PDF(Pubmed)
Abstract：
Genetic variation in Arctic species is often influenced by vicariance during the Pleistocene, as ice sheets fragmented the landscape and displaced populations to low- and high-latitude refugia. The formation of secondary contact or suture zones during periods of ice sheet retraction has important consequences on genetic diversity by facilitating genetic connectivity between formerly isolated populations. Brant geese (Branta bernicla) are a maritime migratory waterfowl (Anseriformes) species that almost exclusively uses coastal habitats. Within North America, brant geese are characterized by two phenotypically distinct subspecies that utilize disjunct breeding and wintering areas in the northern Pacific and Atlantic. In the Western High Arctic of Canada, brant geese consist of individuals with an intermediate phenotype that are rarely observed nesting outside this region. We examined the genetic structure of brant geese populations from each subspecies and areas consisting of intermediate phenotypes using mitochondrial DNA (mtDNA) control region sequence data and microsatellite loci. We found a strong east-west partition in both marker types consistent with refugial populations. Within subspecies, structure was also observed at mtDNA while microsatellite data suggested the presence of only two distinct genetic clusters. The Western High Arctic (WHA) appears to be a secondary contact zone for both Atlantic and Pacific lineages as mtDNA and nuclear genotypes were assigned to both subspecies, and admixed individuals were observed in this region. The mtDNA sequence data outside WHA suggests no or very restricted intermixing between Atlantic and Pacific wintering populations which is consistent with published banding and telemetry data. Our study indicates that, although brant geese in the WHA are not a genetically distinct lineage, this region may act as a reservoir of genetic diversity and may be an area of high conservation value given the potential of low reproductive output in this species.
摘要：
北极物种的遗传变异通常受到更新世期间的代际影响，由于冰盖使景观支离破碎，流离失所的人口流向低纬度和高纬度避难所。在冰盖回缩期间形成二次接触或缝合区，通过促进以前孤立的种群之间的遗传连通性，对遗传多样性产生了重要影响。Brant鹅（Brantabernicla）是一种海上迁徙水禽（Anseriformes）物种，几乎只使用沿海栖息地。在北美，鹅的特征是两个表型不同的亚种，它们利用北太平洋和大西洋的分离繁殖和越冬区。在加拿大西部高北极地区，鹅由具有中间表型的个体组成，很少在该区域外筑巢。我们使用线粒体DNA（mtDNA）控制区序列数据和微卫星基因座，研究了来自每个亚种和由中间表型组成的区域的野鹅种群的遗传结构。我们在两种标记类型中都发现了强烈的东西分区，与避难所种群一致。在亚种内，在mtDNA上也观察到结构，而微卫星数据表明仅存在两个不同的遗传簇。由于mtDNA和核基因型被分配给两个亚种，因此西部高北极（WHA）似乎是大西洋和太平洋血统的次要接触区，在该地区观察到混合个体。WHA以外的mtDNA序列数据表明，大西洋和太平洋越冬种群之间没有或非常有限的混合，这与已发布的条带和遥测数据一致。我们的研究表明,尽管WHA中的燕麦鹅不是遗传上独特的谱系，该地区可能是遗传多样性的储库，并且鉴于该物种的低生殖输出潜力，该地区可能是具有高保护价值的地区。
