Career: Developmental Tradeoffs and Host Race Formation in Rhagoletis Pomonella

9508559农民和种群生物学家都感兴趣的是粉翅蝇Rhagoltis pomonella。这些苍蝇不仅是苹果的主要经济害虫，而且可能还在物种形成过程中。虽然蓬蒙氏杆菌通常被称为“苹果蝇”，但苹果并不是这些苍蝇的原生寄主植物。这一荣誉属于山楂(山楂)。19世纪中期，纽约哈德逊河谷地区的部分波蒙氏菌种群从山楂转移到苹果上，作为一种新的寄主植物开始攻击苹果。从那时起，侵染苹果的蓬蒙氏菌种群已经蔓延到美国东部，最近又被引入加利福尼亚州、俄勒冈州和华盛顿州。遗传研究表明，苹果种群和山楂种群是部分分离的实体。6个基因在苹果和山楂果蝇小种之间持续表现出频率差异。这些研究表明，树蝇在专攻新寄主植物的过程中可能是共生的(即没有地理隔离)。拟议研究的目标有两个：1)为了确定波蒙氏菌是如何适应其生活史的，使其能够成功地攻击苹果作为新的寄主植物。2.)以确定这种生活史上的变化在将苹果与果蝇的山楂小种分开方面所起的作用。由于苹果小实蝇一年只有一代，成虫寿命只有一个月左右，因此苹果小实蝇和山楂小实蝇都面临着与各自寄主植物的发育相匹配的巨大选择压力。为了验证这一假设，费德博士将在实验室对果蝇的饲养条件进行操控，以在寄主种族之间不同的六个遗传标记上引发与环境相关的变化。实际上，他将试图通过选择山楂果蝇来从基因上将山楂寄主种族转变为苹果小种(反之亦然)，就像它们用苹果的早期物候来侵扰果树一样。我们将从拟议的研究中学到什么？首先，这些实验将阐明庞氏杆菌是否以及如何改变了它的生活史，使其能够攻击苹果。其次，研究结果将明确哪些环境因素是庞氏杆菌成功转移宿主所要克服的最重要的因素。通过随后测量这些因素在田间的作用强度，将有可能衡量寄主相关选择在繁殖分离苹果和适应苹果红假单胞菌的发育性状方面的有效性。这些信息将有助于我们制定新的措施来控制苹果蝇和其他果蝇害虫。这一结果还将帮助我们预测哪些作物可能容易受到树梢蛾的攻击，因为这种害虫会蔓延到美国新的水果种植区。费德博士还坚定地致力于将种群生物学的知识传授给其他人。这笔职业资助金也将使他能够继续追求他的教学兴趣。他将在本科生和研究生阶段教授一系列三门课程，让学生了解构成种群生物学和系统学这一研究和其他研究的基础的一般原则和概念。

9508559 FEDER The Tephritid fly Rhagoletis pomonella is of interest to both farmers and population biologists alike. Not only are these flies major economic pests of apples, but they may also be in the process of speciating. Although R. pomonella is commonly referred to as the "Apple Maggot", apples are not the native host plant of these flies. That distinction belongs to hawthorns (thornapples). In the mid-1800's a portion of the R. pomonella populations in the Hudson Valley region of New York shifted from hawthorns and started attacking apples as a new host plant. Since then, apple-infesting populations of R. pomonella have spread across the eastern United States and have recently been introduced into California, Oregon and Washington. Genetic studies indicate that apple and hawthorn populations of R. pomonella are partially isolated entities. Six genes consistently display frequency differences between the apple and hawthorn fly races. These studies suggest that Rhagoletis flies may speciate sympatrically (i.e. without geographic isolation) in the process of specializing on new host plants. The goals of the proposed research are two-fold:1.) To ascertain how R. pomonella has adapted its life history to allow it to successfully attack apples as a new host plant. 2.) To determine the role that such changes in life history play in isolating apples from hawthorn races of the fly. Because R. pomonella flies have only one generation per year and adults live for only about a month, there is strong selection pressure on apple and hawthorn flies to match their development to that of their respective host plants. To test this hypothesis, Dr. Feder will manipulate rearing conditions for flies in the laboratory to induce environment dependent changes at the six genetic markers differing between the host races. In effect, he will be attempting to genetically transform the hawthorn host race into the apple race (and vice-versa) by selecting on hawthorn flies as if they were infesting f ruits with the earlier phenology of apples. What will we learn from the proposed research? First, the experiments will elucidate whether and how R. pomonella has altered its life history so that it can attack apples. Second, the results will pinpoint which environmental factors are most important for R. pomonella to overcome in a successful host shift. By subsequently measuring the intensity with which these factors act in the field, it will be possible to gauge how effective host-associated selection is at reproductively isolating apple and of the development traits adapting R. pomonella to apples. Such information will aid us in devising new measures to control the Apple Maggot and other fruit fly pests. The results will also help us predict what crops are potentially vulnerable to attack by Rhagoletis, as this pest spreads into new, fruit growing regions of the United States. Dr. Feder also has a strong commitment to transfer knowledge of population biology to others. This CAREER grant will also allow him to continue to pursue his teaching interest. He will teach a series of three classes at the undergraduate and graduate levels, exposing students to the general principles and concepts that form the basis for this and other research in population biology & systematics.