Friesen V L, Burg T M, McCoy K D
Department of Biology, Queen's University, Kingston, Ontario, Canada.
Mol Ecol. 2007 May;16(9):1765-85. doi: 10.1111/j.1365-294X.2006.03197.x.
Despite recent advances in population genetic theory and empirical research, the extent of genetic differentiation among natural populations of animals remains difficult to predict. We reviewed studies of geographic variation in mitochondrial DNA in seabirds to test the importance of various factors in generating population genetic and phylogeographic structure. The extent of population genetic and phylogeographic structure varies extensively among species. Species fragmented by land or ice invariably exhibit population genetic structure and most also have phylogeographic structure. However, many populations (26 of 37) display genetic structure in the absence of land, suggesting that other barriers to gene flow exist. In these populations, the extent of genetic structure is best explained by nonbreeding distribution: almost all species with two or more population-specific nonbreeding areas (or seasons) have phylogeographic structure, and all species that are resident at or near breeding colonies year-round have population genetic structure. Geographic distance between colonies and foraging range appeared to have a weak influence on the extent of population genetic structure, but little evidence was found for an effect of colony dispersion or population bottlenecks. In two species (Galapagos petrel, Pterodroma phaeopygia, and Xantus's murrelet, Synthliboramphus hypoleucus), population genetic structure, and even phylogeographic structure, exist in the absence of any recognizable physical or nonphysical barrier, suggesting that other selective or behavioural processes such as philopatry may limit gene flow. Retained ancestral variation may be masking barriers to dispersal in some species, especially at high latitudes. Allopatric speciation undoubtedly occurs in this group, but reproductive isolation also appears to have evolved through founder-induced speciation, and there is strong evidence that parapatric and sympatric speciation occur. While many questions remain unanswered, results of the present review should aid conservation efforts by enabling managers to predict the extent of population differentiation in species that have not yet been studied using molecular markers, and, thus, enable the identification of management units and evolutionary significant units for conservation.
尽管群体遗传学理论和实证研究最近取得了进展，但动物自然种群之间的遗传分化程度仍然难以预测。我们回顾了海鸟线粒体DNA地理变异的研究，以检验各种因素在产生群体遗传和系统发育地理结构中的重要性。群体遗传和系统发育地理结构的程度在不同物种间差异很大。被陆地或冰层分割的物种总是表现出群体遗传结构，而且大多数也具有系统发育地理结构。然而，许多种群（37个中的26个）在没有陆地的情况下也显示出遗传结构，这表明存在其他基因流动障碍。在这些种群中，遗传结构的程度最好由非繁殖分布来解释：几乎所有具有两个或更多特定种群非繁殖区域（或季节）的物种都具有系统发育地理结构，而所有常年栖息在繁殖地或其附近的物种都具有群体遗传结构。繁殖地之间的地理距离和觅食范围似乎对群体遗传结构的程度影响较弱，但几乎没有证据表明繁殖地分散或种群瓶颈有影响。在两个物种（加拉帕戈斯海燕，Pterodroma phaeopygia，和桑氏海雀，Synthliboramphus hypoleucus）中，在没有任何可识别的物理或非物理障碍的情况下存在群体遗传结构，甚至系统发育地理结构，这表明其他选择性或行为过程，如恋巢性，可能会限制基因流动。保留的祖先变异可能掩盖了某些物种，特别是高纬度地区物种的扩散障碍。异域物种形成无疑在这一类群中发生，但生殖隔离似乎也通过奠基者诱导的物种形成而进化，而且有强有力的证据表明发生了邻域物种形成和同域物种形成。虽然许多问题仍未得到解答，但本综述的结果应有助于保护工作，使管理人员能够预测尚未使用分子标记进行研究的物种的群体分化程度，从而能够识别用于保护的管理单元和进化显著单元。
