Data from: The effect of habitat fragmentation on the genetic structure of a top predator: loss of diversity and high differentiation among remnant populations of Atlantic Forest jaguars (Panthera onca)

Habitat fragmentation may disrupt original patterns of gene flow and lead to drift-induced differentiation among local population units. Top predators such as the jaguar may be particularly susceptible to this effect, given their low population densities, leading to small effective sizes in local fragments. On the other hand, the jaguar's high dispersal capabilities and relatively long generation time might counteract this process, slowing the effect of drift on local populations over the time frame of decades or centuries. In this study, we have addressed this issue by investigating the genetic structure of jaguars in a recently fragmented Atlantic Forest region, aiming to test whether loss of diversity and differentiation among local populations are detectable, and whether they can be attributed to the recent effect of drift. We used 13 microsatellite loci to characterize the genetic diversity present in four remnant populations, and observed marked differentiation among them, with evidence of recent allelic loss in local areas. Although some migrant and admixed individuals were identified, our results indicate that recent large-scale habitat removal and fragmentation among these areas has been sufficiently strong to promote differentiation induced by drift and loss of alleles at each site. Low estimated effective sizes supported the inference that genetic drift could have caused this effect within a short time frame. These results indicate that jaguars' ability to effectively disperse across the human-dominated landscapes that separate the fragments is currently very limited, and that each fragment contains a small, isolated population that is already suffering from the effects of genetic drift.

生境破碎化（habitat fragmentation）可能破坏原有的基因流（gene flow）模式，并导致局部种群单元间出现遗传漂变（genetic drift）诱导的分化。诸如美洲豹（Jaguar）这类顶级捕食者，由于其种群密度较低，局部斑块内的有效种群规模（effective sizes）往往偏小，因此对该效应尤为敏感。另一方面，美洲豹较强的扩散能力与相对较长的世代时间，可能会抵消这一过程，在数十年至数百年的时间尺度上减缓遗传漂变对局部种群的影响。本研究聚焦近期遭受破碎化的大西洋森林（Atlantic Forest）区域内的美洲豹种群遗传结构，旨在检验局部种群间的多样性丧失与分化是否可被检测，以及其是否可归因于近期的遗传漂变效应。我们利用13个微卫星位点（microsatellite loci）对4个残存种群的遗传多样性进行了表征，结果显示种群间存在显著分化，且局部区域存在近期等位基因丢失的证据。尽管本研究鉴定出了少量迁移个体与混血个体，但结果表明，上述区域近期发生的大规模生境清除与破碎化，强度已足以推动各斑块内由遗传漂变诱导的分化与等位基因丢失。较低的有效种群规模估算值，佐证了遗传漂变可在较短时间尺度内引发该效应的推论。本研究结果显示，美洲豹穿越分隔斑块的人类主导景观进行有效扩散的能力目前极为有限，且每个残存斑块内均存在小型孤立种群，已开始遭受遗传漂变带来的负面影响。