Phylogenetic Relationships among Populations of Portulaca okinawensis (Portulacaceae) in the Ryukyu Archipelago of Japan Using MIG-seq SNP Data

Abstract

We conducted phylogenetic analyses using multiplexed inter simple sequence repeat genotyping by sequencing (MIG-seq) to clarify the phylogenetic relationship among populations of Portulaca okinawensis var. okinawensis and P. okinawensis var. amamiensis. The analyses supported the monophyly of the two varieties. For P. okinawensis var. okinawensis distributed in the Okinawa island group, our results suggest that the phylogenetic separation of plants collected in Tonaki Island from those collected in other islands might be a result of the geographic isolation between Tonaki Island and other islands. With respect to P. okinawensis var. amamiensis distributed in the Amami island group, plants collected in western Amami Island were phylogenetically separated from those collected in the north part of Amami Island and the remaining islands. This phylogenetic separation may suggest some sort of environmental factors that isolate the former area from the others, that looks consistent with the presence of several relictual deciduous tree species in the western part as a refugium.