1. Climate change is rapidly altering thermal environments across the globe. The effects of increased temperatures in already warm environments may be particularly strong because organisms are likely to be near their thermal safety margins, with limited tolerance to additional heat stress. 2. We conduct an in situ field experiment over two years to investigate the direct effects of temperature on an early-season solitary bee in a warm, arid region of the Southwestern USA. Our field experiment manipulates the thermal environment of Osmia ribifloris (Megachilidae) from larval development through adult emergence, simulating both previous cooler (ca. 1950; nest boxes painted white), and future warmer (2040–2099; nest boxes painted black) climate conditions. In each year we measure adult emergence phenology, linear body size, body mass, fat content, and survival. 3. Bees in the warming treatment exhibit delayed emergence and a substantial increase in phenological variance. Increases in temperature also lead to reductions in body mass and fat content. Whereas bees in the cooling and control treatments experience negligible amounts of mortality, bees in the warming treatment experience 30–75% mortality. 4. Our findings indicate that temperature changes that have occurred since ca. 1950 have likely had relatively weak and non-negative effects, but predicted warmer temperatures create a high stress thermal environment for O. ribifloris. Later and more variable emergence dates under warming likely compromise phenological synchrony with floral resources and the ability of individuals to find mates. The consequences of phenological asynchrony, combined with reductions in body mass and fat content, will likely impose fitness reductions in surviving bees. Combined with high rates of mortality, our results suggest that O. ribifloris may face local extirpation in the warmer parts of its range within the century. 5. Temperature increases in already warm ecosystems can have substantial consequences for key components of life history, physiology, and survival. Our study suggests that the response of ectothermic insects to temperature increases in already warm environments may be insufficient to mitigate the negative consequences of future warming.
Osmia ribifloris temperature experiment responses
These data represent the responses of the solitary bee Osmia ribifloris (Megachilidae) to experimental temperature conditions applied in the field. The experimental temperature treatments represent previous, cooler conditions (cooling), future warmer conditions (warming) and current temperature conditions (control). This field experiment was conducted in the Santa Catalina Mountains outside of Tucson, Arizona, USA. Each row within the data file represents the responses of an individual bee emerging from a nest. The responses in this data file include: emergence_date = the date on which the bee was observed emerging from the nest; emergence_day_of_year = the date (as day of year, where 1 = 1 January) that the bee was observed emerging from the nest; treatment = the experimental temperature treatment (control, cooling, warming); exp_block = the experimental block the nest was part of (this information combined with treatment information represents a unique nest box identification); hole_num = the nest number within each nest box (1=top, 2=middle, 3=bottom); bee_num = an identification number for each bee that emerged (more than one bee can emerge on the same date); sex = the sex of the bee (when not listed as male or female, this means sex could not be determined and instead the developmental stage was included if possible); mass_g = the dry mass of the adult bee in grams; mass_mg = the dry mass of the adult bee in milligrams; mortality = whether the bee died under the experimental conditions (0 = alive, 1 = dead).
osmia_ribifloris_experiment_responses.csv
Osmia ribifloris temperature experiment, lipid content and body size responses
These data represent linear body size and fat (lipid) content responses of adult Osmia ribifloris bees to experimental temperature conditions. The experimental temperature treatments represent previous, cooler conditions (cooling), future warming conditions (warming) and current temperature conditions (control). This field experiment was conducted in the Santa Catalina Mountains outside of Tucson, Arizona, USA. Each row of the dataset represents the responses of an individual bee emerging from a nest. Emergence_date = the date on which the bee was observed emerging from the nest; treatment = the experimental temperature treatment; exp_block = the experimental block the nest was part of (this information combined with treatment information represents a unique nest box identification); hole_num = the nest number within each nest box; sex = the sex of the bee (male or female); id = an identification letter for each bee that emerged from the same nest; it_distance = the intertegular distance measured in millimeters for each individual bee (a measure of linear body size); mass_before_lipid_extraction_mg = the dry mass of the bee measured in milligrams before lipid extraction; mass_after_lipid_extraction_mg = the dry mass of the bee measured in milligrams after lipid extraction; lipid_content_mg = the lipid content of the bee measured in milligrams (this is the difference between the before and after mass measurements); lipid_percent = the proportion of the adult bee's body mass that is represented by lipids (i.e., lipid mass divided by the initial dry weight of the adult bee); lipid_test_box_id = a color code that represents where the individual bee was kept during lipid extraction; lipid_test_box_location = a location code for the specific location of the individual bee during the lipid extraction; lipid_trial = the lipid assay number (not all bees were processed at the same time); sample = a sample identification number; lipid_analysis_start = the date and time when each lipid extraction assay began.
osmia_ribifloris_experiment_lipid_content.csv
