Influence of climate on butterfly community and population dynamics in Western Ohio

Climate influences butterflies both directly and through impacts on their food plants and habitat. We look at the relationship between climate and butterflies in the Aullwood Audubon Center, west central Ohio, using the weekly Long-Term Butterfly Monitoring (LTBM) surveys (April through October 2000-2006) and the annual fourth of July counts (1989-2006). The 18 annual Fourth of July surveys yielded 20,709 butterflies and 59 species. The number of individuals though not species decreased over time. Most but not all of that decrease was from a large drop in Pieris rapae L. (Pieridae). The number of individuals was greatest when the previous and current growing seasons were cool and winter precipitation high. Individual species varied in their response to climate. Recent years have been warmer (all seasons) and have had drier winters than earlier years. The 7 yr of weekly LTBM surveys recorded 5,784 butterflies and 58 species. The total number of individuals has not changed significantly over time. The weather of the day of sampling had some effect: the total number of species was highest on clear days with some wind. The results over the 18 yr are compatible with the hypothesis that global warming has led to a decrease in the number of butterflies. Habitat changes cannot be excluded as an alternate hypothesis, but these effects seem minor. The value of a large, environmentally heterogeneous natural area like Aullwood is that it buffers short-term climatic and weather conditions to provide long-term stability for a diverse butterfly community.