title: Potential for adaptive evolution at species range margins: contrasting interactions between red coral populations and their environment in a changing ocean.
abstract: Studying population-by-environment interactions (PEIs) at species range margins offers the opportunity to characterize the responses of populations facing an extreme regime of selection, as expected due to global change. Nevertheless, the importance of these marginal populations as putative reservoirs of adaptive genetic variation has scarcely been considered in conservation biology. This is particularly true in marine ecosystems for which the deep refugia hypothesis proposes that disturbed shallow and marginal populations of a given species can be replenished by mesophotic ones. This hypothesis therefore assumes that identical PEIs exist between populations, neglecting the potential for adaptation at species range margins. Here, we combine reciprocal transplant and common garden experiments with population genetics analyses to decipher the PEIs in the red coral, Corallium rubrum. Our analyses reveal partially contrasting PEIs between shallow and mesophotic populations separated by approximately one hundred meters, suggesting that red coral populations may potentially be locally adapted to their environment. Based on the effective population size and connectivity analyses, we posit that genetic drift may be more important than gene flow in the adaptation of the red coral. We further investigate how adaptive divergence could impact population viability in the context of warming and demonstrate differential phenotypic buffering capacities against thermal stress. Our study questions the relevance of the deep refugia hypothesis and highlights the conservation value of marginal populations as a putative reservoir of adaptive genetic polymorphism.
authors: CIMAR/CIIMAR, Centro Interdisciplinar de Investigacção Marinha e Ambiental, Universidade do Porto, Rua dos Bragas 177 4050-123, Porto, Portugal ; Institut de Ciencies del Mar CSIC, Passeig Maritim de la Barceloneta 37-49 Barcelona, Spain ; Aix Marseille Universite, CNRS, IRD, Avignon Université, IMBE, UMR 7263 13397, Marseille, France.
authors: Jean-Baptiste
authors: JB
authors: Ledoux
authors: Aix Marseille Universite, CNRS, IRD, Avignon Université, IMBE, UMR 7263 13397, Marseille, France.
authors: Didier
authors: D
authors: Aurelle
authors: IPSO FACTO, SCOPARL, Pôle Océanologie et Limnologie, 37 rue Saint-Sebastien F-13006, Marseille, France.
authors: Nathaniel
authors: N
authors: Bensoussan
authors: Aix Marseille Universite, CNRS, IRD, Avignon Université, IMBE, UMR 7263 13397, Marseille, France.
authors: Christian
authors: C
authors: Marschal
authors: Aix Marseille Universite, CNRS, IRD, Avignon Université, IMBE, UMR 7263 13397, Marseille, France.
authors: Jean-Pierre
authors: JP
authors: Féral
authors: Aix Marseille Universite, CNRS, IRD, Avignon Université, IMBE, UMR 7263 13397, Marseille, France ; Institut de Ciencies del Mar CSIC, Passeig Maritim de la Barceloneta 37-49 Barcelona, Spain.
authors: Joaquim
authors: J
authors: Garrabou
keywords: Common garden; Corallium rubrum; deep refugia hypothesis; marginal populations; phenotypic buffering; potential for local adaptation; reciprocal transplants