Landscape and climatic features drive genetic differentiation processes in a South American coastal plant

Abstract

<jats:title>ABSTRACT</jats:title><jats:sec><jats:title>Background and aims</jats:title><jats:p>Historical and ecological processes shaped the patterns of genetic diversity in plant species; among these, colonization to new environments such as coastal regions generate multiple signals of interest to understand the influence of landscape features on the population differentiation.</jats:p></jats:sec><jats:sec><jats:title>Methods</jats:title><jats:p>We analysed the genetic diversity and population structure of <jats:italic>Calibrachoa heterophylla</jats:italic> to infer the influence of abiotic landscape features on this coastal species’ gene flow in the South Atlantic Coastal Plain (SACP). We used ten microsatellite loci to genotype 253 individuals from 15 populations, covering the species’ entire geographical range. We applied population genetics analyses to determine population diversity and structure along the SACP, migration model inference and correlative analyses to disentangle the most likely drivers of gene flow in the SACP.</jats:p></jats:sec><jats:sec><jats:title>Key Results</jats:title><jats:p>The <jats:italic>C. heterophylla</jats:italic> populations located more distantly from the seashore showed higher genetic diversity than those closer to the sea. The genetic differentiation had a consistent signal of isolation-by-distance. Landscape features, such as water bodies and wind corridors, and raw geographical distances equally explained the genetic differentiation, whereas the precipitation seasonality showed a strong signal for isolation-by-environment in marginal populations. The estimated gene flow suggested that marginal populations had restricted immigration rates, which could enhance the genetic differentiation.</jats:p></jats:sec><jats:sec><jats:title>Conclusions</jats:title><jats:p>The influence of topographical features in population differentiation in <jats:italic>C. heterophylla</jats:italic> is related with the history of the coastal plain deposition. Gene flow is mainly restricted to nearby populations and facilitated by wind fields but with no apparent influence of large water bodies. Furthermore, differential rainfall regimes in marginal populations can promote local genetic differentiation.</jats:p></jats:sec>