What Influences the Prevalence and Intensity of Haemoparasites and Ectoparasites in an Insular Lizard?

Abstract

Island biogeography theories predict that characteristics such as island size, age, and isolation interplay in host-parasite dynamics. In this study, we analyzed haemogregarines of the Aegean wall lizard, Podarcis erhardii, to investigate how island characteristics relate to parasite prevalence and intensity. A previous assessment of 19 Greek island populations suggested that isolation time and host population density were key predictors of haemogregarines. Here, by combining microscopy and genetic techniques, we extend this previous study to four additional islands: Syros, Folegandros, Santorini and Nea Kameni. We also recorded the prevalence of ticks and mites, definitive hosts for these parasites. The genetically identified haemogregarines are part of a clade with parasites from other lizard species, including some considered as Karyolysus, but others assigned to Hepatozoon. The prevalence of these parasites differed significantly between islands, while their intensity did not. The presence of ticks was associated with endoparasite prevalence, and males were more frequently infected by haemogregarines than females. Combining our data with that of the previous study, we found no significant impact of the island age and area on parasite prevalence. We also confirmed the presence of the unrelated parasite genus Schellackia through microscopy and DNA sequencing, which is the first record of this genus in this host species. Our results further highlight the complexity of host-parasite systems.

Lizard host abundances and climatic factors explain phylogenetic diversity and prevalence of blood parasites on an oceanic island

“…Moreover, blood parasites native to the islands can be less virulent to insular hosts and, perhaps for this reason, highly abundant on some islands (García‐Ramírez et al., 2005; Garrido & Pérez‐Mellado, 2013; Magnanou & Morand, 2006; Megía‐Palma, Arregui, et al., 2020; Schall, 1986; Tomás et al., 2022). Recent research found that host density, island age, and vector prevalence are important predictors of blood parasite prevalence across insular populations of lizards (Ferreira et al., 2023; Fornberg & Semegen, 2021). High parasite prevalence might be explained by high transmission rates in highly dense host populations (Arakelyan et al., 2019; Buckley & Jetz, 2007).…”