Trade-offs and resource breadth processes as drivers of performance and specificity in a host-parasite system: a new integrative hypothesis

Abstract

One of the unresolved issues in the ecology of parasites is the relationship between host specificity and performance. Previous studies tested this relationship in different systems and resulted in all possible outcomes. Therefore, two main hypotheses have been proposed to explain those conflicting results: the trade-off and resource breadth hypotheses, which are treated as alternative explanations in the literature and were corroborated by different studies. Here, we performed an extensive study, using specificity indices and network analysis, in order to test for a relationship between host specificity and prevalence in a rich avian malaria system. There was no correlation between specificity and prevalence, which contradicts both the trade off and resource breadth hypotheses. In addition, we detected a modular structure in our host-parasite network and found that its modules were not composed of geographically close, but of phylogenetically close host species. Despite trade-off and resource breadth hypotheses leading to opposite predictions, after performing our study we reached the conclusion that they are not mutually exclusive. As a conceptual solution we propose The Integrative Hypothesis of Parasite Specialization, a novel hypothesis that explains the contradictory results found so far and shows that the trade-off and resource breadth hypotheses are two sides of the same coin.