Cresko William A, Amores Angel, Wilson Catherine, Murphy Joy, Currey Mark, Phillips Patrick, Bell Michael A, Kimmel Charles B, Postlethwait John H
Institute of Neuroscience and Center for Ecology and Evolutionary Biology, University of Oregon, Eugene, OR 97403-1254, USA.
Proc Natl Acad Sci U S A. 2004 Apr 20;101(16):6050-5. doi: 10.1073/pnas.0308479101. Epub 2004 Apr 6.
Most adaptation is thought to occur through the fixation of numerous alleles at many different loci. Consequently, the independent evolution of similar phenotypes is predicted to occur through different genetic mechanisms. The genetic basis of adaptation is still largely unknown, however, and it is unclear whether adaptation to new environments utilizes ubiquitous small-effect polygenic variation or large-effect alleles at a small number of loci. To address this question, we examined the genetic basis of bony armor loss in three freshwater populations of Alaskan threespine stickleback, Gasterosteus aculeatus, that evolved from fully armored anadromous populations in the last 14,000 years. Crosses between complete-armor and low-armor populations revealed that a single Mendelian factor governed the formation of all but the most anterior lateral plates, and another independently segregating factor largely determined pelvic armor. Genetic mapping localized the Mendelian genes to different chromosomal regions, and crosses among these same three widely separated populations showed that both bony plates and pelvic armor failed to fully complement, implicating the same Mendelian armor reduction genes. Thus, rapid and repeated armor loss in Alaskan stickleback populations appears to be occurring through the fixation of large-effect variants in the same genes.
大多数适应性变化被认为是通过在许多不同基因座上固定大量等位基因而发生的。因此，相似表型的独立进化预计是通过不同的遗传机制发生的。然而，适应性的遗传基础在很大程度上仍然未知，并且尚不清楚对新环境的适应是利用普遍存在的小效应多基因变异还是少数基因座上的大效应等位基因。为了解决这个问题，我们研究了阿拉斯加三刺鱼（Gasterosteus aculeatus）三个淡水种群中骨板缺失的遗传基础，这些种群是在过去14000年中从完全有甲的溯河洄游种群进化而来的。全甲种群和低甲种群之间的杂交表明，一个单一的孟德尔因子控制着除最前面的侧板之外所有侧板的形成，另一个独立分离的因子在很大程度上决定了骨盆甲。遗传图谱将孟德尔基因定位到不同的染色体区域，并且在这三个广泛隔离的种群之间的杂交表明，骨板和骨盆甲都没有完全互补，这意味着是相同的孟德尔甲减少基因。因此，阿拉斯加刺鱼种群中快速且反复的甲缺失似乎是通过相同基因中大效应变体的固定而发生的。
