Tropical and Subtropical South America: A Study of Community Turnover Across Environmental Gradients

Abstract

The Tropic of Capricorn, at 23 S, delimits the Tropical and Subtropical regions of the Southern hemisphere and marks a transition of diverse climatic variables that affect the distribution of biodiversity in the South American continent. To study the effect of the Tropic in the distribution of species, and to explore how community composition changes southwards, we analyze patterns of beta-diversity across the Neotropical region. Using locality data from GBIF, we show a latitudinal gradient in the degree of species turnover, but only in the cis-Andean region. Although previous taxon-centric analyses detected breakpoints in the components of beta-diversity at the tropical-subtropical transition, we were unable to identify them at large scale and level of data aggregation studied here: there was no single latitude at which a change in the behavior of beta-diversity could be detected. Although the replacement of species is the main component responsible for the changes in the composition of the communities in South America, the Tropic of Capricorn does not seem to represent a threshold in community turnover at this large scale.