Data from: In situ glacial survival maintains high genetic diversity of Mussaenda kwangtungensis on continental islands in subtropical China

Generally, island populations are predicted to have less genetic variation
than their mainland relatives. However, there has been exceptions,
indicating that the relationships were impacted by several factors, e.g
historical processes. In the present study, we chose a group of
subtropical islands located in South China as the study system, which are
quite younger and much closer to the mainland than most of the previous
studied island systems, to test the hypothesis that in situ glacial
survival contributes to high levels of genetic diversity in island
populations. We conducted a comparison of genetic variation between 12
island and 11 nearby mainland populations of Mussaenda kwangtungensis
using eleven nuclear microsatellite and three chloroplast markers,
evaluated effects of the island area and distance to mainland on genetic
diversity of island populations, and simulated the potential distribution
over the past by ecological niche modelling, together with the genetic
data to detect the role of islands during the glacial periods. The island
populations displayed comparable levels of genetic diversity and
differentiation with mainland populations, overall high levels of unique
polymorphisms, and the greatest values of specific within-population
genetic diversity. No significant correlation was detected between genetic
diversity of island populations and distance to mainland, as well as area
of islands, except that allelic richness was significantly positively
correlated with the area of islands. Nuclear microsatellites revealed two
main clusters, largely corresponding to islands and inland populations,
which divergence dated to a time of island formation by ABC analysis.
Ecological Niche Modelling predicted a highly climatic suitability on
islands during the Last Glacial Maximum (LGM). Our results suggest that
the islands have acted as refugia during the LGM and highlight the role of
in situ glacial survival in maintaining high levels of genetic diversity
of M. kwangtungensis in continental islands of subtropical China.