Desynchronizations in bee–plant interactions cause severe fitness losses in solitary bees

Abstract

Abstract1. Global warming can disrupt mutualistic interactions between solitary bees and plants when increasing temperature differentially changes the timing of interacting partners. One possible scenario is for insect phenology to advance more rapidly than plant phenology.2. However, empirical evidence for fitness consequences due to temporal mismatches is lacking for pollinators and it remains unknown if bees have developed strategies to mitigate fitness losses following temporal mismatches.3. We tested the effect of temporal mismatches on the fitness of three spring-emerging solitary bee species, including one pollen specialist. Using flight cages, we simulated (i) a perfect synchronization (from a bee perspective): bees and flowers occur simultaneously, (ii) a mismatch of 3 days and (iii) a mismatch of 6 days, with bees occurring earlier than flowers in the latter two cases. 4. A mismatch of 6 days caused severe fitness losses in all three bee species, as few bees survived without flowers. Females showed strongly reduced activity and reproductive output compared to synchronized bees. Fitness consequences of a 3-day mismatch were species-specific. Both the early-spring species Osmia cornuta and the mid-spring species Osmia bicornis produced the same number of brood cells after a mismatch of 3 days as under perfect synchronization. However, O. cornuta decreased the number of female offspring, whereas O. bicornis spread the brood cells over fewer nests, which may increase offspring mortality, e.g. due to parasitoids. The late-spring specialist Osmia brevicornis produced fewer brood cells even after a mismatch of 3 days. Additionally, our results suggest that fitness losses after temporal mismatches are higher during warm than cold springs, as the naturally occurring temperature variability revealed that warm temperatures during starvation decreased the survival rate of O. bicornis.5. We conclude that short temporal mismatches can cause clear fitness losses in solitary bees. Although our results suggest that bees have evolved species-specific strategies to mitigate fitness losses after temporal mismatches, the bees were not able to completely compensate for impacts on their fitness after temporal mismatches with their food resources.This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.

Changes in phenology and abundance of suction‐trapped Diptera from a farmland site in the UK over four decades

“…The shift of the main occurrence towards earlier dates is in accordance with other studies from temperate regions (Bartomeus et al, 2011;Thackeray et al, 2016;Cohen et al, 2018). As many fly species fulfil ecosystem services such as pollination (Ssymank et al, 2008;Orford et al, 2015), the shift in phenology might lead to a temporal mismatch between pollinators and the opening of flowers due to different phenological responses, as has been shown in other systems (Schenk et al, 2018). Other beneficial biotic interactions might also be desynchronised as some fly species are natural enemies of crop pests (e.g.…”

Specialization of plant–pollinator interactions increases with temperature at Mt. Kilimanjaro

“…Although the mechanisms behind the temperature—specialization relationship remain speculative, the outstanding role of temperature in structuring plant–pollinator interactions is alarming: global temperatures are predicted to increase by up to 0.7°C in the next two decades (compared to 1985–2005; IPCC, ). So far, climate change was expected to disrupt plant–pollinator interactions by causing spatial and phenological mismatches between interaction partners (Hegland, Nielsen, Lázaro, Bjerknes, & Totland, ), or by increased frequency of extreme weather events (Hoiss et al, ), with negative consequences for interaction resilience and fitness of plants and pollinators (Forrest, ; Schenk, Krauss, & Holzschuh, ). The direct impact of temperature on the specialization of species, which has also been reported from small‐scale climatic gradients for network specialization (Petanidou et al, ), imposes additional challenges to species interactions.…”

Solitary Bee Life History Traits and Sex Mediate Responses to Manipulated Seasonal Temperatures and Season Length

“…A stronger effect of warm, extended fall conditions on winter emergence in males compared to females when spring onset was late suggests that emergence may be more constrained in male O. lignaria, potentially as a result of reduced energy availability at the start of the experiment (i.e., O. lignaria males entered the experiment with 8.5 mg/mm less mass compared to females; t 252 = 9.96, p < 0.001). Emerging prior to the onset of spring would likely increase mortality in O. lignaria due to scarce or absent floral resource availability when they emerge (Schenk et al, 2018b), which could have important implications for O. lignaria populations under climate change. However, given that the likelihood of winter emergence was low when spring-onset was early suggests that climate change may not increase the occurrence of this response.…”