CRB: Inbreeding Depression and Adaptive Genetic Variation in Gila Topminnows

[322655]在这项研究中，PI将研究两代以上的近亲繁殖衰退，以了解不同种群的适合度的几个组成部分，这些种群是濒临灭绝的物种吉拉豚。在一系列的实验中，PI将比较同类交配的后代和同一种群中个体之间随机交配的后代之间的适合度值。接下来，PI将测量来自不同种群的个体杂交对相同适应度成分的影响。人们认为，顶鲦鱼的种群会经历周期性的波动，包括种群瓶颈、局部灭绝、重新定居，甚至种群之间的杂交。因此，确定种群遗传变异的模式是很重要的，无论是来自不同种群的个体之间的杂交与种群内的杂交没有区别，是杂种优势，还是表现出远交抑制。这些杂交应该提供信息，说明不同的种群是固定的有害等位基因，这些等位基因可以通过异种杂交掩盖，还是由于差异太大，导致F1和F2后代的适应性降低。主要组织相容性复合体可能是哺乳动物中最重要的适应性遗传区域，赋予对各种病原体的抗性。最近对鱼类的研究表明，几个物种的MHC存在广泛的变异，这种变异模式与哺乳动物的一致。PI将记录4个大群中MHC的范围和模式，以确定该物种是否在这个重要的适应区域有变异，该物种在除一个种群外的所有种群中都是固定的等位酶变异。保护遗传学的基本原理与近交抑制和潜在适应性遗传变异的保留有关。因此，对特定濒危物种的近交抑制和适应性遗传变异的程度进行表征是至关重要的。在这项研究中，PI有一个独特的机会来测量濒临灭绝的吉拉顶鲦鱼的这些值，这种鱼只存在于亚利桑那州的泉水和源头溪流的子盆地中，只有四个自然种群。此外，这项研究将进一步提供有关主要组织相容性复合体变异性的信息，这在鱼类中只受到有限的关注。＊＊＊

9322655 Hedrick In this research, the PI's will examine inbreeding depression over two generations for several components of fitness in different populations of the endangered species, the Gila topminnow. In a series of experiments, the PI's will compare fitness values between progeny of sib matings and the progeny of random matings between individuals within the same population. Next, the PI's will measure the effect of crossing individuals from different populations on the same fitness components. Populations of topminnows were thought to undergo periodic oscillations with population bottlenecks, local extinctions, recolonizations, and even crossing between populations. As a result, it is important in determining the pattern of genetic variation over populations whether crosses between individuals from different populations are no different than within population crosses, are heterotic, or show outbreeding depression. These crosses should give information on whether the different populations are fixed for detrimental alleles that can be covered up by outcrossing or are so different that F1 and F2 progeny have reduced fitness. The major histocompatibility complex may be the most important adaptive genetic region in mammals, conferring resistance to various pathogens. Recent work in fish has demonstrated that there is extensive variation for MHC in several species and that the pattern of variation is consistent with that in mammals. The PI's will document the extent and pattern of MHC in the four metapopulations of the Gila topminnow to determine if this species, which is fixed for allozymic variation in all populations except one, has variation in this important adaptive region. %%% The primary principles of conservation genetics are related to inbreeding depression and the retention of potentially adaptive genetic variation. It is therefore of fundamental importance to characterize both the extent of inbreeding depression and adaptive genetic variation in particular endangered species. In this study, the PI's have a unique opportunity to measure these values in the endangered Gila topminnow which exists in only four natural populations in sub-basins of springs and headwater streams in Arizona. In addition, this research will add further information on variability in the major histocompatibility complex which has received only limited attention in fish. ***