Comparative phylogeography of bromeliad species: effects of historical processes and mating system on genetic diversity and structure

Abstract

A fundamental challenge in population genetics is to understand the role of ecological and historical processes in shaping genetic diversity patterns within and among species. Based on a set of nuclear microsatellite loci, we conducted a comparative study of the genetic diversity and structure of two epiphytic plant species: Vriesea simplex and V. scalaris (Bromeliaceae), endemic to the Brazilian Atlantic Rainforest. The results showed contrasting genetic diversity and structure patterns according to variation in reproductive systems of these species. High genetic diversity, high effective population sizes and low genetic differentiation were observed in the mainly outcrossing V. simplex populations. In contrast, low genetic diversity, low effective population sizes and high genetic differentiation were detected in the mainly selfing V. scalaris populations. Accordingly, the isolation-by-distance indicated stronger population structures in V. scalaris than in V. simplex. Both species showed a similar phylogeographic north-south split across the Atlantic Rainforest, suggesting possible multiple refugia in this biome. Historical climatic changes during the Pleistocene were possible determinants of the genetic diversity and structure of these species in the Atlantic Rainforest. Divergent mating systems (selfing vs. outcrossing), genetic drift and colonization history influenced the genetic diversity and structure of these Neotropical plant species.