The underrated importance of predation in transmission ecology of direct lifecycle parasites

Abstract

Most parasites with complex life cycles exploit trophic webs to pass from host to host in order to develop and, eventually, reproduce. Thus predation constitutes the necessary route for transmission. Conversely, the transmission of parasites that use a single host to develop and reproduce should be, in principle, not particularly affected by host trophic ecology. Here I challenge this view, showing that predation may be relevant also for direct lifecycle parasites. I used a large dataset of fish trophic interactions to investigate if the degree of monogenean species overlap in predators and prey deviated from randomness. I demonstrated that predators and prey often share more monogenean parasite genera than explained by host habitat ecology, geographical distribution and phylogeny. This suggests that predation may play an important role in promoting monogenean host range expansion. In addition, a non‐negligible proportion of considered prey–predator pairs showed a significantly high overlap in their monogenean parasites at the species level. This may indicate a tendency of some monogenean parasites to evolve transmission strategies targeted towards host interactions. If this hypothesis is true, these monogenean parasites would be much more vulnerable to co‐extinction than previously thought.SynthesisPredation is not expected to play an important role in the ecology and evolution of simple life cycle parasites. Yet, several predator fish tend to share with their prey more monogenean parasites than one would expect predicted from their geographical distribution, habitat preference, and or phylogenetic relationships. This suggests that some monogenean parasites have evolved transmission strategies more targeted towards host interactions than towards species‐specific traits. If this hypothesis is supported, it would have strong implications on host–parasite evolutionary ecology, primarily, suggesting the existence of peculiar situations where some parasites have evolved high specialized host finding behaviors to expand their host range.