Longevity of starved bumblebee queens (Hymenoptera: Apidae) is shorter at high than low temperatures

Abstract

Abstract. Northern bumblebees (Hymenoptera: Apidae) with annual lifecycles depend both on energy stores remaining in their fat body after diapause and a few spring flowering plants. Most temperate bumblebees emerge gradually over several months after winter depending on the species and within species on the location of the overwintering chamber (hibernaculum). Weather can either delay or promote emergence and nectar resources are needed to fuel flight at low ambient temperatures to find a nest site. Several phoretic mites use queens for transportation and have synchronized life cycles with their host species. Their presence on the body of bumblebees is usually harmless but can become harmful when the number of mites increases to hundreds per individual bee. High numbers of mites on queens may also indicate the queens are in poor condition. The effect of temperature and mite load on the time for which queens can survive (d) during a 25-day period of starvation were determined using newly emerged spring queens of B. lucorum. Queens collected from various locations in SW Finland were divided into four groups taking into account their initial load of Parasitellus fucorum mites: (A) 15°C and provided with only water; (B) 24°C and provided with only water; (C) 15°C and provided with pollen and nectar; (D) 24°C and provided with pollen and nectar. There were mites on 65% (50 out of 77) of the queens. All of the fed queens survived and starved queens died, with those kept at 24°C dying approximately 8 days before those kept at 15°C. Queen weight or mite load had no effect on the length of the period for which they survived and there was no difference in the weights of the queens in the different mite load classes. Asynchrony between plants and insect as well as increased frost damage due to climate change may affect nectar availability in spring. Therefore, the survival and long term viability of bumblebee populations should be monitored during variable spring conditions.

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

“…We showed that high ambient temperatures enhanced the negative effect of a temporal mismatch on the survival rate of O. bicornis . Temperature‐dependent survival during starvation periods has also been documented for bumblebees and can be explained by more rapid metabolic function and concomitant higher overall energy expenditure in warm than cold conditions (Vesterlund & Sorvari, ). The temperature‐independent survival rate of O. bicornis individuals in perfect synchronization with their food plants (meaning that energy intake was possible) suggests that not only overall energy expenditure but also overall energy intake is higher in warm than cold conditions.…”

“…Research effort has mostly focused on the fitness consequences for plants but to date fitness consequences have not been investigated for bees (Forrest, ). The few studies available on adult food limitation in pollinating insects examined bumblebees and butterflies in the laboratory (Boggs & Ross, ; Murphy, Launer, & Ehrlich, ; Vesterlund & Sorvari, ). They indicated that fecundity and/or longevity are reduced, implying severe fitness losses for these species.…”

“…In addition, we examined how increasing temperatures modify the impact of temporal mismatches on the fitness of bees. As in warm conditions metabolic functions are faster and overall energy expenditure is higher than in cold conditions (Vesterlund & Sorvari, ), temporal mismatches and therefore starvation during periods of warm temperatures could be greater than during cold periods. As temporal mismatches can also occur due to interannual temperature fluctuations, we cannot neglect the possibility that bees could have evolved strategies to mitigate fitness losses when they are desynchronized with their host plants.…”

Overwintering temperature and body condition shift emergence dates of spring-emerging solitary bees

“…These results are in accordance with previous studies on solitary bees, which have suggested negative effects of increased overwintering temperatures on the body weight and fat body mass of bees ( Fliszkiewicz et al, 2012 ; Fründ, Zieger & Tscharntke, 2013 ; Wasielewski et al, 2013 ). In warm temperatures metabolic functions are more rapid and overall energy expenditure is thus higher than in cold temperatures ( Vesterlund & Sorvari, 2014 ). Further, at the time of emergence, bees overwintering in warm temperatures had, despite emerging about a month earlier than bees in cold temperatures, lower body weight than bees overwintering in medium (females of both species) or cold temperatures (all except male O. cornuta ).…”

Interannual bumble bee abundance is driven by indirect climate effects on floral resource phenology

“…Though research is limited, climate may have negative direct effects on bumble bees if extreme temperatures or precipitation cause high mortality in overwintered queens or colonies (e.g. Vesterlund & Sorvari ; Oyen et al . ) or reduce critical foraging activity (e.g.…”