Parasite infection induces size-dependent host dispersal: consequences for parasite persistence

Abstract

Host dispersal is now recognized as a key predictor of the landscape-level persistence and expansion of parasites. However, current theories treat post-infection dispersal propensities as a fixed trait, and the plastic nature of host's responses to parasite infection has long been underappreciated. Here, we present a mark-recapture experiment in a single host-parasite system (larval parasites of the freshwater mussel and its salmonid fish host) and provide, to our knowledge, the first empirical evidence that parasite infection induces size-dependent host dispersal in the field. In response to parasite infection, large fish become more dispersive, whereas small fish tend to stay at the home patch. The observed plasticity in dispersal is interpretable from the viewpoint of host fitness: expected benefits (release from further infection) may exceed dispersal-associated costs for individuals with high dispersal ability (i.e. large fish) but are marginal for individuals with limited dispersal ability (i.e. small fish). Indeed, our growth analysis revealed that only small fish hosts incurred dispersal costs (reduced growth). Strikingly, our simulation study revealed that this plastic dispersal response of infected hosts substantially enhanced parasite persistence and occupancy in a spatially structured system. These results suggest that dispersal plasticity in host species is critical for understanding how parasites emerge, spatially spread, and persist in nature. Our findings provide a novel starting point for building a reliable, predictive model for parasite/disease management.

A Bayesian approach to inferring dispersal kernels with incomplete mark-recapture data

“…These are a common dataset obtained through a mark-recapture study, so no additional work may be required to use the DOCM. Furthermore, if users have an independent estimate of detection probability ξ through multiple-pass removal (Dorazio et al 2005) or other methods, it is also possible to estimate the true survival rate s that is corrected for permanent emigration (Terui et al 2017). However, there are caveats when interpreting the results.…”

“…Ecologists have been intrigued by the spatial process due to its implications for critical applied issues, such as the metapopulation persistence of endangered species in fragmented landscapes (Hanski 1999). More recently, accumulating evidence suggests that dispersal is highly plastic and context-dependent with significant consequences for landscape-level dynamics (Bonte & de la Pena 2009; Bonte et al 2012; Cote et al 2011; Cote et al 2013; Fronhofer et al 2018; Fronhofer et al 2017; Little et al 2019; Terui et al 2017). For example, Fronhofer et al (2018) have shown that context-dependent dispersal in experimental landscapes has stabilizing effects on local food webs coupled via dispersal.…”

“…Bayesian inference provides a flexible statistical framework that may open the opportunity to overcome challenges in utilizing mark-recapture data (Kéry & Schaub 2012; Terui et al 2017). Here, I introduce a novel Bayesian model that integrates dispersal and observation processes into a single coupled model.…”

Hybrids as potential mediators spreading non‐native genes: Comparison of survival, growth, and movement among native, introduced and their hybrid salmonids

“…Furthermore, stream-dwelling fishes serve as an excellent model system to measure the dispersal distance of individuals (e.g. Pépino, Rodríguez, & Magnan, 2012;Terui, Ooue, Urabe, & Nakamura, 2017), which should be an indication of their gene flow potential. Because stream fishes generally move linearly along the stream, we can easily measure the distance each individual travels by contiguously established study sections.…”

“…number of offspring that survive to juvenile) which had been estimated in our previous study (Fukui et al, 2018). Although dispersal distance is not necessarily equivalent to gene flow, it should be an available indicator for the spread of non-native genes (Pépino et al, 2012;Terui et al, 2017). identified to species level based on appearance (Nakabo, 2000), and fork length measured (nearest mm).…”