Avise John C, Alisauskas Ray T, Nelson William S, Ankney C Davison
Department of Genetics, University of Georgia, Athens, GA, 30602, USA.
Canadian Wildlife Service, 115 Perimeter Road, Saskatoon, Saskatchewan, S7N 0X4, CANADA.
Evolution. 1992 Aug;46(4):1084-1096. doi: 10.1111/j.1558-5646.1992.tb00621.x.
We employ mitochondrial (mt) DNA markers to examine the matrilineal component of population genetic structure in the snow goose Chen caerulescens. From banding returns, it is known that females typically nest at their natal or prior nest site, whereas males pair with females on mixed wintering grounds and mediate considerable nuclear gene flow between geographically separate breeding colonies. Despite site philopatry documented for females, mtDNA markers show no clear distinctions between nesting populations across the species' range from Wrangel Island, USSR to Baffin Island in the eastern Canadian Arctic. Two major mtDNA clades (as well as rare haplotypes) are distributed widely and provide one of the few available examples of a phylogeographic pattern in which phylogenetic discontinuity in a gene tree exists without obvious geographic localization within a species' range. The major mtDNA clades may have differentiated in Pleistocene refugia, and colonized current nesting sites through recent range expansion via pulsed or continual low-level dispersal by females. The contrast between results of banding returns and mtDNA distributions in the snow goose raises general issues regarding population structure: direct contemporary observations on dispersal and gene flow can in some cases convey a misleading impression of phylogeographic population structure, because they fail to access the evolutionary component of population connectedness; conversely, geographic distributions of genetic markers can provide a misleading impression of contemporary dispersal and gene flow because they retain a record of evolutionary events and past demographic parameters that may differ from those of the present. An understanding of population structure requires integration of both evolutionary (genetic) and contemporary (direct observational) perspectives.
我们利用线粒体（mt）DNA标记来研究雪雁（Chen caerulescens）种群遗传结构中的母系成分。从环志回收数据可知，雌性雪雁通常在其出生地产卵或在之前的筑巢地点产卵，而雄性雪雁则在混合的越冬地与雌性交配，并介导了地理上分隔的繁殖群体之间大量的核基因流动。尽管有记录显示雌性雪雁有出生地忠诚度，但mtDNA标记在从苏联弗兰格尔岛到加拿大北极东部巴芬岛的整个物种分布范围内，并未显示出筑巢种群之间有明显差异。两个主要的mtDNA分支（以及罕见的单倍型）分布广泛，提供了少数几个系统发育地理模式的例子之一，即在一个物种分布范围内，基因树中的系统发育间断存在但没有明显的地理定位。主要的mtDNA分支可能在更新世避难所中发生了分化，并通过雌性最近的脉冲式或持续的低水平扩散范围扩张，而定殖到了当前的筑巢地点。雪雁环志回收结果与mtDNA分布之间的差异，引发了关于种群结构的一般性问题：在某些情况下，对扩散和基因流动的直接当代观察可能会传达出关于系统发育地理种群结构的误导性印象，因为它们无法获取种群连通性的进化成分；相反，遗传标记的地理分布可能会给当代扩散和基因流动造成误导性印象，因为它们保留了进化事件和过去人口统计参数的记录，而这些可能与当前的情况不同。对种群结构的理解需要整合进化（遗传）和当代（直接观察）这两个视角。
