Connectivity and edge effects increase bee colonization in an experimentally fragmented landscape

Though landscape corridors increase dispersal of many animals and plants,
it remains unknown whether increased dispersal increases colonization and
establishment of new populations in connected fragments. Working in
experimentally fragmented landscapes, we tested how two aspects of habitat
fragments altered by corridors- connectivity and edge-to-area ratio-
determine patterns of colonization by a solitary, cavity-nesting bee
(Megachile rotundata). We found that though higher connectivity initially
increased rates of nest-site occupation, higher edge-to-area ratio
ultimately increased patch occupation and nest building, likely due to
habitat selection by our focal species. Bee colonization was also higher
in patches with higher abundances of their preferred food resources,
flowers from the Fabaceae family. Our results show the importance of
considering the effects of both connectivity and edge on population
dynamics in habitat-based conservation in fragmented landscapes.

尽管景观廊道（landscape corridor）能够提升多数动植物的扩散能力，但目前仍不清楚扩散增强是否可促进连通生境片段内新生种群的定殖与建立。本研究在实验性破碎化景观中开展实验，旨在探究经廊道改造的生境片段的两项核心特征——连通性（connectivity）与边缘面积比（edge-to-area ratio）——如何调控独居凿洞筑巢蜂（苜蓿切叶蜂，Megachile rotundata）的定殖模式。研究结果显示：尽管更高的连通性最初提升了巢址占用率，但更高的边缘面积比最终提升了生境片段的占有率与筑巢活动，这一现象大概率源于目标物种的生境选择偏好。此外，当生境片段内目标蜂类偏好的食物资源——豆科（Fabaceae）植物的花朵——丰度更高时，蜂类的定殖率也显著提升。本研究结果表明，在破碎化景观的生境保护实践中，同时考量连通性与边缘效应对种群动态的双重影响至关重要。