Importance as pollinators and thermal biology of Andrena bees in southern Spanish montane habitats

Data on bee pollinator composition and air temperature at the foraging sites of different bee species were collected during January-December 1997-2022 in a relatively small area of the Sierra de Cazorla, Jaén Province, southeastern Spain. Some additional field measurements of Andrena thoracic temperature were gathered in February-April 2022 at two locations in Córdoba and Sevilla provinces. Pollinator composition was quantitatively assessed for 275 plant species in 179 genera from 47 families. The proportions of Andrena and non-Andrena bees were obtained for each plant species. Air temperature at bee foraging sites was measured over January-August while they were visiting flowers in fine weather. Foraging bees were hand netted and air temperature (Ta) 2-5 cm away from the flower where the bee had been caught was measured immediately after the bee's capture using a digital thermometer and fast-response thermocouple. Data were obtained in the laboratory and/or the field on the thermal biology of 30 species of Andrena. The ability of live Andrena bees to warm-up spontaneously by endothermy, and the intrinsic warming constants of the same individuals, were assessed experimentally in the laboratory. Free-ranging individuals of Andrena species were hand netted in fine weather while foraging at flowers. Air temperature (Ta) at capture point and thoracic temperature (Tth) were measured. A subset of these individuals were killed immediately after thoracic temperature measurement and their operative temperatures (Te) in the natural environment was estimated. Results obtained for two key thermal features of Andrena bees (warming constant K estimated in the laboratory, and thoracic temperatures of foraging individuals measured in the field) were compared with those obtained previously in the Sierra de Cazorla study region as part of other studies for a taxonomically diverse sample of 20 bee species from five families and 11 genera, using identical field and laboratory procedures. Further details on field, laboratory and statistical methods can be obtained in Herrera, C. M., A. Núñez, L. O. Aguado, and C. Alonso. 2023. Seasonality of pollinators in montane habitats: cool-blooded bees for early-blooming plants. Ecological Monographs, in press.