Recent origin and adaptive diversification of <Emphasis Type="Italic">Ainsliaea</Emphasis> (Asteraceae) in the Ryukyu Islands: molecular phylogenetic inference using nuclear microsatellite markers |
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Authors: | Yuki Mitsui Hiroaki Setoguchi |
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Institution: | (1) Faculty of Agriculture, Tokyo University of Agriculture, Funako 1737, Atsugi Kanagawa, 243-0034, Japan;(2) Graduate School of Human and Environmental Studies, Kyoto University, Yoshida Nihonmatsu-cho, Sakyo-ku, Kyoto 606-8501, Japan |
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Abstract: | We investigated the phylogeny and phylogeography of four closely related Ainsliaea species (Asteraceae) on the continental Ryukyu Islands of eastern Asia, which consist of two flood-adapted “rheophyte” and
two non-rheophyte (inland) species, based on 12 nuclear microsatellite loci. Phylogenetic analyses using 420 individuals from
26 populations showed that rheophytic A. linearis and A. oblonga are genetically distinct. Each species was clustered with the inland species that occur on the same islands, suggesting a
different ancestry for the two rheophytes that evolved independently by local adaptation to flooded habitats. The results
from the neighbor-joining clustering and principal coordinate analysis (PCoA) indicate that the southern populations of A. macroclinidioides are distinct lineages and ancestral to the northern populations as well as the other diverse species complex in the Ryukyus.
These results suggest a pattern of colonization initially from the Asian mainland to the southern islands, followed by the
northern islands via land bridges generated during the Quaternary glaciations. After isolation from southern populations,
species radiation and regional differentiation within the northern clade occurred possibly via local adaptation and/or geographic
isolation of the subdivided island bridge. |
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