Quaternary vicariance of Platypleura (Hemiptera: Cicadidae) in Japan, Ryukyu, and Taiwan Islands

Abstract

There have been no rigorous molecular studies of the Asian Platypleurini cicadas to date. We propose that their history was strongly influenced by Quaternary vicariance. Phylogenetic trees of Platypleura cicadas in the Ryukyu islands and neighbours were reconstructed based on the mitochondrial cytochrome c oxidase subunit 1 (COI) gene (1412 bp), the nuclear 18SrRNA gene (823 bp), and the calmodulin gene (613 bp). A maximum likelihood tree was estimated using raxmlGUI and a Bayesian inference tree of the combined gene data matrix using BEAST. Two morphologically distinguishable groups, one with darker fore wings and one with lighter fore wings, are found among the Platypleura species of the region, and these form monophyletic sister groups in our gene trees. The phylogenetic trees define a polytomy with a single most recent common ancestor (MRCA) for each sister, and calibration was done using the observed MRCAs expansion at 1.55 Mya (= geologically obtained formative time of the Ryukyu islands) following the protocol of BEAUti. The resulting trees contained the following dark-and light-winged clades. The dark-winged clade consists of clade I: Platypleura kaempferi distributed over a wide area encompassing Japan, Tsushima, Korea, China, and northern Tokara; clade II: P. kaempferi on northern Taiwan (Yilan Basin is a barrier for dispersion to southern Taiwan; dark-winged species are lacking on southern Taiwan); and clade III: P. yayeyamana on Ishigaki-jima and Iriomote-jima. The light-winged clade consists of clade IV: P. miyakona on Miyako-jima and Tarama-jima, clade V (sister of clade IV): P. takasagona on whole of Taiwan, clade VI: P. kaempferi on Takara-jima and Amami Oshima, clade VII: P. kaempferi on Tokuno-shima, clade VIII: P. kaempferi on Okinawa-jima, and clade IX (sister of clade VIII): P. kuroiwae extensively dispersed but shallowly differentiated on most of the Amami-Okinawa islands. P. kaempferi on each island are genetically distinct. From our divergence time analyses, we derived estimates of molecular clock rates (mean base substitution rates) for each gene.