Data from: Low functional diversity promotes niche changes in natural island pollinator communities

Functional diversity loss among pollinators has rapidly progressed across the globe and is expected to influence plant–pollinator interactions in natural communities. Although recent findings suggest that the disappearance of a certain pollinator functional group may cause niche expansions and/or shifts in other groups, no study has examined this prediction in natural communities with high plant and pollinator diversities. By comparing coastal pollination networks on continental and oceanic islands, we examined how community-level flower visit patterns are influenced by the relative biomass of long-tongued pollinators (RBLP). We found that RBLP significantly correlated with pollinator functional diversity and was lower in oceanic than in continental islands. Pollinator niches shifted with decreasing RBLP, such that diverse species with various proboscis lengths, especially short-tongued species, increasingly visited long-tubed flowers. However, we found no conspicuous negative impacts of low RBLP and the consequent niche shifts on pollinator visit frequencies to flowers in oceanic island communities. Notably, fruit set significantly decreased as RBLP decreased in a study plant species. These results suggest that niche shifts by other functional groups can generally compensate for a decline in long-tongued pollinators in natural communities, but there may be negative impacts on plant reproduction.

全球范围内传粉者的功能多样性丧失正快速加剧，预计将对自然群落中的植物-传粉者互作（plant–pollinator interactions）产生影响。尽管近期研究表明，某一传粉者功能群（pollinator functional group）的消失可能引发其他类群的生态位扩张（niche expansion）与/或生态位转移（niche shift），但尚无研究在兼具高植物与传粉者多样性的自然群落中验证这一推论。本研究通过对比大陆岛与大洋岛的海岸传粉网络，探究了长舌传粉者相对生物量（relative biomass of long-tongued pollinators, RBLP）对群落水平访花模式的影响。结果显示，RBLP与传粉者功能多样性（pollinator functional diversity）显著相关，且大洋岛的RBLP显著低于大陆岛。随着RBLP降低，传粉者生态位发生转移：具有不同吻长的多样类群（尤以短舌物种为甚）愈发频繁地造访长管花。但本研究未发现RBLP降低及由此引发的生态位转移，会对大洋岛群落中植物的传粉者访花频率产生显著负面影响。值得注意的是，在所研究的植物物种中，坐果率（fruit set）随RBLP降低而显著下降。上述结果表明，其他功能群的生态位转移通常可补偿自然群落中长舌传粉者的减少，但可能对植物繁殖产生负面影响。