One of the most important tasks of any scientific discipline is to reveal general rules that can explain a broad range of facts and phenomena. Ecology is a young science compared, for example, with physics or chemistry. Moreover, ecological systems are enormously complex and affected by multiple extrinsic and intrinsic factors. Even so, some general rules, patterns, and laws determining the abundance, distribution, and diversity of living organisms have been revealed, mainly in the past 50 years (e.g., Brown, 1995, Rosenzweig, 1995, Gaston, 2003, Vandermeer and Goldberg, 2013). Although interest in parasites as agents causing diseases in humans, livestock, and wildlife has a long history, parasite ecology has fallen somewhat behind the ecology of free-living organisms. One of the reasons for this is that parasitism as a consumer strategy originated independently in multiple plant and animal lineages and, often, several times in the same lineage (Poulin, 2007a). As a result, parasites appear in an enormous variety of forms, belonging to different taxa and differing in their origin, patterns of parasitism, and life histories, and they represent a large (if not the largest) proportion of global biodiversity (Windsor, 1998, Dobson et al., 2008, Carlson et al., 2020). Nevertheless, the past three decades have witnessed an outpouring of studies on the ecology of various parasite taxa (Poulin, 2021). This paved the way for one of the first attempts to elucidate general rules governing parasite ecology, undertaken by Poulin (2007b), who concluded that general laws likely exist at the level of parasite populations and host-parasite interaction networks, but that patterns characteristic at the level of parasite communities do not appear to be universal.

The search for common patterns in parasite ecology is usually carried out by reviewing the results of different studies (e.g., Poulin, 2007b, Morand, 2015) or as formal meta-analyses (e.g., Kamiya et al., 2014a, b). Empirical studies have compared ecological patterns in different parasites often considered species belonging to the same higher taxon (e.g., Fantozzi et al., 2022) or those that have similar strategies of parasitism (e.g., intestinal helminths or haematophagous arthropods) in hosts belonging to the same (e.g., de Belocq et al., 2003) or different taxonomic units (e.g., Dallas et al., 2019a, Dáttilo et al., 2020). Ecological patterns in parasites with distinctly different strategies of parasitism (e.g., ectoparasites and endoparasites) in substantially different hosts have been considered in the same study less often (e.g., Vázquez et al., 2005, Vázquez et al., 2007, Dallas et al., 2019b, Brian and Aldridge, 2021, Krasnov et al., 2021). However, elucidating common patterns in parasite ecology requires comparison of the same patterns between substantially different host-parasite associations.

Here, we searched for common patterns in parasite ecology by investigating parasite species and host contributions to the beta-diversity of parasite infracommunities (=assemblages of parasites harboured by a host individual). Beta-diversity is the measure of variability in the species composition of plant, animal, or microbial communities across space or time (Whittaker, 1960, Whittaker, 1972). In the case of parasite communities, beta-diversity reflects the difference in species identities and their numbers between infra-, component (=assemblage of all parasites harboured by a population of conspecific hosts), or compound (=assemblage of all parasites harboured by a host community) communities. Given that many infra-, component, and compound (the latter in case of taxonomically similar hosts across similar environments) communities obviously share many parasite species, the ultimate reasons behind the differences between communities are not always clear. It is commonly accepted that there are two main mechanisms producing these differences (Carvalho et al., 2012, Legendre and de Cáceres, 2013, Legendre, 2014; but see Baselga et al., 2007, Baselga, 2010). These mechanisms are (i) species replacement (=turnover), causing differences in species composition, and (ii) species gains/losses causing differences in species composition. This suggests differential contributions of individual species and their assemblages to beta-diversity (Legendre and de Cáceres, 2013). To estimate the effects of species and their assemblages on beta-diversity, Legendre and de Cáceres (2013) proposed partitioning total beta-diversity into (i) species’ contributions (SCBD; the degree of the relative importance of individual species for between-community differences) and (ii) local contributions (LCBD; the degree of the compositional uniqueness of a given assemblage relative to other assemblages). Studies of SCBD and LCBD in various communities of free-living species demonstrated that SCBD can be associated with species’ traits, whereas LCBD can be associated with the environment in which a given community exists (Heino and Grönroos, 2017, da Silva et al., 2018, Xia et al., 2022).

The concept of beta-diversity partitioning into SCBD and LCBD has rarely been applied to parasite communities. Furthermore, SCBD and LCBD were mainly considered at the scale of parasite component (Biguezoton et al., 2016, Spickett et al., 2019) or compound (Poisot et al., 2017, Krasnov et al., 2019) communities. and only once at the scale of a single host species’ infracommunities (Junker et al., 2023). In the latter case, LCBD can be renamed as HCBD (host contributions to beta-diversity) because it reflects the compositional uniqueness of parasite assemblages in individual hosts and, consequently, may depend on host characteristics similar to the dependence of classical LCBD on sampling sites’ environmental characteristics (e.g., Poisot et al., 2017).

Here, we used data on species composition and numbers in the endoparasite (helminths) infracommunities of three species of ungulates from South Africa and the ectoparasite (fleas) infracommunities of 11 species of rodents from South America. We asked whether (i) parasite species attributes (life cycle, transmission mode, and host specificity in helminths and possession of sclerotized combs, microhabitat preference, and host specificity in fleas) or their population structure (mean abundance and/or prevalence) and (ii) host characteristics (sex and age) affect parasite species contributions and host contributions to beta-diversity (SCBD and HCBD, respectively).