Meeting Abstract

84.3  Sunday, Jan. 6  Heat tolerance of embryos limits the geographic range of Sceloporus undulatus ANGILLETTA, MJ*; LEVY, O; SMITH, C; ZELIC, M; ADRIAN, G; KILBY, D; HURLIMAN, A; BORCHERT, J; BUCKLEY, LB; Arizona State Univ.; Arizona State Univ.; Arizona State Univ.; Arizona State Univ.; Arizona State Univ.; Arizona State Univ.; Arizona State Univ.; Arizona State Univ.; Univ. of North Carolina, Chapel Hill angilletta@asu.edu

To predict how global warming will affect species, ecologists have focused primarily on the increase in mean temperature and its impact on juveniles or adults. Yet, this focus ignores two factors that ecologists must consider to make accurate forecasts. First, future climates will impose acute heat stresses as well as chronic stresses. Second, embryos are most susceptible to acute stress because they cannot behaviorally thermoregulate to the same extent as can juveniles and adults. We quantified the degree to which lizard embryos from four geographically separated populations tolerated acute warming; tolerance was inferred from cardiac performance and survival probability. At a realistic rate of warming, embryos from all populations exhibited cardiac strain at 40°C and experienced cardiac arrest at 45-47°C. By exposing embryos to various diel cycles of temperature, we identified a threshold for survival between 40 and 42°C. In other words, a single brief exposure to 42°C killed all embryos from the four populations, while daily exposures to lower temperatures killed few embryos. Using an individual-based model that considers embryonic survival and development, we predict that environmental warming will affect the distribution of S. undulatus in more complex ways than previously predicted.