Competition from sea to mountain: Interactions and aggregation in low‐diversity monogenean and endohelminth communities in twospot livebearerPseudoxiphophorus bimaculatus(Teleostei: Poeciliidae) populations in a neotropical river

Abstract

The role of interspecific interactions in structuring low‐diversity helminth communities is a controversial topic in parasite ecology research. Most parasitic communities of fish are species‐poor; thus, interspecific interactions are believed to be unimportant in structuring these communities. We explored the factors that might contribute to the richness and coexistence of helminth parasites of a poeciliid fish in a neotropical river. Repeatability of community structure was examined in parasitic communities among 11 populations of twospot livebearer Pseudoxiphophorus bimaculatus in the La Antigua River basin, Veracruz, Mexico. We examined the species saturation of parasitic communities and explored the patterns of species co‐occurrence. We also quantified the associations between parasitic species pairs and analyzed the correlations between helminth species abundance to look for repeated patterns among the study populations. Our results suggest that interspecific competition could occur in species‐poor communities, aggregation plays a role in determining local richness, and intraspecific aggregation allows the coexistence of species by reducing the overall intensity of interspecific competition.

Comparison of methods to detect interspecific competition among parasites in depauperate communities

“…Correlation analyses have a good chance, when competition is strong, of suggesting that there is competition, but they are unlikely to return a conventionally significant result. The results of other studies are consistent with this finding (Salgado-Maldonado et al 2019). Similarly, logistic regression passes the Type I error test of a good analytical technique, but only displays good power when prevalence and species richness are low, and when competition is modelled as a random winner, which is probably the least biologically realistic of the models chosen here.…”

“…Most parasite systems are not particularly amenable to experiments, however, and therefore, the analysis of field-collected data will continue to be the basis of attempts to discern whether the stamp of competition is present in a particular parasite community. Traditional statistical techniques continue to be used by workers seeking negative associations among the patterns of presence and abundance of two or more species in a sample of hosts (Krasnov et al 2005; Poulin 2005; Johnson and Buller 2011; Fenton et al 2014; Salgado-Maldonado et al 2019). In addition, null models have been deployed for analysing such data (Cort et al 1937; Lafferty et al 1994; Lotz and Font 1994; Janovy et al 1995; Gotelli and Rohde 2002; Soldanova et al 2012; Laidemitt et al 2019), and others have used multivariate techniques (Carbaret and Hoste 1998), longitudinal studies (Fenton et al 2014), or other modelling techniques (Fenton et al 2010; Dallas et al 2019).…”

“…Finally, if these results turn out to be more generally applicable, then the literature may have grossly underestimated the effects of competition operating in natural parasite communities. Although long-held to be absent interspecific interactions, the typically low diversity and low intensity communities of parasites in fishes and other hosts do show evidence of negative interspecific interactions (Kennedy 1992; Vidal-Martinez and Kennedy 2000; Salgado-Maldonado et al 2019). The particular communities forming the basis of the current investigation do not display such evidence (Barger 2020, 2021), but further work aimed at improving our ability to detect competition when present may warrant reconsideration of the role of competition in natural parasite communities and therefore reanalysis of existing datasets.…”

“…Discerning whether datasets from natural communities bear the signal of competition is an empirical, analytical problem, not a logical one. For example, intestinal helminth communities of fishes have been characterized as isolationist because most communities consist of relatively few species (compared to the communities of parasites in birds and mammals) that typically infect their hosts at lower intensities and prevalence (Kennedy et al 1986; Salgado-Maldonado et al 2019). Because these systems are intractable experimentally, inferences about the processes that govern community structure will rely on analysis of field-collected data.…”

State of the art of poecilid fish ( Pisces: Poeciliidae) in México

“…The study of diseases of the native poeciliids of Mexico is limited and has been focused on their parasites, both external and internal, as for ectoparasites the lerneosis, a disease caused by copepods, is a great problem in crops of ornamental poecilids, as it causes reproductive damage in the internal and external characteristics, causing death (Maya et al, 2007). The most studied group of internal parasites are the helminths, of which there are 46 species that parasitize native Mexican poecilids, and to a lesser extent the monogeneous, being P. mexicana the host with the most species of registered helminths (24 species), the role of exotic species as vectors of parasites has also been studied, affecting native poecilids, which are especially susceptible due to geographic restriction (Razo-Mendivil et al, 2013;Salgado-Maldonado et al, 2020).…”