Aphid is relatively young group among insects, which radiated contemporaneously with the host plants in angiosperm. Based on recent molecular phylogenetic studies, the tribe Aphidini has been strongly suggested as a primitive group sister to two other tribes, Macrosiphini and Pterocommatini, in the subfamily Aphidinae which is most diversified aphid group. These ideas have been proposed due to the phylogenetic relationships between the groups and the relatively simple morphological characters. Our study is aimed to confirm the evolutionary process of this primitive group in order to understand the diversification of the modern aphids.
Firstly, we obtained the phylogenetic relationships for 59 ingroup species plus 10 outgroup species (6 macrosiphine species, 1 hormaphidine species, and 3 adelgids) based on the combined sequences (2,899 bp) of three mitochondrial genes (COI, COII, CytB) and one nuclear gene (EF1α). The optimal tree topology is obtained by the ML analysis in GARLI 0.95b with Kishino-Hasegawa and Shimodaira-Hasegawa tests in PAUP*4b10, and the posterior probabilities on each node were estimated by MrBayes 3.1.1 under the best fit model (GTR+I+G) tested by MrMODELTEST 3.0. Then, the node ages of the obtained tree were calibrated using the relaxed-clock model implemented in BEAST 1.4.8 and its package programs based on one node fixation of 150 MYA (million years ago) for Aphididae+Adelgidae, and two node constraints as 80-100 MYA for Aphididae crown and 50-70 MYA for Aphidinae crown according to the fossil related publications.
As results, we found four major facts on their evolution: 1) Aphidini radiated from the early Eocene in the Tertiary, 2) however, most lineages rapidly radiated during the late Eocene, 3) common ancestor of the subtribe Aphidina maybe fed on herbs or shrubs in asterids, 4) host alternation trait was lately acquired on Rosaceae- or Rhamnaceae-feeding aphids.

• Hyojoong Kim(Lab. of Insect Biosystematics, Department of Agricultural Biotechnology, Research Institute for Agriculture and Life Sciences, Seoul National University)
• Seunghwan Lee(Lab. of Insect Biosystematics, Department of Agricultural Biotechnology, Research Institute for Agriculture and Life Sciences, Seoul National University)