Patterns of water mite and gregarine parasitism in Ischnura heterosticta (Odonata: Zygoptera) damselfly populations and their impact on body condition

Parasitism is a strong selective agent that affects host fitness, and parasitism may be variable across often broad landscapes and ecological gradients. However, variation may also occur within small geographic areas due to local differences in habitat and climate. Here, we quantified the prevalence and intensity of ectoparasitic water mites (Arrenurus sp.) and endoparasitic gregarines (Apicomplexa: Protozoa) in Australian common bluetail damselflies (Ischnura heterosticta), between sexes and across three populations in Cairns, Australia. We found that more than 42% of the damselflies were coinfected with water mites and gregarines. The prevalence of both parasite taxa differed between sexes, being higher in females, and also varied among the three populations. Furthermore, we investigated whether parasitism was correlated with damselfly body size, mass and lipid content. Water mite parasitism was negatively correlated with host body mass and lipid content; however, gregarine-infected males and females had better body condition, as estimated by body length, mass and lipid content. In conclusion, our study suggests that damselflies with a larger body size have a higher prevalence of gregarine infection; however, the impact on body mass and lipid content may vary with parasite type.