Isolation-by-ecology in a Neotropical savanna tree

Although spatial analysis of population genetic structure has been one of the most important ways to infer microevolutionary processes, these studies are usually focused on neutral dynamics and limited dispersal, interpreted under the theoretical reasoning of isolation-by-distance. More recently, however, there has been a growing interest on how environmental variation is also involved in population differentiation, both by direct effects of local adaptation and other processes related to environmentally or ecologically constrained dispersal. Here we evaluated patterns of genetic population structure and isolation-by-ecology, or environment (IBE), in Eugenia dysenterica DC (Myrtaceae), a fruit tree species of economic potential interest and widely distributed throughout the Central Brazil and endemic to the Cerrado biome (Neotropical savannas). We analyzed population structure using nuclear SSR markers for 736 individuals sampled from 23 localities (local population) and disentangled the effects of genetic molecular variation, estimated by pairwise F-ST (matrix G) and geographical distances (matrix S) into Grinnelian niche of populations (matrix E), based on climate and soil data. Spatial patterns in eigenvectors of G and E reveal northwest-southeast gradients, coherent with geographic range shifts after the Last Glacial Maximum. We used different forms of Mantel regression and correlation and redundancy analyses, as well as simulations of isolation-by-distance, to show that there is a significant partial correlation between G and E taking S into account, thus supporting the IBE process for E. dysenterica, in addition to other processes related to spatially constrained gene flow.

Automated summary

This study evaluated the genetic population structure of a fruit tree species in Central Brazil and found a significant correlation between genetic variation and environmental factors, supporting the involvement of environment in population differentiation.