Community structure of helminth parasites in two closely related South African rodents differing in sociality and spatial behaviour.

To understand the effect of social and spatial behaviour of a host on parasite community organization, we studied species co-occurrence and nestedness of assemblages of gastrointestinal helminths in two closely related rodents, solitary and mobile Rhabdomys dilectus and social and territorially conservative Rhabdomys pumilio, and asked whether helminth communities of the two hosts are characterized by a non-random pattern and whether the occurrence or degree of this non-randomness (a) differs between hosts and (b) is associated with abundance, prevalence and diversity of helminths. We found that although the general pattern of helminth co-occurrence was similar in the two hosts, helminth infracommunities of R. dilectus and R. pumilio differed in the relative frequency of positive and negative pairwise species co-occurrences (only positive in the former and both positive and negative in the latter). Nestedness-related patterns in helminth infracommunities were found in R. pumilio (predominantly anti-nested) but not R. dilectus (predominantly non-nested), whereas the opposite was the case for their component communities (non-nested versus nested, respectively). The level of infection was generally associated with the manifestation of non-randomness in helminth assemblages. Different infection parameters affected different structure patterns in the two hosts. We concluded that community structure of helminths in Rhabdomys spp. results from complex interactions between parasite- and host-associated factors.