CRB: Inbreeding Depression and Adaptive Genetic Variation in Gila Topminnows

9322655海德里克在这项研究中，PI将研究两代人的近亲繁殖衰退，以确定濒危物种吉拉金枪鱼不同种群的几个适合度成分。在一系列实验中，PI将比较同胞交配的后代和同一种群中个体之间随机交配的后代的适应值。接下来，PI将测量来自不同种群的杂交个体对相同适应度成分的影响。顶鱼种群被认为经历了周期性的振荡，种群瓶颈、局部灭绝、重新定居，甚至种群之间的交叉。因此，不同种群的个体之间的杂交是否与种群内的杂交没有区别，是杂种优势，还是表现出远缘繁殖衰退，对于确定种群间的遗传变异模式是重要的。这些杂交应该提供信息，说明不同的群体是否固定了有害的等位基因，这些等位基因可能被异种杂交掩盖，或者差异太大，以至于F1和F2后代的适合度降低。主要组织相容性复合体可能是哺乳动物最重要的适应性遗传区域，对各种病原体具有抵抗力。最近在鱼类中的研究表明，MHC在几个物种中存在广泛的变异，并且这种变异模式与哺乳动物的一致。PI‘s将记录Gila topminnow四个集合种群中MHC的范围和模式，以确定该物种是否在这一重要的适应性区域存在变异。保护遗传学的基本原理与近亲繁殖抑制和保留潜在的适应性遗传变异有关。因此，确定近亲繁殖衰退的程度和特别是濒危物种的适应性遗传变异的特征是至关重要的。在这项研究中，PI夫妇有一个独特的机会来测量濒临灭绝的Gila金枪鱼的这些值，这种鱼只存在于亚利桑那州泉水和源头溪流子盆地的四个自然种群中。此外，这项研究将增加关于主要组织相容性复合体的变异性的进一步信息，该复合体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. ***