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



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Moreno Bofarull, Ana and Arias Royo, Antón and Hernández Fernández, Manuel and Ortiz Jaureguizar, Edgardo and Morales Romero, Jorge (2008) Influence of continental history on the ecological specialization and macroevolutionary processes in the mammalian assemblage of South America: Differences between small and large mammals. BMC evolutionary biology, 8:97 . pp. 1-18. ISSN 1471-2148

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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.

Item Type:Article
Uncontrolled Keywords:Mammalian; South America;
Subjects:Sciences > Geology > Paleontology
Medical sciences > Biology > Mammals
ID Code:12245
Deposited On:15 Feb 2011 12:31
Last Modified:11 Dec 2018 08:42

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