Breeding system data for populations of T. perfoliata

Both intrinsic and extrinsic forces work together to shape connectivity
and genetic variation in populations across the landscape. Here we
explored how geography, breeding system traits, and environmental factors
influence the population genetic patterns of Triodanis perfoliata, a
widespread mix-mating annual plant in the contiguous US. By integrating
population genomic data with spatial analyses and modeling the
relationship between breeding system and genetic diversity, we illustrate
the complex ways in which these forces shape genetic variation.
Specifically, we used 4,705 single nucleotide polymorphisms to assess
genetic diversity, structure, and evolutionary history among 18
populations. Populations with more obligately selfing flowers harbored
less genetic diversity (π: R2 = 0.63, P = 0.01, n = 9 populations), and we
found significant population structuring (FST = 0.48). Both geographic
isolation and environmental factors played significant roles in predicting
the observed genetic diversity: we found that corridors of suitable
environment appear to facilitate gene flow between populations, and that
environmental resistance is correlated with increased genetic distance
between populations. Last, we integrated our genetic results with species
distribution modeling to assess likely patterns of connectivity among our
study populations. Our landscape and evolutionary genetic results suggest
that T. perfoliata experienced a complex demographic and evolutionary
history, particularly in the center of its distribution. As such, there is
no singular mechanism driving this species’ evolution. Together, our
analyses support the hypothesis that breeding system, geography, and
environmental variables shape the patterns of diversity and connectivity
of T. perfoliata in the US.