Kawecki Tadeusz J
Department of Zoology, University of Maryland, College Park, Maryland, 20742.
Evolution. 1997 Dec;51(6):1751-1763. doi: 10.1111/j.1558-5646.1997.tb05099.x.
Theoretical studies have suggested that the evolution of habitat (host) races, regarded as a prelude to sympatric speciation, requires strong trade-offs in adaptation to different habitats: alleles that improve fitness in some habitats and have deleterious effects of similar magnitude in other habitats must be segregating in the population. I argue that such trade-offs are not necessary; the evolution of habitat races can also be driven by genetic variation due to loci that affect fitness in one habitat and are neutral or nearly so in others, that is, when performance in different habitats is genetically independent. One source of such genetic variation are deleterious mutations with habitat-specific fitness effects. I use deterministic two-locus and multilocus models to show that the presence of such mutations in the gene pool results in indirect selection favoring habitat fidelity or habitat preference over acceptance of both suitable habitats. This leads to the evolution of largely genetically isolated populations that use different habitats, from a single panmictic population of individuals accepting both habitats. This study suggests that the conditions favoring habitat race formation, and thus possibly sympatric speciation, are much less stringent than previously thought.
理论研究表明，栖息地（宿主）种群的进化被视为同域物种形成的前奏，需要在适应不同栖息地方面进行强烈的权衡：在某些栖息地提高适应性但在其他栖息地具有类似程度有害影响的等位基因必须在种群中分离。我认为这种权衡并非必要；栖息地种群的进化也可能由基因变异驱动，这种变异源于影响一个栖息地适应性而在其他栖息地为中性或近乎中性的基因座，也就是说，当在不同栖息地的表现是基因独立的时候。这种基因变异的一个来源是具有栖息地特异性适应性效应的有害突变。我使用确定性双基因座和多基因座模型表明，基因库中存在此类突变会导致间接选择，有利于栖息地保真度或栖息地偏好，而不是接受两种适宜栖息地。这导致从接受两种栖息地的单个随机交配个体种群中，演化出大量使用不同栖息地的基因隔离种群。这项研究表明，有利于栖息地种群形成并因此可能有利于同域物种形成的条件，比之前认为的要宽松得多。
