Species＇ partitioning of resources remains one of the most integral components for understanding community assem- bly. Analysis of stable carbon and nitrogen isotopes in animal tissues has the potential to help resol...Species＇ partitioning of resources remains one of the most integral components for understanding community assem- bly. Analysis of stable carbon and nitrogen isotopes in animal tissues has the potential to help resolve patterns of partitioning be- cause these proxies represent the individual＇s diet and trophic niche, respectively. Using free-ranging rodents in a southern Afri- can savanna as a model community, we find that syntopic species within habitats occupy distinct isotope niches. Moreover, spe- cies with strongly overlapping isotope niches did not overlap in their spatial distribution patterns, suggesting an underlying effect of competitive exclusion. Niche conservatism appears to characterize the behaviour of most species in our sample - with little or no observed changes across habitats - with the exception of one species, Mastomys coucha. This species displayed a generalist distribution, being found in similar abundances across a variety of habitats. This spatial pattern was coupled with a generalist isotope niche that shifted across habitats, likely in response to changes in species composition over the same spatial gradient. The case for M. coucha supports contentions that past competition effects played a significant evolutionary role in shaping community structures of today, including the absence of strong interspecific niche overlaps within particular habitats. Our study highlights the value of stable isotope approaches to help resolve key questions in community ecology, and moreover introduces novel ana- lytical approaches to quantifying isotope niche breadths and niche overlaps that are easily comparable with traditional metrices展开更多
Predator-prey size relationships are among the most important patterns underlying the structure and function of ecological communities.Indeed,these relationships have already been shown to be important for understandi...Predator-prey size relationships are among the most important patterns underlying the structure and function of ecological communities.Indeed,these relationships have already been shown to be important for understanding patterns of macroevolution and differential extinction in the terrestrial vertebrate fossil record.Stable isotope analysis(SIA)is a powerful remote approach to examining animal diets and paleodiets.The approach is based on the principle that isotope compositions of consumer tissues reflect those of their prey.In systems where resource isotope compositions are distributed along a body size gradient,SIA could be used to reconstruct predator-prey size relationships.We analyzed stable carbon isotope distributions amongst mammalian herbivores in extant and Plio-Pleistocene African savanna assemblages,and show that the range ofδ^(13)C values among mammalian prey species(herbivores and rodents)increases with body mass(BM),because C_(4) plant feeding(essentially grazing)is more common among larger taxa.Consequently,δ^(13)C values of mammalian carnivores in these systems are related to species’BM,reflecting a higher average C_(4) prey component in the diets of larger-bodied carnivores.This pattern likely emerges because only the largest carnivores in these systems have regular access to the C_(4) prey base,whereas smaller carnivores do not.Theδ^(13)C-BM relationship observed in mammalian carnivores is a potentially powerful approach for reconstructing and parameterizing predator-prey size relationships in contemporary and fossil savanna assemblages,and for interpreting how various behavioral,ecological and environmental factors influence prey size selection.展开更多
基金Acknowledgements This research was funded by the Na- tional Science Foundation （NSF, USA） and the Palaeontolo- gical Scientific Trust （PAST, RSA）. We thank Jurie du Plessis, Isak Sekhuni, Carl Pohl, Bianca Bester, Ethan Codron, and Jesse Codron for assistance in the field. Two anonymous re- viewers and the journal editor are thanked for useful com- ments that helped improve the quality of this paper. The re- search and protocols were approved by the Gauteng Provincial Government, authorization number MA： 8/1/1/6/1-2011/01/001.
文摘Species＇ partitioning of resources remains one of the most integral components for understanding community assem- bly. Analysis of stable carbon and nitrogen isotopes in animal tissues has the potential to help resolve patterns of partitioning be- cause these proxies represent the individual＇s diet and trophic niche, respectively. Using free-ranging rodents in a southern Afri- can savanna as a model community, we find that syntopic species within habitats occupy distinct isotope niches. Moreover, spe- cies with strongly overlapping isotope niches did not overlap in their spatial distribution patterns, suggesting an underlying effect of competitive exclusion. Niche conservatism appears to characterize the behaviour of most species in our sample - with little or no observed changes across habitats - with the exception of one species, Mastomys coucha. This species displayed a generalist distribution, being found in similar abundances across a variety of habitats. This spatial pattern was coupled with a generalist isotope niche that shifted across habitats, likely in response to changes in species composition over the same spatial gradient. The case for M. coucha supports contentions that past competition effects played a significant evolutionary role in shaping community structures of today, including the absence of strong interspecific niche overlaps within particular habitats. Our study highlights the value of stable isotope approaches to help resolve key questions in community ecology, and moreover introduces novel ana- lytical approaches to quantifying isotope niche breadths and niche overlaps that are easily comparable with traditional metrices
基金This research was funded by the NRF-DST Centre of Excellence in Palaoesciences,at the University of the Witwatersrand,Johannesburg and the National Research Foundation’s African Origins Platform(grant no.98836).
文摘Predator-prey size relationships are among the most important patterns underlying the structure and function of ecological communities.Indeed,these relationships have already been shown to be important for understanding patterns of macroevolution and differential extinction in the terrestrial vertebrate fossil record.Stable isotope analysis(SIA)is a powerful remote approach to examining animal diets and paleodiets.The approach is based on the principle that isotope compositions of consumer tissues reflect those of their prey.In systems where resource isotope compositions are distributed along a body size gradient,SIA could be used to reconstruct predator-prey size relationships.We analyzed stable carbon isotope distributions amongst mammalian herbivores in extant and Plio-Pleistocene African savanna assemblages,and show that the range ofδ^(13)C values among mammalian prey species(herbivores and rodents)increases with body mass(BM),because C_(4) plant feeding(essentially grazing)is more common among larger taxa.Consequently,δ^(13)C values of mammalian carnivores in these systems are related to species’BM,reflecting a higher average C_(4) prey component in the diets of larger-bodied carnivores.This pattern likely emerges because only the largest carnivores in these systems have regular access to the C_(4) prey base,whereas smaller carnivores do not.Theδ^(13)C-BM relationship observed in mammalian carnivores is a potentially powerful approach for reconstructing and parameterizing predator-prey size relationships in contemporary and fossil savanna assemblages,and for interpreting how various behavioral,ecological and environmental factors influence prey size selection.
