Unforeseen biogeographical patterns ina multiple parasite system in Macaronesia

AimUnderstanding the reasons why hosts lose, maintain or swap their parasite burden after colonizing new areas has long intrigued island biogeographers. Using molecular markers, we evaluated parasite biogeography of a multiple parasite system of Apicomplexa protozoans (haemosporidian and coccidian parasites) showing different modes of transmission in the spectacled warbler (Sylvia conspicillata), a small passerine with recently founded populations in Macaronesia. LocationTwelve oceanic islands of three Macaronesian archipelagos (Madeira, the Canary Islands and Cape Verde) and two continental areas (the Iberian Peninsula and Morocco). MethodsWe amplified and sequenced fragments of the parasite mitochondrial genome (cytochrome b for haemosporidian and cytochrome c oxidase subunit I for coccidian parasites) to determine the prevalence, richness, diversity and associations between groups of pathogens from the continental sources to the Macaronesian islands. We also built a haplotype network for the coccidian parasites to obtain insights on their evolutionary history. ResultsWe did not find a significant reduction in parasite diversity in the Macaronesian islands compared with the mainland. The prevalence was higher in Macaronesia for both parasite groups than on the mainland, although it was only significant for the haemosporidian parasites. The haplotype network revealed an unexpectedly strong differentiation in the coccidia, with a similar structure to the haplotype topology previously found in the host. Main conclusionsOceanic islands provide model systems for disentangling geographical origins, colonization pathways, and diversification of avian hosts through analysis of parasites. We show that analysis of coccidians, which closely track the evolutionary history of their avian hosts, may illuminate co-speciation processes in both groups. Our results show that coccidian populations in Macaronesia are highly structured but fail to provide support for the predicted impoverishment of parasite assemblages on islands.