The Evolutionary Genetics of an Adaptive Maternal Effect: Egg Size Plasticity in a Seed Beetle

适应性母体效应的进化遗传学：种子甲虫的卵大小可塑性

• 批准号: 9807315
• 负责人: Charles Fox
• 金额: $ 22万
• 依托单位: Fordham University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 1998
• 资助国家: 美国
• 起止时间: 1998-08-01 至 1999-08-06
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9807315&HistoricalAwards=false
• 关键词: Evolutionary; Genetics; Adaptive; Maternal; Effect

Fox 9807315 In many organisms, a female's environment provides a reliable indicator of the environmental conditions that her progeny will encounter. In such cases, maternal effects may evolve as mechanisms for trans-generational phenotypic plasticity, whereby, in response to a predictive environmental cue (such high or low host density, short or long photoperiod), a mother can change the type of eggs that she makes, or can program a developmental switch in her offspring, producing offspring prepared for the environmental conditions predicted by the cue. These maternal effects often have a genetic basis, and appear to be adaptive in many organisms. Yet little is understood about the evolutionary genetics of maternal effects or the nature and consequences of selection on maternal effects, such that the potential for them to respond to natural selection remains largely speculative. This proposal describes a series of experiments designed to test hypotheses that explain the evolution of egg size, egg number, and egg size plasticity (an apparently adaptive maternal effect) in a seed beetle, Stator limbatus. Specifically, this research will (1) quantify the sources of this phenotypic variation (genetic, maternal, paternal, and environmental) in egg size and egg size plasticity within populations of S. limbatus; (2) test the hypothesis that selection for improved survivorship when larvae develop on seeds of Cercidium floridum (blue paloverde) results in the evolution of larger egg size; (3) test the hypothesis that selection for increased fecundity results in the evolution of smaller egg size; (4) test the hypothesis that the evolution of egg size plasticity is constrained by the genetic correlation between the size of eggs laid in response to Acacia greggii (catclaw acacia) and the size of eggs laid on C. floridum; (5) test the hypothesis that the genetic correlation across hosts evolves in response to selection on egg size and egg size plasticity. Maternal effe cts are ubiquitous in nature; they are important in generating many of the phenotypic patterns and population dynamics that we observe, and are often important components of population responses to natural selection. In fact, evolutionary responses to selection may be manifest through maternal effects, such that maternal effects may provide mechanisms for adapting to variable environments. However, the evolutionary dynamics of maternal effects, and characters influenced by maternal effects, have been little explored. In lab and field experiments, selection can be demonstrated to favor or oppose the evolution of maternal effects. However, demonstrating selection favoring the evolution of a maternal effect is not sufficient evidence to demonstrate that a maternal effect has evolved as an adaptation. The same rigorous techniques applied to studies of behavior, morphology, and life history need now be applied to the study of maternal effects to determine how pervasive adaptive maternal effects are in nature and how often maternal effects evolve simply as consequences of the evolution of parental and offspring characters. The objectives of these experiments are (a) to study the evolutionary genetics of an adaptive maternal effect (egg size plasticity in the seed beetle, Stator limbatus), using rigorous quantitative genetic experimental designs, and (b) to simulate natural selection on the maternal effect as it is thought to occur in nature to study the evolution of both the maternal effect and correlated life history characters.

狐狸9807315在许多生物体中，雌性动物的环境为其后代将要遇到的环境条件提供了一个可靠的指示器。在这种情况下，母体效应可能演变为跨代表型可塑性的机制，从而响应预测性的环境提示(寄主密度或高或低，光周期或短或长)，母亲可以改变她产生的卵子的类型，或者可以在她的后代中编程发育转换，产生为该提示预测的环境条件准备的后代。这些母性效应往往有遗传基础，而且似乎在许多生物体中是适应的。然而，人们对母性效应的进化遗传学或选择对母性效应的性质和后果知之甚少，因此它们对自然选择做出反应的潜力在很大程度上仍然是推测的。这项建议描述了一系列旨在测试假设的实验，这些假设解释了种子甲虫的卵大小、卵数和卵大小可塑性(一种明显的适应性母体效应)的进化。具体地说，本研究将(1)量化种群内卵子大小和卵子大小可塑性的表型变异(遗传、母本、父本和环境)的来源；(2)检验这样的假设，即当幼虫在百合花种子上发育时，为了提高存活率而选择会导致较大的卵子大小的进化；(3)检验为了增加繁殖力而选择会导致较小卵子大小的进化的假设；(4)检验卵大小可塑性的进化受金合欢(Aacia Greggii)产卵大小与花背金合欢产卵大小之间的遗传相关性的制约；(5)检验寄主间的遗传相关性是根据对卵大小和卵大小可塑性的选择而进化的假设。母体效应在自然界中普遍存在；它们在我们观察到的许多表型模式和种群动态的产生中起着重要作用，并且往往是种群对自然选择的反应的重要组成部分。事实上，对选择的进化反应可能通过母性效应表现出来，这样母性效应可能提供适应不同环境的机制。然而，母性效应的进化动态以及母性效应影响特征的研究很少。在实验室和田间实验中，可以证明选择有利于或反对母体效应的进化。然而，证明选择有利于母性效应的进化并不足以证明母性效应已经进化为适应。应用于行为、形态和生活史研究的同样严格的技术现在需要应用于母体效应的研究，以确定母体效应在自然界中的普遍程度，以及母体效应仅仅作为父母和后代性格进化的结果而演变的频率。这些实验的目的是(A)使用严格的定量遗传实验设计，研究适应性母体效应(种子甲虫的卵大小可塑性)的进化遗传学，以及(B)模拟自然选择对母体效应的影响，以研究母体效应和相关生活史特征的进化。