Sex Ratio, Species Composition, and Mating Frequency in Damselfly Populations Across Lakes in Värmland

Sammanfattning

Damselflies (Odonata: Zygoptera) are ecologically important insects whose population dynamics and reproductive behavior reflect environmental and demographic conditions. This study investigated ecological and reproductive variation among damselfly populations across five lakes in Värmland, Sweden. Specifically, it examined (1) whether sex ratios and species composition differed among lakes, and (2) whether mating frequency varied between species and sexes. A total of 576 individuals from three species—Coenagrion pulchellum, C. hastulatum, and C. lunulatum—were analyzed. Chi-square tests were used to compare sex ratios, species composition, and mating frequencies. C. pulchellum dominated most lakes, representing 84–100% of individuals in four of the five sites, while C. hastulatum and C. lunulatum occurred almost exclusively in Pond 96. Sex ratios did not differ significantly among lakes, and mating frequency showed no significant variation between species or sexes. These results indicate that while ecological context influences species composition, reproductive patterns remain relatively stable across populations. The dominance of C. pulchellum suggests that this species is particularly well adapted to the environmental conditions of these lakes, whereas the limited occurrence of C. hastulatum and C. lunulatum may reflect habitat specialization or small sample sizes.