Investigating the role of drift and selection on the population differentiation of the Pitcairnia lanuginosa complex (Bromeliaceae) using RAD-seq

Both genetic drift and divergent selection are predicted to be drivers of population differentiation across patchy habitats, but the extent to which these forces act on natural populations to shape traits is strongly affected by species' ecological features. In this study, we infer the genomic structure of Pitcairnia lanuginosa, a widespread herbaceous perennial plant with a patchy distribution. We sampled populations in the Brazilian Cerrado and the Central Andean Yungas and discovered and genotyped SNP markers using double-digest restriction-site associated DNA sequencing. In addition, we analyzed ecophysiological traits obtained from a common garden experiment and compared patterns of phenotypic and genetic divergence (PST-FST comparisons) in a subset of populations from the Cerrado. Specifically, we aimed to: (1) investigate whether the presumed low effective population sizes resulting from isolation and high levels of inbreeding could preclude local adaptation for ecophysiological traits linked to drought, heat, and light stress in this species; (2) assess the relative importance of Isolation by Distance (IBD) and Isolation by Environment (IBE) on the patterns of genetic structure in this species. The wide yet patchy distribution in the Neotropics makes P. lanuginosa a particularly interesting model to investigate how ecological processes affect local adaptation. The information on the genomic and trait variation in this species may thereby shed light on eco-evolutionary processes acting on non-continuously distributed species.