Population genetic structure of the South American species Hypochaeris lutea (Asteraceae)

Abstract

The genus Hypochaeris has a recent evolutionary history caused by long-distance dispersal in conjunction with adaptive radiation in the South American continent. Hypochaeris lutea is a perennial herb that grows mostly at altitudes of around 1000m in cold swamps of the southern regions of Brazil. We investigated the amplified fragment length polymorphism (AFLP) in 270 individuals representing 11 Brazilian populations of H.lutea to elucidate the population genetic structure of this species. The frequencies of polymorphic loci and gene diversity ranged from 83.42% to 91.66% and from 0.26 to 0.34, respectively. Analysis of molecular variance revealed that most of the genetic variability was found within (76.67%) rather than among (23.3%) populations, agreeing with the pattern of genetic distribution within and among populations observed in other allogamous species of Hypochaeris. A Mantel test showed no correlation between genetic and geographic distances when all populations were considered. Simulations performed using a Bayesian approach consistently identified two clusters with different admixture proportions of individuals, as also revealed by a UPGMA dendrogram of populations. The pattern of genetic structure observed in H.lutea is consistent with a process of successive colonization events by long-distance dispersal resembling the rapid and recent radiation that has been proposed to explain the origin of the South American species of Hypochaeris.