Data from: Sporadic genetic connectivity among small insular populations of the rare geoendemic plant Caulanthus amplexicaulis var. barbarae (Santa Barbara Jewelflower)

Globally, a small number of plants have adapted to terrestrial
outcroppings of serpentine geology, which are characterized by soils with
low levels of essential mineral nutrients (N, P, K, Ca, Mo) and toxic
levels of heavy metals (Ni, Cr, Co). Paradoxically, many of these plants
are restricted to this harsh environment. Caulanthus ampexlicaulis var.
barbarae (Brassicaceae) is a rare annual plant that is strictly endemic to
a small set of isolated serpentine outcrops in the coastal mountains of
central California. The goals of the work presented here were to 1)
determine the patterns of genetic connectivity among all known populations
of Caulanthus ampexlicaulis var. barbarae, and 2) estimate contemporary
effective population sizes (Ne), in order to inform ongoing genomic
analyses of the evolutionary history of this taxon, and to provide a
foundation upon which to model its future evolutionary potential and
long-term viability in a changing environment. Eleven populations of this
taxon were sampled, and population-genetic parameters were estimated using
11 nuclear microsatellite markers. Contemporary effective population sizes
were estimated using multiple methods and found to be strikingly small
(typically Ne < 10). Further, our data showed that a substantial
component of genetic connectivity of this taxon is not at equilibrium, and
instead showed sporadic gene flow. Several lines of evidence indicate that
gene flow between isolated populations is maintained through long-distance
seed dispersal (e.g. > 1 km), possibly via zoochory.