Disease‐limited distributions? Contrasts in the prevalence of avian malaria in shorebird species using marine and freshwater habitats

Abstract

. Diseaselimited distributions? Contrasts in the prevalence of avian malaria in shorebird species using marine and freshwater habitats. Á/ Oikos 109: 396 Á/404.Migratory shorebirds show strong dichotomies in habitat choice during both the breeding and nonbreeding season. Whereas High Arctic breeding species are restricted to coastal marine and saline habitats during the nonbreeding season, more southerly breeding species tend to use freshwater habitats away from coasts. It has been proposed that this co-variation in habitat use is a consequence of a single axis of adaptation to pathogens and parasites, which are hypothesized to be relatively scarce in High Arctic, marine, and saline habitats and relatively common at lower latitudes and in freshwater habitats. Here we examine this contrast by comparing the prevalence of avian malaria infections in shorebirds occupying different habitats. We used a PCR-based assay on 1319 individuals from 31 shorebird species sampled in the Arctic, in temperate Europe and in inland and marine habitats in West Africa. Infections mainly occurred in tropical wetlands, with the shorebirds in freshwater inland habitats having significantly higher prevalence of malaria than birds in marine coastal habitats. Infections were not found in birds migrating through Europe even though conspecifics did show infections in tropical Africa. Adults should resist infection better than juveniles, but showed higher malaria prevalence, suggesting that infection probability increases with cumulative exposure. We argue that exposure to vectors is the main factor explaining the habitat-related differences in malaria prevalence.

High prevalence of Leucocytozoon parasites in fresh water breeding gulls

“…One of hypotheses proposed to explain differences in blood parasite prevalence is the vector-density hypothesis (Bennett et al 1992;Tella et al 1996;Piersma 1997;Sol et al 2000;Jovani et al 2001;Martínez-Abraín and Urios 2002;Fokidis et al 2008). Bird species associated with inland environments are expected to be more exposed to the malaria-like parasites than similar bird species inhabiting marine environments as the former provide more suitable breeding areas for vectors (Piersma 1997;Sol et al 2000;Mendes et al 2005). The low diversity or absence of blood parasites previously reported in seabirds is associated with the specific character of marine and coastal habitats that typically are relatively free of parasite vectors (Piersma 1997;Mendes et al 2005).…”

“…Bird species associated with inland environments are expected to be more exposed to the malaria-like parasites than similar bird species inhabiting marine environments as the former provide more suitable breeding areas for vectors (Piersma 1997;Sol et al 2000;Mendes et al 2005). The low diversity or absence of blood parasites previously reported in seabirds is associated with the specific character of marine and coastal habitats that typically are relatively free of parasite vectors (Piersma 1997;Mendes et al 2005). This is also consistent with a biogeographical perspective as the Leucocytozoon vectors, Simuliidae, are more abundant and diverse at higher latitudes (Valkiūnas 2005;Atkinson et al 2008).…”

Untested assumptions about within-species sample size and missing data in interspecific studies

“…We also obtained data from multiple sources that screened blood of captured adult birds of any sex that breed in Europe for haemoparasite prevalence (Bennett et al 1982;Haberkorn 1984;Merino et al 1997;Valkiūnas et al 1999;Krone et al 2001;Shurulinkov and Golemansky 2003;Mendes et al 2005;Palinauskas et al 2005;Wiersch et al 2007;Ishak et al 2008;Krone et al 2008;). This compiled dataset included 150 bird species that had at least one individual sampled, while the maximum within-species sample size was 370 (CV 0 176.8 %).…”

Identifying crucial gaps in our knowledge of the life-history of avian influenza viruses—an Australian perspective

“…For instance, open marine environments and the Arctic tundra have been hypothesised to be characterised by a particularly low density and diversity of pathogens (Piersma 1997;Mendes et al 2005). Given that environmental transmission in aquatic environments is considered critical to the maintenance of infection within the wild bird population Rohani et al 2009), species inhabiting aquatic habitats have received most interest.…”