Comparative population genomics in two sympatric species of Strophostyles (Fabaceae) with contrasting life histories

PREMISE OF THE STUDYLife history is an important predictor of population genetic variation, although this link remains unexplored in numerous important plant lineages. One such lineage is the legume genus Strophostyles, which contains both annual and herbaceous perennial vines native to eastern North America. Specifically, it remains to be determined whether Strophostyles species with different life histories show different patterns of genetic differentiation and diversity, as well as if these species hybridize across their range. METHODSHere we sampled the perennial Strophostyles helvola and annual S. leiosperma in five sites across a latitudinal transect in the central United States, including three sites where the species occur in sympatry. Using genotyping-by-sequencing, we identified 5556 polymorphic SNPs across 166 individuals. KEY RESULTSThere is no evidence that Strophostyles helvola and S. leiosperma hybridize in the populations examined. Within species, Strophostyles helvola (perennial) displays admixture among populations, while S. leiosperma (annual) does not, although both species show more genetic diversity among rather than within populations. Patterns of genetic diversity are varied across populations of both species, with both heterozygote excess and deficiency. CONCLUSIONSThe complex patterns of genetic differentiation and diversity warrant further investigation of life history and population dynamics in Strophostyles, particularly mating system and modes of gene flow. This study exemplifies the diversity of population genetic patterns even within a small genus, and it reinforces the need to characterize such diversity in non-model systems to gain a more complete understanding of how life history contributes to population genetics.