Research Assistant Professor Binghamton University Binghamton, New York, United States
Background/Question/Methods
One step in understanding how climate change will affect ecosystems is determining organisms’ thermal limits. Many biologists have been especially concerned about the thermal limits of tropical organisms that experience narrow temperature ranges throughout the year. However, we also need to consider the possibility that some temperate organisms may face similar challenges. In insects with complex annual life cycles, individuals may only be actively metabolizing and developing for a few months each year, while spending most of the year in a life stage with very limited activity. Depending on when insects are active in temperate environments, they will experience very distinct temperature conditions. To investigate whether caterpillars had different thermal limits throughout the entire growing season, I worked with four cohorts of course-based undergraduate research experience (CURE) students to measure critical thermal maxima (CTmax) an extreme but useful thermal trait.
Results/Conclusions
We measured CTmax for over 200 caterpillars. CTmax increased significantly throughout the season, with the mean CTmax in July (44.5 ± 0.30°C) and September and early October (45.7 ± 0.25°C) significantly higher than in May (43.3 ± 0.80°C) and June (43.8 ± 0.35°C). This pattern is strengthened when the early season, non-native caterpillar Lymantria dispar is omitted from the analysis. Without L. dispar, the mean CTmax for May and June drop to 43.1 ± 0.85°C and 43.0 ± 0.33°C, respectively. While temperatures at our site are unlikely to exceed 37°C, insects often begin to experience negative effects far below their CTmax. Our data suggest warming is more likely to be a problem for spring caterpillars than mid- or late summer ones. Collecting early spring and late summer data in the Northern Hemisphere is often difficult because these seasons generally conflict with the academic calendar. Incorporating such data collection into relevant courses can both benefit ecological research and undergraduate learning.
