Intra- and intertaxon similarity of nematode assemblages among sympatric rodents differing ecologically.

Ecological processes that shape animal assemblages act at multiple levels. Limited information is available on the factors that drive spatial variation in parasite communities, particularly in nematodes. This study aimed to reveal the role of host and environment as determinants of nematode species compositional similarity among three rodent taxa (Rhabdomys spp., Micaelamys namaquensis, and Otomys unisulcatus) that occur sympatrically in the Fynbos and Succulent Karoo biomes of the Western Cape Province of South Africa. In total, eight monoxenous and three heteroxenous nematode species were recorded. Seven species occurred in Rhabdomys spp., six in M. namaquensis, and five in O. unisulcatus. Nematode communities were more similar between Rhabdomys and Otomys, which also share comparable microhabitats. Nematodirus sp. and Neoheligmonella capensis, both with free-living larval stages, contributed strongly to between-host differences that were also correlated with low-lying habitat use. However, part of the between-host differences in species assemblages reflects host-restricted Syphacia spp. The influence of environmental factors on the composition of nematode infracommunities was also contingent on host life history. Overall, host diet, microhabitat use, as well as social and spatial behaviour appeared to exert a strong influence on the composition of nematode infracommunities. Results suggest that microhabitat use plays an important role in nematode community assembly, although direct environmental covariates were not formally analysed. Since between-host dissimilarities were influenced by host-restricted nematode species, habitat-driven patterns should be interpreted after accounting for host identity. The data generated here contribute to a broader understanding of the ecological niches preferred by parasitic nematodes of rodents.