Recent range shifts and the role of sexual signals in premating isolation of sympatric Calopteryx damselflies

Understanding how contemporary evolution in action will mitigate or exacerbate the impacts of climate change on biodiversity is a critical need. We address species isolation in a hybrid zone that may be shifting with global warming. Character displacement of wing pigmentation occurs in sympatric populations of the damselflies Calopteryx aequabilis and C. maculata. This displacement is cited as one of the classic examples of reinforcement and enhanced prezygotic isolation. We address these questions:

1. What is the current range of sympatry between sister species?
2. What is the function of wing pigmentation and how might it affect premating isolation during range shifts?

Surveys of Calopteryx distribution in Michigan indicates that the southern boundary of C. aequabilis is several hundred miles north of where it was 35 years ago. In addition, mating experiments reveal that interspecific mating attempts occur readily, which indicate that range shifts will likely have implications for species isolation.