In and Out the Amazonia: Evolutionary Ecomorphology in Howler and Capuchin Monkeys

摘要

The impact of environmental variation on phenotypic diversification is one major issue in evolutionary studies. Environmental variation is thought to be a primary factor in evolution, especially at high latitudes. In contrast, tropical areas are traditionally viewed as the cradle where the long-term effects of biological interactions on phenotypic change reside. We analyse patterns of skull shape variation in two New World monkey groups: capuchins and howlers. These two monophyletic clades are exceptionally similar in terms of the geographic distribution of their species. Yet, their body size and diet are different: howler monkeys are large and almost exclusively folivorous, whereas capuchins are small omnivorous. We found that the size, and direction of vectors of phenotypic changes across South American biomes in those clades are not statistically different. This similarity persists after removing the strong impact of allometry in our data. Additionally, partial least squares and comparative analyses confirm that "allometry free"skull shape is influenced to the same set of environmental variables in both clades. This study remarks the paramount importance of both body size and environmental variation on phenotypic evolution.