Influence of continental history on the ecological specialization and macroevolutionary processes in the mammalian assemblage of South America: Differences between small and large mammals

Background: This paper tests Vrba's resource-use hypothesis, which predicts that generalist species have lower specialization and extinction rates than specialists, using the 879 species of South American mammals. We tested several predictions about this hypothesis using the biomic specialization index (BSI) for each species, which is based on its geographical range within different climate-zones. The four predictions tested are: (1) there is a high frequency of species restricted to a single biome, which henceforth are referred to as stenobiomic species, (2) certain clades are more stenobiomic than others, (3) there is a higher proportion of biomic specialists in biomes that underwent through major expansion-contraction alternation due to the glacial-interglacial cycles, (4) certain combinations of inhabited biomes occur more frequently among species than do others. Results: Our results are consistent with these predictions. (1) We found that 42 % of the species inhabit only one biome. (2) There are more generalists among species of Carnivora than in clades of herbivores. However, Artiodactyla, shows a distribution along the specialization gradient different from the one expected. (3) Biomic specialists are predominant in tropical rainforest and desert biomes. Nevertheless, we found some differences between small and large mammals in relation to these results. Stenobiomic species of micromammalian clades are more abundant in most biomes than expected by chance, while in the case of macromammalian clades stenobiomic species are more frequent than expected in tropical rainforest, tropical deciduous woodland and desert biomes only. (4) The most frequent combinations of inhabited biomes among the South American mammals are those with few biomes, i.e., the ones that suffered a higher rate of vicariance due to climatic cycles. Conclusion: Our results agree with the resource-use hypothesis and, therefore, with a major role of the past climatic changes as drivers of mammalian evolution. Nevertheless, deviations from the expectations indicate the importance of differences in reproductive traits and paleobiogeographic history for the macroevolutionary processes involved. In the case of South American mammals, the Pliocene Great American Biotic Interchange strongly influences the ecological characteristics of this assemblage. Furthermore, the Andes have acted as a fertile ground for speciation in environments prone to vicariance. Finally, the micromammals appear as more prone to biomic specialization than larger species. These factors are responsible for some of the differences found between South America and Africa in the studied pattern. For example, the extensive South American mountain ranges favour a higher number of combinations of inhabited biomes in comparison with Africa

Influence of continental history on the ecological specialization and macroevolutionary processes in the mammalian assemblage of South America: differences between small and large mammals

Background. This paper tests Vrba's resource-use hypothesis, which predicts that generalist species have lower specialization and extinction rates than specialists, using the 879 species of South American mammals. We tested several predictions about this hypothesis using the biomic specialization index (BSI) for each species, which is based on its geographical range within different climate-zones. The four predictions tested are: (1) there is a high frequency of species restricted to a single biome, which henceforth are referred to as stenobiomic species, (2) certain clades are more stenobiomic than others, (3) there is a higher proportion of biomic specialists in biomes that underwent through major expansion-contraction alternation due to the glacial-interglacial cycles, (4) certain combinations of inhabited biomes occur more frequently among species than do others. Results. Our results are consistent with these predictions. (1) We found that 42 % of the species inhabit only one biome. (2) There are more generalists among species of Carnivora than in clades of herbivores. However, Artiodactyla, shows a distribution along the specialization gradient different from the one expected. (3) Biomic specialists are predominant in tropical rainforest and desert biomes. Nevertheless, we found some differences between small and large mammals in relation to these results. Stenobiomic species of micromammalian clades are more abundant in most biomes than expected by chance, while in the case of macromammalian clades stenobiomic species are more frequent than expected in tropical rainforest, tropical deciduous woodland and desert biomes only. (4) The most frequent combinations of inhabited biomes among the South American mammals are those with few biomes, i.e., the ones that suffered a higher rate of vicariance due to climatic cycles. Conclusion. Our results agree with the resource-use hypothesis and, therefore, with a major role of the past climatic changes as drivers of mammalian evolution. Nevertheless, deviations from the expectations indicate the importance of differences in reproductive traits and paleobiogeographic history for the macroevolutionary processes involved. In the case of South American mammals, the Pliocene Great American Biotic Interchange strongly influences the ecological characteristics of this assemblage. Furthermore, the Andes have acted as a fertile ground for speciation in environments prone to vicariance. Finally, the micromammals appear as more prone to biomic specialization than larger species. These factors are responsible for some of the differences found between South America and Africa in the studied pattern. For example, the extensive South American mountain ranges favour a higher number of combinations of inhabited biomes in comparison with Africa.Facultad de Ciencias Naturales y Muse

Factores macroevolutivos en los mamíferos terrestres de América del Sur

Utilizando la información existente de toda la fauna actual de mamíferos continentales sudamericanos hemos podido probar y dar consistencia a la Hipótesis de Uso de los Recursos propuesta por Vrba, la cual predice que las especies generalistas tienen tasas de especiación y extinción más bajas que las especies especialistas. Hemos utilizado el índice de especialización biómica (BSI) de cada especie, basado en su distribución geográfica dentro de las diferentes zonas climáticas. Nuestros resultados son consistentes con las cuatro predicciones de la Hipótesis del uso de los recursos: (1) existe una elevada frecuencia de especies restringidas a un solo bioma, un 42% son especies estenobiómicas; (2) ciertos clados, como Carnivora, son más eurobiómicos que otros, como los herbívoros. Sin embargo, Artiodactyla, muestra una distribución diferente de la esperada; (3) hay una mayor número de especialistas biómicos en biomas que sufrieron con mayor fuerza los Ciclos de Milankovitch. Los especialistas biómicos son predominantes en los biomas de pluvisilva bosque tropical seco y desierto. No obstante, los micromamíferos son más propensos a la especialización biómica; (4) ciertas combinaciones biómicas aparecen con más frecuencia que otras. Las combinaciones más frecuentes son aquellas con pocos biomas, aquellos que sufrieron altas tasas de vicarianza debido a ciclos climáticos. Los resultados obtenidos apoyan la idea de que los cambios climáticos del pasado son determinantes en la evolución de los mamíferos actuales, y además las desviaciones obtenidas en el estudio proponen una mirada hacia nuevos factores como la historia paleográfica del continente y los caracteres reproductivos de las especies. [ABSTRACT] Using the extant information of the complete fauna of South American terrestrial mammals we proved the Vrba’s resource-use hypothesis, which predicts that speciation and extinction rates are lower in generalist species than specialist. We used the biomic specialization index (BSI) for each species, which is based on its geographical distribution within different climate-zones. Our results are consistent with four predictions of the resource-use hipotesis: (1) there is a high frequency of species restricted to single biomes, which henceforth are referred to as stenobiomic species; we found that 42% of the species inhabit only one biome; (2) certain clades, as Carnivora, are more euryibiomic than others. However, Artiodactyla, shows a distribution along the specialization gradient different from the one expected; (3) there is a higher proportion of biomic specialists in biomes that underwent high fragmentation during the Milankovitch Cycles. The biomic specialists are predominant in rainforest, dry tropical forest and desert biomes. Nevertheless, micromammals appear as more prone to biomic specialization than macromammals; (4) certain climatic combinations occur more frequently than do others. The most frequent combinations are those with few biomes, the ones that suffered a higher rate of vicariance due to climatic cycles. Our results support an idea defending the major role of the past climatic changes as drivers of mammalian evolution, and suggest a new view towards other factors like paleobiogeographic history and the differences in reproductive traits of the species

Influence of continental history on the ecological specialization and macroevolutionary processes in the mammalian assemblage of South America: Differences between small and large mammals-0

<p><b>Copyright information:</b></p><p>Taken from "Influence of continental history on the ecological specialization and macroevolutionary processes in the mammalian assemblage of South America: Differences between small and large mammals"</p><p>http://www.biomedcentral.com/1471-2148/8/97</p><p>BMC Evolutionary Biology 2008;8():97-97.</p><p>Published online 26 Mar 2008</p><p>PMCID:PMC2330041.</p><p></p

Influence of continental history on the ecological specialization and macroevolutionary processes in the mammalian assemblage of South America: Differences between small and large mammals-6

<p><b>Copyright information:</b></p><p>Taken from "Influence of continental history on the ecological specialization and macroevolutionary processes in the mammalian assemblage of South America: Differences between small and large mammals"</p><p>http://www.biomedcentral.com/1471-2148/8/97</p><p>BMC Evolutionary Biology 2008;8():97-97.</p><p>Published online 26 Mar 2008</p><p>PMCID:PMC2330041.</p><p></p

Influence of continental history on the ecological specialization and macroevolutionary processes in the mammalian assemblage of South America: Differences between small and large mammals-7

Not significant.<p><b>Copyright information:</b></p><p>Taken from "Influence of continental history on the ecological specialization and macroevolutionary processes in the mammalian assemblage of South America: Differences between small and large mammals"</p><p>http://www.biomedcentral.com/1471-2148/8/97</p><p>BMC Evolutionary Biology 2008;8():97-97.</p><p>Published online 26 Mar 2008</p><p>PMCID:PMC2330041.</p><p></p

Influence of continental history on the ecological specialization and macroevolutionary processes in the mammalian assemblage of South America: Differences between small and large mammals-2

<p><b>Copyright information:</b></p><p>Taken from "Influence of continental history on the ecological specialization and macroevolutionary processes in the mammalian assemblage of South America: Differences between small and large mammals"</p><p>http://www.biomedcentral.com/1471-2148/8/97</p><p>BMC Evolutionary Biology 2008;8():97-97.</p><p>Published online 26 Mar 2008</p><p>PMCID:PMC2330041.</p><p></p

Macroevolution and climate changes: a global multi-family test supports the resource-use hypothesis in terrestrial mammals

Elisabeth S. Vrba’s resource-use hypothesis suggests that speciation in biomes subjected to successive expansion-contraction-fragmentation during periods of climatic change generates high frequency of species restricted to a single biome (stenobiomic species). We compiled biome occupation for all terrestrial mammals and, using Monte Carlo simulations, demonstrated that patterns of biome occupation are congruent with those predicted by the resource-use hypothesis. Biome specialists are much more speciose than expected by chance, while there are fewer moderate biome generalists than expected. Despite their scarcity, extreme eurybiomic lineages show significant overrepresentation, which suggests they are seldom affected by climate-related extinction processes. Additionally, stenobiomic species are concentrated in biomes placed at the extremes of the climatic gradient, such as equatorial rainforest, subtropical desert, steppe, and tundra. Although this pattern is fairly maintained across different mammalian families, highlighting its universality, our analysis also found great variability. Exceptions to the predictions of the resource-use hypothesis seem to be associated to biome climatic or geographical heterogeneity, which favours vicariance in some biomes not placed in extremes of the climatic gradient (tropical deciduous woodland, sclerophyllous woodland-shrubland), as well as life-history differences across taxa, which generates a stronger trend to specialisation in small body size lineages than in larger mammals