Evolution of parasite island syndromes without long‐term host population isolation: parasite dynamics in Macaronesian blackcaps Sylvia atricapilla

Abstract

AimThe study of parasite biogeography on islands is important for our understanding of both the processes involved in the evolution of parasite assemblages worldwide and the ecology and conservation of insular communities. By studying the haemosporidian blood parasites of a bird that has recently colonized a number of oceanic islands, we were able to test hypotheses relating to the processes of parasite colonization and community assembly prior to the permanent isolation of host species on islands.Location The Atlantic Ocean archipelagos of Madeira and the Canary Islands. MethodsWe used cytochrome b DNA sequences to determine the prevalence and richness of parasites of the genera Haemoproteus, Plasmodium and Leucocytozoon in blackcaps, Sylvia atricapilla, a widespread passerine that colonized these archipelagos during the Last Glacial Maximum. We compared insular blackcap parasite assemblages with those observed in 37 blackcap populations sampled on mainland Europe. ResultsThe insular parasite assemblage was impoverished, containing c. 10% of the parasites found on the continent. None of the parasites observed on the islands were blackcap specific. Some of the observed parasites appear to have switched from blackcaps to other Macaronesian host species, whereas others were of Afrotropical origin and were acquired after blackcaps colonized the islands. The prevalence of parasites in the island populations of blackcaps was lower than in mainland blackcap populations and parasite richness decreased with increasing island distance to the continent.Main conclusions Macaronesian blackcaps do not face the strong parasite load encountered by their mainland counterparts despite the fact that blackcap migration from the continent may directly transport mainland blackcap parasites to the islands. This supports the idea that normal mainland host-parasite associations are compromised on islands and that parasite island syndromes (low richness, frequent host-switching and reduced specialization) evolve even before insular host populations become completely isolated from their mainland counterparts.

Insularity effects on the assemblage of the blood parasite community of the birds from the Gulf of Guinea

“…This suggests that, as predicted by island biogeography theory (MacArthur & Wilson, 1967), a broad ecological niche would be selected as a strategy that decreases the chances of extinction – in this case of parasites colonizing a new area where potential host populations are small (Beadell et al , 2006). The same pattern was also found for the Haemosporidian parasites of a songbird in the Madeira and the Canary islands (Pérez-Rodríguez et al , 2013). …”

“…As generalist parasites are considered poor competitors (Hellgren et al , 2009), an increase of co-infections on islands could play a role in limiting parasite densities and prevalence. Previous studies on the prevalence of blood parasites on islands were inconclusive, with either higher (Illera et al , 2015) or lower prevalence on islands (Pérez-Rodríguez et al , 2013). These conflicting results may arise from the fact that parasite prevalence is also likely to vary in relation to environmental and local factors.…”

“…Although island biogeography of parasites and their colonization histories have received increasing attention in recent years (e.g. Cornuault et al , 2012; Sari et al , 2013; Clark & Clegg, 2015), studies thus far have investigated the effects of insularity on parasite diversity and phylogenetic relationships on islands only (Ishtiaq et al , 2012; Carlson et al , 2013; Olsson-Pons et al , 2015; Ricklefs et al , 2016), or have compared islands with the mainland but taking into consideration only one host species (Pérez-Rodríguez et al , 2013; Sari et al , 2013). It is therefore of interest to test if the core predictions of island biogeography theory apply to parasite communities on a broader scale, i.e.…”

Louse flies of Eleonora’s falcons that also feed on their prey are evolutionary dead‐end hosts for blood parasites

“…Because of the generally low prevalence and diversity of the hemosporidian parasites on islands (Hellgren, Križanauskienė, Hasselquist, & Bensch, ; Martínez‐de la Puente et al, ; Padilla, Illera, Gonzalez‐Quevedo, Villalba, & Richardson, ; Pérez‐Rodríguez, Ramírez, Richardson, & Pérez‐Tris, ; Sari, Klompen, & Parker, ) and the presence of only one potential vector species on the island, we expected to find an essentially simple host‐vector‐parasite system. However, we found that the opportunistic feeding behavior of louse flies resulted in an unexpected massive transmission of haemosporidians from kills to falcons’ louse flies.…”

Reduced parasite diversity and abundance in a marine whelk in its expanded geographical range

“…On the other hand, limited contact between expanded‐ and historical‐range populations, and low densities of expanded‐range populations, could foster escape from natural enemies, including parasites (Phillips et al ., ), such as that observed in species that naturally colonize islands (e.g. see Güoy de Bellocq et al ., ; Pérez‐Rodríguez et al ., ). Additionally, parasites often require different host species in sequence to complete their life cycles, and some of the required host species may be absent or less abundant in expanded ranges: a pattern observed for parasites of invasive species.…”