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

微生物在许多昆虫的生物学中起着重要的作用，其作用从共生到致病不等。从自然种群中取样的蚜虫个体中发现了几种类型的细菌，而不是其他类型的。这些细菌从母体传给子代，因此——如果它们影响宿主的表型——是蚜虫之间遗传变异的一个来源。本研究的目的是评估：(a)这些细菌的传播，(b)它们的适应性效应，以及(c)它们在蚜虫适应中的作用。具体来说，这项工作将测量蚜虫种群中共生体存在的变化，它们的传播率，共生体丰度的遗传力，以及共生体丰度与蚜虫适合度之间的关系。通过长期的选择实验来研究共生体在寄主植物适应中的作用。虽然可遗传的微生物在昆虫中普遍存在，但它们对宿主适应性的影响通常是未知的。这项研究将有助于了解这些生物在蚜虫生物学中的作用。此外，本研究的重要和独特之处在于，它使用蚜虫-共生体群落作为模型来理解不同水平选择之间的相互作用：具有不同共生体群落的蚜虫之间，以及单个蚜虫内部的细菌之间。

Nuzhdin0073072Microorganisms play an important role in the biology of many insects, witheffects ranging from mutualistic to pathogenic. Bacteria of several typesare found in some but not other individual aphids sampled from naturalpopulations. These bacteria are transmitted from mother to daughter, andthus--if they affect the host phenotype--are a source of heritable variation between aphids. The goal of this research is to assess: (a) thetransmission of these bacteria, (b) their fitness effects, and (c) theirrole in aphid adaptation. Specifically, this work will measure variation inthe presence of symbionts across aphid populations, their rate oftransmission, the heritability of symbiont abundance, and the relationshipbetween symbiont abundance and aphid fitness. A long-term selectionexperiment will be conducted to investigate the role of symbionts in hostplant adaptation.Although heritable microorganisms are commonly found in insects, theireffects on host fitness are generally unknown. This study will contributeto understanding the role of such organisms in the biology of aphids, animportant insect pest. Additionally, this study is significant and uniquein that it uses the aphid-symbiont community as a model for understanding interactions between selection acting at different levels: among aphidswith different symbiont communities, and among bacteria within individualaphids.