Several recent studies have shown that amphibian populations may exhibit high genetic subdivision in areas with recent fragmentation and urban development. Less is known about the potential for genetic differentiation in continuous habitats. We studied genetic differentiation of red-backed salamanders (Plethodon cinereus) across a 2-km transect through continuous forest in Virginia, USA. Mark-recapture studies suggest very little dispersal for this species, whereas homing experiments and post-Pleistocene range expansion both suggest greater dispersal abilities. We used six microsatellite loci to examine genetic population structure and differentiation between eight subpopulations of red-backed salamanders at distances from 200 m to 2 km. We also used several methods to extrapolate dispersal frequencies and test for sex-biased dispersal. We found small, but detectable differentiation among populations, even at distances as small as 200 m. Differentiation was closely correlated with distance and both Mantel tests and assignment tests were consistent with an isolation-by-distance model for the population. Extrapolations of intergenerational variance in spatial position (sigma(2)<15 m(2)) and pair-wise dispersal frequencies (4 Nm < 25 for plots separated by 300 m) both suggest limited gene flow. Additionally, tests for sex-biased dispersal imply that dispersal frequency is similarly low for both sexes. We suggest that these low levels of gene flow and the infrequent dispersal observed in mark-recapture studies may be reconciled with homing ability and range expansion if dispersing animals rarely succeed in breeding in saturated habitats, if dispersal is flexible depending on the availability of habitat, or if dispersal frequency varies across the geographic range of red-backed salamanders.

译文

:最近的几项研究表明,两栖动物种群在具有最近的支离破碎和城市发展的地区可能表现出较高的遗传细分。关于连续生境中遗传分化的潜力知之甚少。我们研究了红背sal(Plethodon cinereus)通过美国弗吉尼亚州连续森林跨越2公里的样带的遗传分化。标记捕获研究表明,该物种的扩散能力很小,而归巢实验和更新世后的范围扩展都表明具有较强的扩散能力。我们使用六个微卫星基因座来研究遗传种群的结构以及在200 m至2 km的距离上的红背sal的八个亚群之间的分化。我们还使用了几种方法来推断散布频率并测试性别偏向的散布。我们发现,即使在小至200 m的距离上,种群之间的差异也很小,但可检测到。分化与距离密切相关,Mantel检验和分配检验均与总体的按距离隔离模型一致。空间位置的代际方差的外推法(sigma(2)<15 m(2))和成对的散布频率(4 Nm <25对于由300 m分隔的地块)都表明基因流有限。此外,针对性别偏见的分散测试表明,男女的分散频率同样较低。我们建议,如果分散的动物很少能在饱和的栖息地中成功繁殖,那么这种低水平的基因流动和在标记捕获研究中观察到的不频繁的分散可能与归巢能力和范围扩展相一致;如果分散能够灵活地取决于栖息地的可用性,或分散频率在红背sal的地理范围内变化。

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