Ectoparasitic mites infest common and widespread but not rare and red-listed dragonfly species

Freshwater ectoparasitic mites negatively alter host population dynamics by reducing survivorship, mating success, fitness and altering activity patterns. Hosts commonly include dragonflies. The Kogelberg Biosphere Reserve, South Africa, is a major hotspot for endemic dragonflies. All 38 dragonfly species in the reserve were sampled for ectoparasitic mites, but only 2 common, widespread spp. of Zygoptera, Ischnura senegalensis and Ceriagrion glabrum, were infested with Arrenurus or Leptus mite spp. None of the endemic or red-listed dragonflies were infested. Parasitism level was 3.5% for C. glabrum and 38% for I. senegalensis. Intensity of ectoparasites on individuals was high, with about eight ectoparasitic larva per individual. Larval mites preferentially associated with individual hosts already harbouring mites. High levels of species-specific parasitism likely reflects shared environmental requirements, preferential species selection, and lack of defensive behaviours to resist infestation. Characteristic scars from previous mite attachment observed on older individuals of I. senegalensis indicate that a much larger percentage of the population was actually parasitized, but detached as the individual aged. That the rare and red-listed species were apparently immune from infestation is a positive note for their conservation.