Microsatellite data from: Multiple colonizations and genetic differentiation from the mainland populations in insular populations of the perennial herb Solidago virgaurea complex (Asteraceae) on recently formed nearshore oceanic islands

Aim: Although the evolution of island endemic plants has long
been investigated, the majority of such studies have focused on species
with remarkable levels of morphological variation and on islands
substantially far from the mainland. Except for a few examples such as the
Canary Islands, endemic plants on nearshore oceanic islands have received
less attention. In this study, we examined the Solidago virgaurea complex
on the Japanese mainland Honshu and the adjacent Izu Islands to
investigate the population genetic structure and dynamics in plants
endemic to nearshore and recently formed oceanic islands.
Location: Japanese mainland Honshu and the adjacent Izu Islands
Taxon: Solidago virgaurea (Asteraceae) Methods: Sixteen
and nine populations of S. virgaurea complex were sampled from the
mainland and islands, respectively; phylogeographic and population
genetics analyses were performed using plastid DNA and nuclear
microsatellite DNA variations. Results: Phylogenetically close
plastid DNA haplotypes were shared between the mainland and islands,
although the populations of S. virgaurea from different islands tended to
exhibit phylogenetically distinct haplotypes. Admixture analyses based on
nuclear DNA variations revealed distinct genetic structures between the
mainland and island populations. Gene flow among islands is restricted but
may partially offset genetic drift on each island. Main
conclusions: The genetic structure observed in this study may not
have originated from a single dispersal event and successive expansion but
rather from at least three colonization events and subsequent gene flow
among island populations. Based on the nuclear DNA variations, the Izu
Island populations of S. virgaurea are genetically distinct from the
mainland ones. Repeated colonization events may have provided sufficient
genetic diversity, which would generally be susceptible to founder effects
and exert a driving force for evolutionary adaptation, to these oceanic
island populations.