Off-host longevity of the winged dispersal stage of Carnus hemapterus (Insecta: Diptera) modulated by gender, body size and food provisioning

Highlighting the dispersal ecology of parasites is important for understanding epidemiological, demographic and coevolutionary aspects of host-parasite interactions. Yet, critical aspects of the dispersal stage of parasites, such as longevity and the factors influencing it, are poorly known. Here we study the lifespan of the dispersal stage of an ectoparasitic dipteran, Carnus hemapterus, and the impact of gender, body size and food provisioning on longevity. We found that freshly emerged imagoes survive at most less than 4 days. Longevity increased with body size and, since this parasite exhibits sexual size dimorphism, the bigger females lived longer than males. However, controlling for body size suggests that males lived relatively longer than females. Furthermore, a humid environment and food provisioning (flowers) significantly increased individual life spans. We discuss the relative importance of spatial and temporal dispersal in relation to the infectious potential of this parasite.

Defining host range: host-parasite compatibility during the non-infective phase of the parasite also matters

Host range and parasite specificity determine key epidemiological, ecological and evolutionary aspects of host-parasite interactions. Parasites are usually classified as generalists or specialists based on the number of hosts they feed on. Yet, the requirements of the various stages of a parasite may influence the suitability of a given host species. Here, we investigate the generalist nature of three common ectoparasites (the dipteran Carnus hemapterus and two species of louse flies, Pseudolynchia canariensis and Ornithophila metallica), exploiting two avian host species (the European roller Coracias garrulus and the Rock pigeon Columba livia), that frequently occupy the same breeding sites. We explore the prevalence and abundance of both the infective and the puparial stages of the ectoparasites in both host species. Strong preferences of Pseudolynchia canariensis for pigeons and of Carnus hemapterus for rollers were found. Moderate prevalence of Ornithophila metallica was found in rollers but this louse fly avoided pigeons. In some cases, the infestation patterns observed for imagoes and puparia were consistent whereas in other cases host preferences inferred from imagoes differed from the ones suggested by puparia. We propose that the adult stages of these ectoparasites are more specialist than reported and that the requirements of non-infective stages can restrict the effective host range of some parasites.