Survey of haemosporidian parasite infections in an endangered high alpine bird.

The Brown-capped Rosy-Finch is an endangered high alpine specialist that breeds on cliffs in the Rocky Mountains of North America. We know little about the parasites that infect these birds but filling this knowledge gap is important for understanding their population decline. The aim of this study was to survey haemosporidian parasite infections in Brown-capped Rosy-Finches. We sampled 104 Brown-capped Rosy-Finches during their breeding season at six sampling sites spanning the Colorado Rocky Mountains where they are nearly endemic. We used nested PCR methods to screen birds for parasite infections, and Sanger sequencing data were used to identify parasite lineages. Four of the sampling sites had birds with infections. Females were more often infected than males (prevalence = 15.6% and 9.7%, respectively). We observed twice as many infected birds sampled in July compared to birds sampled in June (prevalence = 12.5% and 6.25%, respectively). The percent of infected birds by sampling site ranged from 0 to over 20%. In total we identified eight different genetic lineages of haemosporidian parasites infecting Brown-capped Rosy-Finches-seven were in the genus Leucocytozoon, and one was in the genus Haemoproteus. Network analysis clearly separates Haemoproteus from Leucocytozoon, with Leucocytozoon lineages comprising two major clusters. Based on reports made to the MalAvi database, all lineages in Cluster 1 have the same reported insect vector, Simulium silvestre. We report that Brown-capped Rosy-Finches experience infections with haemosporidian parasites and that the percentage of infected birds differed markedly between sampling sites. We hypothesize that vector ecology and associated variation in climate at sampling sites explain our observations.

A highly invasive malaria parasite has expanded its range to non-migratory birds in North America.

Parasite range expansions are a direct consequence of globalization and are an increasing threat to biodiversity. Here, we report a recent range expansion of the SGS1 strain of a highly invasive parasite, Plasmodium relictum, to two non-migratory passerines in North America. Plasmodium relictum is considered one of the world's most invasive parasites and causes the disease avian malaria: this is the first reported case of SGS1 in wild non-migratory birds on the continent. Using a long-term database where researchers report avian malaria parasite infections, we summarized our current understanding of the geographical range of SGS1 and its known hosts. We also identified the most likely geographical region of this introduction event using the MSP1 allele. We hypothesize that this introduction resulted from movements of captive birds and subsequent spillover to native bird populations, via the presence of competent vectors and ecological fitting. Further work should be conducted to determine the extent to which SGS1 has spread following its introduction in North America.

Annual environmental variation influences host tolerance to parasites.

When confronted with a parasite or pathogen, hosts can defend themselves by resisting or tolerating the attack. While resistance can be diminished when resources are limited, it is unclear how robust tolerance is to changes in environmental conditions. Here, we investigate the sensitivity of tolerance in a single host population living in a highly variable environment. We manipulated the abundance of an invasive parasitic fly, Philornis downsi, in nests of Galápagos mockingbirds ( Mimus parvulus) over four field seasons and measured host fitness in response to parasitism. Mockingbird tolerance to P. downsi varied significantly among years and decreased when rainfall was limited. Video observations indicate that parental provisioning of nestlings appears key to tolerance: in drought years, mockingbirds likely do not have sufficient resources to compensate for the effects of P. downsi. These results indicate that host tolerance is a labile trait and suggest that environmental variation plays a major role in mediating the consequences of host-parasite interactions.

Parasites and Host Species Barriers in Animal Hybrid Zones.

Species barriers are tested in hybrid zones when gene flow occurs between hybridizing species. Hybridization can erode species barriers, lead to the introgression of adaptive traits, or remain stable through time. Outcomes in hybrid zones are influenced by divergence between the hybridizing taxa, behavior, ecology, and geography. Parasites and pathogens play a major role in host fitness and appear to have varied impacts on species barriers in hybrid zones. We comprehensively reviewed the literature on parasitism in animal hybrid zones and present an evolutionary framework within which to consider parasite-hybrid interactions. Parasites most frequently show potential to contribute to species barrier breakdown in hybrid zones, but also frequently show potential to facilitate the maintenance of species barriers. Incorporating eco-immunology, parasite community theory, and spatiotemporal approaches will be important as genomic tools allow researchers to examine parasites and hybrid zones at greater resolution and in a diversity of natural habitats.