Starkloff, N. C., W. C. Turner, A. M. FitzGerald, M. C. Oftedal, E. S. Martinsen, and J. J. Kirchman. 2021. Disentangling the effects of host relatedness and elevation on haemosporidian parasite turnover in a clade of songbirds. Ecosphere. 12(5):e03497
The persistence of a parasite species in an ecological community is determined together by its environmental tolerance and host breadth. The relative contribution of these niche characteristics to parasite community structure is challenging to parse because host persistence is also a consequence of extrinsic environmental factors. We investigated haemosporidian parasites (genera Plasmodium, Leucocytozoon and Haemoproteus) in a clade of avian hosts in eastern North America. This clade of Catharus thrushes contains species that occupy specific elevational bands in a non-phylogenetically determined manner. This allowed us to tease apart the effects of host relatedness and elevation on parasite diversity, community structure and infection prevalence. We screened blood and tissue samples from 414 birds from four mountain ranges in the Appalachian Highlands for blood parasites using a cytochrome-b nested PCR protocol and identified parasite lineages by sequencing. We found an overall infection prevalence of 88.4% and identified a total of 38 parasite lineages including seven novel lineages. Host relatedness rather than elevational zone predicted the beta turnover and phylobetaturnover of Leucocytozoon parasites, where closely related host species had more similar parasites. While this pattern was not seen in Plasmodium parasites, the diversity of this parasite genus varied considerably in the high elevational zones among mountain ranges, i.e. a sky-island effect. Additionally, the alpha diversity of Haemosporidians did not vary by host species or elevational zone, Plasmodium and Leucocytozoon infection prevalence was determined by one or two of these predictors, respectively. Haemoproteus parasites were rare in this study system. Our study suggests that the mechanisms that underlie the community structuring vary between haemosporidian genera due to differences in the degree of host sharing among lineages.