What structures diurnal visitation rates to flowering trees in an Afrotropical lowland rainforest understory?

As environmental change and degradation accelerate, perturbing insect populations, we need to better understand the resource use dynamics of diverse wild pollinators. Most tropical trees are adapted for biotic pollination, yet we still know little about plant-pollinator interactions in African rainforests. We addressed this gap from a community perspective, identifying what floral traits - colour, scent, reward accessibility and visibility - structure visitation patterns among insect functional groups to tree species flowering in the understory of Korup National Park, Cameroon. To understand how visitor groups share resources, we used joint modelling that explicitly considers zero-inflation in visitation rates and correlation among visitor groups. Most tree species had exposed floral rewards, and all were visited by multiple insect groups among which ants, bees, beetles, and flies were most abundant. Visitation rates varied more among tree species than among individual trees. Floral scent differences were important for structuring visits, particularly for flies, bees, and ants. Ant and bee visitation rates decreased while fly visits increased marginally throughout the season, correlated with the dry to wet season transition. Comparison with other lowland tropical understories suggests flies may be uniquely diverse and important to this system, and differences in seasonality and forest structure may be drivers of community differences. Floral scent is likely a key functional trait structuring flower-insect interactions in tropical forest environments and should be emphasised in future studies. Lastly, a joint modelling approach can elucidate community structure, particularly in communities with ecologically generalised interactions.

Automated summary

This study examined plant-pollinator interactions in African rainforests using a community perspective, focusing on tree species and insect functional groups in the understory of Korup National Park. Floral scent was found to be a key factor structuring visitation patterns, with ants, bees, beetles, and flies being the main visitor groups. Flies were suggested to be uniquely diverse and important to this system, with differences in seasonality and forest structure driving community variations.