Large-herbivore nemabiomes: patterns of parasite diversity and sharing

Abstract

Amidst global shifts in the distribution and abundance of wildlife and livestock, we have only a rudimentary understanding of ungulate parasite communities and parasite-sharing patterns. We used qPCR and DNA metabarcoding of fecal samples to characterize gastrointestinal nematode (Strongylida) community composition and sharing among 17 sympatric species of wild and domestic large mammalian herbivore in central Kenya. We tested a suite of hypothesis-driven predictions about the role of host traits and phylogenetic relatedness in describing parasite infections. Host species identity explained 27–53% of individual variation in parasite prevalence, richness, community composition and phylogenetic diversity. Host and parasite phylogenies were congruent, host gut morphology predicted parasite community composition and prevalence, and hosts with low evolutionary distinctiveness were centrally positioned in the parasite-sharing network. We found no evidence that host body size, social-group size or feeding height were correlated with parasite composition. Our results highlight the interwoven evolutionary and ecological histories of large herbivores and their gastrointestinal nematodes and suggest that host identity, phylogeny and gut architecture—a phylogenetically conserved trait related to parasite habitat—are the overriding influences on parasite communities. These findings have implications for wildlife management and conservation as wild herbivores are increasingly replaced by livestock.

Population genomics of helminth parasites

“…They found previously unreported families from some primates and that closely related primate species had greater parabiome similarity. Titcomb et al (2022) tested for associations between the nemabiome and host traits or phylogenetic relatedness across 17 species of sympatric mammalian herbivores in Kenya as well as assessed parasite-sharing networks among hosts. Key findings included 53% of the nemabiome dissimilarity among faecal samples explained by host species, significant congruence between host and parasite phylogenies, and that host gut morphology predicted nematode community composition.…”

“…Additionally, they suggested that central host species (i.e. hosts that shared parasite species with many other hosts) could be targeted for management strategies where deworming these hosts might limit the spread of parasites to threatened wildlife (Titcomb et al , 2022).…”

“…A primary utility of a parabiome approach is in estimating parasite richness, especially regarding the detection of low frequency and morphologically indistinguishable species. However, both Avramenko et al (2015) and Titcomb et al (2022) have noted important caveats about quantifying parasite abundance. In particular, cell number, rDNA copy number, variation in primer binding efficiency across species and amplification efficiency of sequence variants are factors that can skew true abundance.…”

“…Controlled experiments can be used to correct for some of these latter factors (see Avramenko et al, 2015), but many natural systems may have undescribed species or species not yet represented with sequence data (e.g. Titcomb et al, 2022). Also, as source material are parasite offspring from faecal samples, abundance inferences need to be restricted to what will be seeding the next generation of infections.…”

Contrasting seasonal patterns in diet and dung‐associated invertebrates of feral cattle and horses in a rewilding area

“…Megafauna has been present in most of the world's terrestrial ecosystems since the mid Cenozoic and is expected to have shaped the evolution of many extant species (Galetti et al, 2018; Malhi et al, 2016; Smith et al, 2018; Titcomb et al, 2022). Since the Late Pleistocene, there has been a high extinction‐selectivity for megafauna, with the result that most contemporary terrestrial ecosystems are deprived of megafauna and the functions they provide (Malhi et al, 2016; Smith et al, 2018).…”