Brown Anthony P, Greenway Ryan, Morgan Samuel, Quackenbush Corey R, Giordani Luca, Arias-Rodriguez Lenin, Tobler Michael, Kelley Joanna L
School of Biological Sciences, Washington State University, Pullman, WA, USA.
Division of Biology, Kansas State University, Manhattan, KS, USA.
Mol Ecol. 2017 Oct;26(19):4920-4934. doi: 10.1111/mec.14249. Epub 2017 Aug 24.
Populations with limited ranges can be highly vulnerable to changes in their environment and are, thus, of high conservation concern. Populations that experience human-induced range reductions are often highly inbred and lack genetic diversity, but it is unknown whether this is also the case for populations with naturally small ranges. The fishes Poecilia sulphuraria (listed as critically endangered) and Poecilia thermalis, which are endemic to small hydrogen sulphide-rich springs in southern Mexico, are examples of such populations with inherently small habitats. We used geometric morphometrics and population genetics to quantify phenotypic and genetic variation within and among two populations of P. sulphuraria and one population of P. thermalis. Principal component analyses revealed phenotypic and genetic differences among the populations. Evidence for inbreeding was low compared to populations that have undergone habitat reduction. The genetic data were also used to infer the demographic history of these populations to obtain estimates for effective population sizes and migration rates. Effective population sizes were large given the small habitats of these populations. Our results imply that these three endemic extremophile populations should each be considered separately for conservation purposes. Additionally, this study suggests that populations in naturally small habitats may have lower rates of inbreeding and higher genetic diversity than expected, and therefore may be better equipped to handle environmental perturbations than anticipated. We caution, however, that the inferred lack of inbreeding and the large effective population sizes could potentially be a result of colonization by genetically diverse ancestors.
分布范围有限的种群极易受到环境变化的影响，因此受到高度的保护关注。经历了人为导致的分布范围缩小的种群通常近亲繁殖程度很高且缺乏遗传多样性，但对于自然分布范围较小的种群是否也是如此尚不清楚。墨西哥南部富含硫化氢的小泉中的特有鱼类硫色食蚊鱼（被列为极度濒危物种）和温泉食蚊鱼就是这类栖息地天生狭小的种群的例子。我们使用几何形态测量学和种群遗传学来量化硫色食蚊鱼的两个种群内部和之间以及温泉食蚊鱼的一个种群内部和之间的表型和遗传变异。主成分分析揭示了种群之间的表型和遗传差异。与经历过栖息地减少的种群相比，近亲繁殖的证据较少。遗传数据还被用于推断这些种群的种群历史，以获得有效种群大小和迁移率的估计值。鉴于这些种群的栖息地较小，有效种群大小却很大。我们的结果表明，出于保护目的，这三个特有嗜极生物种群应分别予以考虑。此外，这项研究表明，自然栖息地狭小的种群近亲繁殖率可能低于预期且遗传多样性更高，因此可能比预期更有能力应对环境扰动。然而，我们提醒，推断出的近亲繁殖缺乏和较大的有效种群大小可能潜在地是由遗传多样的祖先进行殖民的结果。
