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Marine Ecology Progress Series

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MEPS 674:143-162 (2021)  -  DOI:

Environmental stressors induced strong small-scale phenotypic differentiation in a wide-dispersing marine snail

Nicolás Bonel1,2,3,*, Jean-Pierre Pointier4, Pilar Alda1,2

1Centro de Recursos Naturales Renovables de la Zona Semiárida (CERZOS—CCT—CONICET Bahía Blanca), Camino de la Carrindanga km 7, Bahía Blanca 8000, Argentina
2Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), C1425FQB CABA, Argentina
3Centre d’Écologie Fonctionnelle et Évolutive, UMR 5175, CNRS—Université de Montpellier, Université Paul-Valéry Montpellier—École Pratique des Hautes Études—IRD, 34293 Montpellier Cedex 05, France
4PSL Research University, USR 3278 CNRS—EPHE, CRIOBE Université de Perpignan, 66860 Perpignan CEDEX, France
*Corresponding author:

ABSTRACT: Heterogeneous environments pose a particular challenge for organisms because a single phenotype is unlikely to perform best across the variety of encountered stressors. To understand how species meet this challenge, we investigated the extent to which contrasting environmental pressures induced ecological and phenotypic responses in a natural population of a wide-dispersing marine snail at a small spatial scale. We analyzed several traits of Heleobia australis (Rissooidea: Cochliopidae) collected from heterogeneous, but highly connected, habitats from the intertidal area of the Bahía Blanca estuary, Argentina. We also conducted molecular analyses by amplifying the COI gene in individuals sampled from each habitat. We found that sympatric subpopulations of H. australis exhibited a strong phenotypic divergence in shell characters and body weight in response to thermal, saline, and dehydration stress, crab predation risk, and parasitic castrators. We proved that this differentiation occurred even early in life, as most of the characters observed in juveniles mirrored those found in adults. We also found a divergence in penis size in snails collected from each habitat and raised in common garden laboratory conditions. Molecular analyses confirmed that the individuals studied constituted a single species, despite the strong phenotypic differences among subpopulations. The small-scale phenotypic differentiation suggests that H. australis experienced a fine-grained environment where conditions imposed by different sources of stress favored the expression of beneficial traits. We discuss the role of plasticity in shaping adaptive phenotypic responses that increase the likelihood of persistence of subpopulations facing environmental stress conditions.

KEY WORDS: Adaptive plasticity · Shell characters · Genital morphology · Intertidal zonation · Contrasting selection pressures · Planktotrophic snail · High dispersal potential

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Cite this article as: Bonel N, Pointier JP, Alda P (2021) Environmental stressors induced strong small-scale phenotypic differentiation in a wide-dispersing marine snail. Mar Ecol Prog Ser 674:143-162.

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