The role of temperature in structuring a Sierra Nevadan ant community

Arthropod activity times are often determined by changes in temperature, ambient light, predator abundance, or resource availability. Ground and wood-dwelling ants have particularly strong responses to fluctuations in temperature and light, due their ability to use nests as thermal refugia when environmental conditions become unfavorable. Through the selective foraging of local ant species, epigeal ant communities fluctuate in species composition. In order to determine the role of temperature fluctuations on seasonal and diel scales in structuring ant communities in time, I built time-sorting pitfall traps with built-in thermocouple dataloggers to capture 1-hour intervals of ant activity. I then deployed these time-sorting pitfall traps in the month of June at Sagehen Creek Reserve near Truckee, CA, to investigate activity patterns of species occurrence over the course of the day. Average activity times varied by species, with several species demonstrating crepuscular patterns of activity. Litter depth had a large impact of the identity and number of species encountered and the time of day ants were active. No ants were found to be truly nocturnal, with average nighttime lows approaching freezing. Similarly, few ants persisted in the hottest environments monitored in mid afternoon.