Numerical Taxonomy Of Rhus Gall Aphids (Hemiptera: Pemphigidae) From East Asia And North America

The Rhus gall aphids (Insecta:Hemiptera:Pemphigidae:Fordinae: Melaphidini) parasitize on the primary host-plant Rhus to form galls known as Woo-pei-tsze or the Chinese gall, which are important medicines and industrial materials. To complete their life cycle, it is necessary for these aphids to shift hosts between the primary (summer) host Rhus species and the secondary (winter) host mosses. Rhus gall aphids include six genera and twelve species, and mainly distribute in East-Asia with only one species Melaphis rhois in North America. So far, there have been some studies on the morphological characteristics and phylogeny of Rhus gall aphids in China, but little attention has been paid to morphological characteristics of the North America species Melaphis rhois and the phylogeny of Rhus gall aphids from both East Asia and North America.In this study, the phylogeny of Rhus gall aphids was examined using morphological characteristics. Based on hierarchical clustering analysis, the numerical taxonomy on 179 individuals from six genera and eight species of Rhus gall aphids was studied. A total of 108 characters belong to external morphology was evaluated from different parts of aphid body, among which 48 characters were directly measured from the alate adults head, thorax and abdomen,31 characters were the ratio from two measured characters, and the rest were numerical values converted from morphological character. The cladistic analysis based on the Euclidean distance showed that the eight Rhus gall aphid species were clustered into three clades, among which the North America species M. rhois was closely clustered with the two species S. peitan and S. chinensis from the genus Schlechtendalia, the two species N. shiraii and N. yanoniella from the genus Nurudea, and F. meitanensis, M. elongallis and two subspecies K. rhusicola ovogallis, K. rhusicola ensigallis from the genus Kaburagia were clustered as a group, respectively. The cladistic analysis based on correlative coefficient showed that the eight Rhus gall aphid species were clustered into three clades, among which M. rhois was clustered with S. peitan and S. chinensis, F. meitanensis, M. elongallis and two subspecies K. rhusicola ovogallis, K. rhusicola ensigallis from the genus Kaburagia were clustered as a group, the two species N. shiraii and N. yanoniella from the genus Nurudea were clustered as a group. In addition, the MP and ML phylogenetic trees based on DNA sequences of the mitochondrial DNA cytochrome C oxidase unit I gene showed the inconsistent clusters with the morphological data. The eight Rhus gall aphid species were clustered into three clades, among which the F. meitanensis and M. elongallis, the two species N. shiraii and N. yanoniella and two subspecies K. rhusicola ovogallis and K. rhusicola ensigallis were clustered as a group, respectively, but the North America species M. rhois was clustered closely with the genera Schlechtendalia in both of the methods. It's still necceasry to do further research on the phylogenetic relationship of the Rhus gall aphids.