OPS 1-1
Using NPN observations to validate a simulation model that explores the effects of climate change on the phenology and voltinism of a butterfly hybrid zone
For many insect populations, phenology—the timing of life cycle events—and voltinism—the number of generations a population has in a given year—are both greatly influenced by climate. While the consequences of climate induced changes in phenology and voltinism could substantially impact insect populations, it remains unclear what impacts changes in climate will have on the population dynamics and evolution of insect populations. This study investigates how climate-induced changes in voltinism and phenology affect large-scale patterns of hybridization between two species of butterfly, Papilio glaucus and Papilio canadensis. Using an agent-based model we simulated the effects of climate on the phenology and voltinism of P. glaucus, P. Canadensis and their hybrids. First, the model was parameterized with a number of growth chamber experiments that determined genotype specific developmental rates and critical photoperiods. Next, the model was first evaluated and recalibrated using data from independent growth chamber experiments. Then, using real climate data we compared model predictions to field observations obtained from a number of citizen science projects (e.g., National Phenology Network) and museum and recent field collections to determine how well our model could predict large-scale phenological and voltinism patterns in Wisconsin.
Results/Conclusions
As expected, our model predictions of voltinism matched closely with the known geographic distribution of genetic markers linked to obligate diapause (and thus voltinism). The lower percentage of hybrids completing two generations than the parental P. glaucus, provides further evidence that climate may be playing a primary role in maintaining divergence between portions of the genomes of P. glaucus and P. canadensis. Our model also did fairly well at predicting the phenology of P. glaucus, P. Canadensis and their hybrids. Interestingly, we found that not only did climate influence geographic patterns of voltinism which was expected, but that species-specific introgression (hybridization) may vary between warm and cool years. The difference in emergence dates between species and between warm and cool years strongly suggests that the interaction between climate and phenology may be affecting patterns of gene flow in the hybrid zone and that these patterns will likely be sensitive to increases in global temperature. Results from this work strongly suggest that changes in climate is influencing the genetic composition of this hybrid zone, by differentially affecting traits associated with voltinism and phenology in turn affecting the amount of introgression between the two species.