of Gall-Forming Aphids

Gall-forming aphids are highly specific to their host plants, and speciation in galling aphids has pro-ceeded in association with a single species or species group of host plants (primary host). This study firstly aims to revise the associations between galling aphids and their host plants by focus-ing on historical changes in the distribution of host plants. Aphids of the Eriosomatinae are typi-cally associated with the primary and secondary host plants and alternate host plants seasonally, with sexual reproduction on the primary host plant. However, some species are not host-alternating and are wholly parthenogenetic on the secondary host plant. This study secondly aims to test the possibility of long-term persistence of an aphid species by means of parthenogenesis (relict hypothesis). The eriosomatine genus Colopha is a small aphid group represented by three sexual and three asexual species. The sexual species are associated with two Ulmus sister species distrib-uted disjunctly in Europe and eastern North America. In East Asia, an asexual species, Colopha kansugei, is distributed widely on the secondary host. This study tested whether the relict hypothe-sis is applicable to C. kansugei by comparing DNA sequences. A high rate of substitution (3.4 % at the maximum) was found in the mitochondrial COI sequence between local populations. Availabl