Mapping of Genetic Factors Causing Genotype-Environment Interaction for Fitness in Drosophila melanogaster

9707470鱼苗自然种群动植物通常具有可遗传或基于遗传的变异，其特征与生殖适合性密切相关，例如幼体存活或产卵。这种变异的存在是一个谜，因为自然选择有望消除低适应度的变异。根据环境异质性假说，由于不同的基因类型在不同的时间或不同的地点具有最高的适合度，所以适合度性状的遗传变异保持不变。尽管许多间接证据支持这一假说，但事实证明，全面评估这一假说是困难的，因为要做到这一点，需要了解不同的等位基因(单个基因的变种)如何在不同的环境中影响适应性，而这些信息很少获得。特别是，为了使环境异质性保持变异，必须存在“权衡”，这样在某些环境中增加适应度的等位基因就会降低其他环境中的适应度。在这项拟议的工作中，将确定果蝇黑腹果蝇在不同饮食中影响健康的基因的染色体位置，以确定是否存在权衡。乙醇是黑腹金龟子繁殖地的天然成分，乙醇水平的变化被认为是维持该物种种群遗传变异的关键。拟议的工作利用了大量的实验室种群，这些种群适应于含有或不含乙醇的食物；在每种食物类型上，保持在该食物类型上的两个种群比保持在另一种食物类型上的种群具有更高的适合度。负责这些适应性差异的染色体区域将被绘制出来，以确定在一种食物类型上导致较高适应性的区域是否会导致另一种食物类型的较低适应性。如果这项工作提供了权衡取舍的证据，环境异质性假说的一个重要假设将得到支持。环境异质性是否保持适合性状的遗传变异对许多重要的生物学问题都有影响，包括新物种是如何形成的，以及是什么决定了种群的生态专业化程度。此外，充分了解保持适宜性状遗传变异的因素，对于分析害虫物种适应新作物品种或杀虫剂的潜力，以及设计维持稀有、濒危物种种群长期生存的战略非常重要。因此，拟议的工作将在基础战线和应用战线上作出贡献。

9707470 Fry Natural populations of animals and plants often harbor heritable or genetically-based variation for traits closely related to reproductive fitness, such as juvenile survival or egg production. The existence of this variation presents a puzzle, because natural selection is expected to eliminate variants with low fitness. According to the environmental heterogeneity hypothesis, genetic variation for fitness traits is maintained because different genotypes have highest fitness at different times or in different places. Although much indirect evidence supports this hypothesis, fully evaluating the hypothesis has proven difficult, because to do so requires knowledge of how different alleles (variants of individual genes) affect fitness in different environments, information that is seldom available. In particular, for environmental heterogeneity to maintain variation, "trade-offs" must be present, such that alleles that increase fitness in some environments decrease fitness in others. In the proposed work, the chromosomal locations of genes affecting fitness on different diets, food with and without ethanol, will be determined in the fruit fly Drosophila melanogaster, in order to determine whether trade-offs are present. Ethanol is a natural component of breeding sites of D. melanogaster, and variation in ethanol levels has been proposed to maintain genetic variation in populations of this species. The proposed work makes use of large laboratory populations that are adapted to food either containing or lacking ethanol; on each type of food, the two populations maintained on that food type have substantially higher fitness than the populations maintained on the other food type. Chromosomal regions responsible for these fitness differences will be mapped, in order to determine whether regions causing higher fitness on one food type give rise to lower fitness on the other. If this work produces evidence for trade-offs, an important assumption of the environmental heterogene ity hypothesis will be supported. Whether environmental heterogeneity maintains genetic variation for fitness traits has implications for a number of important biological issues, including how new species are formed, and what determines the degree of ecological specialization of populations. In addition, a full understanding of the factors maintaining genetic variation for fitness traits is important for analyzing the potential for pest species to adapt to new crop varieties or pesticides, and for designing strategies for maintaining the long-term viability of populations of rare, endangered species. The proposed work will therefore make contributions on both basic and applied fronts.