Mulvaney Jake M, Matthee Conrad A, Cherry Michael I
Department of Botany and Zoology Stellenbosch University Matieland South Africa.
Evol Appl. 2021 Oct 28;14(11):2680-2697. doi: 10.1111/eva.13306. eCollection 2021 Nov.
Species confined to naturally fragmented habitats may exhibit intrinsic population complexity which may challenge interpretations of species response to anthropogenic landscape transformation. In South Africa, where native forests are naturally fragmented, forest-dependent birds have undergone range declines since 1992, most notably among insectivores. These insectivores appear sensitive to the quality of natural matrix habitats, and it is unknown whether transformation of the landscape matrix has disrupted gene flow in these species. We undertook a landscape genetics study of four forest-dependent insectivorous songbirds across southeast South Africa. Microsatellite data were used to conduct a priori optimization of landscape resistance surfaces (land cover, rivers and dams, and elevation) using cost-distances along least-cost pathway (LCP), and resistance distances (IBR). We detected pronounced declines in effective population sizes over the past two centuries for the endemic forest specialist and , alongside recent gene flow disruption in , and . Landscape resistance modelling showed both native forest and dense thicket configuration facilitates gene flow in , and . Facultative dispersal of through dense thicket likely aided resilience against historic landscape transformation, whereas combined forest-thicket degradation adversely affected the forest generalist . By contrast, appears least reliant upon landscape features to maintain gene flow and was least impacted by anthropogenic landscape transformation. Collectively, gene flow in all four species is improved at lower elevations, along river valleys, and riparian corridors- where native forest and dense thicket better persist. Consistent outperformance of LCP over IBR land-cover models for , and demonstrates the benefits of wildlife corridors for South African forest-dependent bird conservation, to ameliorate the extinction debts from past and present anthropogenic forest exploitation.
局限于自然碎片化栖息地的物种可能表现出内在的种群复杂性，这可能对物种对人为景观转变的反应的解释构成挑战。在南非，原生森林自然碎片化，自1992年以来，依赖森林的鸟类数量减少，最明显的是食虫鸟类。这些食虫鸟类似乎对自然基质栖息地的质量敏感，目前尚不清楚景观基质的转变是否扰乱了这些物种的基因流动。我们对南非东南部四种依赖森林的食虫鸣禽进行了景观遗传学研究。利用微卫星数据，沿着最小成本路径（LCP）和抗性距离（IBR）的成本距离，对景观抗性表面（土地覆盖、河流和水坝以及海拔）进行了先验优化。我们检测到，在过去两个世纪中，特有森林专家物种和的有效种群数量显著下降，同时，、和近期出现了基因流动中断。景观抗性模型表明，原生森林和茂密灌木丛的配置有利于、和的基因流动。通过茂密灌木丛的兼性扩散可能有助于抵御历史景观转变，而森林-灌木丛的综合退化对森林通才物种产生了不利影响。相比之下，似乎最不依赖景观特征来维持基因流动，受人为景观转变的影响也最小。总体而言，在较低海拔、河谷和河岸走廊，所有四个物种的基因流动都有所改善，这些地方原生森林和茂密灌木丛保存得更好。对于、和，LCP土地覆盖模型始终优于IBR模型，这表明野生动物走廊对南非依赖森林的鸟类保护有益，可减轻过去和现在人为森林开发造成的灭绝债务。
