Seasonality of pollinators in Mediterranean montane habitats: cool-blooded bees for early-blooming plants

Aguado³

et al. 2023

Ecological Monographs

Understanding the factors that drive community‐wide assembly of plant‐pollinator systems along environmental gradients has considerable evolutionary, ecological, and applied significance. Variation in thermal environments combined with intrinsic differences among pollinators in thermal biology have been proposed as drivers of community‐wide pollinator gradients, but this suggestion remains largely speculative. We test the hypothesis that seasonality in bee pollinator composition in Mediterranean montane habitats of southeastern Spain, which largely reflects the prevalence during the early flowering season of mining bees (Andrena), is a consequence of the latter's thermal biology. Quantitative information on seasonality of Andrena bees in the whole plant community (275 plant species) and their thermal microenvironment was combined with field and laboratory data on key aspects of the thermal biology of 30 species of Andrena (endothermic ability, warming constant, relationships of body temperature with ambient and operative temperatures). Andrena bees were a conspicuous, albeit strongly seasonal component of the pollinator assemblage of the regional plant community, visiting flowers of 153 different plant species (57% of total). The proportion of Andrena relative to all bees reached a maximum among plant species which flowered in late winter and early spring, and declined precipitously from May onward. Andrena were recorded only during the cooler segment of the annual range of air temperatures experienced at flowers by the whole bee assemblage. These patterns can be explained by features of Andrena's thermal biology: null to weak endothermy; ability to forage at much lower body temperature than strongly endothermic bees (difference ~ 10°C); low upper tolerable limit of body temperature, beyond which thermal stress presumably precluded foraging at the warmest period of year; weak thermoregulatory capacity; and high warming constant enhancing ectothermic warming. Our results demonstrate the importance of lineage‐specific pollinator traits as drivers of seasonality in community‐wide pollinator composition; show that exploitation of cooler microclimates by bees does not require strong endothermy; and suggest that intense endothermy and precise thermoregulation probably apply to a minority of bees. Medium‐ and large‐sized bees with low upper thermal limits and weak thermoregulatory ability can actually be more adversely affected by climate warming than large, hot‐blooded, extremely endothermic species.

Section: Methodsmentioning

confidence: 86%

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

See 2 more Smart Citations

Seasonality of pollinators in montane habitats: Cool‐blooded bees for early‐blooming plants

Aguado³

et al. 2023

Ecological Monographs

“…As part of other studies (Herrera 1995, 1997, Herrera et al 2022, a total of 1,186 solitary bees from 108 species, 25 genera and six families (Andrenidae, Apidae, Colletidae, Halictidae, Megachilidae, Melittidae; see Appendix S1: Table S1, for species and sample sizes) were handnetted in the field during 1990-1997 ("old period" hereafter; N = 472 individuals, 46 species) and 2022 ("recent period"; N = 714 individuals, 99 species), in 47 localities located in the core area of the Sierras de Cazorla, Segura y Las Villas Natural Park, a 2,140 km 2 protected area in Jaén Province, southeastern Spain. The species sampled represented ~30% of all species of bees occurring in the region, and mostly belonged to the genera Andrena (643 individuals, 32 species), Colletes (82, 4), Anthophora (81, 10), Osmia (72, 4), Anthidium (64, 2) and Xylocopa (51, 3) (Appendix S1: Table S1).…”

Section: Methodsmentioning

confidence: 98%

Body mass decline in a Mediterranean community of solitary bees supports the size shrinking effect of climatic warming

Valverde

et al. 2022

Preprint

Self Cite

The long-known, widely documented inverse relationship between body size and environmental temperature ('temperature-size rule') has recently led to predictions of body size decline following current climatic warming ('size shrinking effect'). For keystone pollinators such as wild bees, body shrinking in response to warming can have pervasive effects on pollination processes, but there is still little evidence of the phenomenon because adequate tests require controlling for climate-linked confounding factors (e.g., urbanization, land use change). This paper tests the shrinking effect in a diverse community of solitary bees from well-preserved habitats in the core of a large nature reserve undergoing fast climatic warming but not disturbances or habitat changes. Long-term variation in mean body mass was evaluated using data from 1,186 individual bees (108 species, 25 genera, 6 families) sampled over 1990-2022. Climate of the region warmed at a fast rate during this period and changes in bee body mass verified expectations from the size shrinking effect. Mean individual body mass of the regional community of solitary bees declined significantly, shrinking being particularly intense for female individuals and large-bodied species. As a consequence, the pollination and mating systems of many bee-pollinated plants in the region are likely undergoing important alterations.

Body mass decline in a Mediterranean community of solitary bees supports the size shrinking effect of climatic warming

Valverde

et al. 2023

Ecology

The long‐known, widely documented inverse relationship between body size and environmental temperature (“temperature‐size rule”) has recently led to predictions of body size decline following current climatic warming (“size shrinking effect”). For keystone pollinators such as wild bees, body shrinking in response to warming can have significant effects on pollination processes but there is still little direct evidence of the phenomenon because adequate tests require controlling for confounding factors linked to climate change (e.g., habitat change). This paper assesses the shrinking effect in a community of solitary bees from well‐preserved habitats in the core of a large nature reserve experiencing climatic warming without disturbances or habitat changes. Long‐term variation in mean body mass was evaluated using data from 1704 individual bees (137 species, 27 genera, 6 families) sampled over 1990–2023. Climate warmed at a fast rate during this period, annual mean of daily maximum temperature increasing 0.069°C/year on average during 2000–2020. Changes in bee body mass verified expectations from the size shrinking effect. The mean individual body mass of the community of solitary bees declined significantly, irrespective of whether the analysis referred to the full species sample or only to the subset of species that were sampled in both the old (1990–1997) and recent (2022–2023) periods. On average, body mass declined ~0.7%·year−1, or an estimated average cumulative reduction of ~20 mg per individual bee from 1990 to 2023. Proportional size reduction was greatest among large‐bodied species, ranging from around −0.6%·year−1 for the smallest species to −0.9%·year−1 for the largest ones. Declining rate was steeper for cavity‐nesting than ground‐nesting species. The pollination and mating systems of bee‐pollinated plants in the study region are probably undergoing significant alterations as a consequence of supra‐annual decline in bee body mass.