Detection of intra-snacific variations and analysis of nonulation structure in spider mites, using genetic markers

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Two species of spider mites, Tetranychus urticae and T.kanzawai, are both highly polyphagous and occur widely in Japan. This study compared the variation in diapause characteristics of the two species and determined the phylogenetic relationship between the two forms of T.urticae (green and red) and also between those of T.kanzawai (K and T).The diapause of Japanese T.uticae is highly variable and diapause percentage ranged from 100% in the north to nearly zero in southwestern Honshu and Kyushu, but no difference was detected among populations from different host types. On the other hand, T.kanzawai had a strong diapause capacity and populations in the 4 main islands of Japan exhibited nearly 100% diapause. However, diapause percentage drastically decreased in populations from Okinawa Islands. T.kanzawai populations derived from tea had weaker diapause capacity than those derived from herbaceous and deciduous hosts.Analysis of COI gene (mitochondrial cytochrome oxidase subunit I) showed that the two forms of T.urticae were recognized in a single cluster and the existence of haplotypes with phylogenetical divergence suggested that multiple accidental immigrations of the mite had occurred in Japan.The phylogenetic trees constructed using the DNA sequences (COI and ITS1) failed to clearly distinguish between the two types T and K of T.kanzawai. The results suggested that the T types were derived from the K type.