Long‐Term Isolation Segregates Species on Islands With Contrasting Life‐History Strategies
Yiyao Huang, Yuxin Lu, Yuhao Zhao, Chengxiu Zhan, Yanping Wang, Chuanwu ChenABSTRACT
Aim
Unravelling interactions between environmental stresses and species adaptation in habitat patches is vital for elucidating community assembly and guiding conservation. Despite growing attention to rapid habitat alteration, few studies have explored how biotic and abiotic factors jointly shape species' responses to long‐term isolation. Our objective was to address this gap by identifying the key factors that determine community assembly across distinct size gradients on land‐bridge islands.
Location
Zhoushan Archipelago, the largest archipelago of China.
Taxa
Amphibians.
Methods
We surveyed amphibian distributions on 37 islands. Using segmented regressions, we explored whether thresholds exist in the diversity–area relationships across taxonomic, functional and phylogenetic dimensions. Incorporating life‐history traits into variation partitioning analyses, we further assessed the relative contributions of species' life‐history strategies and biogeographic factors in determining species distribution patterns along the island‐size gradient.
Results
Area thresholds were observed in the diversity–area relationships across three dimensions of diversity. Below these thresholds, smaller islands consistently showed neutral standardized effect sizes for functional and phylogenetic diversity, indicating a weak influence of island area on species assembly or a predominance of random processes. Additionally, small islands favoured a group of r ‐strategy species characterized by large clutch sizes and short larval stage durations. Furthermore, fast‐slow life‐history strategies had significantly greater pure explanatory power than island area on smaller islands. Beyond these thresholds, island area became substantially more influential.
Main Conclusions
Our study highlights the contrasting roles of functional adaptive strategies and biogeography in shaping amphibian distributions on islands. The identified area thresholds are critical for species conservation and indicate that management should consider the ecological strategies of target species. Specifically, small reserves may support diverse ‘fast’ amphibians but require connectivity to prevent genetic isolation. Larger reserves should preserve environmental gradients and microhabitats to sustain species with specific niche needs.