title: Tight species cohesion among sympatric insular wild gingers (Asarum spp. Aristolochiaceae) on continental islands: Highly differentiated floral characteristics versus undifferentiated genotypes.
abstract: The Amami Island group of the Ryukyu Archipelago, Japan, harbors extensive species diversity of Asarum in a small landmass. The fine-scale population genetic structure and diversity of nine insular endemic Asarum species were examined using nuclear DNA microsatellite loci and ITS sequences. High population genetic diversity (HS = 0.45-0.79) was estimated based on the microsatellites, implying outcrossing of Asarum species within populations accompanied by inbreeding. Bayesian clustering analyses revealed that species were divided into three robust genetic clusters and that the species within each cluster had a homogeneous genetic structure, indicating incomplete lineage sorting. This conclusion was supported by an ITS phylogeny. The degree of genetic differentiation among species was very low both within and between clusters (FST = 0.096-0.193, and 0.096-0.266, respectively). Although species can be crossed artificially to produce fertile hybrids, our results indicate that there is very little evidence of hybridization or introgression occurring among species in the wild, even within stands composed of multiple sympatric species. The highly differentiated floral morphology of the studied species is likely to impose reproductive isolation between them and maintain their integrity in the wild. A lack of genetic differentiation between sympatric species suggests that speciation within this group occurred rapidly and recently.
authors.affiliation: Graduate School of Human and Environmental Studies, Kyoto University, Yoshida Nihonmatsu-cho, Sakyo-ku, Kyoto, Japan.
authors.forename: Junshi
authors.initials: J
authors.lastname: Matsuda
authors.affiliation: Faculty of Science, Kagoshima University, Kagoshima, Japan.
authors.forename: Yoshiyuki
authors.initials: Y
authors.lastname: Maeda
authors.affiliation: Kyoto Botanical Garden, Shimokamo Hangi-cho, Sakyo-ku, Kyoto, Japan.
authors.forename: Junichi
authors.initials: J
authors.lastname: Nagasawa
authors.affiliation: Graduate School of Human and Environmental Studies, Kyoto University, Yoshida Nihonmatsu-cho, Sakyo-ku, Kyoto, Japan.
authors.forename: Hiroaki
authors.identifier: http://orcid.org/0000-0003-0808-7502
authors.initials: H
authors.lastname: Setoguchi
mesh_terms: D044822:Biodiversity; D035264:Flowers / Q000502:physiology*; D017343:Genes, Plant; D020939:Zingiber officinale / Q000145:classification* / Q000235:genetics; D007564:Japan; D010802:Phylogeny; D013045:Species Specificity