Buerkle C Alex
Department of Biology, Indiana University, Jordan Hall 142, Bloomington, Indiana, 47405.
Evolution. 1999 Dec;53(6):1915-1924. doi: 10.1111/j.1558-5646.1999.tb04572.x.
Within a group of interbreeding organisms, the balance of gene flow among populations and microevolutionary forces acting within populations is expected to result in clinal transitions in the phenotypes possessed by members of differentiated populations. Discontinuous variation between geographically adjacent populations suggests the presence of a significant barrier to gene flow. Here I present genetic evidence for restricted gene flow between migratory and nonmigratory populations of prairie warblers. The nonmigratory form of this species is restricted to coastal mangroves in Florida and is morphologically distinguishable from the typical, migratory form that occurs across the remainder of the eastern United States. Pairs of migratory populations exhibited little population subdivision (Φ ⩽ 0.09), whereas pairs of migratory and nonmigratory populations are much more differentiated (Φ = 0.27-0.42). A phylogenetic analysis of mitochondrial DNA haplotypes did not offer evidence of long-term isolation of migratory and nonmigratory populations. Together with the population genetic analysis, the phylogenetic relationship of haplotypes suggests that isolation between these forms must have arisen relatively recently in their history. Evidence for significant population structure is unexpected, given the geographic proximity of migratory and nonmigratory populations, the capacity for long-distance movements (e.g., migration) by prairie warblers, and several previous studies of population structure in North American birds. However, the findings are consistent with the geographic distribution of morphological and behavioral variation and demonstrate that significant boundaries between populations of vagile organisms may be relatively cryptic.
在一组相互交配的生物群体中，种群间基因流动的平衡以及种群内部作用的微观进化力量，预计会导致分化种群成员所拥有的表型出现渐变。地理上相邻种群之间的不连续变异表明存在显著的基因流动障碍。在此，我提供了草原莺迁徙种群和非迁徙种群之间基因流动受限的遗传证据。该物种的非迁徙形态局限于佛罗里达州的沿海红树林，在形态上可与分布于美国东部其他地区的典型迁徙形态区分开来。成对的迁徙种群表现出很少的种群细分（Φ⩽0.09），而成对的迁徙种群和非迁徙种群则差异大得多（Φ = 0.27 - 0.42）。对线粒体DNA单倍型的系统发育分析并未提供迁徙种群和非迁徙种群长期隔离的证据。结合种群遗传分析，单倍型的系统发育关系表明这些形态之间的隔离肯定是在它们历史上相对较近的时期出现的。鉴于迁徙种群和非迁徙种群在地理上接近、草原莺具有长距离移动（如迁徙）的能力以及之前对北美鸟类种群结构的几项研究，出现显著种群结构的证据是出乎意料的。然而，这些发现与形态和行为变异的地理分布一致，并表明易迁徙生物种群之间的显著界限可能相对难以察觉。
