Meeting Abstract

69.3  Wednesday, Jan. 6  Effects of nighttime temperature on reproduction of side-blotched lizards (Uta stansburiana) ZANI, Peter A.; Gonzaga University zani@gonzaga.edu

The life-historical responses of organisms are often temperature dependent, particularly in ectotherms, which respond to a favorable growing season by investing in growth and reproduction. Environmental variation in temperature (e.g., along latitudinal clines or between years) may affect reproductive investment and timing. However, as other factors that influence reproduction (e.g., food, moisture) may confound spatial and temporal variation, I used a surrogate for natural thermal variation in which I tested the effects of nighttime temperature on the production of second clutches of eggs in side-blotched lizards (Uta stansburiana). Starting on the first day of the reproductive cycle (i.e., the day after oviposition), females (12 in each treatment) were exposed to warm (27°C), cold (5°C) or intermediate (16°C) nights, but given a common-garden environment during the day with unlimited food and thermoregulatory opportunity. There was no difference among temperature treatments in the probability of females laying a second clutch (~75%). Nor was there any difference among treatments in clutch size (4.4 eggs), egg mass (0.34 g per egg), relative clutch mass (55% of dam mass), or egg incubation period (50 d). The only effect was on reproductive timing; females exposed to cold nights laid second clutches 6 d later than those from warm nights (inter-clutch interval = 40 vs. 34 d, respectively), with those from intermediate nights falling in between (36 d). These results indicate that nighttime temperatures do not affect life history via reproductive effort, but only timing. Furthermore, these effects do not hold over to embryo development. In other words, if given ample daytime thermoregulatory opportunity, female lizards are able to compensate for environmental variation in nighttime temperature in every way except reproductive timing.