Microsatellite Markers Reveal Genetic Differentiation of an Invasive Mulberry, Morus australis Poir. (Moraceae), among the Island Groups in Japan and its Introduction to the Ogasawara Islands

Abstract

Invasive alien species are serious threats to the biota of the Ogasawara Islands, and Morus australis is one of them. To clarify the invasion routes and the genetic composition of the founding populations, plant samples were collected from 32 populations of M. australis from Japan, including 12 from the Ogasawara Islands, for population genetic analyses using 14 microsatellite markers. The UPGMA dendrogram based on Nei’s genetic distance, Principal Coordinate Analysis based on pairwise FST values, and Bayesian Clustering using STRUCTURE software indicated that the populations of M. australis in the Ogasawara Islands are genetically similar to those in the Ryukyu Islands, but clearly differentiated from those in the Izu Islands and mainland of Japan. The level of genetic diversity in the Ogasawara Islands (AR = 4.24; HE = 0.60) was similar to that in the Ryukyu Islands (AR = 4.70; HE = 0.66). The findings from this study strongly suggested that M. australis plants now in the Ogasawara Islands are descendants of those introduced from the Ryukyu Islands; the numbers of transplanted individuals from the Ryukyu Islands were large. Such high genetic diversity may have enhanced the invasiveness of M. australis in the Ogasawara Islands.