The influence of vagrant hosts and weather patterns on the colonization and persistence of blood parasites in an island bird

Abstract

Aim Colonization and extinction are important drivers of island biogeography, but they are difficult to study. We used a long‐term dataset to determine the mechanisms that contribute to colonization and persistence for vector‐borne blood parasites in an island population of birds that regularly receives infected vagrant conspecifics and wind‐assisted potential vectors from the mainland. Location Heron Island (Australia) and the Australian mainland. Methods We determined the prevalence, temporal stability and host‐specificity of Haemoproteus and Plasmodium parasites in resident and mainland‐vagrant silvereyes (Zosterops lateralis) on Heron Island over seven years (1999–2003 and 2012–2013). We carried out simulations using mainland infection data and vagrant arrival scenarios to test whether transmission from vagrants influences infection patterns in island residents. We tested whether variation in island parasite prevalence was predicted by abiotic factors associated with vector breeding and dispersal. Results Parasite prevalence and composition on the island varied considerably across years. Host‐specialist Haemoproteus species exhibited lower prevalence than expected and frequent absence despite a high probability of arriving via vagrants. In contrast, host‐generalist Plasmodium species exhibited a low probability of arriving via vagrants but were temporally persistent in island silvereyes. Increases in prevalence and diversity of Plasmodium species were associated with episodes of offshore winds. Main conclusions This study shows that parasites that are abundant in source populations do not necessarily exhibit increased colonization success via vagrant host movement. Vagrant silvereyes are not likely to shape infection patterns in island‐resident silvereyes. Instead, indirect evidence of associations between weather patterns and parasite dynamics suggests that the insular parasite community may be limited by vector establishment. Our results support the hypothesis that host‐specificity is important in determining a parasite's ability to persist on islands, with host‐specialists at greater risk of failing to establish after their initial arrival.

Co‐infections and environmental conditions drive the distributions of blood parasites in wild birds

“…Only two co‐infections were observed for each of the above parasite pairs , despite each parasite occurring on all islands and habitats. Considering that H. zosteropis and H. killangoi are avian host specialists that appear restricted to Zosteropidae (Valkiūnas ; Clark & Clegg ), our results may be evidence of interspecific competition. We also found a striking difference in likelihoods of microfilaria co‐infection for the two Haemoproteus species.…”

“…Eight known co‐infections produced Haemoproteus sequences, while a further six produced double peaks (re‐sequencing of all six producing clean Plasmodium sequences). Haemoproteus lineages were therefore characterized using genus‐specific primers designed from sequences recovered in Australasian hosts (Clark & Clegg ; Clark, Clegg & Klaassen ). These primers successfully amplified Haemoproteus DNA from all visually observed Plasmodium / Haemoproteus co‐infections.…”

Differences in host species relationships and biogeographic influences produce contrasting patterns of prevalence, community composition and genetic structure in two genera of avian malaria parasites in southern Melanesia

“…Members of the Zosterops spp. Haemoproteus clade are within 1–3% nucleotide divergence of ZOSLAT04H, a lineage reported in Australian Z. lateralis that has been microscopically confirmed as the Zosteropidae‐restricted Haemoproteus zosteropis (Clark & Clegg ). In contrast, lineages from the second Haemoproteus clade averaged over 5% nucleotide divergence from lineages in the Zosterops spp.…”

“…A more complete description of the parasite communities and genetic connectivity of numerous host and vector species would be required to establish whether a relationship exists, and if so, to determine whether parasite community is shaped by movement patterns of hosts, or whether gene flow patterns of hosts are shaped by parasite community incompatibilities. In one population of silvereyes ( Zosterops lateralis chlorocephalus ) on Heron Island on the southern Great Barrier Reef of Australia, a combination of empirical infection data and simulations showed that the arrival of parasites via mainland vagrant silvereyes was not consistent with parasite community patterns in the island bird population, and instead, vector movement was a likely influence (Clark & Clegg ).…”

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

“…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.…”