, increased rarity or certain morphological traits valued by consumers as being particularly prevalent in trade. We then review the ecological implications of this trade-driven selection, revealing direct effects of trade on natural selection and populations for traded species, which includes selection against desirable traits. Additionally, there exists a positive feedback loop between rarity and trade and depleted populations tend to have easy human access points, which can result in species being harvested to extinction and has the potential to alter source-sink dynamics. Wider cascading ecosystem repercussions from trade-induced declines include altered seed dispersal networks, trophic cascades, long-term compositional changes in plant communities, altered forest carbon stocks, and the introduction of harmful invasive species. Because it occurs across multiple scales with diverse drivers, wildlife trade requires multi-faceted conservation actions to maintain biodiversity and ecological function, including regulatory and enforcement approaches, bottom-up and community-based interventions, captive breeding or wildlife farming, and conservation translocations and trophic rewilding. We highlight three emergent research themes at the intersection of trade and community ecology: (1) functional impacts of trade; (2) altered provisioning of ecosystem services; and (3) prevalence of trade-dispersed diseases. Outside of the primary objective that exploitation is sustainable for traded species, we must urgently incorporate consideration of the broader consequences for other species and ecosystem processes when quantifying sustainability.
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Affiliation(s)
- Liam J. Hughes
- Ecology and Evolutionary Biology School of Biosciences, University of Sheffield South Yorks S10 2TN Sheffield UK
| | - Oscar Morton
- Ecology and Evolutionary Biology School of Biosciences, University of Sheffield South Yorks S10 2TN Sheffield UK
| | - Brett R. Scheffers
- Department of Wildlife Ecology and Conservation Institute of Food and Agricultural Sciences, University of Florida Gainesville FL 32611 USA
| | - David P. Edwards
- Ecology and Evolutionary Biology School of Biosciences, University of Sheffield South Yorks S10 2TN Sheffield UK
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4
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Ungulates and Their Impact on Reptiles: A Review of Interspecific Relationships. DIVERSITY 2022. [DOI: 10.3390/d15010028] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Several ungulate species are showing increasing population patterns within their geographical distribution ranges, leading to constant interactions with other animal species. Varying densities and activities of different ungulates may result in diverse impacts on other coexisting species groups, including large numbers of threatened species, such as reptiles. In this study, we performed an analysis of the available literature to investigate the impacts of ungulates on reptiles. We aimed to reveal the diversity of: (1) the geographical and environmental distribution of related investigations; (2) the ungulate and reptile species involved; and (3) the characteristics of interactions (direct or indirect, positive or negative) from 69 publications. Our results show that the most papers were reported from the Americas (42%) and Australia (28%). The proportions of studies were balanced for wild ungulates (53%) and livestock (47%). Wild boar (Sus scrofa) was found to be the most problematic species on reptiles whereas reptiles which suffered the harshest impacts were Squamates (i.e., lizards, and snakes). Ungulate activities (e.g., digging by wild boar) may directly harm reptiles (consuming or killing them) or indirectly affect them by modifying their habitats or destroying their hideouts. Some preferential effects were also noted (e.g., by moderate livestock grazing or when wild ungulates are prey for large reptiles). Published livestock impacts were mainly indirect and mostly negatively linked to overgrazing. We conclude that it is important to manage and monitor the densities of ungulates to minimize their negative impacts on reptile species, especially in case of wild boar and grazing livestock, but also to maintain their moderate beneficial effects (e.g., as prey basis).
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5
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Glass A, Eichholz MW. Snakes on the plains: The impacts of habitat structure on snake communities in Illinois grasslands. WILDLIFE SOC B 2022. [DOI: 10.1002/wsb.1366] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Affiliation(s)
- Alex Glass
- Cooperative Wildlife Research Laboratory Southern Illinois University Carbondale 1125 Lincoln Drive Carbondale IL 62901 USA
| | - Michael W. Eichholz
- Cooperative Wildlife Research Laboratory and Center for Ecology Southern Illinois University Carbondale 1125 Lincoln Drive Carbondale IL 62901 USA
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6
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Fox LR, Potts SE. Herbivory mediates direct and indirect interactions in long‐unburned chaparral. ECOL MONOGR 2022. [DOI: 10.1002/ecm.1546] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Affiliation(s)
- Laurel R. Fox
- Department of Ecology and Evolutionary Biology University of California, Santa Cruz California USA
| | - Stephen E. Potts
- Department of Biological Sciences Louisiana State University, Baton Rouge Louisiana USA
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7
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Little J, Rubenstein DR, Guindre-Parker S. Plasticity in social behaviour varies with reproductive status in an avian cooperative breeder. Proc Biol Sci 2022; 289:20220355. [PMID: 35506224 PMCID: PMC9065970 DOI: 10.1098/rspb.2022.0355] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Cooperatively breeding vertebrates are common in unpredictable environments where the costs and benefits of providing offspring care fluctuate temporally. To balance these fitness outcomes, individuals of cooperatively breeding species often exhibit behavioural plasticity according to environmental conditions. Although individual variation in cooperative behaviours is well-studied, less is known about variation in plasticity of social behaviour. Here, we examine the fitness benefits, plasticity and repeatability of nest guarding behaviour in cooperatively breeding superb starlings (Lamprotornis superbus). After demonstrating that the cumulative nest guarding performed at a nest by all breeders and helpers combined is a significant predictor of reproductive success, we model breeder and helper behavioural reaction norms to test the hypothesis that individuals invest more in guarding in favourable seasons with high rainfall. Variation in nest guarding behaviour across seasons differed for individuals of different reproductive status: breeders showed plastic nest guarding behaviour in response to rainfall, whereas helpers did not. Similarly, we found that individual breeders show repeatability and consistency in their nest guarding behaviour while individual helpers did not. Thus, individuals with the potential to gain direct fitness benefits exhibit greater plasticity and individual-level repeatability in cooperative behaviour.
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Affiliation(s)
- Jasmine Little
- Department of Ecology, Evolution, and Organismal Biology, Kennesaw State University, Kennesaw, Georgia
| | - Dustin R Rubenstein
- Department of Ecology, Evolution and Environmental Biology, Columbia University, New York, NY, USA.,Center for Integrative Animal Behavior, Columbia University, New York, NY, USA
| | - Sarah Guindre-Parker
- Department of Ecology, Evolution, and Organismal Biology, Kennesaw State University, Kennesaw, Georgia
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8
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Laverty TM, Berger J. Indirect effects of African megaherbivore conservation on bat diversity in the world's oldest desert. CONSERVATION BIOLOGY : THE JOURNAL OF THE SOCIETY FOR CONSERVATION BIOLOGY 2022; 36:e13780. [PMID: 34061400 DOI: 10.1111/cobi.13780] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/14/2020] [Revised: 05/22/2021] [Accepted: 05/24/2021] [Indexed: 06/12/2023]
Abstract
In extreme environments, temperature and precipitation are often the main forces responsible for structuring ecological communities and species distributions. The role of biotic interactions is typically thought to be minimal. By clustering around rare and isolated features, like surface water, however, effects of herbivory by desert-dwelling wildlife can be amplified. Understanding how species interact in these environments is critical to safeguarding vulnerable or data-deficient species. We examined whether African elephants (Loxodonta africana), black rhinoceros (Diceros bicornis), and southern giraffe (Giraffa giraffa) modulate insectivorous bat communities around permanent waterholes in the Namib Desert. We estimated megaherbivore use of sites based on dung transects, summarized vegetation productivity from satellite measurements of the normalized difference vegetation index, and surveyed local bat communities acoustically. We used structural equation models to identify relationships among megaherbivores and bat species richness and dry- (November 2016-January 2017) and wet- (February-May 2017) season bat activity. Site-level megaherbivore use in the dry season was positively associated with bat activity-particularly that of open-air foragers-and species richness through indirect pathways. When resources were more abundant (wet season), however, these relationships were weakened. Our results indicate that biotic interactions contribute to species distributions in desert areas and suggest the conservation of megaherbivores in this ecosystem may indirectly benefit insectivorous bat abundance and diversity. Given that how misunderstood and understudied most bats are relative to other mammals, such findings suggest that managers pursue short-term solutions (e.g., community game guard programs, water-point protection near human settlements, and ecotourism) to indirectly promote bat conservation and that research includes megaherbivores' effects on biodiversity at other trophic levels.
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Affiliation(s)
- Theresa M Laverty
- Department of Fish, Wildlife, and Conservation Biology, Colorado State University, Fort Collins, Colorado, USA
| | - Joel Berger
- Department of Fish, Wildlife, and Conservation Biology, Colorado State University, Fort Collins, Colorado, USA
- Wildlife Conservation Society, Bronx, New York, USA
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9
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Guindre-Parker S, Rubenstein DR. Long-Term Measures of Climate Unpredictability Shape the Avian Endocrine Stress Axis. Am Nat 2021; 198:394-405. [PMID: 34403319 DOI: 10.1086/715628] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
AbstractThe vertebrate glucocorticoid stress response is an important mechanism facilitating pleiotropic phenotypic adjustments for coping with environmental change and optimizing fitness. Although circulating glucocorticoid hormones are mediators of plasticity that individuals can adjust rapidly in response to environmental challenges, they are also shaped by ecological selection. It remains unclear, however, how environmental variation on different timescales influences glucocorticoids. Here, we use an intraspecific comparative approach to determine how variation in precipitation on different timescales (months, years, decades) shapes distinct components of the glucocorticoid response. We sampled superb starlings (Lamprotornis superbus) at eight sites across Kenya in multiple years that differed in precipitation. Among-population variation in baseline glucocorticoids was shaped by both short- and long-term precipitation, whereas variation in stress-induced levels was poorly explained by precipitation on any timescale. Adrenal sensitivity, quantified via adrenocorticotropic hormone injections, was shaped by long-term precipitation and was highest in unpredictable environments. Together, these results suggest that variation in glucocorticoids can be best explained by environmental variation at timescales that extend beyond the lives of individuals, although baseline glucocorticoids also reflect short-term environmental conditions. Patterns of long-term precipitation may represent a microevolutionary selective pressure shaping the endocrine stress axis across populations and influencing how individuals cope with environmental change.
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10
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Tchouassi DP, Torto B, Sang R, Riginos C, Ezenwa VO. Large herbivore loss has complex effects on mosquito ecology and vector-borne disease risk. Transbound Emerg Dis 2020; 68:2503-2513. [PMID: 33170555 DOI: 10.1111/tbed.13918] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2020] [Revised: 09/25/2020] [Accepted: 11/06/2020] [Indexed: 12/15/2022]
Abstract
Loss of biodiversity can affect transmission of infectious diseases in at least two ways: by altering host and vector abundance or by influencing host and vector behaviour. We used a large herbivore exclusion experiment to investigate the effects of wildlife loss on the abundance and feeding behaviour of mosquito vectors and to explore consequences for vector-borne disease transmission. Large herbivore loss affected both mosquito abundance and blood-feeding behaviour. For Aedes mcintoshi, the dominant mosquito species in our study and a primary vector of Rift Valley fever virus (RVFV), abundance decreased with large herbivore loss, while blood feeding on humans increased. Despite an elevated human biting rate in the absence of large herbivores, we estimated that the potential for RVFV transmission to humans doubles in the presence of large herbivores. These results demonstrate that multiple effects of biodiversity loss on vectors can lead to counterintuitive outcomes for human disease risk.
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Affiliation(s)
- David P Tchouassi
- International Centre of Insect Physiology and Ecology, Nairobi, Kenya
| | - Baldwyn Torto
- International Centre of Insect Physiology and Ecology, Nairobi, Kenya
| | - Rosemary Sang
- International Centre of Insect Physiology and Ecology, Nairobi, Kenya
| | | | - Vanessa O Ezenwa
- Odum School of Ecology and Department of Infectious Diseases, College of Veterinary Medicine, University of Georgia, Athens, GA, USA
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11
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Guindre-Parker S, Rubenstein DR. Survival Benefits of Group Living in a Fluctuating Environment. Am Nat 2020; 195:1027-1036. [PMID: 32469654 DOI: 10.1086/708496] [Citation(s) in RCA: 26] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
Abstract
Group living is predicted to arise only when the fitness benefits outweigh the costs of sociality. Group-living species-including cooperatively breeding and family-living birds and mammals-occur most frequently in environments where climatic conditions fluctuate unpredictably from year to year. The fitness consequences of group living are thus expected to vary with changing environmental conditions, though few studies have examined this possibility. We examined whether living in large social groups improves adult survivorship in cooperatively breeding superb starlings (Lamprotornis superbus). We also tested the hypothesis that larger groups buffer against harsh conditions by increasing survivorship most under periods of low rainfall. We found that group size was positively correlated with adult survival but in a sex-specific manner: female survival increased with group size across all environmental conditions, whereas male survival increased with group size only in wet years. Together with previous work in this system, our results suggest that larger groups confer survival benefits by reducing predation, rather than by improving access to food or buffering against physiological stress. Although group living does not appear to buffer against harsh conditions in adult starlings living in a fluctuating environment, living in larger groups does confer a survival advantage.
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12
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Coombs G. Does partial concealment influence predation attempts on small model snakes in South Africa? AFR J HERPETOL 2019. [DOI: 10.1080/21564574.2019.1645745] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Affiliation(s)
- Gareth Coombs
- Independent Researcher, Grahamstown, Eastern Cape, South Africa
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13
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Wigley BJ, Coetsee C, Kruger LM, Ratnam J, Sankaran M. Ants, fire, and bark traits affect how African savanna trees recover following damage. Biotropica 2019. [DOI: 10.1111/btp.12683] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Affiliation(s)
- Benjamin J. Wigley
- National Centre for Biological Sciences Tata Institute of Fundamental Research Bangalore India
- School of Natural Resource Management Nelson Mandela University George South Africa
| | - Corli Coetsee
- School of Natural Resource Management Nelson Mandela University George South Africa
- Scientific Services Kruger National Park Skukuza South Africa
| | - Laurence M. Kruger
- Organisation for Tropical Studies Skukuza South Africa
- Biology Department University of Cape Town Rondebosch South Africa
| | - Jayashree Ratnam
- National Centre for Biological Sciences Tata Institute of Fundamental Research Bangalore India
| | - Mahesh Sankaran
- National Centre for Biological Sciences Tata Institute of Fundamental Research Bangalore India
- School of Biology Faculty of Biological Sciences University of Leeds Leeds UK
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14
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Large mammals generate both top-down effects and extended trophic cascades on floral-visitor assemblages. JOURNAL OF TROPICAL ECOLOGY 2019. [DOI: 10.1017/s0266467419000142] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
AbstractCascading effects of high trophic levels onto lower trophic levels have been documented in many ecosystems. Some studies also show evidence of extended trophic cascades, in which guilds dependent on lower trophic levels, but uninvolved in the trophic cascade themselves, are affected by the trophic cascade due to their dependence on lower trophic levels. Top-down effects of large mammals on plants could lead to a variety of extended trophic cascades on the many guilds dependent on plants, such as pollinators. In this study, floral-visitor and floral abundances and assemblages were quantified within a series of 1-ha manipulations of large-mammalian herbivore density in an African savanna. Top-down effects of large mammals on the composition of flowers available for floral visitors are first shown, using regressions of herbivore activity on metrics of floral and floral-visitor assemblages. An extended trophic cascade is also shown: the floral assemblage further altered the assemblage of floral visitors, according to a variety of approaches, including a structural equation modelling approach (model with an extended trophic cascade was supported over a model without, AICc weight = 0.984). Our study provides support for extended trophic cascades affecting floral visitors, suggesting that trophic cascades can have impacts throughout entire communities.
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15
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Khadiejah S, Razak N, Ward-Fear G, Shine R, Natusch DJD. Asian water monitors (Varanus salvator) remain common in Peninsular Malaysia, despite intense harvesting. WILDLIFE RESEARCH 2019. [DOI: 10.1071/wr18166] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
Context
Each year, between 50000 and 120000 Asian water monitors (Varanus salvator, to >2 m total length) are harvested from the wild in Peninsular Malaysia for their skins. Under the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES), international trade is allowable only if it is sustainable.
Aims
To assess the sustainability of Malaysia’s harvest of water monitors by quantifying the abundance and demography of V. salvator in the wild, and to develop cost-effective methods for estimating the parameters needed to evaluate sustainability.
Methods
We conducted trapping surveys to determine the abundance, population demography and density of V. salvator in four habitat types in five states in Peninsular Malaysia in 2010, 2011, 2012 and 2018.
Key results
Of 1025 lizards captured, only 63% (mostly females) were within the preferred body-size range exploited for commercial trade. Densities were high (37–372 lizards km–2 based on estimated population sizes; 1–35 lizards km–2 based on number of animals captured). Anthropogenic habitats (e.g. oil palm plantations) contained denser populations of monitors than did natural habitats where no hunting occurs, but mean body sizes were smaller.
Conclusions
Despite intensive harvesting for many decades, V. salvator remains abundant and widespread. Harvesting alters the demographic structure of lizard populations, but harvests of V. salvator in Malaysia are likely to be sustainable because a significant proportion of the population is not exploited.
Implications
Ongoing monitoring is required to continually reassess harvest sustainability. For this purpose, relatively simple population approaches, such as line-trapping transects to elucidate relative abundances, can provide important data on the makeup of hunted populations of water monitors more cost-effectively than can mark–recapture studies for assessments of sustainable use of these economically important lizards.
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16
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Bergstrom BJ, Sensenig RL, Augustine DJ, Young TP. Searching for cover: soil enrichment and herbivore exclusion, not fire, enhance African savanna small‐mammal abundance. Ecosphere 2018. [DOI: 10.1002/ecs2.2519] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Affiliation(s)
| | - Ryan L. Sensenig
- Department of Biological Sciences Goshen College Goshen Indiana 46526 USA
| | - David J. Augustine
- Rangeland Resources Research Unit USDA–Agricultural Research Service Fort Collins Colorado 80526 USA
| | - Truman P. Young
- Department of Plant Sciences University of California Davis California 95616 USA
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17
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Ostfeld JK, Keesing F. Impacts of large mammals on movements of the pouched mouse (
Saccostomus mearnsi
) in central Kenya. Afr J Ecol 2018. [DOI: 10.1111/aje.12549] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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18
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Goheen JR, Augustine DJ, Veblen KE, Kimuyu DM, Palmer TM, Porensky LM, Pringle RM, Ratnam J, Riginos C, Sankaran M, Ford AT, Hassan AA, Jakopak R, Kartzinel TR, Kurukura S, Louthan AM, Odadi WO, Otieno TO, Wambua AM, Young HS, Young TP. Conservation lessons from large-mammal manipulations in East African savannas: the KLEE, UHURU, and GLADE experiments. Ann N Y Acad Sci 2018; 1429:31-49. [DOI: 10.1111/nyas.13848] [Citation(s) in RCA: 36] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2017] [Revised: 04/03/2018] [Accepted: 04/06/2018] [Indexed: 11/26/2022]
Affiliation(s)
- Jacob R. Goheen
- Department of Zoology and Physiology; University of Wyoming; Laramie Wyoming
- Mpala Research Centre; Nanyuki Kenya
| | | | - Kari E. Veblen
- Department of Wildland Resources and Ecology Center; Utah State University; Logan Utah
| | - Duncan M. Kimuyu
- Department of Wildland Resources and Ecology Center; Utah State University; Logan Utah
- Mpala Research Centre; Nanyuki Kenya
| | - Todd M. Palmer
- Department of Biology; University of Florida; Gainesville Florida
- Mpala Research Centre; Nanyuki Kenya
| | | | - Robert M. Pringle
- Department of Ecology and Evolutionary Biology; Princeton University; Princeton New Jersey
- Mpala Research Centre; Nanyuki Kenya
| | | | | | - Mahesh Sankaran
- National Centre for Biological Sciences, TIFR; Bangalore India
- School of Biology, University of Leeds; Leeds United Kingdom
| | - Adam T. Ford
- Department of Biology; University of British Columbia; Kelowna British Columbia Canada
| | | | - Rhiannon Jakopak
- Department of Zoology and Physiology; University of Wyoming; Laramie Wyoming
| | - Tyler R. Kartzinel
- Department of Ecology and Evolutionary Biology; Brown University; Providence Rhode Island
| | | | | | - Wilfred O. Odadi
- Department of Natural Resources; Egerton University; Egerton Kenya
- Mpala Research Centre; Nanyuki Kenya
| | | | - Alois M. Wambua
- Department of Wildland Resources and Ecology Center; Utah State University; Logan Utah
- Mpala Research Centre; Nanyuki Kenya
| | - Hillary S. Young
- Department of Ecology, Evolution and Marine Biology; University of California; Santa Barbara California
| | - Truman P. Young
- Department of Plant Sciences; University of California; Davis California
- Mpala Research Centre; Nanyuki Kenya
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19
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Granados A, Brodie JF, Bernard H, O'Brien MJ. Defaunation and habitat disturbance interact synergistically to alter seedling recruitment. ECOLOGICAL APPLICATIONS : A PUBLICATION OF THE ECOLOGICAL SOCIETY OF AMERICA 2017; 27:2092-2101. [PMID: 28660670 DOI: 10.1002/eap.1592] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/29/2016] [Accepted: 05/31/2017] [Indexed: 06/07/2023]
Abstract
Vertebrate granivores destroy plant seeds, but whether animal-induced seed mortality alters plant recruitment varies with habitat context, seed traits, and among granivore species. An incomplete understanding of seed predation makes it difficult to predict how widespread extirpations of vertebrate granivores in tropical forests might affect tree communities, especially in the face of habitat disturbance. Many tropical forests are simultaneously affected by animal loss as well as habitat disturbance, but the consequences of each for forest regeneration are often studied separately or additively, and usually on a single plant demographic stage. The combined impacts of these threats could affect plant recruitment in ways that are not apparent when studied in isolation. We used wire cages to exclude large (elephants), medium, (sambar deer, bearded pigs, muntjac deer), and small (porcupines, chevrotains) ground-dwelling mammalian granivores and herbivores in logged and unlogged forests in Malaysian Borneo. We assessed the interaction between habitat disturbance (selective logging) and experimental defaunation on seed survival, germination, and seedling establishment in five dominant dipterocarp tree species spanning a 21-fold gradient in seed size. Granivore-induced seed mortality was consistently higher in logged forest. Germination of unpredated seeds was reduced in logged forest and in the absence of small to large-bodied mammals. Experimental defaunation increased germination and reduced seed removal but had little effect on seed survival. Seedling recruitment however, was more likely where logging and animal loss occurred together. The interacting effects of logging and hunting could therefore, actually increase seedling establishment, suggesting that the loss of mammals in disturbed forest could have important consequences for forest regeneration and composition.
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Affiliation(s)
- Alys Granados
- Department of Zoology and Biodiversity Research Centre, University of British Columbia, Vancouver, British Columbia, V6T 1Z4, Canada
| | - Jedediah F Brodie
- Department of Zoology and Biodiversity Research Centre, University of British Columbia, Vancouver, British Columbia, V6T 1Z4, Canada
- Division of Biological Sciences and Wildlife Biology Program, University of Montana, Missoula, Montana, 59812, USA
| | - Henry Bernard
- Institute for Tropical Biology and Conservation, University Malaysia Sabah, Kota Kinabalu, Sabah, Malaysia
| | - Michael J O'Brien
- Consejo Superior de Investigaciones Científicas, Estación Experimental de Zonas Áridas, Carretera de Sacramento s/n, E-04120, La Cañada, Almería, Spain
- The South East Asia Rainforest Research Partnership, Danum Valley Field Centre, P.O. Box 60282, 91112, Lahad Datu, Sabah, Malaysia
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20
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Weinstein S, Titcomb G, Agwanda B, Riginos C, Young H. Parasite responses to large mammal loss in an African savanna. Ecology 2017; 98:1839-1848. [PMID: 28403506 DOI: 10.1002/ecy.1858] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/21/2016] [Revised: 03/01/2017] [Accepted: 04/05/2017] [Indexed: 11/11/2022]
Abstract
Biodiversity loss can alter disease transmission; however, the magnitude and direction of these effects vary widely across ecosystems, scales, and pathogens. Here we experimentally examine the effects of one of the most globally pervasive patterns of biodiversity decline, the selective loss of large wildlife, on infection probability, intensity and population size of a group of common rodent-borne parasites - macroparasitic helminths. Consistent with previous work on vector-borne pathogens, we found that large wildlife removal causes strong and systematic increases of rodent-borne parasites, largely due to increases in rodent density, as rodents are released from competition with larger herbivores. Although we predicted that increased host density would also increase per capita infection among all directly transmitted parasites, this additional amplification occurred for only two of three examined parasites. Furthermore, the actual effects of large mammal loss on per capita infection were mediated by the complex suite of abiotic and biotic factors that regulate parasite transmission. Thus, while these results strongly suggest that large wildlife loss will cause systematic increases in rodent parasite populations, they also underscore the difficulty of making more specific predictions for a given parasite based on simple attributes such as transmission mode or life history strategy. Instead, detailed information on the ecology of each parasite species would be necessary to make more accurate predictions of how biodiversity loss will affect infection.
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Affiliation(s)
- Sara Weinstein
- Department of Ecology, Evolution and Marine Biology, University of California Santa Barbara, Santa Barbara, California, USA
| | - Georgia Titcomb
- Department of Ecology, Evolution and Marine Biology, University of California Santa Barbara, Santa Barbara, California, USA.,Mpala Research Centre, Nanyuki, Kenya
| | - Bernard Agwanda
- Zoology Department, Mammalogy Section, National Museums Kenya, Nairobi, Kenya
| | - Corinna Riginos
- Mpala Research Centre, Nanyuki, Kenya.,Department of Zoology and Physiology, University of Wyoming, Laramie, Wyoming, USA
| | - Hillary Young
- Department of Ecology, Evolution and Marine Biology, University of California Santa Barbara, Santa Barbara, California, USA.,Mpala Research Centre, Nanyuki, Kenya
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21
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Long RA, Wambua A, Goheen JR, Palmer TM, Pringle RM. Climatic variation modulates the indirect effects of large herbivores on small-mammal habitat use. J Anim Ecol 2017; 86:739-748. [PMID: 28342277 DOI: 10.1111/1365-2656.12669] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2016] [Accepted: 03/07/2017] [Indexed: 11/29/2022]
Abstract
Large mammalian herbivores (LMH) strongly shape the composition and architecture of plant communities. A growing literature shows that negative direct effects of LMH on vegetation frequently propagate to suppress the abundance of smaller consumers. Indirect effects of LMH on the behaviour of these consumers, however, have received comparatively little attention despite their potential ecological significance. We sought to understand (i) how LMH indirectly shape small-mammal habitat use by altering the density and distribution of understorey plants; (ii) how these effects vary with climatic context (here, seasonality in rainfall); and (iii) the extent to which behavioural responses of small mammals are contingent upon small-mammal density. We tested the effects of a diverse LMH community on small-mammal habitat use using 4 years of spatially explicit small-mammal trapping and vegetation data from the UHURU Experiment, a replicated set of LMH exclosures in semi-arid Kenyan savanna. Small-mammal habitat use was positively associated with tree density and negatively associated with bare (unvegetated) patches in all plots and seasons. In the presence of LMH, and especially during the dry season, small mammals consistently selected tree cover and avoided bare patches. In contrast, when LMH were excluded, small mammals were weakly associated with tree cover and did not avoid bare patches as strongly. These behavioural responses of small mammals were largely unaffected by changes in small-mammal density associated with LMH exclusion. Our results show that LMH indirectly affect small-mammal behaviour, and that these effects are influenced by climate and can arise via density-independent mechanisms. This raises the possibility that anthropogenic LMH declines might interact with changing patterns of rainfall to alter small-mammal distribution and behaviour, independent of numerical responses by small mammals to these perturbations. For example, increased rainfall in East Africa (as predicted in many recent climate-model simulations) may relax constraints on small-mammal distribution where LMH are rare or absent, whereas increased aridity and/or drought frequency may tighten them.
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Affiliation(s)
- Ryan A Long
- Department of Ecology and Evolutionary Biology, Princeton University, Princeton, NJ, 08544, USA
| | - Alois Wambua
- Mpala Research Centre, PO Box 555 Rumuruti Road, Nanyuki, Kenya
| | - Jacob R Goheen
- Mpala Research Centre, PO Box 555 Rumuruti Road, Nanyuki, Kenya.,Department of Zoology and Physiology, University of Wyoming, Laramie, WY, 82071, USA
| | - Todd M Palmer
- Mpala Research Centre, PO Box 555 Rumuruti Road, Nanyuki, Kenya.,Department of Biology, University of Florida, Gainesville, FL, 32611, USA
| | - Robert M Pringle
- Department of Ecology and Evolutionary Biology, Princeton University, Princeton, NJ, 08544, USA.,Mpala Research Centre, PO Box 555 Rumuruti Road, Nanyuki, Kenya
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22
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Young HS, McCauley DJ, Galetti M, Dirzo R. Patterns, Causes, and Consequences of Anthropocene Defaunation. ANNUAL REVIEW OF ECOLOGY EVOLUTION AND SYSTEMATICS 2016. [DOI: 10.1146/annurev-ecolsys-112414-054142] [Citation(s) in RCA: 233] [Impact Index Per Article: 29.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Anthropocene defaunation, the global extinction of faunal species and populations and the decline in abundance of individuals within populations, has been predominantly documented in terrestrial ecosystems, but indicators suggest defaunation has been more severe in freshwater ecosystems. Marine defaunation is in a more incipient stage, yet pronounced effects are already apparent and its rapid acceleration seems likely. Defaunation now impacts the planet's wildlife with profound cascading consequences, ranging from local to global coextinctions of interacting species to the loss of ecological services critical for humanity. Slowing defaunation will require aggressively reducing animal overexploitation and habitat destruction; mitigating climate disruption; and stabilizing the impacts of human population growth and uneven resource consumption. Given its omnipresence, defaunation should receive status of major global environmental change and should be addressed with the same urgency as deforestation, pollution, and climatic change. Global action is needed to prevent defaunation's current trajectory from catalyzing the planet's sixth major extinction.
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Affiliation(s)
- Hillary S. Young
- Department of Ecology, Evolution, and Marine Biology, University of California, Santa Barbara, California 93106
| | - Douglas J. McCauley
- Department of Ecology, Evolution, and Marine Biology, University of California, Santa Barbara, California 93106
| | - Mauro Galetti
- Departamento de Ecologia, Universidade Estadual Paulista (UNESP), 13506–900 Rio Claro, São Paulo, Brazil
| | - Rodolfo Dirzo
- Department of Biology, Stanford University, Stanford, California 94305
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23
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McCauley DJ, Hardesty‐Moore M, Halpern BS, Young HS. A mammoth undertaking: harnessing insight from functional ecology to shape de‐extinction priority setting. Funct Ecol 2016. [DOI: 10.1111/1365-2435.12728] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Affiliation(s)
- Douglas J. McCauley
- Department of Ecology, Evolution, and Marine Biology University of California Santa Barbara CA93106 USA
| | - Molly Hardesty‐Moore
- Department of Ecology, Evolution, and Marine Biology University of California Santa Barbara CA93106 USA
| | - Benjamin S. Halpern
- Bren School of Environmental Science & Management University of California Santa Barbara CA93106 USA
- National Center for Ecological Analysis and Synthesis University of California 735 State St. Suite 300 Santa Barbara CA93101 USA
- Imperial College London Silwood Park Campus Buckhurst Rd AscotSL57PY UK
| | - Hillary S. Young
- Department of Ecology, Evolution, and Marine Biology University of California Santa Barbara CA93106 USA
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24
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Weir SM, Knox A, Talent LG, Anderson TA, Salice CJ. Direct and indirect effects of petroleum production activities on the western fence lizard (Sceloporus occidentalis) as a surrogate for the dunes sagebrush lizard (Sceloporus arenicolus). ENVIRONMENTAL TOXICOLOGY AND CHEMISTRY 2016; 35:1276-1283. [PMID: 26456391 DOI: 10.1002/etc.3279] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/28/2015] [Revised: 07/27/2015] [Accepted: 10/07/2015] [Indexed: 06/05/2023]
Abstract
The dunes sagebrush lizard (Sceloporus arenicolus) is a habitat specialist of conservation concern limited to shin oak sand dune systems of New Mexico and Texas (USA). Because much of the dunes sagebrush lizard's habitat occurs in areas of high oil and gas production, there may be direct and indirect effects of these activities. The congeneric Western fence lizard (Sceloporus occidentalis) was used as a surrogate species to determine direct effects of 2 contaminants associated with oil and gas drilling activities in the Permian Basin (NM and TX, USA): herbicide formulations (Krovar and Quest) and hydrogen sulfide gas (H2S). Lizards were exposed to 2 concentrations of H2 S (30 ppm or 90 ppm) and herbicide formulations (1× or 2× label application rate) representing high-end exposure scenarios. Sublethal behavioral endpoints were evaluated, including sprint speed and time to prey detection and capture. Neither H2S nor herbicide formulations caused significant behavioral effects compared to controls. To understand potential indirect effects of oil and gas drilling on the prey base, terrestrial invertebrate biomass and order diversity were quantified at impacted sites to compare with nonimpacted sites. A significant decrease in biomass was found at impacted sites, but no significant effects on diversity. The results suggest little risk from direct toxic effects, but the potential for indirect effects should be further explored.
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Affiliation(s)
- Scott M Weir
- Department of Environmental Toxicology, Texas Tech University, Lubbock, Texas, USA
| | - Ami Knox
- Department of University Studies, Texas Tech University, Lubbock, Texas, USA
| | - Larry G Talent
- Department of Natural Resource Ecology and Management, Oklahoma State University, Stillwater, Oklahoma, USA
| | - Todd A Anderson
- Department of Environmental Toxicology, Texas Tech University, Lubbock, Texas, USA
| | - Christopher J Salice
- Department of Environmental Toxicology, Texas Tech University, Lubbock, Texas, USA
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25
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Daskin JH, Pringle RM. Does primary productivity modulate the indirect effects of large herbivores? A global meta-analysis. J Anim Ecol 2016; 85:857-68. [PMID: 27007672 DOI: 10.1111/1365-2656.12522] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2015] [Accepted: 03/11/2016] [Indexed: 12/13/2022]
Abstract
Indirect effects of large mammalian herbivores (LMH), while much less studied than those of apex predators, are increasingly recognized to exert powerful influences on communities and ecosystems. The strength of these effects is spatiotemporally variable, and several sets of authors have suggested that they are governed in part by primary productivity. However, prior theoretical and field studies have generated conflicting results and predictions, underscoring the need for a synthetic global analysis. We conducted a meta-analysis of the direction and magnitude of large mammalian herbivore-initiated indirect interactions using 67 published studies comprising 456 individual responses. We georeferenced 41 of these studies (comprising 253 responses from 33 locations on five continents) to a satellite-derived map of primary productivity. Because predator assemblages might also influence the impact of large herbivores, we conducted a similar analysis using a global map of large carnivore species richness. In general, LMH reduced the abundance of other consumer species and also tended to reduce consumer richness, although the latter effect was only marginally significant. There was a pronounced reduction in the strength of negative (i.e. suppressive, due e.g., to competition) indirect effects of LMH on consumer abundance in more productive ecosystems. In contrast, positive (facilitative) indirect effects were not significantly correlated with productivity, likely because these comprised a more heterogeneous array of mechanisms. We found no effect of carnivore species richness on herbivore-initiated indirect effect strength. Our findings help to resolve the fundamental problem of ecological contingency as it pertains to the strength of an understudied class of multitrophic interactions. Moreover, these results will aid in predicting the indirect effects of anthropogenic wildlife declines and irruptions, and how these effects might be mediated by climatically driven shifts in resource availability. To the extent that intact ungulate guilds help to suppress populations of small animals that act as agricultural pests and disease reservoirs, the negative impacts of large mammal declines on human well-being may be relatively stronger in low-productivity areas.
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Affiliation(s)
- Joshua H Daskin
- Department of Ecology and Evolutionary Biology, 106A Guyot Hall, Princeton University, Princeton, NJ, 08540, USA
| | - Robert M Pringle
- Department of Ecology and Evolutionary Biology, 106A Guyot Hall, Princeton University, Princeton, NJ, 08540, USA
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26
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Impact of invasive spotted deer (Axis axis) on tropical island lizard communities in the Andaman archipelago. Biol Invasions 2015. [DOI: 10.1007/s10530-015-1006-0] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
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27
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Galetti M, Guevara R, Galbiati LA, Neves CL, Rodarte RR, Mendes CP. Seed Predation by Rodents and Implications for Plant Recruitment in Defaunated Atlantic Forests. Biotropica 2015. [DOI: 10.1111/btp.12246] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Mauro Galetti
- Laboratório de Biologia da Conservação; Departamento de Ecologia; Universidade Estadual Paulista (UNESP); 13506-900 Rio Claro SP Brazil
| | - Roger Guevara
- Instituto de Ecología; A.C. Red de Biología Evolutiva; Carretera Antigua a Coatepec 351 El Haya Xalapa Veracruz Mexico
| | - Lígia A. Galbiati
- Laboratório de Biologia da Conservação; Departamento de Ecologia; Universidade Estadual Paulista (UNESP); 13506-900 Rio Claro SP Brazil
| | - Carolina L. Neves
- Laboratório de Biologia da Conservação; Departamento de Ecologia; Universidade Estadual Paulista (UNESP); 13506-900 Rio Claro SP Brazil
| | - Raisa R. Rodarte
- Laboratório de Biologia da Conservação; Departamento de Ecologia; Universidade Estadual Paulista (UNESP); 13506-900 Rio Claro SP Brazil
| | - Calebe P. Mendes
- Laboratório de Biologia da Conservação; Departamento de Ecologia; Universidade Estadual Paulista (UNESP); 13506-900 Rio Claro SP Brazil
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28
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Young HS, Dirzo R, Helgen KM, McCauley DJ, Nunn CL, Snyder P, Veblen KE, Zhao S, Ezenwa VO. Large wildlife removal drives immune defence increases in rodents. Funct Ecol 2015. [DOI: 10.1111/1365-2435.12542] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Hillary S. Young
- University of California Santa Barbara Santa Barbara California 93106 USA
- Division of Mammals National Museum of Natural History Smithsonian Institution Washington District of Columbia 20013 USA
- Mpala Research Centre Box 555 Nanyuki Kenya
| | - Rodolfo Dirzo
- Department of Biology Stanford University Stanford California 94305 USA
| | - Kristofer M. Helgen
- Division of Mammals National Museum of Natural History Smithsonian Institution Washington District of Columbia 20013 USA
| | - Douglas J. McCauley
- University of California Santa Barbara Santa Barbara California 93106 USA
- Mpala Research Centre Box 555 Nanyuki Kenya
| | - Charles L. Nunn
- Department of Evolutionary Anthropology Duke University Durham North Carolina 27708 USA
- Duke Global Health Institute Duke University Durham North Carolina 27708 USA
| | - Paul Snyder
- Odum School of Ecology and Department of Infectious Diseases College of Veterinary Medicine University of Georgia Athens Georgia 30602 USA
- Department of Integrative Biology Oregon State University Corvallis Oregon 97331 USA
| | - Kari E. Veblen
- Mpala Research Centre Box 555 Nanyuki Kenya
- Department of Wildland Resources and Ecology Center Utah State University Logan Utah 84322 USA
| | - Serena Zhao
- Division of Mammals National Museum of Natural History Smithsonian Institution Washington District of Columbia 20013 USA
- Mpala Research Centre Box 555 Nanyuki Kenya
| | - Vanessa O. Ezenwa
- Mpala Research Centre Box 555 Nanyuki Kenya
- Odum School of Ecology and Department of Infectious Diseases College of Veterinary Medicine University of Georgia Athens Georgia 30602 USA
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29
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Reeder NMM, Byrnes RM, Stoelting RE, Swaim KE. An endangered snake thrives in a highly urbanized environment. ENDANGER SPECIES RES 2015. [DOI: 10.3354/esr00677] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
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30
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Young HS, McCauley DJ, Dirzo R, Goheen JR, Agwanda B, Brook C, Otarola-Castillo E, Ferguson AW, Kinyua SN, McDonough MM, Palmer TM, Pringle RM, Young TP, Helgen KM. Context-dependent effects of large-wildlife declines on small-mammal communities in central Kenya. ECOLOGICAL APPLICATIONS : A PUBLICATION OF THE ECOLOGICAL SOCIETY OF AMERICA 2015; 25:348-60. [PMID: 26263659 DOI: 10.1890/14-0995.1] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
Many species of large wildlife have declined drastically worldwide. These reductions often lead to profound shifts in the ecology of entire communities and ecosystems. However, the effects of these large-wildlife declines on other taxa likely hinge upon both underlying abiotic properties of these systems and on the types of secondary anthropogenic changes associated with wildlife loss, making impacts difficult to predict. To better understand how these important contextual factors determine the consequences of large-wildlife declines on other animals in a community, we examined the effects of three common forms of large-wildlife loss (removal without replacement [using fences], removal followed by replacement with domestic stock, and removal accompanied by crop agricultural use) on small-mammal abundance, diversity, and community composition, in landscapes that varied in several abiotic attributes (rainfall, soil fertility, land-use intensity) in central Kenya. We found that small-mammal communities were indeed heavily impacted by all forms of large-wildlife decline, showing, on average: (1) higher densities, (2) lower species richness per site, and (3) different species assemblages in sites from which large wildlife were removed. However, the nature and magnitude of these effects were strongly context dependent. Rainfall, type of land-use change, and the interaction of these two factors were key predictors of both the magnitude and type of responses of small mammals. The strongest effects, particularly abundance responses, tended to be observed in low-rainfall areas. Whereas isolated wildlife removal primarily led to increased small-mammal abundance, wildlife removal associated with secondary uses (agriculture, domestic stock) had much more variable effects on abundance and stronger impacts on diversity and composition. Collectively, these results (1) highlight the importance of context in determining the impacts of large-wildlife decline on small-mammal communities, (2) emphasize the challenges in extrapolating results from controlled experimental studies to predict the effects of wildlife declines that are accompanied by secondary land-uses, and (3) suggest that, because of the context-dependent nature of the responses to large-wildlife decline, large-wildlife status alone cannot be reliably used to predict small-mammal community changes.
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31
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McCauley DJ, Pinsky ML, Palumbi SR, Estes JA, Joyce FH, Warner RR. Marine defaunation: Animal loss in the global ocean. Science 2015; 347:1255641. [PMID: 25593191 DOI: 10.1126/science.1255641] [Citation(s) in RCA: 401] [Impact Index Per Article: 44.6] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Affiliation(s)
- Douglas J McCauley
- Department of Ecology, Evolution, and Marine Biology, University of California, Santa Barbara, CA 93106, USA.
| | - Malin L Pinsky
- Department of Ecology, Evolution, and Natural Resources, Institute of Marine and Coastal Sciences, Rutgers University, New Brunswick, NJ 08901, USA
| | - Stephen R Palumbi
- Department of Biology, Stanford University, Hopkins Marine Station, Pacific Grove, CA 93950, USA
| | - James A Estes
- Department of Ecology and Evolutionary Biology, University of California, Santa Cruz, CA 95060, USA
| | - Francis H Joyce
- Department of Ecology, Evolution, and Marine Biology, University of California, Santa Barbara, CA 93106, USA
| | - Robert R Warner
- Department of Ecology, Evolution, and Marine Biology, University of California, Santa Barbara, CA 93106, USA
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32
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Galetti M, Bovendorp RS, Guevara R. Defaunation of large mammals leads to an increase in seed predation in the Atlantic forests. Glob Ecol Conserv 2015. [DOI: 10.1016/j.gecco.2015.04.008] [Citation(s) in RCA: 55] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022] Open
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33
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Byrom AE, Nkwabi AJK, Metzger K, Mduma SAR, Forrester GJ, Ruscoe WA, Reed DN, Bukombe J, Mchetto J, Sinclair ARE. Anthropogenic stressors influence small mammal communities in tropical East African savanna at multiple spatial scales. WILDLIFE RESEARCH 2015. [DOI: 10.1071/wr14223] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Context Protection of natural ecosystems undoubtedly safeguards ecological communities, with positive benefits for ecosystem processes and function. However, ecosystems are under threat from anthropogenic stressors that reduce the resilience both of component species and the system as a whole. Aims To determine how anthropogenic stressors (land use and climate change) could impact the diversity and resilience of a small mammal community in the greater Serengeti ecosystem, an East African savanna comprising Serengeti National Park (SNP) and adjacent agro-ecosystems, at local (SNP) and Africa-wide geographic scales. Methods We recorded small mammal species in 10 habitats in the greater Serengeti ecosystem, including the agro-ecosystem, over 48 years (1962–2010). We calculated richness and diversity for each habitat type, and used an index of similarity to quantify differences in the community among habitats. Species accumulation curves were also generated for each habitat type. Key results We recorded 40 species of small mammals in the greater Serengeti ecosystem. At the local scale, restricted habitat types in SNP (each <1% of the total area) made a disproportionately large contribution to diversity. Agro-ecosystems had lower richness and were less likely to contain specialist species. At regional and Africa-wide scales, local endemics were less likely to be recorded in the agro-ecosystem (57% species loss) compared with those with regional (33% loss) or Africa-wide (31%) geographic distributions. Conclusions At the local scale, the variety of habitats in SNP contributed to overall diversity. However, the ability to maintain this diversity in the adjacent agro-ecosystem was compromised for localised endemics compared with species with Africa-wide ranges. Land use intensification adjacent to SNP and projected changes in rainfall patterns for East Africa under global climate scenarios may compromise the future resilience of the small mammal community in this tropical savanna ecosystem. Implications The loss of rare or specialised species from protected areas and human-modified ecosystems could be mitigated by: (1) increasing habitat complexity and maintaining specialist habitats in the agro-ecosystem; and (2) creating buffers at the boundary of protected natural ecosystems that accommodate regime shifts in response to climatic change. These measures would increase the resilience of this coupled human–natural savanna ecosystem.
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Seki Y, Okuda K, Koganezawa M. Indirect Effects of Sika Deer on Japanese Badgers. MAMMAL STUDY 2014. [DOI: 10.3106/041.039.0403] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
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Affiliation(s)
- Rodolfo Dirzo
- Department of Biology, Stanford University, Stanford, CA 94305, USA.
| | - Hillary S Young
- Department of Ecology, Evolution, and Marine Biology, University of California Santa Barbara, Santa Barbara, CA 93106, USA
| | - Mauro Galetti
- Departamento de Ecologia, Universidade Estadual Paulista, Rio Claro, SP, 13506-900, Brazil
| | - Gerardo Ceballos
- Instituto de Ecología, Universidad Nacional Autónoma de México, AP 70-275, México D.F. 04510, Mexico
| | - Nick J B Isaac
- Natural Environment Research Council (NERC) Centre for Ecology and Hydrology, Benson Lane, Crowmarsh Gifford, Oxfordshire, OX10 8BB, UK
| | - Ben Collen
- Centre for Biodiversity and Environment Research, Department of Genetics, Evolution and Environment, University College London, Gower Street, London WC1E 6BT, UK
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Keesing F, Young TP. Cascading Consequences of the Loss of Large Mammals in an African Savanna. Bioscience 2014. [DOI: 10.1093/biosci/biu059] [Citation(s) in RCA: 78] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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Declines in large wildlife increase landscape-level prevalence of rodent-borne disease in Africa. Proc Natl Acad Sci U S A 2014; 111:7036-41. [PMID: 24778215 DOI: 10.1073/pnas.1404958111] [Citation(s) in RCA: 79] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
Populations of large wildlife are declining on local and global scales. The impacts of this pulse of size-selective defaunation include cascading changes to smaller animals, particularly rodents, and alteration of many ecosystem processes and services, potentially involving changes to prevalence and transmission of zoonotic disease. Understanding linkages between biodiversity loss and zoonotic disease is important for both public health and nature conservation programs, and has been a source of much recent scientific debate. In the case of rodent-borne zoonoses, there is strong conceptual support, but limited empirical evidence, for the hypothesis that defaunation, the loss of large wildlife, increases zoonotic disease risk by directly or indirectly releasing controls on rodent density. We tested this hypothesis by experimentally excluding large wildlife from a savanna ecosystem in East Africa, and examining changes in prevalence and abundance of Bartonella spp. infection in rodents and their flea vectors. We found no effect of wildlife removal on per capita prevalence of Bartonella infection in either rodents or fleas. However, because rodent and, consequently, flea abundance doubled following experimental defaunation, the density of infected hosts and infected fleas was roughly twofold higher in sites where large wildlife was absent. Thus, defaunation represents an elevated risk in Bartonella transmission to humans (bartonellosis). Our results (i) provide experimental evidence of large wildlife defaunation increasing landscape-level disease prevalence, (ii) highlight the importance of susceptible host regulation pathways and host/vector density responses in biodiversity-disease relationships, and (iii) suggest that rodent-borne disease responses to large wildlife loss may represent an important context where this relationship is largely negative.
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Byrom AE, Craft ME, Durant SM, Nkwabi AJK, Metzger K, Hampson K, Mduma SAR, Forrester GJ, Ruscoe WA, Reed DN, Bukombe J, Mchetto J, Sinclair ARE. Episodic outbreaks of small mammals influence predator community dynamics in an east African savanna ecosystem. OIKOS 2014. [DOI: 10.1111/oik.00962] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
| | - Meggan E. Craft
- Veterinary Population Medicine, University of Minnesota; 1988 Fitch Ave St Paul MN 55108 USA
| | - Sarah M. Durant
- Inst. of Zoology, Zoological Society of London, Regent's Park; London NW1 4RY UK
- Tanzania Wildlife Research Inst.; PO Box 661 Arusha Tanzania
| | - Ally J. K. Nkwabi
- Tanzania Wildlife Research Inst.; PO Box 661 Arusha Tanzania
- Serengeti Biodiversity Program, Tanzania Wildlife Research Inst.; PO Box 661 Arusha Tanzania
| | - Kristine Metzger
- Beaty Biodiversity Centre, Univ. of British Columbia; Vancouver BC V6T 1Z4 Canada
| | - Katie Hampson
- Boyd Orr Centre for population and Ecosystem Health, Inst. for Biodiversity, Animal Health and Comparative Medicine, College of Medical, Veterinary and Life Sciences, Univ. of Glasgow; Glasgow UK
| | - Simon A. R. Mduma
- Tanzania Wildlife Research Inst.; PO Box 661 Arusha Tanzania
- Serengeti Biodiversity Program, Tanzania Wildlife Research Inst.; PO Box 661 Arusha Tanzania
| | | | | | - Denne N. Reed
- Dept of Anthropology; Univ. of Texas Austin; 1 University Station C3200 Austin TX 78712 USA
| | - John Bukombe
- Tanzania Wildlife Research Inst.; PO Box 661 Arusha Tanzania
- Serengeti Biodiversity Program, Tanzania Wildlife Research Inst.; PO Box 661 Arusha Tanzania
| | - John Mchetto
- Tanzania Wildlife Research Inst.; PO Box 661 Arusha Tanzania
- Serengeti Biodiversity Program, Tanzania Wildlife Research Inst.; PO Box 661 Arusha Tanzania
| | - A. R. E. Sinclair
- Beaty Biodiversity Centre, Univ. of British Columbia; Vancouver BC V6T 1Z4 Canada
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Tambling CJ, Minnie L, Adendorff J, Kerley GI. Elephants facilitate impact of large predators on small ungulate prey species. Basic Appl Ecol 2013. [DOI: 10.1016/j.baae.2013.09.010] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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Wilkerson ML, Roche LM, Young TP. Indirect effects of domestic and wild herbivores on butterflies in an African savanna. Ecol Evol 2013; 3:3672-82. [PMID: 24198932 PMCID: PMC3810867 DOI: 10.1002/ece3.744] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2013] [Revised: 07/16/2013] [Accepted: 07/30/2013] [Indexed: 11/30/2022] Open
Abstract
Indirect interactions driven by livestock and wild herbivores are increasingly recognized as important aspects of community dynamics in savannas and rangelands. Large ungulate herbivores can both directly and indirectly impact the reproductive structures of plants, which in turn can affect the pollinators of those plants. We examined how wild herbivores and cattle each indirectly affect the abundance of a common pollinator butterfly taxon, Colotis spp., at a set of long-term, large herbivore exclosure plots in a semiarid savanna in central Kenya. We also examined effects of herbivore exclusion on the main food plant of Colotis spp., which was also the most common flowering species in our plots: the shrub Cadaba farinosa. The study was conducted in four types of experimental plots: cattle-only, wildlife-only, cattle and wildlife (all large herbivores), and no large herbivores. Across all plots, Colotis spp. abundances were positively correlated with both Cadaba flower numbers (adult food resources) and total Cadaba canopy area (larval food resources). Structural equation modeling (SEM) revealed that floral resources drove the abundance of Colotis butterflies. Excluding browsing wildlife increased the abundances of both Cadaba flowers and Colotis butterflies. However, flower numbers and Colotis spp. abundances were greater in plots with cattle herbivory than in plots that excluded all large herbivores. Our results suggest that wild browsing herbivores can suppress pollinator species whereas well-managed cattle use may benefit important pollinators and the plants that depend on them. This study documents a novel set of ecological interactions that demonstrate how both conservation and livelihood goals can be met in a working landscape with abundant wildlife and livestock.
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Affiliation(s)
- Marit L Wilkerson
- Department of Plant Sciences, University of California Davis, California
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Keesing F, Allan BF, Young TP, Ostfeld RS. Effects of wildlife and cattle on tick abundance in central Kenya. ECOLOGICAL APPLICATIONS : A PUBLICATION OF THE ECOLOGICAL SOCIETY OF AMERICA 2013; 23:1410-8. [PMID: 24147412 DOI: 10.1890/12-1607.1] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
In African savannas, large mammals, both wild and domestic, support an abundant and diverse population of tick ectoparasites. Because of the density of ticks and the many pathogens that they vector, cattle in East Africa are often treated with acaricides. While acaricides are known to be effective at reducing tick burdens on cattle, their effects on the overall abundance and community composition of ticks in savanna ecosystems are less well understood. It is also not known how well tick populations can be maintained in the absence of large mammals. We evaluated the effects of wildlife and of acaricide-treated cattle on host-seeking tick populations in a long-term, exclusion experiment in central Kenya. Over seven years, we sampled larval, nymphal, and adult ticks monthly on replicated treatment plots that controlled for the presence of cattle and for the presence of two guilds of large wild mammals: megaherbivores (giraffes and elephants) and all other large wild herbivores (> 15 kg). Two species of ticks were found in this habitat; across all surveys, 93% were Rhipicephalus pulchellus and 7% were R. praetextatus. The presence of acaricide-treated cattle dramatically reduced the abundance of host-seeking nymphal and adult ticks but did not affect the abundance of host-seeking larval ticks. The abundance of larval ticks was determined by the presence of large wild mammals, which appear to import gravid female ticks into the experimental plots. On plots with no large mammals, either wild or domestic, larval and nymphal ticks were rare. Adult R. pulchellus were most abundant in plots that allowed wildlife but excluded cattle. Adult R. praetextatus were relatively abundant in plots without any large mammals. These differences suggest that these ticks utilize different members of the host community. The reduction in ticks that results from the presence of acaricide-treated cattle has potential health benefits for humans and wildlife, but these benefits must be weighed against potential costs, including reduced availability of food for birds such as oxpeckers that feed on ticks.
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Affiliation(s)
- Felicia Keesing
- Program in Biology, Bard College, P.O. Box 5000, Annandale-on-Hudson, New York 12504, USA.
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Pedersen S, Andreassen HP, Keith DA, Skarpe C, Dickman CR, Gordon IJ, Crowther MS, McArthur C. Relationships between native small mammals and native and introduced large herbivores. AUSTRAL ECOL 2013. [DOI: 10.1111/aec.12072] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Affiliation(s)
- Simen Pedersen
- Department of Forestry and Wildlife Management; Faculty of Applied Ecology and Agricultural Sciences; Hedmark University College; Evenstad NO-2480 Koppang Norway
- Department of Biology; Faculty of Natural Sciences and Technology; Norwegian University of Science and Technology; Trondheim Norway
| | - Harry P. Andreassen
- Department of Forestry and Wildlife Management; Faculty of Applied Ecology and Agricultural Sciences; Hedmark University College; Evenstad NO-2480 Koppang Norway
| | - David A. Keith
- Australian Wetlands and Rivers Centre; University of NSW; Sydney New South Wales Australia
- NSW Office of Environment & Heritage; Sydney New South Wales Australia
| | - Christina Skarpe
- Department of Forestry and Wildlife Management; Faculty of Applied Ecology and Agricultural Sciences; Hedmark University College; Evenstad NO-2480 Koppang Norway
| | - Christopher R. Dickman
- School of Biological Sciences; The University of Sydney; Sydney New South Wales Australia
| | | | - Mathew S. Crowther
- School of Biological Sciences; The University of Sydney; Sydney New South Wales Australia
| | - Clare McArthur
- School of Biological Sciences; The University of Sydney; Sydney New South Wales Australia
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Young HS, McCauley DJ, Helgen KM, Goheen JR, Otárola-Castillo E, Palmer TM, Pringle RM, Young TP, Dirzo R. Effects of mammalian herbivore declines on plant communities: observations and experiments in an African savanna. THE JOURNAL OF ECOLOGY 2013; 101:1030-1041. [PMID: 24014216 PMCID: PMC3758959 DOI: 10.1111/1365-2745.12096] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/18/2012] [Accepted: 03/21/2013] [Indexed: 05/29/2023]
Abstract
1. Herbivores influence the structure and composition of terrestrial plant communities. However, responses of plant communities to herbivory are variable and depend on environmental conditions, herbivore identity and herbivore abundance. As anthropogenic impacts continue to drive large declines in wild herbivores, understanding the context dependence of herbivore impacts on plant communities becomes increasingly important. 2. Exclosure experiments are frequently used to assess how ecosystems reorganize in the face of large wild herbivore defaunation. Yet in many landscapes, declines in large wildlife are often accompanied by other anthropogenic activities, especially land conversion to livestock production. In such cases, exclosure experiments may not reflect typical outcomes of human-driven extirpations of wild herbivores. 3. Here, we examine how plant community responses to changes in the identity and abundance of large herbivores interact with abiotic factors (rainfall and soil properties). We also explore how effects of wild herbivores on plant communities differ between large-scale herbivore exclosures and landscape sites where anthropogenic activity has caused wildlife declines, often accompanied by livestock increases. 4. Abiotic context modulated the responses of plant communities to herbivore declines with stronger effect sizes in lower-productivity environments. Also, shifts in plant community structure, composition and species richness following wildlife declines differed considerably between exclosure experiments and landscape sites in which wild herbivores had declined and were often replaced by livestock. Plant communities in low wildlife landscape sites were distinct in both composition and physical structure from both exclosure and control sites in experiments. The power of environmental (soil and rainfall) gradients in influencing plant response to herbivores was also greatly dampened or absent in the landscape sites. One likely explanation for these observed differences is the compensatory effect of livestock associated with the depression or extirpation of wildlife. 5.Synthesis. Our results emphasize the importance of abiotic environmental heterogeneity in modulating the effects of mammalian herbivory on plant communities and the importance of such covariation in understanding effects of wild herbivore declines. They also suggest caution when extrapolating results from exclosure experiments to predict the consequences of defaunation as it proceeds in the Anthropocene.
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Affiliation(s)
- Hillary S Young
- Division of Mammals, Smithsonian InstitutionWashington, DC, 20013, USA
- Department of Biology, Stanford UniversityStanford, CA, 94305, USA
- Mpala Research CentreBox 555, Nanyuki, Kenya
- Harvard University Center for the EnvironmentCambridge, MA, 02138, USA
| | - Douglas J McCauley
- Mpala Research CentreBox 555, Nanyuki, Kenya
- Department of Environmental Science, Policy, and Management, University of California at BerkeleyBerkeley, CA, 94720, USA
| | | | - Jacob R Goheen
- Mpala Research CentreBox 555, Nanyuki, Kenya
- Department of Zoology and Physiology, University of WyomingLaramie, WY, 82071, USA
| | - Erik Otárola-Castillo
- Department of Human Evolutionary Biology, Harvard UniversityCambridge, MA, 02138, USA
- Department of Ecology, Evolution and Organismal Biology, Iowa State UniversityAmes, IO, 50010, USA
| | - Todd M Palmer
- Mpala Research CentreBox 555, Nanyuki, Kenya
- Department of Zoology, University of FloridaGainesville, FL, 32611, USA
| | - Robert M Pringle
- Mpala Research CentreBox 555, Nanyuki, Kenya
- Department of Ecology and Evolutionary Biology, Princeton UniversityPrinceton, NJ, 08544, USA
| | - Truman P Young
- Mpala Research CentreBox 555, Nanyuki, Kenya
- Department of Plant Sciences, University of CaliforniaDavis, CA, 95616, USA
| | - Rodolfo Dirzo
- Department of Biology, Stanford UniversityStanford, CA, 94305, USA
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Goheen JR, Palmer TM, Charles GK, Helgen KM, Kinyua SN, Maclean JE, Turner BL, Young HS, Pringle RM. Piecewise disassembly of a large-herbivore community across a rainfall gradient: the UHURU experiment. PLoS One 2013; 8:e55192. [PMID: 23405122 PMCID: PMC3566220 DOI: 10.1371/journal.pone.0055192] [Citation(s) in RCA: 72] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2012] [Accepted: 12/19/2012] [Indexed: 11/19/2022] Open
Abstract
Large mammalian herbivores (LMH) strongly influence plant communities, and these effects can propagate indirectly throughout food webs. Most existing large-scale manipulations of LMH presence/absence consist of a single exclusion treatment, and few are replicated across environmental gradients. Thus, important questions remain about the functional roles of different LMH, and how these roles depend on abiotic context. In September 2008, we constructed a series of 1-ha herbivore-exclusion plots across a 20-km rainfall gradient in central Kenya. Dubbed "UHURU" (Ungulate Herbivory Under Rainfall Uncertainty), this experiment aims to illuminate the ecological effects of three size classes of LMH, and how rainfall regimes shape the direction and magnitude of these effects. UHURU consists of four treatments: total-exclusion (all ungulate herbivores), mesoherbivore-exclusion (LMH >120-cm tall), megaherbivore-exclusion (elephants and giraffes), and unfenced open plots. Each treatment is replicated three times at three locations (“sites”) along the rainfall gradient: low (440 mm/year), intermediate (580 mm/year), and high (640 mm/year). There was limited variation across sites in soil attributes and LMH activity levels. Understory-plant cover was greater in plots without mesoherbivores, but did not respond strongly to the exclusion of megaherbivores, or to the additional exclusion of dik-dik and warthog. Eleven of the thirteen understory plant species that responded significantly to exclusion treatment were more common in exclusion plots than open ones. Significant interactions between site and treatment on plant communities, although uncommon, suggested that differences between treatments may be greater at sites with lower rainfall. Browsers reduced densities of several common overstory species, along with growth rates of the three dominant Acacia species. Small-mammal densities were 2–3 times greater in total-exclusion than in open plots at all sites. Although we expect patterns to become clearer with time, results from 2008–2012 show that the effects of excluding successively smaller-bodied subsets of the LMH community are generally non-additive for a given response variable, and inconsistent across response variables, indicating that the different LMH size classes are not functionally redundant. Several response variables showed significant treatment-by-site interactions, suggesting that the nature of plant-herbivore interactions can vary across restricted spatial scales.
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Affiliation(s)
- Jacob R. Goheen
- Department of Zoology and Physiology, University of Wyoming, Laramie, Wyoming, United States of America
- Department of Botany, University of Wyoming, Laramie, Wyoming, United States of America
- Mpala Research Centre, Nanyuki, Kenya
| | - Todd M. Palmer
- Mpala Research Centre, Nanyuki, Kenya
- Department of Biology, University of Florida, Gainesville, Florida, United States of America
| | | | - Kristofer M. Helgen
- Division of Mammals, National Museum of Natural History, Washington, District of Columbia, United States of America
| | - Stephen N. Kinyua
- Mpala Research Centre, Nanyuki, Kenya
- Department of Wildlife Management, Moi University, Eldoret, Kenya
| | - Janet E. Maclean
- Mpala Research Centre, Nanyuki, Kenya
- Department of Zoology, University of British Columbia, Vancouver, British Columbia, Canada
| | | | - Hillary S. Young
- Mpala Research Centre, Nanyuki, Kenya
- Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, Massachusetts, United States of America
| | - Robert M. Pringle
- Mpala Research Centre, Nanyuki, Kenya
- Department of Ecology and Evolutionary Biology, Princeton University, Princeton, New Jersey, United States of America
- * E-mail:
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Parsons EWR, Maron JL, Martin TE. Elk herbivory alters small mammal assemblages in high-elevation drainages. J Anim Ecol 2012; 82:459-67. [DOI: 10.1111/1365-2656.12009] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2012] [Accepted: 09/09/2012] [Indexed: 11/30/2022]
Affiliation(s)
| | - John L. Maron
- Division of Biological Sciences; University of Montana; Missoula; MT; 59812; USA
| | - Thomas E. Martin
- U.S. Geological Survey Montana Cooperative Wildlife Research Unit; University of Montana; Missoula; MT; 59812; USA
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Direct and Indirect Effects of Grazing by Introduced Mammals on a Native, Arboreal Gecko (Naultinus gemmeus). J HERPETOL 2012. [DOI: 10.1670/10-315] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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From wing to wing: the persistence of long ecological interaction chains in less-disturbed ecosystems. Sci Rep 2012; 2:409. [PMID: 22624091 PMCID: PMC3354671 DOI: 10.1038/srep00409] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2012] [Accepted: 04/16/2012] [Indexed: 11/08/2022] Open
Abstract
Human impact on biodiversity usually is measured by reduction in species abundance or richness. Just as important, but much more difficult to discern, is the anthropogenic elimination of ecological interactions. Here we report on the persistence of a long ecological interaction chain linking diverse food webs and habitats in the near-pristine portions of a remote Pacific atoll. Using biogeochemical assays, animal tracking, and field surveys we show that seabirds roosting on native trees fertilize soils, increasing coastal nutrients and the abundance of plankton, thus attracting manta rays to native forest coastlines. Partnered observations conducted in regions of this atoll where native trees have been replaced by human propagated palms reveal that this complex interaction chain linking trees to mantas readily breaks down. Taken together these findings provide a compelling example of how anthropogenic disturbance may be contributing to widespread reductions in ecological interaction chain length, thereby isolating and simplifying ecosystems.
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Kutt AS, Gordon IJ. Variation in terrestrial mammal abundance on pastoral and conservation land tenures in north-eastern Australian tropical savannas. Anim Conserv 2012. [DOI: 10.1111/j.1469-1795.2012.00530.x] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- A. S. Kutt
- Ecosystem Sciences; CSIRO; Aitkenvale; Queensland; Australia
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Kutt AS, Vanderduys EP, O'Reagain P. Spatial and temporal effects of grazing management and rainfall on the vertebrate fauna of a tropical savanna. RANGELAND JOURNAL 2012. [DOI: 10.1071/rj11049] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
Grazing by domestic livestock is one of the most widespread uses of the rangelands of Australia. There is limited information on the effects of grazing by domestic livestock on the vertebrate fauna of Australia and the establishment of a long-term grazing experiment in north-eastern Queensland at Wambiana provided an opportunity to attempt an examination of the changes in vertebrate fauna as a consequence of the manipulation of stocking rates. The aim was to identify what the relative effects of vegetation type, stocking rate and other landscape-scale environmental factors were on the patterns recorded. Sixteen 1-ha sites were established within three replicated treatments (moderate, heavy and variable stocking rates). The sites were sampled in the wet and dry seasons in 1999–2000 (T0) and again in 2003–04 (T1). All paddocks of the treatments were burnt in 1999. Average annual rainfall declined markedly between the two sampling periods, which made interpretation of the data difficult. A total of 127 species of vertebrate fauna comprising five amphibian, 83 bird, 27 reptile and 12 mammal species were recorded. There was strong separation in faunal composition from T0 to T1 although changes in mean compositional dissimilarity between the grazing stocking rate treatments were less well defined. There was a relative change in abundance of 24 bird, four mammal and five reptile species from T0 to T1. The generalised linear modelling identified that, in the T1 data, there was significant variation in the abundance of 16 species explained by the grazing and vegetation factors. This study demonstrated that vertebrate fauna assemblage did change and that these changes were attributable to the interplay between the stocking rates, the vegetation types on the sites surveyed, the burning of the experimental paddocks and the decrease in rainfall over the course of the two surveys. It is recommended that the experiment is sampled again but that the focus should be on a rapid survey of abundant taxa (i.e. birds and reptiles) to allow an increase in the frequency of sampling and replication of the data. This would help to articulate more clearly the trajectory of vertebrate change due to the relative effects of stocking rates compared with wider landscape environmental changes. Given the increasing focus on pastoral development in northern Australia, any opportunity to incorporate the collection of data on biodiversity into grazing manipulation experiments should be taken for the assessment of the effects of land management on faunal species.
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Nasseri NA, McBrayer LD, Schulte BA. The impact of tree modification by African elephant (Loxodonta africana) on herpetofaunal species richness in northern Tanzania. Afr J Ecol 2010. [DOI: 10.1111/j.1365-2028.2010.01238.x] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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