Many species are currently changing their distributions and subsequently form sympatric zones with hybridization between formerly allopatric species as one possible consequence. The damselflyIschnura eleganshas recently expanded south into the range of its ecologically and morphologically similar sister speciesIschnura graellsii. Molecular work shows ongoing introgression between these species, but the extent to which this species mixing is modulated by ecological niche use is not known. Here, we (1) conduct a detailed population genetic analysis based on molecular markers and (2) model the ecological niche use of both species in allopatric and sympatric regions. Population genetic analyses showed chronic introgression betweenI. elegansandI. graellsiiacross a wide part of Spain, and admixture analysis corroborated this, showing that the majority ofI. elegansfrom the sympatric zone could not be assigned to either theI. elegansorI. graellsiispecies cluster. Niche modeling demonstrated thatI. eleganshas modified its environmental niche following hybridization and genetic introgression withI. graellsii, making niche space of introgressedI. eleganspopulations more similar toI. graellsii. Taken together, this corroborates the view that adaptive introgression has moved genes fromI. graellsiiintoI. elegansand that this process is enabling SpanishI. elegansto occupy a novel niche, further facilitating its expansion. Our results add to the growing evidence that hybridization can play an important and creative role in the adaptive evolution of animals.

Genetic polymorphisms are powerful model systems to study the maintenance of diversity in nature. In some systems, polymorphisms are limited to female coloration; these are thought to have arisen as a consequence of reducing male mating harassment, commonly resulting in negative frequency‐dependent selection on female color morphs. One example is the damselfly Ischnura elegans, which shows three female color morphs and strong sexual conflict over mating rates. Here, we present research integrating male tactics, and female evolutionary strategies (female mating behavior and morph‐specific female fecundity) in populations with different morph‐specific mating frequencies, to obtain an understanding of mating rates in nature that goes beyond the mere measure of color frequencies. We found that female morph behavior differed significantly among but not within morphs (i.e., female morph behavior was fixed). In contrast, male tactics were strongly affected by the female morph frequency in the population. Laboratory work comparing morph‐specific female fecundity revealed that androchrome females have lower fecundity than both of the gynochrome female morphs in the short term (3‐days), but over a 10‐day period one of the gynochrome female morphs became more fecund than either of the other morphs. In summary, our study found sex‐specific dynamics in response to different morph frequencies and also highlights the importance of studying morph‐specific fecundities across different time frames to gain a better understanding of the role of alternative reproductive strategies in the maintenance of female‐limited color polymorphism.