Genetic Variations in Platypus quercivorus Populations Inhabiting the Izu, Tsushima, Shodoshima, and Shikoku Islands

Abstract

The Japanese populations of Platypus quercivorus, the oak ambrosia beetle, are classified into two groups, namely groups A and B. These are based on the molecular sequence of D1-D2 segments of 28S ribosomal DNA, and each group consists of several sequence types. The sequence types were determined for beetles collected from Izu (Hachijo, Mikura, and Miyake), Tsushima, Shodoshima, and Shikoku islands, where Japanese oak wilt disease has been reported recently. Beetle populations from Hachijo, Shodoshima, and Tokushima (Shikoku) belonged to types 4c-e of group B, whereas those from Mikura, Miyake, Tsushima, and Kochi (Shikoku) belonged to types 1a-d of group A. The sequence types newly recognized in this study are not considerably different from previously reported types, and the previously described sequence types from the Ryukyu islands were not detected. The distribution pattern observed in the present study was found to be consistent with the results of previous studies. Because of the recent expansion of the P. quercivorus population, further sequence type analyses as well as disease monitoring are necessary to understand their population structure and for effective disease control.