TIL20: A review of island biogeography and habitat fragmentation studies on subtropical reservoir islands of Thousand Island Lake, China

Reservoir islands formed by dam construction have the same history,clear boundaries,and large numbers that provide a natural platform for testing theories in ecology and biogeography.In this paper,we review studies of multiple zoological taxa on reservoir islands of a large lake in eastern China(Thousand Island Lake).This lake,created in 1959,has 1078 artificial land-bridge islands of varying areas and isolation.Our review summarizes the decades-long studies in island biogeography and habitat fragmentation from this island system,grouped into three topics:species richness(“how many species are there”),community structure(“who are they”),and species interaction(“how they interact with each other”).Our findings support the predictions of the Equilibrium Theory of Island Biogeography and extend this theory to predict community structure of island faunas by moving beyond assumptions of species equivalency.In addition,the extensive studies on ecological networks,including mutualistic,antagonistic,and parasitic interactions,reveal the negative impacts of habitat loss on the maintenance of such networks,even as increasing forest edge enhances the robustness of pollination networks.At the end of this review,we proposed several future research directions based on current studies that are simultaneously at the frontier of ecology and biogeography.

千岛湖陆桥岛屿地表蚂蚁群落物种多样性空间格局及其影响因素

为了探讨千岛湖岛屿景观参数对地表蚂蚁群落物种α和β多样性空间格局的影响,作者分别于2017和2018年的5–8月,采用陷阱法、凋落物分拣法和手捡法调查了千岛湖33个岛屿上的地表蚂蚁群落,并依据食性将其划分为捕食性蚂蚁和杂食性蚂蚁。利用回归模型分析了全部蚂蚁、捕食性蚂蚁和杂食性蚂蚁群落α和β多样性与岛屿景观参数的关系。结果表明,岛屿面积对全部蚂蚁、捕食性蚂蚁和杂食性蚂蚁的物种丰富度均有显著的正向影响,而隔离度则无显著作用。蚂蚁群落的β多样性由空间周转组分主导。岛屿面积差对全部蚂蚁、捕食性蚂蚁和杂食性蚂蚁群落β多样性的嵌套组分有正向影响,隔离度差只对杂食性蚂蚁的总体β多样性有正向影响。因此,岛屿面积是影响千岛湖地表蚂蚁群落物种丰富度的主要因素,并且岛屿面积通过嵌套组分来影响蚂蚁群落的β多样性,表现出选择性灭绝过程。此外,不同食性蚂蚁可能因为扩散能力的差异对岛屿景观参数产生不同的响应。

Rodent abundance triggered switch between the relative mutualism and predation in a rodent-seed system of the subtropical island forest

Density-dependent non-monotonic species interactions are important in maintaining ecosystem stability and function,but empirical evidences are still rare.Rodents,as both seed dispersers and seed predators,have dual effects on plant regeneration and may result in non-monotonic rodent-plant interactions.According to the non-monotonic models,the relative positive or negative effects of rodents on seedling establishment can be measured based on the positive or negative association of seedling recruitment rate and rodent abundance.In this study,we investigated the fates of acorns of Quercus serrata by tracking tagged seeds on 21 fragmented subtropical islands in the Thousand Island Lake,China.We found that the proportion of germinated seeds of all released seeds showed a dome-shaped association with rodent abundance per seed.The proportion of removed seeds and cached seeds showed a saturated-and a weak dome-shaped association with rodent abundance per seed,respectively.Our results demonstrated a clear empirical evidence that rodent abundance per seed triggered a switch between the relative mutualism and predation in a rodent-seed system.Our study implied that the observed non-monotonic interactions between plants and animals may play a significant role in maintaining biodiversity and ecosystem function.We appeal for more investigations of the complex non-monotonic interactions in various ecosystems.