Species distributions are quickly changing in response to human induced changes in landscape and climate. As populations shift their ranges, entire communities can be altered within ecosystems. These changes can be problematic for species who are locally adapted to the presence or absence of closely related species.
Calopteryx splendens and virgo are two similar damselfly species that co-occur in the southern part of Sweden, with only C. virgo being distributed in the north. In the south, local populations may have both species or only one of the two. As hybridization produces unfit offspring, populations where both occur have adapted increased species discrimination, with populations unexposed to the other species showing more frequent cross-species matings. As the climate warms, the range edge of this southern zone is expected to move northward. This could potentially lead to an increase in disadvantageous hybridization in areas where populations have not adapted to co-existence with their close relative.
To assess the consequences of changes in relative abundance and new co-existence, we have performed surveys of these two species at sites across a transect across Sweden, collecting population samples at each site. We assess the change in species composition across time through comparing the frequencies with estimates from previous studies at the same sites. Using the population samples, we will produce whole genome data and determine how common hybridization is, and if it is more common where frequencies have changed or at range edges. These results can help to enlighten how human-induced changes are impacting distributions and hybridization in species where sexual selection is important for maintaining species differences.