Population genetic and environmental data for Chamaecrista fasciculata

Chamaecrista fasciculata is a widely distributed, phenotypically variable
species in the eastern U.S. Whereas studies have demonstrated genetic
structure and local adaptation in northern areas of its distribution,
there has been no comparison of genetic variability among populations at
the southern extent where phenotypic variation is more complex. We
characterized genetic variation at 14 microsatellite loci for populations
in Mississippi and Alabama and compared this to variation in a phenotypic
trait, leaf pubescence. Geographic distance, climatic variables, and
elevation were evaluated as factors to explain the observed patterns of
genetic diversity. A significant amount of variation (19%) resided among
populations, but most variation (68%) was among individuals. Assignment of
individuals into genetic groups suggests two primary clusters, but these
groups are not concordant with known geographical or ecological breaks,
nor phenotypic variants. Genetic structure at a regional scale can be
characterized as isolation by distance, while environmental factors may
play a secondary role in limiting gene flow at local scales. Mean
population FST is strongly associated with allelic diversity and
heterozygosity, suggesting that genetic drift influences population
variation. Despite the presence of genetic and phenotypic variation in
southern populations of C. fasciculata, the lack of concordant patterns
between these types of variation indicate that they are not driven by the
same factors. This study demonstrates how local factors differentially
influence the maintenance of intraspecific variation and suggest the
southern distributional range is an active area of evolution for C.
fasciculata