Diversity, Loss, and Gain of Malaria Parasites in a Globally Invasive Bird

Abstract

Invasive species can displace natives, and thus identifying the traits that make aliens successful is crucial for predicting and preventing biodiversity loss. Pathogens may play an important role in the invasive process, facilitating colonization of their hosts in new continents and islands. According to the Novel Weapon Hypothesis, colonizers may out-compete local native species by bringing with them novel pathogens to which native species are not adapted. In contrast, the Enemy Release Hypothesis suggests that flourishing colonizers are successful because they have left their pathogens behind. To assess the role of avian malaria and related haemosporidian parasites in the global spread of a common invasive bird, we examined the prevalence and genetic diversity of haemosporidian parasites (order Haemosporida, genera Plasmodium and Haemoproteus) infecting house sparrows (Passer domesticus). We sampled house sparrows (N = 1820) from 58 locations on 6 continents. All the samples were tested using PCR-based methods; blood films from the PCR-positive birds were examined microscopically to identify parasite species. The results show that haemosporidian parasites in the house sparrows' native range are replaced by species from local host-generalist parasite fauna in the alien environments of North and South America. Furthermore, sparrows in colonized regions displayed a lower diversity and prevalence of parasite infections. Because the house sparrow lost its native parasites when colonizing the American continents, the release from these natural enemies may have facilitated its invasion in the last two centuries. Our findings therefore reject the Novel Weapon Hypothesis and are concordant with the Enemy Release Hypothesis.

Maternal effects, malaria infections and the badge size of the house sparrow

“…Avian malaria infections can be caused by by three genuses of apicomplexans: Haemoproteus, Plasmodium and Leucocytozoon which are transmitted by hippoboscid flies, Culex-mosquitoes and blackflies respectively. The considerable heterogeneity in transmission of vector-transmitted diseases across time and space in conjunction with the high prevalence in affected bird populations across the world make these infections a major source of divergent selection pressures to host populations that drive genetic evolution (Bonneaud et al 2006;Randolph and Rogers 2010;Marzal et al 2011). To explore the effect of malaria and developmental testosterone exposure on badge size we needed sufficient sample sizes of birds that differ in their infection status but should otherwise experience a similar environment.…”

Local parasite lineage sharing in temperate grassland birds provides clues about potential origins of Galapagos avian Plasmodium

“…(2008); 23, Marzal et al. (2011); 24, Merino et al. (2008); 25, Outlaw and Ricklefs (2009); 26, Pagenkopp et al.…”

“…These resources allow for large‐scale comparisons of haemosporidian parasites among hosts and geographic locations (e.g., Marzal et al. 2011; Ewen et al. 2012).…”

Recent Advances in Studies on Avian Malaria Parasites

“…Just recently, an international team formed by 27 researchers has presented the most extensive study of the geographic distribution of a species rich group of parasites in a globally distributed vertebrate in the wild (Marzal et al, 2011). They examined these two important hypotheses (Enemy Release Hypothesis and Novel Weapon Hypothesis) to assess the role of avian malaria in the global spread of a common invasive bird.…”