1
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Mitchell DR, Sherratt E, Weisbecker V. Facing the facts: adaptive trade-offs along body size ranges determine mammalian craniofacial scaling. Biol Rev Camb Philos Soc 2024; 99:496-524. [PMID: 38029779 DOI: 10.1111/brv.13032] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2023] [Revised: 11/12/2023] [Accepted: 11/14/2023] [Indexed: 12/01/2023]
Abstract
The mammalian cranium (skull without lower jaw) is representative of mammalian diversity and is thus of particular interest to mammalian biologists across disciplines. One widely retrieved pattern accompanying mammalian cranial diversification is referred to as 'craniofacial evolutionary allometry' (CREA). This posits that adults of larger species, in a group of closely related mammals, tend to have relatively longer faces and smaller braincases. However, no process has been officially suggested to explain this pattern, there are many apparent exceptions, and its predictions potentially conflict with well-established biomechanical principles. Understanding the mechanisms behind CREA and causes for deviations from the pattern therefore has tremendous potential to explain allometry and diversification of the mammalian cranium. Here, we propose an amended framework to characterise the CREA pattern more clearly, in that 'longer faces' can arise through several kinds of evolutionary change, including elongation of the rostrum, retraction of the jaw muscles, or a more narrow or shallow skull, which all result in a generalised gracilisation of the facial skeleton with increased size. We define a standardised workflow to test for the presence of the pattern, using allometric shape predictions derived from geometric morphometrics analysis, and apply this to 22 mammalian families including marsupials, rabbits, rodents, bats, carnivores, antelopes, and whales. Our results show that increasing facial gracility with size is common, but not necessarily as ubiquitous as previously suggested. To address the mechanistic basis for this variation, we then review cranial adaptations for harder biting. These dictate that a more gracile cranium in larger species must represent a structural sacrifice in the ability to produce or withstand harder bites, relative to size. This leads us to propose that facial gracilisation in larger species is often a product of bite force allometry and phylogenetic niche conservatism, where more closely related species tend to exhibit more similar feeding ecology and biting behaviours and, therefore, absolute (size-independent) bite force requirements. Since larger species can produce the same absolute bite forces as smaller species with less effort, we propose that relaxed bite force demands can permit facial gracility in response to bone optimisation and alternative selection pressures. Thus, mammalian facial scaling represents an adaptive by-product of the shifting importance of selective pressures occurring with increased size. A reverse pattern of facial 'shortening' can accordingly also be found, and is retrieved in several cases here, where larger species incorporate novel feeding behaviours involving greater bite forces. We discuss multiple exceptions to a bite force-mediated influence on facial proportions across mammals which lead us to argue that ecomorphological specialisation of the cranium is likely to be the primary driver of facial scaling patterns, with some developmental constraints as possible secondary factors. A potential for larger species to have a wider range of cranial functions when less constrained by bite force demands might also explain why selection for larger sizes seems to be prevalent in some mammalian clades. The interplay between adaptation and constraint across size ranges thus presents an interesting consideration for a mechanistically grounded investigation of mammalian cranial allometry.
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Affiliation(s)
- D Rex Mitchell
- College of Science and Engineering, Flinders University, GPO Box 2100, Adelaide, South Australia, 5001, Australia
- Australian Research Council Centre of Excellence for Australian Biodiversity and Heritage, Wollongong, New South Wales, 2522, Australia
| | - Emma Sherratt
- School of Biological Sciences, The University of Adelaide, Adelaide, South Australia, 5005, Australia
- South Australian Museum, Adelaide, South Australia, 5000, Australia
| | - Vera Weisbecker
- College of Science and Engineering, Flinders University, GPO Box 2100, Adelaide, South Australia, 5001, Australia
- Australian Research Council Centre of Excellence for Australian Biodiversity and Heritage, Wollongong, New South Wales, 2522, Australia
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2
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Harvey Sky N, Britnell J, Antwis R, Kartzinel T, Rubenstein D, Toye P, Karani B, Njeru R, Hinchcliffe D, Gaymer J, Mutisya S, Shultz S. Linking diet switching to reproductive performance across populations of two critically endangered mammalian herbivores. Commun Biol 2024; 7:333. [PMID: 38491117 PMCID: PMC10943211 DOI: 10.1038/s42003-024-05983-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2023] [Accepted: 02/27/2024] [Indexed: 03/18/2024] Open
Abstract
Optimal foraging theory predicts that animals maximise energy intake by consuming the most valuable foods available. When resources are limited, they may include lower-quality fallback foods in their diets. As seasonal herbivore diet switching is understudied, we evaluate its extent and effects across three Kenyan reserves each for Critically Endangered eastern black rhino (Diceros bicornis michaeli) and Grevy's zebra (Equus grevyi), and its associations with habitat quality, microbiome variation, and reproductive performance. Black rhino diet breadth increases with vegetation productivity (NDVI), whereas zebra diet breadth peaks at intermediate NDVI. Black rhino diets associated with higher vegetation productivity have less acacia (Fabaceae: Vachellia and Senegalia spp.) and more grass suggesting that acacia are fallback foods, upending conventional assumptions. Larger dietary shifts are associated with longer calving intervals. Grevy's zebra diets in high rainfall areas are consistently grass-dominated, whereas in arid areas they primarily consume legumes during low vegetation productivity periods. Whilst microbiome composition between individuals is affected by the environment, and diet composition in black rhino, seasonal dietary shifts do not drive commensurate microbiome shifts. Documenting diet shifts across ecological gradients can increase the effectiveness of conservation by informing habitat suitability models and improving understanding of responses to resource limitation.
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Affiliation(s)
- Nick Harvey Sky
- Department of Earth and Environmental Sciences, University of Manchester, Manchester, M13 9NT, UK.
- North of England Zoological Society, Chester Zoo, Upton-by-Chester, CH2 1LH, UK.
| | - Jake Britnell
- Department of Earth and Environmental Sciences, University of Manchester, Manchester, M13 9NT, UK
- North of England Zoological Society, Chester Zoo, Upton-by-Chester, CH2 1LH, UK
| | - Rachael Antwis
- School of Environment and Life Sciences, University of Salford, Salford, M5 4WX, UK
| | - Tyler Kartzinel
- Department of Ecology, Evolution, and Organismal Biology, Brown University, 85 Waterman Street, Providence, RI, 02912, USA
- Institute at Brown for Environment and Society, Brown University, 85 Waterman Street, Providence, RI, 02912, USA
| | - Daniel Rubenstein
- Department of Ecology and Evolutionary Biology, Princeton University, Princeton, NJ, 08544-2016, USA
| | - Phil Toye
- International Livestock Research Institute and Centre for Tropical Livestock Genetics and Health, Nairobi, P.O. Box 30709-00100, Kenya
| | - Benedict Karani
- International Livestock Research Institute and Centre for Tropical Livestock Genetics and Health, Nairobi, P.O. Box 30709-00100, Kenya
| | - Regina Njeru
- International Livestock Research Institute and Centre for Tropical Livestock Genetics and Health, Nairobi, P.O. Box 30709-00100, Kenya
| | - Danielle Hinchcliffe
- School of Biological and Environmental Sciences, Liverpool John Moores University, Liverpool, L3 3AF, UK
| | | | | | - Susanne Shultz
- Department of Earth and Environmental Sciences, University of Manchester, Manchester, M13 9NT, UK
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3
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Anderson TM, Hepler SA, Holdo RM, Donaldson JE, Erhardt RJ, Hopcraft JGC, Hutchinson MC, Huebner SE, Morrison TA, Muday J, Munuo IN, Palmer MS, Pansu J, Pringle RM, Sketch R, Packer C. Interplay of competition and facilitation in grazing succession by migrant Serengeti herbivores. Science 2024; 383:782-788. [PMID: 38359113 DOI: 10.1126/science.adg0744] [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: 11/30/2022] [Accepted: 01/10/2024] [Indexed: 02/17/2024]
Abstract
Competition, facilitation, and predation offer alternative explanations for successional patterns of migratory herbivores. However, these interactions are difficult to measure, leaving uncertainty about the mechanisms underlying body-size-dependent grazing-and even whether succession occurs at all. We used data from an 8-year camera-trap survey, GPS-collared herbivores, and fecal DNA metabarcoding to analyze the timing, arrival order, and interactions among migratory grazers in Serengeti National Park. Temporal grazing succession is characterized by a "push-pull" dynamic: Competitive grazing nudges zebra ahead of co-migrating wildebeest, whereas grass consumption by these large-bodied migrants attracts trailing, small-bodied gazelle that benefit from facilitation. "Natural experiments" involving intense wildfires and rainfall respectively disrupted and strengthened these effects. Our results highlight a balance between facilitative and competitive forces in co-regulating large-scale ungulate migrations.
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Affiliation(s)
- T Michael Anderson
- Department of Biology, Wake Forest University, Winston-Salem, NC 27109, USA
| | - Staci A Hepler
- Department of Statistical Sciences, Wake Forest University, Winston-Salem, NC 27109, USA
| | - Ricardo M Holdo
- Odum School of Ecology, University of Georgia, Athens, GA 30602, USA
| | - Jason E Donaldson
- Odum School of Ecology, University of Georgia, Athens, GA 30602, USA
| | - Robert J Erhardt
- Department of Statistical Sciences, Wake Forest University, Winston-Salem, NC 27109, USA
| | - J Grant C Hopcraft
- School of Biodiversity, One Health and Veterinary Medicine, University of Glasgow, Glasgow G61 1QH, UK
| | - Matthew C Hutchinson
- Department of Life & Environmental Sciences, University of California Merced, Merced, CA 95343, USA
| | - Sarah E Huebner
- Department of Ecology, Evolution and Behavior, University of Minnesota, St. Paul, MN 55108, USA
| | - Thomas A Morrison
- School of Biodiversity, One Health and Veterinary Medicine, University of Glasgow, Glasgow G61 1QH, UK
| | - Jeffry Muday
- Department of Biology, Wake Forest University, Winston-Salem, NC 27109, USA
| | - Issack N Munuo
- Serengeti Wildlife Research Centre, 2113 Lemara, Arusha, TZ
| | - Meredith S Palmer
- Department of Ecology and Evolutionary Biology, Princeton University, Princeton, NJ 08544, USA
| | - Johan Pansu
- Department of Ecology and Evolutionary Biology, Princeton University, Princeton, NJ 08544, USA
| | - Robert M Pringle
- Department of Ecology and Evolutionary Biology, Princeton University, Princeton, NJ 08544, USA
| | - Robert Sketch
- Department of Statistical Sciences, Wake Forest University, Winston-Salem, NC 27109, USA
| | - Craig Packer
- Department of Ecology, Evolution and Behavior, University of Minnesota, St. Paul, MN 55108, USA
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4
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Britnell JA, Kerley GIH, Antwis R, Shultz S. A grazer's niche edge is associated with increasing diet diversity and poor population performance. Ecol Lett 2024; 27:e14357. [PMID: 38193626 DOI: 10.1111/ele.14357] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2023] [Revised: 11/09/2023] [Accepted: 12/05/2023] [Indexed: 01/10/2024]
Abstract
The core-periphery hypothesis predicts niche cores should be associated with greater survivorship, reproductive output and population performance rates than marginal habitats at niche edges. However, there is very little empirical evidence of whether niche centrality influences population trends in animals. Using the Cape mountain zebra (Equus zebra zebra) as a model system, we evaluated whether niche centrality is associated with population trends, resource availability and diet across a core-periphery gradient. Population growth rates and density progressively declined towards niche peripheries. Niche peripheries were resource-poor and Cape mountain zebra consumed more phylogenetically diverse diets dominated by non-grass families. In core habitats they consumed grass-rich diets and female reproductive success was higher. This combination of spatial niche modelling and functional ecology provides a novel evaluation of how bottom-up resource limitation can shape species distributions, population resilience and range change and can guide conservation management.
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Affiliation(s)
- J A Britnell
- School of Earth and Environmental Sciences, University of Manchester, Manchester, UK
- North of England Zoological Society (Chester Zoo), Upton-by-Chester, UK
| | - G I H Kerley
- Centre for African Conservation Ecology, Nelson Mandela University, Gqeberha, South Africa
| | | | - S Shultz
- School of Earth and Environmental Sciences, University of Manchester, Manchester, UK
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5
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Gill BA, Wittemyer G, Cerling TE, Musili PM, Kartzinel TR. Foraging history of individual elephants using DNA metabarcoding. ROYAL SOCIETY OPEN SCIENCE 2023; 10:230337. [PMID: 37416829 PMCID: PMC10320352 DOI: 10.1098/rsos.230337] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 03/18/2023] [Accepted: 06/07/2023] [Indexed: 07/08/2023]
Abstract
Individual animals should adjust diets according to food availability. We used DNA metabarcoding to construct individual-level dietary timeseries for elephants from two family groups in Kenya varying in habitat use, social position and reproductive status. We detected at least 367 dietary plant taxa, with up to 137 unique plant sequences in one fecal sample. Results matched well-established trends: elephants tended to eat more grass when it rained and other plants when dry. Nested within these switches from 'grazing' to 'browsing' strategies, dietary DNA revealed seasonal shifts in food richness, composition and overlap between individuals. Elephants of both families converged on relatively cohesive diets in dry seasons but varied in their maintenance of cohesion during wet seasons. Dietary cohesion throughout the timeseries of the subdominant 'Artists' family was stronger and more consistently positive compared to the dominant 'Royals' family. The greater degree of individuality within the dominant family's timeseries could reflect more divergent nutritional requirements associated with calf dependency and/or priority access to preferred habitats. Whereas theory predicts that individuals should specialize on different foods under resource scarcity, our data suggest family bonds may promote cohesion and foster the emergence of diverse feeding cultures reflecting links between social behaviour and nutrition.
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Affiliation(s)
- Brian A. Gill
- Department of Ecology, Evolution, and Organismal Biology, Brown University, Providence, RI 02912, USA
- Institute at Brown for Environment and Society, Brown University, Providence, RI 02912, USA
| | - George Wittemyer
- Department of Fish, Wildlife, and Conservation Biology, Colorado State University, Fort Collins, CO 80523, USA
- Save the Elephants, Nairobi, Kenya
| | - Thure E. Cerling
- Department of Geology and Geophysics, University of Utah, Salt Lake City, UT 84112, USA
- Department of Biology, University of Utah, Salt Lake City, UT 84112, USA
| | - Paul M. Musili
- Botany Department, East African Herbarium, National Museums of Kenya, Nairobi, Kenya
| | - Tyler R. Kartzinel
- Department of Ecology, Evolution, and Organismal Biology, Brown University, Providence, RI 02912, USA
- Institute at Brown for Environment and Society, Brown University, Providence, RI 02912, USA
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6
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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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7
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Negash EW, Barr WA. Relative abundance of grazing and browsing herbivores is not a direct reflection of vegetation structure: Implications for hominin paleoenvironmental reconstruction. J Hum Evol 2023; 177:103328. [PMID: 36857987 DOI: 10.1016/j.jhevol.2023.103328] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2022] [Revised: 01/23/2023] [Accepted: 01/23/2023] [Indexed: 03/03/2023]
Abstract
The diet of fossil herbivores inferred from enamel stable carbon isotopes is often used to make paleoenvironmental reconstructions. While many studies have focused on using environmental indicator taxa to make paleoenvironmental reconstructions, community-based approaches are considered to provide a more complete picture of paleolandscapes. These studies assume that the diet and relative abundance of herbivores are related to the areal extent of different vegetation types on the landscape. Here, we quantitatively test this assumption in 16 modern ecosystems in eastern and southern Africa with a wide range of woody vegetation cover. We conducted a landscape-level spatial analysis of vegetation patterns using a published land cover data set and computed landscape metrics. We compiled data on relative abundance and diet of herbivores inferred from carbon isotope studies for all large herbivores in these ecosystems. We found that despite differences in the total areal extent of different vegetation types, numerous sizable patches of each vegetation type are available in most ecosystems. However, despite variation across the ecosystems examined, grazers are typically the most abundant herbivores even in sites that have a higher proportion of forest and shrub cover. This indicates that the diet and relative abundance of herbivores is not a simple reflection of the total areal extent of vegetation types available on the landscape. The higher proportion of grazers observed in these ecosystems is a result of multiple factors including habitat heterogeneity, differences in biomass turnover rate between grasses and woody vegetation, resource partitioning, and the advantages of group living in open environments. Comparison of diet and relative abundance of herbivores in modern ecosystems to fossil herbivore assemblages shows that very different vegetation regimes can support similar herbivore assemblages. This study has significant implications for paleolandscape reconstructions and cautions against a simplistic wooded vs. grassland paleoenvironmental interpretations based on fossil herbivore assemblages.
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Affiliation(s)
- Enquye W Negash
- Center for the Advanced Study of Human Paleobiology, George Washington University, 800 22nd Street, Northwest, Washington D.C. 20052, USA.
| | - W Andrew Barr
- Center for the Advanced Study of Human Paleobiology, George Washington University, 800 22nd Street, Northwest, Washington D.C. 20052, USA
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8
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Lu Q, Cheng C, Xiao L, Li J, Li X, Zhao X, Lu Z, Zhao J, Yao M. Food webs reveal coexistence mechanisms and community organization in carnivores. Curr Biol 2023; 33:647-659.e5. [PMID: 36669497 DOI: 10.1016/j.cub.2022.12.049] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2022] [Revised: 11/11/2022] [Accepted: 12/20/2022] [Indexed: 01/20/2023]
Abstract
Globally, massive carnivore guild extirpations have led to trophic downgrading and compromised ecosystem services. However, the complexity of multi-carnivore food webs complicates accurate identification of species interactions and community organization. Here, we used fecal DNA metabarcoding to investigate three communities that together encompass eight large- and meso-carnivore species and their 44 prey taxa of the Qinghai-Tibet Plateau (QTP), one of the last places on Earth that still harbors intact carnivore assemblages. Quantitative food-web analyses revealed pronounced interspecific variations in the carnivores' prey compositions and dietary partitioning both between and within guilds. Additionally, body masses of the carnivores and their prey exhibited consistent hump-shaped correlations across communities. Overall, differences in prey diversity, size category, and proportional utilization among the carnivore species result in trophic niche segregation that likely promotes carnivore coexistence in the harsh QTP environment. Network structure analyses detected significant modularity in all food webs but nestedness in only one. Furthermore, network characterization identified pikas (Ochotona spp.), bharal (Pseudois nayaur), and domestic yak (Bos grunniens) as potential keystone prey across the areas. Our results paint a holistic and detailed picture of the QTP carnivore assemblages' trophic networks and demonstrate that the combined use of the molecular dietary approach and network analysis can generate structural insights into carnivore coexistence and can identify functionally important species in complex communities. Such knowledge can help safeguard carnivore guild integrity and enhance community resilience to environmental perturbations in the sensitive QTP ecosystems.
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Affiliation(s)
- Qi Lu
- School of Life Sciences, Peking University, Beijing 100871, China; Institute of Ecology, College of Urban and Environmental Sciences, Peking University, Beijing 100871, China
| | - Chen Cheng
- Center for Nature and Society, School of Life Sciences, Peking University, Beijing 100871, China; Shan Shui Conservation Center, Beijing 100871, China
| | - Lingyun Xiao
- School of Life Sciences, Peking University, Beijing 100871, China; Department of Health and Environmental Sciences, Xi'an Jiaotong Liverpool University, Suzhou, Jiangsu 215123, China
| | - Juan Li
- School of Life Sciences, Peking University, Beijing 100871, China; Department of Health and Environmental Sciences, Xi'an Jiaotong Liverpool University, Suzhou, Jiangsu 215123, China
| | - Xueyang Li
- School of Life Sciences, Peking University, Beijing 100871, China
| | - Xiang Zhao
- Shan Shui Conservation Center, Beijing 100871, China
| | - Zhi Lu
- School of Life Sciences, Peking University, Beijing 100871, China; Institute of Ecology, College of Urban and Environmental Sciences, Peking University, Beijing 100871, China; Center for Nature and Society, School of Life Sciences, Peking University, Beijing 100871, China; Shan Shui Conservation Center, Beijing 100871, China
| | - Jindong Zhao
- School of Life Sciences, Peking University, Beijing 100871, China; Institute of Ecology, College of Urban and Environmental Sciences, Peking University, Beijing 100871, China
| | - Meng Yao
- School of Life Sciences, Peking University, Beijing 100871, China; Institute of Ecology, College of Urban and Environmental Sciences, Peking University, Beijing 100871, China.
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9
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Walker RH, Hutchinson MC, Potter AB, Becker JA, Long RA, Pringle RM. Mechanisms of individual variation in large herbivore diets: Roles of spatial heterogeneity and state-dependent foraging. Ecology 2023; 104:e3921. [PMID: 36415899 PMCID: PMC10078531 DOI: 10.1002/ecy.3921] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/09/2022] [Revised: 10/05/2022] [Accepted: 10/06/2022] [Indexed: 11/24/2022]
Abstract
Many populations of consumers consist of relatively specialized individuals that eat only a subset of the foods consumed by the population at large. Although the ecological significance of individual-level diet variation is recognized, such variation is difficult to document, and its underlying mechanisms are poorly understood. Optimal foraging theory provides a useful framework for predicting how individuals might select different diets, positing that animals balance the "opportunity cost" of stopping to eat an available food item against the cost of searching for something more nutritious; diet composition should be contingent on the distribution of food, and individual foragers should be more selective when they have greater energy reserves to invest in searching for high-quality foods. We tested these predicted mechanisms of individual niche differentiation by quantifying environmental (resource heterogeneity) and organismal (nutritional condition) determinants of diet in a widespread browsing antelope (bushbuck, Tragelaphus sylvaticus) in an African floodplain-savanna ecosystem. We quantified individuals' realized dietary niches (taxonomic richness and composition) using DNA metabarcoding of fecal samples collected repeatedly from 15 GPS-collared animals (range 6-14 samples per individual, median 12). Bushbuck diets were structured by spatial heterogeneity and constrained by individual condition. We observed significant individual-level partitioning of food plants by bushbuck both within and between two adjacent habitat types (floodplain and woodland). Individuals with home ranges that were closer together and/or had similar vegetation structure (measured using LiDAR) ate more similar diets, supporting the prediction that heterogeneous resource distribution promotes individual differentiation. Individuals in good nutritional condition had significantly narrower diets (fewer plant taxa), searched their home ranges more intensively (intensity-of-use index), and had higher-quality diets (percent digestible protein) than those in poor condition, supporting the prediction that animals with greater endogenous reserves have narrower realized niches because they can invest more time in searching for nutritious foods. Our results support predictions from optimal foraging theory about the energetic basis of individual-level dietary variation and provide a potentially generalizable framework for understanding how individuals' realized niche width is governed by animal behavior and physiology in heterogeneous landscapes.
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Affiliation(s)
- Reena H Walker
- Department of Fish and Wildlife Sciences, University of Idaho, Moscow, Idaho, USA
| | - Matthew C Hutchinson
- Department of Ecology and Evolutionary Biology, Princeton University, Princeton, New Jersey, USA
| | - Arjun B Potter
- Department of Ecology and Evolutionary Biology, Princeton University, Princeton, New Jersey, USA
| | - Justine A Becker
- Department of Ecology and Evolutionary Biology, Princeton University, Princeton, New Jersey, USA.,Department of Zoology and Physiology, University of Wyoming, Laramie, Wyoming, USA
| | - Ryan A Long
- Department of Fish and Wildlife Sciences, University of Idaho, Moscow, Idaho, USA
| | - Robert M Pringle
- Department of Ecology and Evolutionary Biology, Princeton University, Princeton, New Jersey, USA
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10
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Refining the stress gradient hypothesis for mixed species groups of African mammals. Sci Rep 2022; 12:17715. [PMID: 36271133 PMCID: PMC9587046 DOI: 10.1038/s41598-022-22593-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2022] [Accepted: 10/17/2022] [Indexed: 01/18/2023] Open
Abstract
Species interactions such as facilitation and predation influence food webs, yet it is unclear how they are mediated by environmental gradients. Here we test the stress gradient hypothesis which predicts that positive species interactions increase with stress. Drawing upon spatially-explicit data of large mammals in an African savanna, we tested how predation risk and primary productivity mediate the occurrence of mixed species groups. Controlling for habitat structure, predation risk by lions and primary productivity affected the frequency of mixed species groups in species-specific ways, likely reflecting distinct stress perceptions. To test whether mixed species groups indicate positive interactions, we conducted network analyses for specific scenarios. Under predation risk, dyadic associations with giraffes were more pronounced and metrics of animal networks changed markedly. However, dyadic association and network metrics were weakly mediated by primary productivity. The composition of mixed species groups was associated with similarities in prey susceptibility but not with similarities in feeding habits of herbivores. Especially predation risk favoured the frequency of mixed species groups and pronounced dyadic associations which dilute predation risk and increase predator detection. While our results provide support for the stress gradient hypothesis, they also highlight that the relative importance of stressors is context-dependent.
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11
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The generality of cryptic dietary niche differences in diverse large-herbivore assemblages. Proc Natl Acad Sci U S A 2022; 119:e2204400119. [PMID: 35994662 PMCID: PMC9436339 DOI: 10.1073/pnas.2204400119] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
Ecological niche differences are necessary for stable species coexistence but are often difficult to discern. Models of dietary niche differentiation in large mammalian herbivores invoke the quality, quantity, and spatiotemporal distribution of plant tissues and growth forms but are agnostic toward food plant species identity. Empirical support for these models is variable, suggesting that additional mechanisms of resource partitioning may be important in sustaining large-herbivore diversity in African savannas. We used DNA metabarcoding to conduct a taxonomically explicit analysis of large-herbivore diets across southeastern Africa, analyzing ∼4,000 fecal samples of 30 species from 10 sites in seven countries over 6 y. We detected 893 food plant taxa from 124 families, but just two families-grasses and legumes-accounted for the majority of herbivore diets. Nonetheless, herbivore species almost invariably partitioned food plant taxa; diet composition differed significantly in 97% of pairwise comparisons between sympatric species, and dissimilarity was pronounced even between the strictest grazers (grass eaters), strictest browsers (nongrass eaters), and closest relatives at each site. Niche differentiation was weakest in an ecosystem recovering from catastrophic defaunation, indicating that food plant partitioning is driven by species interactions, and was stronger at low rainfall, as expected if interspecific competition is a predominant driver. Diets differed more between browsers than grazers, which predictably shaped community organization: Grazer-dominated trophic networks had higher nestedness and lower modularity. That dietary differentiation is structured along taxonomic lines complements prior work on how herbivores partition plant parts and patches and suggests that common mechanisms govern herbivore coexistence and community assembly in savannas.
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12
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Daskin JH, Becker JA, Kartzinel TR, Potter AB, Walker RH, Eriksson FAA, Buoncore C, Getraer A, Long RA, Pringle RM. Allometry of behavior and niche differentiation among congeneric African antelopes. ECOL MONOGR 2022. [DOI: 10.1002/ecm.1549] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Joshua H. Daskin
- Department of Ecology & Evolutionary Biology Princeton University Princeton NJ USA
- Archbold Biological Station Venus FL USA
| | - Justine A. Becker
- Department of Ecology & Evolutionary Biology Princeton University Princeton NJ USA
- Department of Zoology & Physiology University of Wyoming Laramie WY USA
| | - Tyler R. Kartzinel
- Department of Ecology & Evolutionary Biology Brown University Providence RI USA
| | - Arjun B. Potter
- Department of Ecology & Evolutionary Biology Princeton University Princeton NJ USA
| | - Reena H. Walker
- Department of Fish and Wildlife Sciences University of Idaho Moscow ID USA
| | | | - Courtney Buoncore
- Department of Ecology & Evolutionary Biology Princeton University Princeton NJ USA
| | - Alexander Getraer
- Department of Ecology & Evolutionary Biology Princeton University Princeton NJ USA
| | - Ryan A. Long
- Department of Fish and Wildlife Sciences University of Idaho Moscow ID USA
| | - Robert M. Pringle
- Department of Ecology & Evolutionary Biology Princeton University Princeton NJ USA
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13
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Titcomb GC, Pansu J, Hutchinson MC, Tombak KJ, Hansen CB, Baker CCM, Kartzinel TR, Young HS, Pringle RM. Large-herbivore nemabiomes: patterns of parasite diversity and sharing. Proc Biol Sci 2022; 289:20212702. [PMID: 35538775 PMCID: PMC9091847 DOI: 10.1098/rspb.2021.2702] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
Amidst global shifts in the distribution and abundance of wildlife and livestock, we have only a rudimentary understanding of ungulate parasite communities and parasite-sharing patterns. We used qPCR and DNA metabarcoding of fecal samples to characterize gastrointestinal nematode (Strongylida) community composition and sharing among 17 sympatric species of wild and domestic large mammalian herbivore in central Kenya. We tested a suite of hypothesis-driven predictions about the role of host traits and phylogenetic relatedness in describing parasite infections. Host species identity explained 27-53% of individual variation in parasite prevalence, richness, community composition and phylogenetic diversity. Host and parasite phylogenies were congruent, host gut morphology predicted parasite community composition and prevalence, and hosts with low evolutionary distinctiveness were centrally positioned in the parasite-sharing network. We found no evidence that host body size, social-group size or feeding height were correlated with parasite composition. Our results highlight the interwoven evolutionary and ecological histories of large herbivores and their gastrointestinal nematodes and suggest that host identity, phylogeny and gut architecture-a phylogenetically conserved trait related to parasite habitat-are the overriding influences on parasite communities. These findings have implications for wildlife management and conservation as wild herbivores are increasingly replaced by livestock.
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Affiliation(s)
- Georgia C. Titcomb
- Department of Fish, Wildlife, and Conservation Biology, Colorado State University, Fort Collins, CO, USA,Department of Ecology, Evolution, and Marine Biology, University of California, Santa Barbara, CA, USA,Mpala Research Centre, Nanyuki, Kenya
| | - Johan Pansu
- Department of Ecology and Evolutionary Biology, Princeton University, Princeton, NJ, USA,ISEM, Université de Montpellier, CNRS, IRD, EPHE, Montpellier, France
| | - Matthew C. Hutchinson
- Department of Ecology and Evolutionary Biology, Princeton University, Princeton, NJ, USA
| | - Kaia J. Tombak
- Mpala Research Centre, Nanyuki, Kenya,Department of Ecology and Evolutionary Biology, Princeton University, Princeton, NJ, USA,Department of Anthropology, Hunter College of the City University of New York, New York, NY, USA
| | - Christina B. Hansen
- Department of Ecology and Evolutionary Biology, Princeton University, Princeton, NJ, USA
| | - Christopher C. M. Baker
- Department of Ecology and Evolutionary Biology, Princeton University, Princeton, NJ, USA,US Army ERDC Cold Regions Research and Engineering Laboratory, Hanover, NH, USA
| | - Tyler R. Kartzinel
- Department of Ecology and Evolutionary Biology, Princeton University, Princeton, NJ, USA,Department of Ecology, Evolution, and Organismal Biology, Brown University, Providence, RI, USA,Institute at Brown for Environment and Society, Brown University, Providence, RI, USA
| | - Hillary S. Young
- Department of Ecology, Evolution, and Marine Biology, University of California, Santa Barbara, CA, USA,Mpala Research Centre, Nanyuki, Kenya
| | - Robert M. Pringle
- Department of Ecology and Evolutionary Biology, Princeton University, Princeton, NJ, USA
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14
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DNA metabarcoding uncovers the diet of subterranean rodents in China. PLoS One 2022; 17:e0258078. [PMID: 35482781 PMCID: PMC9049501 DOI: 10.1371/journal.pone.0258078] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2021] [Accepted: 04/02/2022] [Indexed: 01/04/2023] Open
Abstract
OBJECTIVE A type of rodent called a zokor causes great harm to agriculture and forestry production due to its large and sophisticated diet. As this rodent lives subterrane for most of its life, researchers know little about its dietary habits. Further understanding of its diet is important for developing green and sustainable control strategies for the zokor. METHODS Chloroplast trnL gene and internal transcription spacer 1 primers were selected for high-throughput sequencing of stomach contents of captured zokor by DNA metabarcoding. RESULTS A total of 25 zokors were selected, the food list of 32 families, 80 genera, and 154 species was obtained. At the family level, it was found that zokors mainly fed on Asteraceae, Poaceae, Rosaceae, Pinaceae, Brassicaceae, and Apiaceae. At the genus level, zokors mainly fed on Echinops, Littledalea, Artemisia, Picea, Cirsium, and Elymus. The diet alpha diversity of Eospalax cansus was slightly higher than that of Eospalax cansus (P>0.05). The zokor's diet is highly phconsistent with the resources of its habitat. Most food choices tend to be the same between the two zokors. They fed primarily on Calamagrostis, Cirsium, Echinops, Medicago, Sanguisorba, and Taraxacum. Zokors mainly fed on the roots of perennial herbs, which are important source of energy. CONCLUSION High-throughput sequencing-based DNA metabarcoding technology has effectively revealed the diet of zokors and indicated that zokors are food generalists.
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15
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Thompson PR, Lewis MA, Edwards MA, Derocher AE. Time-dependent memory and individual variation in Arctic brown bears (Ursus arctos). MOVEMENT ECOLOGY 2022; 10:18. [PMID: 35410401 PMCID: PMC8996616 DOI: 10.1186/s40462-022-00319-4] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 12/22/2021] [Accepted: 03/24/2022] [Indexed: 06/14/2023]
Abstract
BACKGROUND Animal movement modelling provides unique insight about how animals perceive their landscape and how this perception may influence space use. When coupled with data describing an animal's environment, ecologists can fit statistical models to location data to describe how spatial memory informs movement. METHODS We performed such an analysis on a population of brown bears (Ursus arctos) in the Canadian Arctic using a model incorporating time-dependent spatial memory patterns. Brown bear populations in the Arctic lie on the periphery of the species' range, and as a result endure harsh environmental conditions. In this kind of environment, effective use of memory to inform movement strategies could spell the difference between survival and mortality. RESULTS The model we fit tests four alternate hypotheses (some incorporating memory; some not) against each other, and we found a high degree of individual variation in how brown bears used memory. We found that 71% (15 of 21) of the bears used complex, time-dependent spatial memory to inform their movement decisions. CONCLUSIONS These results, coupled with existing knowledge on individual variation in the population, highlight the diversity of foraging strategies for Arctic brown bears while also displaying the inference that can be drawn from this innovative movement model.
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Affiliation(s)
- Peter R Thompson
- Department of Biological Sciences, University of Alberta, Edmonton, AB, Canada.
| | - Mark A Lewis
- Department of Biological Sciences, University of Alberta, Edmonton, AB, Canada
- Department of Mathematical and Statistical Sciences, University of Alberta, Edmonton, AB, Canada
| | - Mark A Edwards
- Mammalogy Department, Royal Alberta Museum, Edmonton, AB, Canada
- Department of Renewable Resources, University of Alberta, Edmonton, AB, Canada
| | - Andrew E Derocher
- Department of Biological Sciences, University of Alberta, Edmonton, AB, Canada
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16
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Potgieter T, Kerley GIH. The zebra as a grazer: Selectivity for grass consumption differs as grass availability varies. Afr J Ecol 2022. [DOI: 10.1111/aje.12992] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Affiliation(s)
- Tayla‐Lee Potgieter
- Centre for African Conservation Ecology Nelson Mandela University Gqeberha South Africa
| | - Graham I. H. Kerley
- Centre for African Conservation Ecology Nelson Mandela University Gqeberha South Africa
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17
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Littleford‐Colquhoun BL, Freeman PT, Sackett VI, Tulloss CV, McGarvey LM, Geremia C, Kartzinel TR. The precautionary principle and dietary DNA metabarcoding: Commonly used abundance thresholds change ecological interpretation. Mol Ecol 2022; 31:1615-1626. [PMID: 35043486 PMCID: PMC9303378 DOI: 10.1111/mec.16352] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2021] [Revised: 12/06/2021] [Accepted: 01/07/2022] [Indexed: 01/13/2023]
Abstract
Dietary DNA metabarcoding enables researchers to identify and characterize trophic interactions with a high degree of taxonomic precision. It is also sensitive to sources of bias and contamination in the field and laboratory. One of the earliest and most common strategies for dealing with such sensitivities has been to remove all low-abundance sequences and conduct ecological analyses based on the presence or absence of food taxa. Although this step is now often perceived to be necessary, evidence of its sufficiency is lacking and more attention to the risk of introducing other errors is needed. Using computer simulations, we demonstrate that common strategies to remove low-abundance sequences can erroneously eliminate true dietary sequences in ways that impact downstream inferences. Using real data from well-studied wildlife populations in Yellowstone National Park, we further show how these strategies can markedly alter the composition of dietary profiles in ways that scale-up to obscure ecological interpretations about dietary generalism, specialism, and composition. Although the practice of removing low-abundance sequences may continue to be a useful strategy to address research questions that focus on a subset of relatively abundant foods, its continued widespread use risks generating misleading perceptions about the structure of trophic networks. Researchers working with dietary DNA metabarcoding data-or similar data such as environmental DNA, microbiomes, or pathobiomes-should be aware of drawbacks and consider alternative bioinformatic, experimental, and statistical solutions.
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Affiliation(s)
- Bethan L. Littleford‐Colquhoun
- Department of Ecology, Evolution, and Organismal BiologyBrown UniversityProvidenceRhode IslandUSA,Institute at Brown for Environment and SocietyBrown UniversityProvidenceRhode IslandUSA
| | - Patrick T. Freeman
- Department of Ecology, Evolution, and Organismal BiologyBrown UniversityProvidenceRhode IslandUSA,Institute at Brown for Environment and SocietyBrown UniversityProvidenceRhode IslandUSA
| | - Violet I. Sackett
- Department of Ecology, Evolution, and Organismal BiologyBrown UniversityProvidenceRhode IslandUSA,Institute at Brown for Environment and SocietyBrown UniversityProvidenceRhode IslandUSA
| | - Camille V. Tulloss
- Department of Ecology, Evolution, and Organismal BiologyBrown UniversityProvidenceRhode IslandUSA,Institute at Brown for Environment and SocietyBrown UniversityProvidenceRhode IslandUSA
| | - Lauren M. McGarvey
- Yellowstone Center for Resources, Yellowstone National ParkMammoth Hot SpringsWyomingUSA
| | - Chris Geremia
- Yellowstone Center for Resources, Yellowstone National ParkMammoth Hot SpringsWyomingUSA
| | - Tyler R. Kartzinel
- Department of Ecology, Evolution, and Organismal BiologyBrown UniversityProvidenceRhode IslandUSA,Institute at Brown for Environment and SocietyBrown UniversityProvidenceRhode IslandUSA
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18
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Wells HBM, Crego RD, Ekadeli J, Namoni M, Kimuyu DM, Odadi WO, Porensky LM, Dougill AJ, Stringer LC, Young TP. Less Is More: Lowering Cattle Stocking Rates Enhances Wild Herbivore Habitat Use and Cattle Foraging Efficiency. Front Ecol Evol 2022. [DOI: 10.3389/fevo.2022.825689] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Over a quarter of the world’s land surface is grazed by cattle and other livestock, which are replacing wild herbivores and widely regarded as drivers of global biodiversity declines. The effects of livestock presence versus absence on wild herbivores are well documented. However, the environmental context-specific effects of cattle stocking rate on biodiversity and livestock production are poorly understood, precluding nuanced rangeland management recommendations. To address this, we used a long term exclosure experiment in a semi-arid savanna ecosystem in central Kenya that selectively excludes cattle (at different stocking rates), wild mesoherbivores, and megaherbivores. We investigated the individual and interactive effects of cattle stocking rate (zero/moderate/high) and megaherbivore (>1,000 kg) accessibility on habitat use (measured as dung density) by two dominant wild mesoherbivores (50–1,000 kg; zebra Equus quagga and eland Taurotragus oryx) across the “wet” and “dry” seasons. To explore potential tradeoffs or co-benefits between cattle production and wildlife conservation, we tested for individual and interactive effects of cattle stocking rate and accessibility by wild mesoherbivores and megaherbivores (collectively, large wild herbivores) on the foraging efficiency of cattle across both seasons. Eland habitat use was reduced by cattle at moderate and high stocking rates across both dry and wet seasons and regardless of megaherbivore accessibility. We observed a positive effect of megaherbivores on zebra habitat use at moderate, but not high, stocking rates. Cattle foraging efficiency (g dry matter step–1 min–1) was lower in the high compared to moderate stocking rate treatments during the dry season, and was non-additively reduced by wild mesoherbivores and high cattle stocking rates during the wet season. These results show that high stocking rates are detrimental to wild mesoherbivore habitat use and cattle foraging efficiency, while reducing to moderate stocking rates can benefit zebra habitat use and cattle foraging efficiency. Our findings demonstrate that ecosystem management and restoration efforts across African rangelands that involve reducing cattle stocking rates may represent a win-win for wild herbivore conservation and individual performance of livestock.
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19
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Hutchinson MC, Dobson AP, Pringle RM. Dietary abundance distributions: Dominance and diversity in vertebrate diets. Ecol Lett 2021; 25:992-1008. [PMID: 34967090 DOI: 10.1111/ele.13948] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2021] [Revised: 08/08/2021] [Accepted: 11/23/2021] [Indexed: 01/31/2023]
Abstract
Diet composition is among the most important yet least understood dimensions of animal ecology. Inspired by the study of species abundance distributions (SADs), we tested for generalities in the structure of vertebrate diets by characterising them as dietary abundance distributions (DADs). We compiled data on 1167 population-level diets, representing >500 species from six vertebrate classes, spanning all continents and oceans. DADs near-universally (92.5%) followed a hollow-curve shape, with scant support for other plausible rank-abundance-distribution shapes. This strong generality is inherently related to, yet incompletely explained by, the SADs of available food taxa. By quantifying dietary generalisation as the half-saturation point of the cumulative distribution of dietary abundance (sp50, minimum number of foods required to account for 50% of diet), we found that vertebrate populations are surprisingly specialised: in most populations, fewer than three foods accounted for at least half the diet. Variation in sp50 was strongly associated with consumer type, with carnivores being more specialised than herbivores or omnivores. Other methodological (sampling method and effort, taxonomic resolution), biological (body mass, frugivory) and biogeographic (latitude) factors influenced sp50 to varying degrees. Future challenges include identifying the mechanisms underpinning the hollow-curve DAD, its generality beyond vertebrates, and the biological determinants of dietary generalisation.
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Affiliation(s)
- Matthew C Hutchinson
- Department of Ecology and Evolutionary Biology, Princeton University, Princeton, New Jersey, USA.,Institute of Evolutionary Biology and Environmental Studies, Universität Zürich, Zürich, Switzerland
| | - Andrew P Dobson
- Department of Ecology and Evolutionary Biology, Princeton University, Princeton, New Jersey, USA
| | - Robert M Pringle
- Department of Ecology and Evolutionary Biology, Princeton University, Princeton, New Jersey, USA
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20
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Shao X, Lu Q, Xiong M, Bu H, Shi X, Wang D, Zhao J, Li S, Yao M. Prey partitioning and livestock consumption in the world's richest large carnivore assemblage. Curr Biol 2021; 31:4887-4897.e5. [PMID: 34551283 DOI: 10.1016/j.cub.2021.08.067] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2021] [Revised: 05/13/2021] [Accepted: 08/30/2021] [Indexed: 12/26/2022]
Abstract
Large mammalian carnivores have undergone catastrophic declines during the Anthropocene across the world. Despite their pivotal roles as apex predators in food webs and ecosystem dynamics, few detailed dietary datasets of large carnivores exist, prohibiting deep understanding of their coexistence and persistence in human-dominated landscapes. Here, we present fine-scaled, quantitative trophic interactions among sympatric carnivores from three assemblages in the Mountains of Southwest China, a global biodiversity hotspot harboring the world's richest large-carnivore diversity, derived from DNA metabarcoding of 1,097 fecal samples. These assemblages comprise a large-carnivore guild ranging from zero to five species along with two mesocarnivore species. We constructed predator-prey food webs for each assemblage and identified 95 vertebrate prey taxa and 260 feeding interactions in sum. Each carnivore species consumed 6-39 prey taxa, and dietary diversity decreased with increased carnivore body mass across guilds. Dietary partitioning was more evident between large-carnivore and mesocarnivore guilds, yet different large carnivores showed divergent proportional utilization of different-sized prey correlating with their own body masses. Large carnivores particularly selected livestock in Tibetan-dominated regions, where the indigenous people show high tolerance toward wild predators. Our results suggest that dietary niche partitioning and livestock subsidies facilitate large-carnivore sympatry and persistence and have key implications for sustainable conservation promoting human-carnivore coexistence.
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Affiliation(s)
- Xinning Shao
- School of Life Sciences, Peking University, Beijing 100871, China; Institute of Ecology, College of Urban and Environmental Sciences, Peking University, Beijing 100871, China
| | - Qi Lu
- School of Life Sciences, Peking University, Beijing 100871, China; Institute of Ecology, College of Urban and Environmental Sciences, Peking University, Beijing 100871, China
| | - Mengyin Xiong
- School of Life Sciences, Peking University, Beijing 100871, China
| | - Hongliang Bu
- School of Life Sciences, Peking University, Beijing 100871, China
| | - Xiaoyun Shi
- School of Life Sciences, Peking University, Beijing 100871, China; Institute of Ecology, College of Urban and Environmental Sciences, Peking University, Beijing 100871, China
| | - Dajun Wang
- School of Life Sciences, Peking University, Beijing 100871, China
| | - Jindong Zhao
- School of Life Sciences, Peking University, Beijing 100871, China; Institute of Ecology, College of Urban and Environmental Sciences, Peking University, Beijing 100871, China
| | - Sheng Li
- School of Life Sciences, Peking University, Beijing 100871, China; Institute of Ecology, College of Urban and Environmental Sciences, Peking University, Beijing 100871, China.
| | - Meng Yao
- School of Life Sciences, Peking University, Beijing 100871, China; Institute of Ecology, College of Urban and Environmental Sciences, Peking University, Beijing 100871, China.
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21
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Abstract
Resource partitioning stabilizes species coexistence but has long been difficult to measure. DNA metabarcoding reveals previously hidden dimensions of this problem and insights relevant for understanding and fostering coexistence - not just among wild carnivores, but also between carnivores and people.
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Affiliation(s)
- Robert M Pringle
- Department of Ecology and Evolutionary Biology, Princeton University, Princeton, NJ 08544, USA.
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22
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Large herbivores suppress liana infestation in an African savanna. Proc Natl Acad Sci U S A 2021; 118:2101676118. [PMID: 34580170 DOI: 10.1073/pnas.2101676118] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/13/2021] [Indexed: 11/18/2022] Open
Abstract
African savannas are the last stronghold of diverse large-mammal communities, and a major focus of savanna ecology is to understand how these animals affect the relative abundance of trees and grasses. However, savannas support diverse plant life-forms, and human-induced changes in large-herbivore assemblages-declining wildlife populations and their displacement by livestock-may cause unexpected shifts in plant community composition. We investigated how herbivory affects the prevalence of lianas (woody vines) and their impact on trees in an East African savanna. Although scarce (<2% of tree canopy area) and defended by toxic latex, the dominant liana, Cynanchum viminale (Apocynaceae), was eaten by 15 wild large-herbivore species and was consumed in bulk by native browsers during experimental cafeteria trials. In contrast, domesticated ungulates rarely ate lianas. When we experimentally excluded all large herbivores for periods of 8 to 17 y (simulating extirpation), liana abundance increased dramatically, with up to 75% of trees infested. Piecewise exclusion of different-sized herbivores revealed functional complementarity among size classes in suppressing lianas. Liana infestation reduced tree growth and reproduction, but herbivores quickly cleared lianas from trees after the removal of 18-y-old exclosure fences (simulating rewilding). A simple model of liana contagion showed that, without herbivores, the long-term equilibrium could be either endemic (liana-tree coexistence) or an all-liana alternative stable state. We conclude that ongoing declines of wild large-herbivore populations will disrupt the structure and functioning of many African savannas in ways that have received little attention and that may not be mitigated by replacing wildlife with livestock.
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23
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Wells HBM, Crego RD, Opedal ØH, Khasoha LM, Alston JM, Reed CG, Weiner S, Kurukura S, Hassan AA, Namoni M, Ekadeli J, Kimuyu DM, Young TP, Kartzinel TR, Palmer TM, Pringle RM, Goheen JR. Experimental evidence that effects of megaherbivores on mesoherbivore space use are influenced by species' traits. J Anim Ecol 2021; 90:2510-2522. [PMID: 34192343 DOI: 10.1111/1365-2656.13565] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2021] [Accepted: 06/23/2021] [Indexed: 11/27/2022]
Abstract
The extinction of 80% of megaherbivore (>1,000 kg) species towards the end of the Pleistocene altered vegetation structure, fire dynamics and nutrient cycling world-wide. Ecologists have proposed (re)introducing megaherbivores or their ecological analogues to restore lost ecosystem functions and reinforce extant but declining megaherbivore populations. However, the effects of megaherbivores on smaller herbivores are poorly understood. We used long-term exclusion experiments and multispecies hierarchical models fitted to dung counts to test (a) the effect of megaherbivores (elephant and giraffe) on the occurrence (dung presence) and use intensity (dung pile density) of mesoherbivores (2-1,000 kg), and (b) the extent to which the responses of each mesoherbivore species was predictable based on their traits (diet and shoulder height) and phylogenetic relatedness. Megaherbivores increased the predicted occurrence and use intensity of zebras but reduced the occurrence and use intensity of several other mesoherbivore species. The negative effect of megaherbivores on mesoherbivore occurrence was stronger for shorter species, regardless of diet or relatedness. Megaherbivores substantially reduced the expected total use intensity (i.e. cumulative dung density of all species) of mesoherbivores, but only minimally reduced the expected species richness (i.e. cumulative predicted occurrence probabilities of all species) of mesoherbivores (by <1 species). Simulated extirpation of megaherbivores altered use intensity by mesoherbivores, which should be considered during (re)introductions of megaherbivores or their ecological proxies. Species' traits (in this case shoulder height) may be more reliable predictors of mesoherbivores' responses to megaherbivores than phylogenetic relatedness, and may be useful for predicting responses of data-limited species.
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Affiliation(s)
- Harry B M Wells
- Lolldaiga Hills Research Programme, Nanyuki, Kenya.,Sustainability Research Institute, School of Earth and Environment, University of Leeds, Leeds, UK.,Space for Giants, Nanyuki, Kenya
| | - Ramiro D Crego
- National Zoo and Smithsonian Conservation Biology Institute, Conservation Ecology Center, Front Royal, VA, USA
| | | | - Leo M Khasoha
- Mpala Research Centre, Nanyuki, Kenya.,Program in Ecology, Department of Zoology and Physiology, University of Wyoming, Laramie, WY, USA
| | - Jesse M Alston
- Program in Ecology, Department of Zoology and Physiology, University of Wyoming, Laramie, WY, USA.,Center for Advanced Systems Understanding (CASUS), Görlitz, Germany
| | - Courtney G Reed
- Mpala Research Centre, Nanyuki, Kenya.,Institute at Brown for Environment and Society, Brown University, Providence, RI, USA.,Department of Ecology and Evolutionary Biology, Brown University, Providence, RI, USA
| | - Sarah Weiner
- Mpala Research Centre, Nanyuki, Kenya.,Program in Ecology, Department of Zoology and Physiology, University of Wyoming, Laramie, WY, USA
| | | | | | | | | | - Duncan M Kimuyu
- Mpala Research Centre, Nanyuki, Kenya.,Department of Natural Resources, Karatina University, Karatina, Kenya
| | - Truman P Young
- Mpala Research Centre, Nanyuki, Kenya.,Department of Plant Sciences and Ecology Graduate Group, University of California, Davis, CA, USA
| | - Tyler R Kartzinel
- Mpala Research Centre, Nanyuki, Kenya.,Institute at Brown for Environment and Society, Brown University, Providence, RI, USA.,Department of Ecology and Evolutionary Biology, Brown University, Providence, RI, USA
| | - Todd M Palmer
- Mpala Research Centre, Nanyuki, Kenya.,Department of Biology, University of Florida, Gainesville, FL, USA
| | - Robert M Pringle
- Department of Ecology and Evolutionary Biology, Princeton University, Princeton, NJ, USA
| | - Jacob R Goheen
- Mpala Research Centre, Nanyuki, Kenya.,Program in Ecology, Department of Zoology and Physiology, University of Wyoming, Laramie, WY, USA
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Rojas CA, Ramírez-Barahona S, Holekamp KE, Theis KR. Host phylogeny and host ecology structure the mammalian gut microbiota at different taxonomic scales. Anim Microbiome 2021; 3:33. [PMID: 33892813 PMCID: PMC8063394 DOI: 10.1186/s42523-021-00094-4] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2020] [Accepted: 04/04/2021] [Indexed: 12/13/2022] Open
Abstract
The gut microbiota is critical for host function. Among mammals, host phylogenetic relatedness and diet are strong drivers of gut microbiota structure, but one factor may be more influential than the other. Here, we used 16S rRNA gene sequencing to determine the relative contributions of host phylogeny and host diet in structuring the gut microbiotas of 11 herbivore species from 5 families living sympatrically in southwest Kenya. Herbivore species were classified as grazers, browsers, or mixed-feeders and dietary data (% C4 grasses in diet) were compiled from previously published sources. We found that herbivore gut microbiotas were highly species-specific, and that host taxonomy accounted for more variation in the gut microbiota (30%) than did host dietary guild (10%) or sample month (8%). Overall, similarity in the gut microbiota increased with host phylogenetic relatedness (r = 0.74) across the 11 species of herbivores, but among 7 closely related Bovid species, dietary %C4 grass values more strongly predicted gut microbiota structure (r = 0.64). Additionally, within bovids, host dietary guild explained more of the variation in the gut microbiota (17%) than did host species (12%). Lastly, while we found that the gut microbiotas of herbivores residing in southwest Kenya converge with those of distinct populations of conspecifics from central Kenya, fine-scale differences in the abundances of bacterial amplicon sequence variants (ASVs) between individuals from the two regions were also observed. Overall, our findings suggest that host phylogeny and taxonomy strongly structure the gut microbiota across broad host taxonomic scales, but these gut microbiotas can be further modified by host ecology (i.e., diet, geography), especially among closely related host species.
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Affiliation(s)
- Connie A. Rojas
- Department of Integrative Biology, Michigan State University, East Lansing, MI USA
- Ecology, Evolution, and Behavior Program, Michigan State University, East Lansing, MI USA
- BEACON Center for the Study of Evolution in Action, Michigan State University, East Lansing, MI USA
| | - Santiago Ramírez-Barahona
- Departament of Botany, Institute of Biology, Universidad Nacional Autónoma de México, Mexico City, MX Mexico
| | - Kay E. Holekamp
- Department of Integrative Biology, Michigan State University, East Lansing, MI USA
- Ecology, Evolution, and Behavior Program, Michigan State University, East Lansing, MI USA
- BEACON Center for the Study of Evolution in Action, Michigan State University, East Lansing, MI USA
| | - Kevin R. Theis
- BEACON Center for the Study of Evolution in Action, Michigan State University, East Lansing, MI USA
- Department of Biochemistry, Microbiology and Immunology, Wayne State University School of Medicine, Detroit, MI USA
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Maity B, Cao Z, Kumawat J, Gupta V, Cavallo L. A Multivariate Linear Regression Approach to Predict Ethene/1-Olefin Copolymerization Statistics Promoted by Group 4 Catalysts. ACS Catal 2021. [DOI: 10.1021/acscatal.0c04856] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Affiliation(s)
- Bholanath Maity
- King Abdullah University of Science and Technology (KAUST) KAUST Catalysis Center (KCC), Thuwal 23955-6900, Saudi Arabia
| | - Zhen Cao
- King Abdullah University of Science and Technology (KAUST) KAUST Catalysis Center (KCC), Thuwal 23955-6900, Saudi Arabia
| | - Jugal Kumawat
- Reliance Research & Development Centre, Reliance Corporate Park, Reliance Industries Limited, Navi Mumbai 400 701, India
| | - Virendrakumar Gupta
- Reliance Research & Development Centre, Reliance Corporate Park, Reliance Industries Limited, Navi Mumbai 400 701, India
| | - Luigi Cavallo
- King Abdullah University of Science and Technology (KAUST) KAUST Catalysis Center (KCC), Thuwal 23955-6900, Saudi Arabia
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Neophobia in 10 ungulate species-a comparative approach. Behav Ecol Sociobiol 2021; 75:102. [PMID: 34177046 PMCID: PMC8219784 DOI: 10.1007/s00265-021-03041-0] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2021] [Revised: 05/25/2021] [Accepted: 05/27/2021] [Indexed: 02/06/2023]
Abstract
ABSTRACT Neophobia (the fearful reaction to novel stimuli or situations) has a crucial effect on individual fitness and can vary within and across species. However, the factors predicting this variation are still unclear. In this study, we assessed whether individual characteristics (rank, social integration, sex) and species socio-ecological characteristics (dietary breadth, group size, domestication) predicted variation in neophobia. For this purpose, we conducted behavioral observations and experimental tests on 78 captive individuals belonging to 10 different ungulate species-an ideal taxon to study inter-specific variation in neophobia given their variety in socio-ecological characteristics. Individuals were tested in their social groups by providing them with familiar food, half of which had been positioned close to a novel object. We monitored the individual latency to approach and eat food and the proportion of time spent in its proximity. Using a phylogenetic approach and social network analyses, we showed that across ungulate species neophobia was higher in socially more integrated individuals, as compared to less integrated ones. In contrast, rank and sex did not predict inter-individual differences in neophobia. Moreover, species differed in their levels of neophobia, with Barbary sheep being on average less neophobic than all the other study species. As group size in Barbary sheep was larger than in all the other study species, these results support the hypothesis that larger group size predicts lower levels of neophobia, and confirm ungulates as a highly promising taxon to study animal behavior and cognition with a comparative perspective. SIGNIFICANCE STATEMENT In several species, individuals may respond fearfully to novel stimuli, therefore reducing the risks they may face. However, it is yet unclear if certain individuals or species respond more fearfully to novelty. Here, we provided food to 78 individual ungulates with different characteristics (e.g., sex, rank, social integration, group size, domestication, dietary breadth) in different controlled conditions (e.g., when food was close to novel or to familiar objects). Across species, we found that socially integrated individuals responded more fearfully in all species. Moreover, being in larger groups decreased the probability of fearfully responding to novelty. SUPPLEMENTARY INFORMATION The online version contains supplementary material available at 10.1007/s00265-021-03041-0.
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Pringle RM, Hutchinson MC. Resolving Food-Web Structure. ANNUAL REVIEW OF ECOLOGY, EVOLUTION, AND SYSTEMATICS 2020. [DOI: 10.1146/annurev-ecolsys-110218-024908] [Citation(s) in RCA: 24] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Food webs are a major focus and organizing theme of ecology, but the data used to assemble them are deficient. Early debates over food-web data focused on taxonomic resolution and completeness, lack of which had produced spurious inferences. Recent data are widely believed to be much better and are used extensively in theoretical and meta-analytic research on network ecology. Confidence in these data rests on the assumptions ( a) that empiricists correctly identified consumers and their foods and ( b) that sampling methods were adequate to detect a near-comprehensive fraction of the trophic interactions between species. Abundant evidence indicates that these assumptions are often invalid, suggesting that most topological food-web data may remain unreliable for inferences about network structure and underlying ecological and evolutionary processes. Morphologically cryptic species are ubiquitous across taxa and regions, and many trophic interactions routinely evade detection by conventional methods. Molecular methods have diagnosed the severity of these problems and are a necessary part of the cure.
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Affiliation(s)
- Robert M. Pringle
- Department of Ecology and Evolutionary Biology, Princeton University, Princeton, New Jersey 08544, USA
| | - Matthew C. Hutchinson
- Department of Ecology and Evolutionary Biology, Princeton University, Princeton, New Jersey 08544, USA
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