Data from: Tropical forest fragmentation limits movements, but not occurrence of a generalist pollinator species

Habitat loss and fragmentation influence species distributions and therefore ecological processes that depend upon them. Pollination may be particularly susceptible to fragmentation, as it depends on frequent pollinator movement. Unfortunately, most pollinators are too small to track efficiently which has precluded testing the hypothesis that habitat fragmentation reduces or eliminates pollen flow by disrupting pollinator movement. We used radio-telemetry to examine space use of the green hermit hummingbird (Phaethornis guy), an important 'hub' pollinator of understory flowering plants across substantial portions of the neotropics and the primary pollinator of a keystone plant which shows reduced pollination success in fragmented landscapes. We found that green hermits strongly avoided crossing large stretches of non-forested matrix and preferred to move along stream corridors. Forest gaps as small as 50 m diminished the odds of movement by 50%. Green hermits occurred almost exclusively inside the forest, with the odds of occurrence being 8 times higher at points with >95% canopy cover compared with points having <5% canopy cover. Nevertheless, surprisingly. the species occurred in fragmented landscapes with low amounts of forest (~30% within a 2 km radius). Our results indicate that although green hermits are present even in landscapes with low amounts of tropical forest, movement within these landscapes ends up strongly constrained by forest gaps. Restricted movement of pollinators may be an underappreciated mechanism for widespread declines in pollination and plant fitness in fragmented landscapes, even when in the presence of appropriate pollinators.生境丧失与片段化会改变物种分布格局，进而影响依赖于此的各类生态过程。授粉过程尤其易受生境片段化的干扰，因其依赖传粉者的高频移动。遗憾的是，绝大多数传粉者体型微小，难以实现高效追踪，这使得学界无法验证下述假说：生境片段化会通过干扰传粉者移动，减少甚至阻断花粉流。本研究采用无线电遥测技术（radio-telemetry），探究绿隐蜂鸟（Phaethornis guy）的空间利用模式。该蜂鸟是新热带区多数区域林下开花植物的重要枢纽传粉者，同时也是某一关键植物物种的主要传粉者——这类植物在片段化生境中的授粉成功率会出现显著下降。研究结果显示，绿隐蜂鸟会极力规避穿越大片非森林基质，更偏好沿溪流廊道移动。即便仅50米宽的林隙，也会使蜂鸟的移动几率降低50%。绿隐蜂鸟几乎仅分布于森林内部，冠层覆盖度大于95%的区域，其出现几率是冠层覆盖度小于5%区域的8倍。但令人意外的是，该物种仍可在森林覆盖率较低的片段化生境中存续：在2千米半径范围内，森林占比仅约30%的区域亦有其分布。本研究结果表明，尽管绿隐蜂鸟可在热带森林覆盖率较低的生境中存活，但这类生境中的蜂鸟移动仍会受到林隙的强烈限制。即便生境中存在适宜的传粉者，传粉者移动受限也可能是片段化生境中授粉普遍下降、植物适合度降低的一个被低估的作用机制。