Habitat selection by ovipositing species is critical for larval survival and performance, and resulting parental fitness, since there is typically little parental care beyond oviposition site choice. Numerous axes of patch quality have been identified and quantified, but the perceived quality of a habitat may shift as changes in global climate increase water temperatures and rates of eutrophication, affecting species with different life histories in various ways. Three outdoor mesocosm experiments were conducted using two species with complex life cycles and very different life histories; Cope’s Gray tree frog (Hyla chrysoscelis) and the mosquito (Culex restuans). To test the oviposition site choice of each species, gradients of temperature and nutrients were established in a completely crossed design in mesocosms that were left open for oviposition. It would be expected that adult oviposition site choice should match the habitat where larvae have the highest performance. There is sufficient information about larval performance in response to temperature and nutrients for C. restuans, but there is little parallel information about H. chrysoscelis larval performance. To test the gray treefrog larval performance, a third mesocosm experiment measured frog metamorph body metrics of individuals reared in each of the temperature and nutrient combinations.
Results/Conclusions
Preliminary results indicate slightly elevated temperatures with ambient nutrient levels were utilized the most by ovipositing H. chrysoscelis, while the least oviposition occurred in mesocosms at the highest temperatures. Larval gray tree frogs had larger body sizes and metamorphosed slightly faster in the extra heated treatments, but also had lower survival rates and a significant rate of deformity, possibly due to stress or disease. Thus, female oviposition site preference provided a good match to larval performance. C. restuans oviposited most often in the highest temperature treatment with supplemental nutrients, which correlates well with prior work on offspring performance. Thus, for H. chrysoscelis, female oviposition behavior may serve to mitigate against negative impacts of elevated temperatures on larval performance, provided habitats of the optimal temperature range remain available. In contrast, rising temperatures may prove beneficial to C. restuans, provided the behavioral algorithm involved in choosing the highest available temperature is modified near the critical thermal maximum for larvae. Determining the oviposition preference and performance of these species informs questions about future species distribution and population sizes as global warming and eutrophication affect the quality of freshwater systems.