Investigating phenological mismatches between bumblebees and their brood parasites in a bumblebee-diversity hotspot
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Department of Ecological and Biological Science, Università della Tuscia, Largo dell’Università, Viterbo, VT - 01100, Italia
Cuckoo bumblebees (Bombus, subgenus Psithyrus) are obligate social parasites of other bumblebee species. Although they share habitats with their hosts, their parasitic lifestyle imposes additional ecological and phenological constraints, such as a dependence of the temporal window to host development and activity patterns. A delayed emergence is thought to be adaptive, yet phenological mismatches between hosts and parasites remain largely unquantified, and the extent to which these dynamics are modulated by the environmental context remains unclear. With this study we examine whether mismatches in host–parasite timing are consistent across parasite species and how these coevolved phenologies may be affected by environmental changes. To this end, we analysed phenological patterns of multiple host–parasite pairs naturally co-occurring in a southern Mediterranean hotspot of bumblebee diversity. As expected, cuckoo bumblebees exhibited narrower and more temporally restricted flight periods compared to their hosts, suggesting a constrained phenological strategy tightly aligned with host colony cycles. However, we found distinct patterns of asynchrony depending on the examined host–parasite pair. These results suggest that phenological mismatches are not fixed traits but are shaped by species interactions and ecological contexts. Still, host phenology displayed a significant and strong association with temperature, particularly pre-season warming, while parasite responses were weaker and more variable, suggesting limited ability to cope with temperature changes. This different response to temperature may compromise coevolved synchrony under climate change, which deserve consideration in conservation initiatives applied to pollinator communities.
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