Hilbish Thomas J, Koehn Richard K
Department of Ecology and Evolution, State University of New York, Stony Brook, NY, 11794.
Evolution. 1985 Nov;39(6):1302-1317. doi: 10.1111/j.1558-5646.1985.tb05696.x.
An extensive research program was undertaken to evaluate the contribution of genetic variation at the Lap locus to variation in physiological traits under natural conditions. Rates of carbon and nitrogen metabolism were monitored in a population of the mussel Mytilus edulis near the center of the Lap allele frequency cline on the north shore of Long Island. The goal of this research was to establish whether the previously described genotype-dependent differences in physiological phenotype are meaningful in ecologically relevant circumstances. It was predicted from laboratory studies that, in nature, genotype-dependent differences will exist for rates of nitrogen excretion and that other aspects of the animal's physiology, particularly rates of carbon metabolism, will be unaffected by Lap genotype. Rates of amino acid and ammonia excretion were significantly dependent upon Lap genotype; individuals with the Lap allele exhibited greater rates of nitrogen loss. These differences among genotypes were most evident in the fall, between September and December. The genotype-dependent component of rates of nitrogen loss were also largest relative to the total rate of excretion during the fall period. As predicted, other aspects of the nitrogen metabolism (acquisition) and rates of carbon metabolism were independent of Lap genotype. There was a striking congruity among a variety of observations that all indicate that phenotypic differences in nitrogen metabolism are the basis of natural selection at the Lap locus in Long Island Sound. Rates of growth were minimal during the fall months (Hilbish, 1985) and mussels are known to lose weight in a genotype-specific manner during this period (Koehn et al., 1980). Rates of elemental gain and loss were summed to produce carbon and nitrogen budgets; these data show the fall to be a period of extended deficit in carbon and nitrogen balance. Genotype-dependent losses of ammonia and amino acids were greatest during the fall months. Finally, selection against the Lap allele occurs predominantly in the fall (Hilbish, 1985). The data indicate that the depletion of nitrogen resources provides the basis for selection against Lap genotypes during the fall months.
开展了一项广泛的研究计划，以评估Lap基因座的遗传变异对自然条件下生理性状变异的贡献。在长岛北岸Lap等位基因频率渐变群中心附近的紫贻贝种群中监测了碳和氮代谢率。这项研究的目的是确定先前描述的生理表型中基因型依赖性差异在生态相关环境中是否有意义。根据实验室研究预测，在自然环境中，氮排泄率会存在基因型依赖性差异，而动物生理学的其他方面，特别是碳代谢率，将不受Lap基因型的影响。氨基酸和氨的排泄率显著依赖于Lap基因型；携带Lap等位基因的个体表现出更高的氮损失率。这些基因型之间的差异在秋季（9月至12月）最为明显。秋季氮损失率的基因型依赖性成分相对于总排泄率也最大。正如预测的那样，氮代谢（获取）的其他方面和碳代谢率与Lap基因型无关。各种观察结果之间存在显著的一致性，所有这些都表明氮代谢的表型差异是长岛海峡Lap基因座自然选择的基础。秋季几个月的生长率最低（希尔比什，1985年），并且已知贻贝在此期间会以基因型特异性方式减重（科恩等人，1980年）。将元素的获取和损失率相加得出碳和氮预算；这些数据表明秋季是碳和氮平衡长期亏缺的时期。秋季几个月氨和氨基酸的基因型依赖性损失最大。最后，对Lap等位基因的选择主要发生在秋季（希尔比什，1985年）。数据表明，氮资源的消耗为秋季几个月对Lap基因型的选择提供了基础。
