The adaptive value of phenotypic plasticity in two ecotypes of a marine gastropod

Johan Hollander,Roger K Butlin

doi:10.1186/1471-2148-10-333

Abstract

BackgroundFew surveys have concentrated on studying the adaptive value of phenotypic plasticity within genetically-distinct conspecific ecotypes. Here, we conduct a test to assess the adaptive value that partial phenotypic plasticity may have for survival in the marine gastropod Littorina saxatilis. This species has evolved canalized ecotypes but, nevertheless, the ecotypes show some phenotypic plasticity for the traits under divergent selection between wave-exposed and high-predation habitats.ResultsWe exposed juveniles of each ecotype to several environmental treatments under laboratory conditions in order to produce shape variation associated with plasticity. The two ecotypes from different treatments were then transplanted to the wave-exposed habitat and the survival rate was monitored. Ecotype explained the largest distinction in survival rate while treatment caused variation in survival rate within the ecotype released into its parental habitat which was correlated with plastic changes in shell shape. Snails that had experienced a treatment mimicking the environment of the transplantation location survived with the highest rate, while individuals from the contrary experimental treatment had lower survivorship.ConclusionsWe conclude that the partial plastic response shown in Littorina saxatilis has a significant impact on fitness, although this remains small compared to the overall adaptive difference between ecotypes.

Highlights

Few surveys have concentrated on studying the adaptive value of phenotypic plasticity within genetically-distinct conspecific ecotypes
Hollander et al [31] showed that the plastic responses of the E and the S ecotype of Littorina saxatilis develop in the same direction, but specific for their parental habitats since the magnitude of the plasticity was greatest in the resident habitat
Studies in plants evaluating the magnitude of plasticity in different ecotypes, the fitness effects that result and the specificity of the phenotypic plasticity [20,21,39,40] show that the observed plasticity is not a relic but an adaptive trait

Summary

Introduction

Few surveys have concentrated on studying the adaptive value of phenotypic plasticity within genetically-distinct conspecific ecotypes. We conduct a test to assess the adaptive value that partial phenotypic plasticity may have for survival in the marine gastropod Littorina saxatilis. This species has evolved canalized ecotypes but, the ecotypes show some phenotypic plasticity for the traits under divergent selection between wave-exposed and high-predation habitats. The resulting phenotypic flexibility may increase an organism’s fitness in a heterogeneous environment and phenotypic plasticity is a common feature in nature across many taxa [5-9]. Phenotypic plasticity can operate jointly with ecotype formation and may further increase fitness. We use the term ‘partial plasticity’ to refer to cases where the plastic response can explain only a limited proportion of the phenotypic difference between individuals occupying different environments, i.e. cases where genetically distinct ecotypes exist but their phenotypes may be adjusted by plastic responses

Methods

Results

Discussion

Conclusion