Parasitic infracommunities of the Aegean wall lizard Podarcis erhardii (Lacertidae, Sauria): isolation and impoverishment in small island populations

Abstract

AbstractThe Aegean wall lizard Podarcis erhardii, is widely distributed across the islands of the Aegean Sea (Greece). While there exists a relatively substantial body of knowledge on the ecology and life history of the species, the parasite communities of the taxon remain almost completely unknown. Quantifying the composition of these communities in P. erhardii is not only important for autoecological reasons, but also because inter-island comparisons of this lizard's parasite communities can shed light on the factors that structure parasite diversity in general. Here we investigate the gastrointestinal parasite communities of P. erhardii populations occurring on 16 landbridge islands of the Sporades group in the NW Aegean Sea by examining the gastrointestinal tracts of 113 lizards. In all, 8 species of helminths were found: 1 Trematode (Paradistomum mutabile), 1 Cestode (Oochoristica sp.) and 6 Nematodes (Parapharyngodon micipsae, Parapharyngodon bulbosus, Parapharyngodon echinatus, Spauligodon sp., Abbreviata sp., and Skrjabinelazia sp.). The prevalence, mean intensity, and mean abundance of infection were respectively 63.71%; 6.01 (±11.71; range 1-90); and 3.57 (±9.5; range 0-90). Brillouin's index of diversity for the Sporades was 0.048 (±0.13; range 0-0.142). These values were lower than for most other mainland and insular lacertid populations, and suggest that the investigated island populations harbor very depauperate helminth communities. The severe impoverishment of the parasite communities and the differential persistence of generalist parasite species with simple life cycles is most likely the result of a combination of insular environmental conditions (spatial and temporal isolation, arid climate, small host population sizes) and host life history characteristics (diet, simple gastrointestinal tract architecture). The paucity of parasites in these relictual island populations suggests that small reptile populations fragmented by anthropogenic activities may not be able to sustain their native parasite communities over the long term.