Data from: The contribution of hybridization to range‐wide population genetic structure in a Pacific coastal dune plant

Premise of the study: Interspecific hybridization can cause genetic
structure across species ranges if the mating system and degree of
sympatry/parapatry with close relatives varies geographically. The coastal
dune endemic Camissoniopsis cheiranthifolia (Onagraceae) exhibits genetic
subdivisions across its range, some of which are associated with shifts in
mating system from outcrossing to selfing, while others are not. For
instance, strong differentiation between large-flowered, self-incompatible
(LF-SI) and large-flowered, self-compatible (LF-SC) populations occurs
without much reduction in outcrossing or obvious barriers to gene flow. We
hypothesized that LF-SI diverged from LF-SC via hybridization with the
predominantly inland SI sister species C. bistorta. Methods: We analyzed
spatial proximity using 1460 herbarium records, and genetic variation at
12 microsatellites assayed for 805 and 404 individuals from 32 C.
cheiranthifolia and 18 C. bistorta populations, respectively. We also
assayed nine chloroplast microsatellites for 124 and 111 individuals from
27 and 19 populations, respectively.  Key results: Closer
parapatry was associated with unexpectedly high genetic continuity between
LF-SI C. cheiranthifolia and C. bistorta. LF-SI genotypes clustered with
C. bistorta exclusive of other C. cheiranthifolia genotypes. Similarly,
pairwise FST among SI C. cheiranthifolia and C. bistorta, adjusted for
geographic proximity, was not higher between heterospecific than
conspecific populations.  Conclusions: The lack of genetic
differentiation between LF-SI C. cheiranthifolia and C. bistorta
populations, even those located away from the zone of parapatry, suggests
that LF-SI C. cheiranthifolia instead of hybridizing with C. bistorta is
rather an ecotype of C. bistorta that has adapted to coastal dune habitat
independent of other lineages in C. cheiranthifolia proper.