Aphids (Hemiptera: Aphididae) are well known as micro-insect pests, which are very specific to their host plants, sucking phloem for acquiring nutrients, and most of them have successfully maintained parthenogenetic generations cyclically or permanently. In the world, the approximately 5,000 described aphid species belong to the family Aphididae, which has taxonomically been subdivided into 27 subfamilies in current. The diversification of host plants, especially angiosperms, has played an important role in their evolution. Major questions about aphid evolution include origins of host alternation as well as age and patterns of diversification in relation to host plants. To address these, I did both macroscale (phylogenetics) and microscale (population genetics) researches on aphids. First I reconstructed the phylogeny of the three major aphid groups, Aphidini, Macrosiphini, and Pterocommatinae, which are the most diverse in the world and constitute more than 60% of the total species. These major lineages demonstrate the evolutionary history of aphids interacting with their host plants. I also used molecular dating method to calculate reasonable divergence time on each clade. Based on phylogenetic and dating analyses, most generic divergences in Aphidinae occurred in the Middle Tertiary when primary hosts, mainly Rosaceae, were diverging, whereas species-level divergences were related with diversification of secondary hosts such as Poaceae in the Middle to Late Tertiary. Most generic divergences in Aphidini occurred in the Middle Tertiary, and species-level divergences occurred between the Middle and Late Tertiary. The divergence times of aphid lineages at the generic or subgeneric levels are close to those of their primary hosts. Second I performed population genetics of the polyphagous cotton-melon aphid, Aphis gossypii Glover. I analyzed population genetic structure between 570 aphids collected from 41 plant species of primary and secondary, mostly wild, hosts using 9 microsatellite loci. As results, population structure of A. gossypii revealed that several genetic affinities in common use of some secondary and primary hosts are detected. Host preference in secondary host is higher than that in primary host, and woody plants share same genetic structure. This species might speciated by the related mechanisms such as host alternation and loss of primary host. I will propose macro- and micro-evolutionary patterns of the Aphidini aphids based on integrating phylogenetic and population genetic approaches

• Hyojoong Kim(Department of Biology, College of Natural Sciences, Kunsan National University)