| The genus Schiedea (Caryophyllaceae) represents an adaptive radiation of 32 extant species that are endemic to Hawaii. Schiedea species exhibit a wide range of morphologies, breeding systems, and habitats making this an excellent model group for understanding insular evolution, including shifts to different breeding systems in plants. Recent nuclear genealogies inferred for Schiedea conflict with chloroplast histories and suggest past reticulate evolution. In particular, two rare species (S. spergulina and S. stellarioides), which have very different nuclear genealogies come out as sister to each other in the reconstruction of chloroplast histories, suggesting chloroplast introgression and capture. The population structure of both species was examined using nuclear microsatellites, for three populations of S. spergulina and two populations S. stellarioides, which represent the only remaining populations known of these species. Levels of genetic variation in both species are low, and genetic structure and inbreeding coefficient values are consistent with a past population bottleneck in S. stellarioides , which had been thought to be extinct, but was rediscovered on Kauai recently. PCA analyses of microsatellite data indicate that the Lawai Valley population of S. spergulina is well differentiated from other populations of that species on Kauai, which may support previous classifications recognizing the Lawai population as separate variety. Phylogenetic analyses indicate that the Lawai population of S. spergulina has a distinct chloroplast haplotype from populations of S. spergulina found in Waimea Canyon. This result, along with other evidence, could indicate that the Lawai Valley population of S. spergulina is genetically distinct from other populations of S. spergulina in addition to being morphologically and geographically distinct. |
