Data from: Exploring mechanisms and origins of reduced dispersal in island Komodo dragons

Loss of dispersal typifies island biotas, but the selective processes driving this phenomenon remain contentious. This is because selection via, both indirect (e.g. relaxed selection or island syndromes) and direct (e.g. natural selection or spatial sorting) processes may be involved, and no study has yet convincingly distinguished between these alternatives. Here we combined observational and experimental analyses of an island lizard, the Komodo dragon (Varanus komodoensis, the world’s largest lizard), to provide evidence for the actions of multiple processes that could contribute to island dispersal loss. In the Komodo dragon, concordant results from telemetry, simulations, experimental translocations, mark-recapture and gene flow studies indicated that despite impressive physical and sensory capabilities for long distance movement, Komodo dragons exhibited near complete dispersal restriction: individuals rarely moved beyond the valleys they were born/captured in. Importantly, lizard site-fidelity was insensitive to common agents of dispersal evolution (i.e. indices of risk for inbreeding, kin and intraspecific competition and low habitat quality) that consequently reduced survival of resident individuals. We suggest that direct selection restricts movement capacity (e.g. via benefits of spatial philopatry and increased costs of dispersal) alongside use of dispersal-compensating traits (e.g. intraspecific niche partitioning) to constrain dispersal in island species.扩散丧失是岛屿生物群（island biotas）的典型特征，但驱动这一现象的选择过程仍颇具争议。这是因为间接选择（如放松选择（relaxed selection）或岛屿综合征（island syndromes））与直接选择（如自然选择（natural selection）或空间分选（spatial sorting））均可能参与其中，且目前尚无研究能够令人信服地区分这些备选机制。本研究针对岛屿蜥蜴类群——科莫多巨蜥（Varanus komodoensis，全球现存体型最大的蜥蜴）——开展观测与实验结合的分析，为多种可能导致岛屿物种扩散丧失的作用过程提供了实证依据。针对科莫多巨蜥的遥测（telemetry）、模拟、实验易位（experimental translocations）、标记重捕（mark-recapture）与基因流（gene flow）研究得到了协同一致的结果：尽管该物种拥有卓越的长距离移动物理能力与感官功能，但其几乎完全受到扩散限制——个体极少离开其出生或被捕获所在的山谷范围。值得注意的是，科莫多巨蜥的栖居忠实性（site-fidelity）不受扩散演化常见驱动因素的影响，即近交风险、亲缘竞争、种内竞争风险以及低生境质量相关的风险指数，而这些因素本会降低定居个体的存活率。我们认为，直接选择可通过空间恋家行为（spatial philopatry）的收益与扩散成本提升等途径限制移动能力，并结合扩散补偿性状（如种内生态位分化（intraspecific niche partitioning）），从而约束岛屿物种的扩散行为。