| Summary: | Trabajo presentado en el 5th International Palaeontological Congress, celebrado en París (Francia) del 9 al 13 de julio de 2018 With a current diversity approaching 300 species, squirrels have conquered all the world’s biomes and almost all the continents (except Antarctica and Australia) since their origin in the Eocene, which makes them an exceptional group for studying ecological preferences evolution. Therefore, we performed a multifossil-calibrated phylogenetic tree including 229 species of Sciuridae (Rodentia, Mammalia) and we calculated the diversification rates. Then, we tested one of the predictions of the resource-use hypothesis proposed by E.S. Vrba, which foretells that generalist species have lower diversification rates than specialist species due to a better adaptive capacity during an environmental change episode. We compared speciation rates between biome specialists (stenobiomic species) and biome generalists (eurybiomic species) using a Multiple State ’Speciation’ and Extinction model (”MuSSE”) in R. We considered three groups relaying on the biomic specialization index (BSI), which is based on the number of biomes occupied by each species: specialists (BSI = 1), generalists (BSI between 1 and 5) and extreme generalists (BSI≥5). Furthermore, we performed an ancestral reconstruction of biomic specialization in the phylogenetic tree. Our results are consistent with the predictions of the resource-use hypothesis, which predicts a higher speciation rate of lineages restricted to a single biome (specialists) than lineages which occupied several biomes (generalists). Additionally, we found that the biomes with higher proportions of specialist species are the tropical rainforest (I) with around 36% of species restricted to this biome and the steppes and cold-deserts (VII) in which inhabit 24 stenobiomic species (32.4%). This is also congruent with the resource-use hypothesis, which predicts higher specialization of species inhabiting biomes that underwent a high degree of fragmentation and ...
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