Genetic and phenotypic influences on clone‐level success and host specialization in a generalist parasite

Abstract

Studying resource specialization at the individual level can identify factors constraining the evolution of generalism. We quantified genotypic and phenotypic variability among infective stages of 20 clones of the parasitic trematode Maritrema novaezealandensis and measured their infection success and post‐infection fitness (growth, egg output) in several crabs and amphipods. First, different clones varied in their infection success of different crustaceans. Second, neither genetic nor phenotypic traits had consistent effects on infection success across all host species. Although the results suggest a relationship between infection success and phenotypic variability, phenotypically variable clones were not better at infecting more host species than less variable ones. Third, genetic and phenotypic traits also showed no consistent correlations with post‐infection fitness measures. Overall, we found no consistent clone‐level specialization, with some clones acting as specialists and others, generalists. The trematode population therefore maintains an overall generalist strategy by comprising a mixture of clone‐level specialists and generalists.

Rapid transcriptional plasticity of duplicated gene clusters enables a clonally reproducing aphid to colonise diverse plant species

“…Despite the tendency for parasites to evolve highly specialised relationships with their hosts, occasionally, genuine generalist species with broad host ranges have evolved. For example, clonally produced individuals of the parasitic trematode Maritrema novaezealandensis are able to colonise a broad range of crustacean species [ 8 ] and the giant round worm Ascaris lumbricoides , which causes Ascariasis and infects an estimated 0.8 billion people worldwide, is able to infect both humans and pigs [ 9 ]. Often, however, generalist parasite species have turned out to be cryptic specialists, made up of host adapted biotypes / races or cryptic species complexes [ 10 – 12 ].…”

Seasonality of parasitic and saprotrophic zoosporic fungi: linking sequence data to ecological traits

“…Host specificity of Z. affluens has not been investigated, however, differences between Z. affluens and Fragilaria-CHY1 in host specificity and introns may suggest genetic isolation with ongoing diversification and host specialization [ 63 ]. Or, as seen in other host-parasite systems, both specialist and generalist strains likely coexist [ 64 ]. In case Fragilaria-CHY1 would have a more generalist lifestyle, we would expect it to occur also during times when Fragilaria is absent or not infected, indicating its potential to reproduce on alternative host species.…”

Integrating chytrid fungal parasites into plankton ecology: research gaps and needs

“…This potentially masks several hidden host-chytrid interactions and their dynamics. As seen in many other host-parasite systems, it is likely that within a single chytrid species both specialist and generalist strains coexist (Koehler et al, 2012). Extrapolations of results from cross-infection assays between single chytrid and host strains to the population level have, therefore, to be taken with caution.…”