EvEel (evolutionary ecology-based model for eel): a model to explore the role of phenotypic plasticity as an adaptive response of three temperate eels to spatially structured environments

Abstract

Anguilla anguilla, Anguilla japonica, and Anguilla rostrata are three widely distributed catadromous and semelparous species characterized by a long and passive oceanic larval drift between their marine spawning grounds and nursery areas in continental waters. Their large, spatially heterogeneous environments combined with population panmixia and long and passive larval drift impair the possibility of local adaptation and favour the development of phenotypic plasticity. In this context, we developed EvEel (evolutionary ecology-based model for eel), a model that aims to explore the role of phenotypic plasticity as an adaptive response of eels. Results suggest that the spatial patterns in terms of sex ratio, length-at-silvering, and habitat use observed at both the distribution area and river catchment scales may actually be the result of three adaptive mechanisms to maximize individual fitness in spatially structured environments. We believe that considering phenotypic plasticity as a paradigm is required to develop appropriate models for this species.Résumé : Anguilla anguilla, Anguilla japonica et Anguilla rostrata sont trois espèces catadromes et sémelpares très répandues caractérisées par la dérive océanique prolongée et passive des larves entre leurs aires de frai marines et leurs aires de croissance en eaux continentales. Leurs vastes milieux hétérogènes, combinés à la panmixie des populations et la dérive passive prolongée des larves limitent la possibilité d'adaptation locale et favorisent le développement d'une plasticité phénotypique. Dans ce contexte, nous avons mis au point EvEel (un modèle d'écologie évolutive pour l'anguille), un modèle conçu pour explorer le rôle de la plasticité phénotypique en tant que réaction d'adaptation des anguilles. Les résultats donnent à penser que les répartitions spatiales du rapport des sexes, de la longueur au moment de l'argenture et de l'utilisation de l'habitat observées à l'échelle tant de l'aire de répartition que du bassin versant pourraient en fait résulter de trois mécanismes d'adaptation qui maximisent l'aptitude individuelle dans des milieux spatialement structurés. Nous pensons que, pour élaborer des modèles adaptés à ces espèces, il est nécessaire de considérer la plasticité phénotypique en tant que paradigme. [Traduit par la Rédaction]

RAD Sequencing Highlights Polygenic Discrimination of Habitat Ecotypes in the Panmictic American Eel

“…This is complementary to the phenotypic plasticity known to occur in the species [35] and other recent studies indicating differences in reaction norms to salinity levels among sampling locations differs [8,9]. We cannot rule out or support the presence of sex-specific strategies.…”

Silver eel downstream migration in fragmented rivers: use of a Bayesian model to track movements triggering and duration★

“…To achieve this quantification, a better knowledge on the time required to migrate to spawning grounds and on the continental escapement deadline would be necessary. The pattern of sex-ratio between the downstream (male biased) and upstream (more or exclusively females) area of a river catchment (Oliveira and McCleave, 2000;Tesch, 2003;Drouineau et al, 2014) combined with the impact of obstacles may also lead to arrival mismatch between males and females or to gender disparities in terms of escapement success. Increased energy costs and injuries caused by passing through downstream obstacles may also impair escapement success for silver eels, which stop feeding during reproduction migration (Bruijs and Durif, 2009).…”

Freshwater eels: A symbol of the effects of global change

“…These glass eels also display a more gregarious and less aggressive behaviour (Geffroy & Bardonnet, ). Habitat selection could be a trade‐off between growth (generally higher in downstream habitats), survival (generally higher in upstream habitats), competition avoidance (higher competition in downstream habitats) and energetic cost of migration (Drouineau et al., ; Edeline, ; Mateo, Lambert, Tétard, Castonguay, et al., ). Habitat selection is also partly related to genetic or epigenetic polymorphism (Côté et al., ; Gagnaire et al., ; Mateo, Lambert, Tétard, Castonguay, et al., ; Pavey et al., ; Podgorniak, Milan, et al., ).…”

“…These correlations are thought to result from spatially variable selection (some individuals are genetically more adapted than others to survive in some habitats) or of genetically based habitat selection (some types of individuals tend to settle preferentially in some habitats to maximize their fitness). The existence of genetically distinct types of individuals which are more or less adapted to the different types of habitats available within their distribution area (northern vs southern habitats, marine vs brackish vs freshwater habitats), that is ecotypes (Pavey et al., ), combined with a large phenotypic plasticity are assumed to play the main role in eel adaptive capacity, enabling the species to address the wide environmental heterogeneity at both the distribution and catchment scale (Drouineau et al., ; Mateo, Lambert, Tétard, Castonguay, et al., ). In such a scheme, individuals are able to grow and survive in a wide range of habitats thanks to phenotypic plasticity but some individuals are more adapted to some habitats than others (ecotypes), and all individuals reproduce together (panmixia) ensuring that ecotypes are reshuffled in each generation.…”