Data from: Rain shadow effects predict population differences in thermal tolerance of leaf-cutting ant workers (Atta cephalotes)
Description
Tests of hypotheses for the evolution of thermal physiology often rely on mean temperatures, but mounting evidence suggests geographic variation in temperature extremes is also an important predictor of species' thermal tolerances. Although the tropics are less thermally variable than higher latitude regions, rain shadows on the leeward sides of mountains can experience greater diel and seasonal variation in temperature than windward sites. Rain shadows provide opportunities to test predictions about the relationships of extreme temperatures with thermal physiology while controlling for latitude. We tested the hypothesis that populations of leaf-cutting ants (Atta cephalotes) in leeward, montane, and windward sites in Costa Rica would differ in upper thermal tolerances (CTmax) of workers. As predicted from rain shadow effects via extreme high temperatures, the leeward rain-shadow site yielded the highest mean CTmax (rain shadow site 42.1±0.3 °C, Montane site 38.2±0.5 °C, windward site 38.2±0.3 °C). This suggests that high-temperature extremes in tropical rain shadow forests can select for higher thermal tolerances. CTmax increased with worker body size within sites, but CTmax increased with body size more gradually at the two lowland sites, as predicted if local high temperatures selected more strongly on the most thermally vulnerable society members (small workers). This suggests that warmer lowland climates selected for colonies with less variation in heat tolerance than cooler high elevation climates.
Notes
Most headers have been named intuitively, with abbreviations such as "Avg." meaning "average" and "SD" indicating "standard deviation". All temperatures and CTmax values are reported in degrees celcius. Below is a list of less intuitive headers within these files and their exact meaning.
Downloaded bioclim data based on nest coordinates:
BC_MAT - mean annual temperature (BIO1)
BC_MDRngT - Mean Diurnal Range (Mean of monthly (max temp - min temp)) (BIO2)
BC_TARng - temperature annual range (BIO7)
BC_Aprecip - Annual precipitation (BIO12)
BC_PrecipSnlty - Precipitation seasonality (Coefficient of Variation) (BIO15)
BC_MaxTWM - Maximum temperature of warmest month (BIO5)
BC_MinTCM - Minimum temperature of coldest month (BIO6)
Ibutton-based data in master CTmax file:
ibutton_Min - average minimum daily temperature for this site
ibutton_Max - average maximum daily temperature for this site
ibutton_Avg - average daily temperature for this site
Warming tolerances (discussed only in supplementary material):
Night_Warming_Tolerance - individual ant CTmax minus average daily minimum temperature (ibutton data)
Day_Warming_Tolerance - individual ant CTmax minus average daily maximum temperature (ibutton data)
Mean_Warming_Tolerance - individual ant CTmax minus average mean daily temperature (ibutton data)
Funding provided by: Organization for Tropical Studies
Crossref Funder Registry ID:
Award Number: Tyson Research Fellowship
Funding provided by: The Academy of Natural Sciences of Drexel University
Crossref Funder Registry ID: http://dx.doi.org/10.13039/100005319
Award Number: William L. McLean III Fellowship