RESUMEN
Managed and wild pollinators often cohabit in both managed and natural ecosystems. The western honeybee, Apis mellifera, is the most widespread managed pollinator species. Due to its density and behaviour, it can potentially influence the foraging activity of wild pollinators, but the strength and direction of this effect are often context-dependent. Here, we observed plant-pollinator interactions in 51 grasslands, and we measured functional traits of both plants and pollinators. Using a multi-model inference approach, we explored the effects of honeybee abundance, temperature, plant functional diversity, and trait similarity between wild pollinators and the honeybee on the resource overlap between wild pollinators and the honeybee. Resource overlap decreased with increasing honeybee abundance only in plant communities with high functional diversity, suggesting a potential diet shift of wild pollinators in areas with a high variability of flower morphologies. Moreover, resource overlap increased with increasing trait similarity between wild pollinators and the honeybee. In particular, central-place foragers of family Apidae with proboscis length similar to the honeybee exhibited the highest resource overlap. Our results underline the importance of promoting functional diversity of plant communities to support wild pollinators in areas with a high density of honeybee hives. Moreover, greater attention should be paid to areas where pollinators possess functional traits similar to the honeybee, as they are expected to be more prone to potential competition with this species.
Asunto(s)
Ecosistema , Polinización , Animales , Abejas , Dieta , Flores , FenotipoRESUMEN
Elevational gradients are characterized by strong abiotic variation within small geographical distances and provide a powerful tool to evaluate community response to variation in climatic and other environmental factors. We explored how temperature and habitat diversity shape the diversity of holometabolous predator and parasitoid insects along temperate elevational gradients in the European Alps. We surveyed insect communities along 12 elevational transects that were selected to separate effects of temperature from those of habitat diversity. Pitfall traps and pan traps were placed every 100 m of elevation increment along the transects ranging from 120 to 2200 m a.s.l. Sampling took place once a month from June to September 2015. Four groups characterized by having at least one life stage behaving as predator or parasitoid were examined: tachinids (Diptera), hoverflies (Diptera), sphecids (Hymenoptera) and ground beetles (Coleoptera). Species richness and evenness changed with elevation, but the shape and direction of the elevation-diversity patterns varied between groups. The effect of temperature on species richness was positive for all groups except for hoverflies. Habitat diversity did not affect species richness, while it modulated the evenness of most groups. Often, elevational patterns of species richness and evenness were contrasting. Our study indicates that natural enemies characterized by diverse ecological requirements can be differentially affected by temperature and habitat diversity across the same elevational gradients. As climate warming is predicted to increase mean annual temperatures and exacerbate weather variability, it is also expected to strongly influence natural enemies and their ability to regulate herbivore populations.