Functional connectivity and population persistence in woodland birds: insights for management from a multi-species conservation genetics study

Conservation management of wildlife benefits from understanding the genetic factors underlying individual fitness and population evolution. Habitat loss and fragmentation reduce genetic diversity and functional connectivity, limiting population persistence and adaptation to changing environments. Here we review and synthesise results from the Birds in Fragmented Landscapes program in central Victoria, Australia. Building on research on <i>patterns</i> of occurrence of woodland-dependent bird species, we conducted conservation genetic studies of ~3,500 individuals from 10 woodland bird species sampled in twelve 100 km² ‘landscapes’ with different levels of habitat loss, to assess multiple conservation-relevant <i>processes</i> of response to habitat alteration. This program employed connectivity modelling and landscape-, acoustic- and population genetic analyses to understand mobility of birds, their genes and songs at different scales, relating these elements of functional connectivity to landscape structure for each sex in each species. At the regional scale, most species displayed unexpectedly high levels of genetic connectivity. At local-scales, there were strong signals of disrupted population processes (e.g. mating system) and reduced functional connectivity for several more-mobile and all less-mobile ‘decliner’ species. This underlines that high genetic connectivity does not necessarily signal genetically and demographically healthy populations. In some species, declines in mobility were greater in one sex but not necessarily the more philopatric sex. We derive conservation management recommendations in five concept areas: maintain existing and restore degraded habitat, reconnect the landscape, use species- and sex-specific information where possible, work across multiple scales, and conserve evolutionary processes (by genetic management where appropriate).

野生动物保护管理若要取得实效，需先明晰个体适合度（fitness）与种群演化背后的遗传机制。生境丧失与片段化会降低物种遗传多样性与功能连通性（functional connectivity），进而限制种群存续能力及对环境变化的适应潜力。本研究回顾并综合了澳大利亚维多利亚州中部「破碎景观中的鸟类」（Birds in Fragmented Landscapes）研究计划的相关成果。本研究依托针对林地依赖型鸟类物种出现模式（patterns）的前期研究基础，对采自12个面积为100平方千米、生境丧失程度各异的「景观」单元中的10种林地鸟类的约3500个个体开展保护遗传学研究，以评估多种与保护相关的、针对生境改变的响应过程（processes）。该研究计划采用连通性建模、景观分析、声学分析及种群遗传学分析方法，在不同空间尺度下解析鸟类的移动能力、其携带的基因及鸣唱特征，并针对每个物种的不同性别，将功能连通性的这些组成要素与景观结构建立关联。在区域尺度下，多数物种展现出远超预期的高水平遗传连通性。在局地尺度下，若干移动能力较强的物种以及所有移动能力较弱的衰退类物种均呈现出种群过程（如交配系统）受到干扰、功能连通性下降的显著信号。这一结果表明，高水平的遗传连通性并不一定代表种群在遗传与种群统计层面均处于健康状态。在部分物种中，某一性别的移动能力下降幅度更为显著，但这未必对应恋乡性（philopatry）更强的性别。本研究从五个核心概念维度提出保护管理建议：维持现有生境并修复退化生境、连通破碎化景观、尽可能采用物种类别与性别特异性的保护信息、开展多尺度协同保护、以及在适宜情况下通过遗传管理手段保护演化过程。