Keep your cool: Overwintering physiology in response to urbanization in the acorn ant, Temnothorax curvispinosus
Description
Is there evolutionary divergence in Acorn Ant Overwintering physiology across the urbanization gradient? We expected that warm adapted urban populations would have lower performance in cold tolerance (longer recovery time) and higher metabolic rate at cold temperatures while expressing higher heat tolerance (higher temperature to loss of muscle control). We also expected greater population loss in urban populations under cold acclimation temperatures. To test our hypotheses, we ran a common garden rearing design for field caught urban and rural ants under overwintering conditions and then tested their heat tolerance, cold tolerance, metabolic rate and survival. We found no differences in cold tolerance or metabolic rate in urban and rural populations but did find higher heat tolerance in urban populations. The following descriptions show what each data set and R script sets up: Scripts R code for each physiological measure under overwintering conditions - OvW_Count: worker count / Survival: collected data on the number of workers at the start and end of the experiment - OvW_MR_script: Metabolic Rate: collected routine metabolic rate (mLCO2 / min) at two temperatures (4 and 10 C) for all populations. - OvW_CCRT: Chill Coma Recovery Time (CCRT): cold tolerance measure of recovery time from an acute cold temperature stress that induces chill coma (ours was measured at -10 C) and measured as time until leg / antennae movement. - OvW_CTmax: Critical Thermal Maximum (CTmax): heat tolerance measure of muscular control under a dynamic ramping assay measured as the temperature at which loss of muscle control was observed. Metadata for each data file description of variables within each dataset ### CCRT - CCRT csv file in minutes; code changes to seconds for modeling as an integer - Treatment (source population: urban or rural) and Collection season are factor variables - Colony ID is randomly generated value ### CTmax - CTmax csv file: ctmax in degrees C - Treatment (source population: urban or rural) and Collection season are factor variables - Colony ID is randomly generated value ### Worker Count / Survival - Worker start and end are the number of workers at the beginning (0) and end (4) months of the experiment - Source population (urban or rural) is a factor variable - Colony ID is randomly generated value ### metabolic rate - mean MR = average metabolic rate in CO2 (mL CO2/min) - mean MR RA = avg metabolic rate in CO2 rolling average (not used in analyses) - Chamber index = chamber where colony was; chamber 8 = control or blank container - Q10 = thermal sensitivity quotient of the two metabolic rates at two temperatures raised to the 10th power divided by the temperature difference - Collection date = similar to collection season factor from ccrt and ctmax files above - Source.pop = factor variable (urban or rural) - Colony ID is randomly generated value