Date of Graduation


Document Type


Degree Name

Bachelor of Science in Biology

Degree Level



Biological Sciences


Siepielski, Adam

Committee Member/Reader

Beaulieu, Jeremy

Committee Member/Second Reader

Kennefick, Julia

Committee Member/Third Reader

Chen, Jingyi


Climate change has led to changes in both mean temperatures and temperature extremes over the recent years. These changes have had differential effects on animals throughout the world. Ectotherms depend on their external environment for thermal regulation, making them especially susceptible to temperature extremes. It is not yet clear whether there is a relationship between physical traits in ectotherms, and survivorship throughout a heat wave. That is, whether or not temperature extremes driven survival selection. In this study, a heat wave was simulated artificially using thermally regulated mesocosms at different temperatures (18°C, 22° C, 26° C, 30° C) with a population of Enallagma damselflies, a type of aquatic ectotherm. Physical traits of body length, head width, lamellae area, and lamellae remaining were examined before and after the heat wave, and analyzed to determine whether temperature imposed selection was present in the surviving damselflies. Results indicated that the mean values for each trait, except lamellae remaining, following the simulated heat wave were statistically different, though this relationship was not linear, and the amount of variance accounted for by temperature was relatively low. Survivorship peaked at an intermediate temperature of 22°C, and decreased as the temperature increased or decreased from there. This survivorship curve is consistent with other research on ectotherms, however, further research is needed to determine whether natural selection arises through a relationship between morphological traits and survivorship following a heat wave.


ectotherms, temperature extremes, survivorship