Drivers of community turnover differ between avian hemoparasite genera along a North American latitudinal gradient

Abstract

The latitudinal diversity gradient (LDG) is an established macroecological pattern, but is poorly studied in microbial organisms, particularly parasites. In this study, we tested whether latitude, elevation, and host species predicted patterns of prevalence, alpha diversity, and community turnover of hemosporidian parasites. We expected parasite diversity to decrease with latitude, alongside the diversity of their hosts and vectors. Similarly, we expected infection prevalence to decrease with latitude as vector abundances decrease. Lastly, we expected parasite community turnover to increase with latitudinal distance and to be higher between rather than within host species. We tested these hypotheses by screening blood and tissue samples of three closely related avian species in a clade of North American songbirds (Turdidae: Catharus, n = 466) across 17.5° of latitude. We used a nested PCR approach to identify parasites in hemosporidian genera that are transmitted by different dipteran vectors. Then, we implemented linear‐mixed effects and generalized dissimilarity models to evaluate the effects of latitude, elevation, and host species on parasite metrics. We found high diversity of hemosporidian parasites in Catharus thrushes (n = 44 lineages) but no evidence of latitudinal gradients in alpha diversity or prevalence. Parasites in the genus Leucocytozoon were most prevalent and lineage rich in this study system; however, there was limited turnover with latitude and host species. Contrastingly, Plasmodium parasites were less prevalent and diverse than Leucocytozoon parasites, yet communities turned over at a higher rate with latitude and host species. Leucocytozoon communities were skewed by the dominance of one or two highly prevalent lineages with broad latitudinal distributions. The few studies that evaluate the hemosporidian LDG do not find consistent patterns of prevalence and diversity, which makes it challenging to predict how they will respond to global climate change.

Geographic and host distribution of haemosporidian parasite lineages from birds of the family Turdidae

“…mostly breed at high-latitude sites in North America where the overall prevalence of Plasmodium is quite low (Spencer Galen, personal communication). However, after this manuscript was submitted, [54] published a study on haemosporidian parasites of Catharus spp. sampled in eastern North America and found seven new lineages in two species of this genus.…”

“…In the case of Leucocytozoon parasites this problem seems to be even more severe than in the case of Plasmodium and Haemoproteus infections [48], but still remains insufficiently addressed. After this manuscript was submitted, [54] published a study for which they screened 460 individuals of C. minimus, C. fuscescens, and Catharus bicknelli for haemosporidian parasites. They identified 16 new Leucocytozoon lineages (lCATBIC01-06, lCATBIC10-13, lCATFUS01-02, lCATFUS04-09, and lCATMIN11) in these three bird species, which were not included in the present study.…”

Disentangling the effects of host relatedness and elevation on haemosporidian parasite turnover in a clade of songbirds

“…Indeed, L_CATUST11 and L_CATMIN07 infect all four host species with high prevalence. These two lineages may be in competition with one another as we see a fluctuation in their dominance at larger spatial scales, where L_CATMIN07 is more prevalent than L_CATUST11 further south of our study system (Starkloff et al, 2020).…”

“…Leucocytozoon parasites are typically more prevalent and abundant in colder, temperate climates, as are their black fly vectors (Haas et al 2012, McCreadie and Adler 2014, Oakgrove et al 2014, McCreadie et al 2018, Cuevas et al 2020, Fecchio et al 2020). The temperate, forested breeding habitats of Catharus thrushes provide ideal conditions for high Leucocytozoon infection rates across their geographic ranges (Galen et al 2018; Starkloff et al, 2020). Consistent with these patterns, we found the Catharus thrushes in this study infected at a very high prevalence by Leucocytozoon parasites (88.4% on average).…”

“…1; Able and Noon 1976). Haemosporidian parasites (order Haemospororida) have been studied in Catharus thrushes across large geographic scales and through their circannual cycle (Dodge et al 2013, Pulgarín‐R et al 2019; Starkloff et al, 2020); however, little is known about the variability in infection among host species. The diversity of this parasite group allows for a thorough exploration of the variation in host sharing and specialization.…”