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Garrido M, Halle S, Flatau R, Cohen C, Navarro-Castilla Á, Barja I, Hawlena H. The dilution effect behind the scenes: testing the underlying assumptions of its mechanisms through quantifying the long-term dynamics and effects of a pathogen in multiple host species. Proc Biol Sci 2021; 288:20210773. [PMID: 34102894 PMCID: PMC8187991 DOI: 10.1098/rspb.2021.0773] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2021] [Accepted: 05/12/2021] [Indexed: 01/01/2023] Open
Abstract
Disentangling the mechanisms that mediate the relationships between species diversity and disease risk has both theoretical and applied implications. We employed a model system of rodents and their Mycoplasma pathogens, in which an extreme negative diversity-disease relationship was demonstrated, to test the assumptions underlying three mechanisms that may explain this field pattern. Through quantifying the long-term dynamics and effects of the pathogen in its three host species, we estimated the between-host differences in pathogen spreading and transmission potentials, and host recovery potential and vulnerability to infection. The results suggest that one of the hosts is a pathogen amplifier and the other two hosts function as diluters. Considering the similarity in infection success and intensity among hosts, and the failure to detect any pathogen-induced damage, we could not validate the assumption underlying the hypotheses that diluters reduce the overall transmission or increase the mortality of infected hosts in the system. Instead, the results demonstrate that diluters clear the infection faster than amplifiers, supporting the possibility that the addition of diluters to the community may reduce the overall number of infected hosts through this mechanism. This study highlights the contribution of experimental studies that simultaneously explore different aspects of host-pathogen interactions in multiple hosts, in diversity-disease research.
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Affiliation(s)
- Mario Garrido
- Jacob Blaustein Center for Scientific Cooperation, Ben-Gurion University of the Negev, 849900 Midreshet Ben-Gurion, Israel
| | - Snir Halle
- Mitrani Department of Desert Ecology, Swiss Institute for Dryland Environmental and Energy Research, The Jacob Blaustein Institutes for Desert Research, Ben-Gurion University of the Negev, 849900 Midreshet Ben-Gurion, Israel
| | - Ron Flatau
- Mitrani Department of Desert Ecology, Swiss Institute for Dryland Environmental and Energy Research, The Jacob Blaustein Institutes for Desert Research, Ben-Gurion University of the Negev, 849900 Midreshet Ben-Gurion, Israel
| | - Carmit Cohen
- Mitrani Department of Desert Ecology, Swiss Institute for Dryland Environmental and Energy Research, The Jacob Blaustein Institutes for Desert Research, Ben-Gurion University of the Negev, 849900 Midreshet Ben-Gurion, Israel
| | - Álvaro Navarro-Castilla
- Etho-Physiology Group. Unit of Zoology. Department of Biology. Faculty of Sciences, the Autonomous University of Madrid, Spain
| | - Isabel Barja
- Etho-Physiology Group. Unit of Zoology. Department of Biology. Faculty of Sciences, the Autonomous University of Madrid, Spain
- Center for Research on Biodiversity and Global Change (CIBC-UAM), the Autonomous University of Madrid, Spain
| | - Hadas Hawlena
- Mitrani Department of Desert Ecology, Swiss Institute for Dryland Environmental and Energy Research, The Jacob Blaustein Institutes for Desert Research, Ben-Gurion University of the Negev, 849900 Midreshet Ben-Gurion, Israel
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Saar M, Subach A, Reato I, Liber T, Pruitt JN, Scharf I. Consistent differences in foraging behavior in 2 sympatric harvester ant species may facilitate coexistence. Curr Zool 2018; 64:653-661. [PMID: 30323844 PMCID: PMC6178789 DOI: 10.1093/cz/zox054] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2017] [Accepted: 09/06/2017] [Indexed: 11/14/2022] Open
Abstract
The co-occurrence of 2 similar species depends on their ability to occupy different ecological niches. Here, we compared the consistency of different aspects of foraging behavior in 2 co-occurring harvester ant species (Messor ebeninus and Messor arenarius), under field conditions. The 2 species are active concomitantly and display a similar diet, but M. arenarius features smaller colonies, larger workers on average, and a broader range of foraging strategies than M. ebeninus. We characterized the flora in the 2 species' natural habitat, and detected a nesting preference by M. arenarius for more open, vegetation-free microhabitats than those preferred by M. ebeninus. Next, we tested the food preference of foraging colonies by presenting 3 non-native seed types. Messor arenarius was more selective in its food choice. Colonies were then offered 1 type of seeds over 3 days in different spatial arrangements from the nest entrance (e.g., a seed plate close to the nest entrance, a seed plate blocked by an obstacle, or 3 plates placed at increasing distances from the nest entrance). While both species were consistent in their foraging behavior, expressed as seed collection, under different treatments over time, M. ebeninus was more consistent than M. arenarius. These differences between the species may be explained by their different colony size, worker size, and range of foraging strategies, among other factors. We suggest that the differences in foraging, such as in food preference and behavioral consistency while foraging, could contribute to the co-occurrence of these 2 species in a similar habitat.
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Affiliation(s)
- Maya Saar
- Department of Zoology, Faculty of Life Sciences, Tel Aviv University, Tel Aviv, Israel
| | - Aziz Subach
- Department of Zoology, Faculty of Life Sciences, Tel Aviv University, Tel Aviv, Israel
| | - Illan Reato
- Department of Zoology, Faculty of Life Sciences, Tel Aviv University, Tel Aviv, Israel
| | - Tal Liber
- Department of Zoology, Faculty of Life Sciences, Tel Aviv University, Tel Aviv, Israel
| | - Jonathan N Pruitt
- Department of Ecology, Evolution, and Marine Biology, University of California, Santa Barbara, CA, USA
| | - Inon Scharf
- Department of Zoology, Faculty of Life Sciences, Tel Aviv University, Tel Aviv, Israel
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Eckrich CA, Flaherty EA, Ben-David M. Functional and numerical responses of shrews to competition vary with mouse density. PLoS One 2018; 13:e0189471. [PMID: 29298313 PMCID: PMC5752000 DOI: 10.1371/journal.pone.0189471] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2017] [Accepted: 11/28/2017] [Indexed: 11/18/2022] Open
Abstract
For decades, ecologists have debated the importance of biotic interactions (e.g., competition) and abiotic factors in regulating populations. Competition can influence patterns of distribution, abundance, and resource use in many systems but remains difficult to measure. We quantified competition between two sympatric small mammals, Keen's mice (Peromyscus keeni) and dusky shrews (Sorex monticolus), in four habitat types on Prince of Wales Island in Southeast Alaska. We related shrew density to that of mice using standardized regression models while accounting for habitat variables in each year from 2010-2012, during which mice populations peaked (2011) and then crashed (2012). Additionally, we measured dietary overlap and segregation using stable isotope analysis and kernel utilization densities and estimated the change in whole community energy consumption among years. We observed an increase in densities of dusky shrews after mice populations crashed in 2012 as expected under competitive release. In addition, competition coefficients revealed that the influence of Keen's mice was dependent on their density. Also in 2012, shrew diets shifted, indicating that they were able to exploit resources previously used by mice. Nonetheless, increases in shrew numbers only partially compensated for the community energy consumption because, as insectivores, they are unlikely to utilize all food types consumed by their competitors. In pre-commercially thinned stands, which exhibit higher diversity of resources compared to other habitat types, shrew populations were less affected by changes in mice densities. These spatially and temporally variable interactions between unlikely competitors, observed in a relatively simple, high-latitude island ecosystem, highlight the difficulty in assessing the role of biotic factors in structuring communities.
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Affiliation(s)
- Carolyn A. Eckrich
- Oregon Department of Fish and Wildlife, La Grande, OR, United States of America
| | - Elizabeth A. Flaherty
- Department of Forestry and Natural Resources, Purdue University, West Lafayette, IN, United States of America
| | - Merav Ben-David
- Department of Zoology and Physiology and Program in Ecology, University of Wyoming, Laramie, WY, United States of America
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Kelt DA. Comparative ecology of desert small mammals: a selective review of the past 30 years. J Mammal 2011. [DOI: 10.1644/10-mamm-s-238.1] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
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Berger-Tal O, Kotler BP. State of emergency: Behavior of gerbils is affected by the hunger state of their predators. Ecology 2010; 91:593-600. [DOI: 10.1890/09-0112.1] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
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Ovadia O, Abramsky Z, Kotler BP, Pinshow B. Inter-specific competitors reduce inter-gender competition in Negev Desert gerbils. Oecologia 2004; 142:480-8. [PMID: 15655694 DOI: 10.1007/s00442-004-1726-9] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2002] [Accepted: 09/09/2004] [Indexed: 11/24/2022]
Abstract
We examined gender-dependent competitive interactions between two nocturnal desert gerbil species, Gerbillus andersoni allenbyi and G. pyramidum, by a field manipulation experiment. The study was done in two 1-ha enclosed plots and included allopatric (only G. a. allenbyi) and sympatric (both species together) treatments. Seed trays and thermal imaging cameras were used to observe the gerbils' foraging activities and aggressive interactions. We found that the negative effect of the competitively dominant species, G. pyramidum, on time spent in seed trays, and ability to control these artificial food patches, was stronger on male than on female G. a. allenbyi. Consequently, the aggression of male G. a. allenbyi towards female G. a. allenbyi was markedly reduced, indicating that the dominant species mediated competition between the genders of the subordinate species. Furthermore, this interference-mediated indirect effect was associated with a decrease in the body mass of male G. a. allenbyi and an increase in the survival of female G. a. allenbyi. We suggest that both the reduction in intra-specific aggression and the positive effect on female survival can potentially stabilize competitive interactions and promote coexistence in this small mammal community.
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Affiliation(s)
- Ofer Ovadia
- Department of Life Sciences, Ben-Gurion University of the Negev, POB 653, 84105 Beer-Sheva, Israel.
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Shargal E, Kronfeld-Schor N, Dayan T. POPULATION BIOLOGY AND SPATIAL RELATIONSHIPS OF COEXISTING SPINY MICE (ACOMYS) IN ISRAEL. J Mammal 2000. [DOI: 10.1644/1545-1542(2000)081<1046:pbasro>2.0.co;2] [Citation(s) in RCA: 45] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
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Hodara K, Busch M, Kittlein MJ, Kravetz FO. Density-dependent habitat selection between maize cropfields and their borders in two rodent species (Akodon azarae and Calomys laucha) of Pampean agroecosystems. Evol Ecol 2000. [DOI: 10.1023/a:1010823128530] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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Degen AA, Kam M. Average daily metabolic rate of gerbils of two species:Gerbillus pyramidumandGerbillus allenbyi. J Zool (1987) 1991. [DOI: 10.1111/j.1469-7998.1991.tb04755.x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Shachak M, Brand S. Relationship among settling, demography and habitat selection: an approach and a case study. Oecologia 1988; 76:620-626. [DOI: 10.1007/bf00397879] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/1988] [Indexed: 11/28/2022]
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Meentemeyer V, Box EO. Scale Effects in Landscape Studies. LANDSCAPE HETEROGENEITY AND DISTURBANCE 1987. [DOI: 10.1007/978-1-4612-4742-5_2] [Citation(s) in RCA: 144] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
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Can interaction coefficients be determined from cencus data? Oecologia 1985; 66:194-198. [DOI: 10.1007/bf00379854] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/1984] [Indexed: 10/24/2022]
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Estimating competition coefficients from census data. Oecologia 1985; 67:588-590. [DOI: 10.1007/bf00790031] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/1985] [Indexed: 10/26/2022]
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