Quaternary vicariance of Ypthima butterflies (Lepidoptera, Nymphalidae, Satyrinae) and systematics in the Ryukyu Islands and Oriental region

Ypthima ring butterflies fly short distances over grasslands. In spite of their weak flying ability, Ypthima are widely distributed in the Old World tropics extending to temperate regions. Our study provides the first phylogenetic scenario for Ypthima butterflies based on mitochondrial COI, nuclear EF-1 alpha and RpS5 genes. Bayesian inference trees were constructed and calibrated using an assumption of most recent common ancestor (MRCA) expansion due to vicariance at 1.55 Mya (= geologically obtained formative time of the Ryukyu Islands) following the protocol of BEAUti. The trees contain seven clades of the morphological motschuskyi + sordina group which form a polytomy with a single MRCA. These clades are Ypthima multistriata, divided into three main subspecies in Japan, Tsushima-Korea-China and Taiwan, Ypthima akragas on Taiwan highlands, Ypthima riukiuana on Okinawa and Ypthima masakii on Ishigaki-Iriomote, Ryukyu and Ypthima kitawakii + Ypthima phania in Yunnan. These endemic species are characterized by having three ocelli on the ventral surface of the hindwing. The Ypthima tree consists of two major clades (subgena Ypthima and Thymipa primarily with three or four to five ocelli), concordant to a morphology-based cladogram (Shirozu & Shima, 1979; Shima, 1988). The latter five-ocellus subclade of philomela includes the seven-ocellus African genus Ypthimomorpha, hitherto suggested on morphological grounds to be weakly separated from Ypthima.