Dissertation Research: Aphid Endosymbionts: Their Population Biology and Role in Aphid Adaptation

University Of California-Davis, Davis CA

Investigators

Abstract

Nuzhdin 0073072 Microorganisms play an important role in the biology of many insects, with effects ranging from mutualistic to pathogenic. Bacteria of several types are found in some but not other individual aphids sampled from natural populations. These bacteria are transmitted from mother to daughter, and thus--if they affect the host phenotype--are a source of heritable variation between aphids. The goal of this research is to assess: (a) the transmission of these bacteria, (b) their fitness effects, and (c) their role in aphid adaptation. Specifically, this work will measure variation in the presence of symbionts across aphid populations, their rate of transmission, the heritability of symbiont abundance, and the relationship between symbiont abundance and aphid fitness. A long-term selection experiment will be conducted to investigate the role of symbionts in host plant adaptation. Although heritable microorganisms are commonly found in insects, their effects on host fitness are generally unknown. This study will contribute to understanding the role of such organisms in the biology of aphids, an important insect pest. Additionally, this study is significant and unique in that it uses the aphid-symbiont community as a model for understanding interactions between selection acting at different levels: among aphids with different symbiont communities, and among bacteria within individual aphids.