Host specificity and co-speciation in avian haemosporidia in the Western Cape, South Africa

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.

Figure 1. Wetland sampling sites in the Western Cape.

Figure 2. Variations in Plasmodium and Haemoproteus spp. prevalence amongst infected avian families.

Number of birds sampled per family is indicated above each column (Plasmodium: n = 913; Haemoproteus: n = 857).

Figure 3. CCA scaling ordination bi-plot.

Displayed are weighted correlations between Plasmodium/Haemoproteus clades (indicated by clade letters in front of divergent arrows) and avian family groups. Eigenvalues on axes and arrow lengths act as an approximate guideline to the strength of correlations and highlights the infection trends between parasitic clades and heavily infected family groups (circled).

Figure 4

Fig. 4a Plasmodium phylogenetic tree with bootstrap values (>50%) displayed. Nodal support values from maximum likelihood analysis are displayed above branches and those from Bayesian analysis are below. Letters identify the clade (n = 9) with clade infection prevalence in brackets (n = 218). Samples are labelled by host latin name - number infected. GenBank strains are labelled by accession number (lineage code) – host latin name and location sampled. Avian families are represented by the following symbols: ▴Ploceidae; •Sylviidae; ▸Muscicapidae; ▪Zosteropidae; ΔPasseridae; ♣Motacillidae; ○Laniidae; *Estrildidae; ♦Cisticolidae; ◊Hirundinidae; ⁃Promeropidae; □Nectariniidae. Other samples are species from uninfected or unrepresented families, or are samples of undefined origin. Fig. 4b. Haemoproteus phylogenetic tree with bootstrap values (>50%) displayed. Figures from maximum likelihood analysis are displayed above branches, whilst figures from Bayesian analysis are below. Coding for avian families is as for Fig. IVa (clades = 7). Blocks emphasize apparent patterns of lineage separation by host family group (n = 7).

Figure 5. Phylogenetic distance and diversity between host species infected by Plasmodium and Haemoproteus spp.