Abstract
Host and pathogen ecology are often closely linked, with evolutionary processes often leading to the development of host specificity traits in some pathogens. Host specificity may range from ‘generalist’, where pathogens infect any available competent host; to ‘specialist’, where pathogens repeatedly infect specific host species or families. Avian malaria ecology in the region remains largely unexplored, despite the presence of vulnerable endemic avian species. We analysed the expression of host specificity in avian haemosporidia, by applying a previously developed host specificity index to lineages isolated from wetland passerines in the Western Cape, South Africa. Parasite lineages were isolated using PCR and identified when possible using matching lineages deposited in GenBank and in MalAvi. Parasitic clades were constructed from phylogenetic trees consisting of Plasmodium and Haemoproteus lineages. Isolated lineages matched some strains of Plasmodium relictum, P. elongatum, Haemoproteus sylvae and H. lanii. Plasmodium lineages infected a wide range of hosts from several avian families in a generalist pattern of infection. Plasmodium spp. also exhibited an infection trend according to host abundance rather than host species. By contrast, Haemoproteus lineages were typically restricted to one or two host species or families, and displayed higher host fidelity than Plasmodium spp. The findings confirm that a range of host specificity traits are exhibited by avian haemosporidia in the region. The traits show the potential to not only impact infection prevalence within specific host species, but also to affect patterns of infection at the community level.
Highlights
Recent advances in molecular ecology have profoundly altered the nature of research on parasites and parasitism
Overall infection prevalence Plasmodium spp accounted for the greatest prevalence of infections among wetland passerines, with Plasmodium infections being generally widespread and the sole cause of infection in five avian families (Fig. 2)
The overall Plasmodium infection prevalence (17%) and prevalence range (3–25%) were lower than that found in West African birds (45%; [39]), which had a much wider prevalence range (1–69%)
Summary
Recent advances in molecular ecology have profoundly altered the nature of research on parasites and parasitism. For many parasitic microorganisms, such as malaria parasites, molecular ecology has provided both a newfound ability to identify parasites accurately and the tools for understanding how and when hostparasite coevolution occurs. Within the broader context of hostparasite relationships, one of the more intriguing questions that molecular methods have opened up is that of how differences in the degree of host specialization in closely related parasites have arisen. Each clade represents a persistent [successful] solution to a complex problem that incorporates environmental influences as well as elements of parasite, vector, and host ecology and physiology. Unravelling the roles of these different elements in host-parasite coevolution has the potential to offer profound insights into parasite ecology, and more generally into the process of speciation in heterogeneous habitats and communities
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