title: Phenotypic variation and fitness in a metapopulation of tubeworms (Ridgeia piscesae Jones) at hydrothermal vents.
abstract: We examine the nature of variation in a hot vent tubeworm, Ridgeia piscesae, to determine how phenotypes are maintained and how reproductive potential is dictated by habitat. This foundation species at northeast Pacific hydrothermal sites occupies a wide habitat range in a highly heterogeneous environment. Where fluids supply high levels of dissolved sulphide for symbionts, the worm grows rapidly in a "short-fat" phenotype characterized by lush gill plumes; when plumes are healthy, sperm package capture is higher. This form can mature within months and has a high fecundity with continuous gamete output and a lifespan of about three years in unstable conditions. Other phenotypes occupy low fluid flux habitats that are more stable and individuals grow very slowly; however, they have low reproductive readiness that is hampered further by small, predator cropped branchiae, thus reducing fertilization and metabolite uptake. Although only the largest worms were measured, only 17% of low flux worms were reproductively competent compared to 91% of high flux worms. A model of reproductive readiness illustrates that tube diameter is a good predictor of reproductive output and that few low flux worms reached critical reproductive size. We postulate that most of the propagules for the vent fields originate from the larger tubeworms that live in small, unstable habitat patches. The large expanses of worms in more stable low flux habitat sustain a small, but long-term, reproductive output. Phenotypic variation is an adaptation that fosters both morphological and physiological responses to differences in chemical milieu and predator pressure. This foundation species forms a metapopulation with variable growth characteristics in a heterogeneous environment where a strategy of phenotypic variation bestows an advantage over specialization.
authors.affiliation: Department of Biology, University of Victoria, Victoria, British Columbia, Canada; School of Earth & Ocean Sciences, University of Victoria, Victoria, British Columbia, Canada.
authors.forename: Verena
authors.initials: V
authors.lastname: Tunnicliffe
authors.affiliation: Department of Biology, University of Victoria, Victoria, British Columbia, Canada.
authors.forename: Candice
authors.initials: C
authors.lastname: St Germain
authors.affiliation: Departamento de Biologia and Centro de Estudos do Ambiente e do Mar, Universidade de Aveiro, Campus de Santiago, Aveiro, Portugal.
authors.forename: Ana
authors.initials: A
authors.lastname: Hilário
mesh_terms: D000818:Animals; D005260:Female; D056084:Genetic Fitness; D006066:Gonads / Q000166:cytology; D060086:Hydrothermal Vents; D008297:Male; D010641:Phenotype; D011077:Polychaeta / Q000166:cytology / Q000502:physiology*; D012098:Reproduction