Landscape genetics reveal low diversity and adaptive divergence in Portulaca hatschbachii (Portulacaceae): an endangered species endemic to rocky outcrops of the Atlantic Forest

Abstract

Abstract Portulaca hatschbachii is endemic to the basaltic rocky outcrops that are distributed, in a discontinuous way, along the Third Plateau of Paraná State, Brazil, composing environments that form the Subtropical Highland Grasslands of the Atlantic Forest Biome. Considering the risk of extinction of the species and the massive anthropization of these outcrops, we applied AFLP, ITS and rps16 molecular markers in ten populations throughout the area of occurrence of the species to generate information about the genetic status of P. hatschbachii and contribute to the development of conservation strategies. Low rates of genetic diversity, high population structure, restricted gene flow and the presence of diversifying selection were observed for the populations. The analysis of variation partitioning (R2adj. = 63.60%) showed that environmental variables have a greater influence on the distribution of variation of loci under selection (R2adj. = 26.70%) than geographical isolation (R2adj. = 1.20%). The strong population structure, for both neutral and selected loci, suggests an isolation by adaptation mechanism (IBA) occurring in populations and highlights the need and urgency for in situ conservation plans for the species and its occurrence on rocky outcrops.