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，影响范围从互惠到致病。在从自然种群中采样的一些个体蚜虫中发现了几种类型的细菌，但没有发现其他个体的细菌。这些细菌在母亲和女儿之间传播，因此--如果它们影响寄主的表型--是蚜虫之间可遗传变异的来源。这项研究的目的是评估：(A)这些细菌的传播，(B)它们的适合性影响，以及(C)它们在蚜虫适应中的作用。具体地说，这项工作将测量蚜虫种群中共生菌的存在、它们的传播率、共生菌丰度的遗传力以及共生菌丰度与蚜虫适合度之间的关系。为了研究共生体在寄主植物适应中的作用，将进行一项长期的选择实验。虽然可遗传微生物普遍存在于昆虫中，但它们对寄主适合性的影响通常是未知的。这项研究将有助于理解这些微生物在重要害虫--蚜虫生物学中的作用。此外，这项研究具有重要而独特的意义，因为它使用了蚜虫-共生体群落作为一个模型来理解不同水平上的选择之间的相互作用：具有不同共生体群落的蚜虫之间的相互作用，以及个体蚜虫内的细菌之间的相互作用。

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.