Corallium rubrum is an octocoral (Cnidaria, Anthozoa) distributed in the Mediterranean Sea and in the neighboring North-Eastern Atlantic. Due to its arborescent morphology, this habitat-forming species displays a key structural role in biodiversity-rich benthic communities. C. rubrum is also an iconic species with high cultural and economic values which has been actively harvested since Ancient times.
A well conserved population of the red coral, Corallium rubrum in the Scandola Marine Reserve.
Yet, C. rubrum is under conservation concerns due to overharvesting and anthropogenic climate change. C. rubrum received conservation attention both from the scientific and biodiversity managers communities. International (Barcelona and Bern Conventions, EU Habitat Directive) and national legislations on harvesting were not able to reverse the demographic decline and C. rubrum has been recognized as “endangered” on the IUCN red list of Anthozoans in the Mediterranean (Otero et al. 2017). While the demographic decline is well characterized, the impact of overharvesting and mass mortality events on the species genetic make-up is still poorly understood, mostly because of the limited genetic resources available to date. Crucial questions regarding admixture among lineages, demographic history, effective population sizes, selection, including local adaptation, are still open. These gaps of knowledge prevent us from fully understanding the species evolutionary building-up and to support conservation policies.
Close-up photos of the Mediterranean red coral. The last two photos show red coral colonies suffering from tissue necrosis as a consequence of marine heatwaves. Photos by Joaquim Garrabou
The objectives of the RED-COR project, “Conservation genomics of the Mediterranean red coral, Corallium rubrum: a habitat-forming octocoral threatened by overharvesting and anthropogenic climate change” are twofold:
Covering a large part of the species distribution range, we aim to set up the evolutionary stage of the species. We will: i) characterize the full spectrum of genetic diversity and structure, including admixture pattern; ii) infer the species demographic history and, iii) explore for the first time the genomic landscape of the species (e.g. islands of differentiation, large structural variants).
Focusing on two Marine Protected Areas along the Catalan Coast (Parc natural del Montgrí, les Illes Medes i Baix Ter and Parc Natural del Cap de Creus), where C. rubrum populations are monitored since almost 20 years (including impact of marine heatwaves), we will: iv) look for local adaptation and v) test for a genetic determinism in the differential responses to thermal stress, contrasting “resistant” with “sensitive” individuals.
Diver sampling red coral colonies. Photo by Alexis Rosenfeld.
This project relies on an international team of scientists and will benefit from the reference genome we assembled in the Catalan Biogenome Project (sN50 > 18Mb; sL50=7; size = 532 Mb; Busco:86% complete genes; QVscore 42; Ledoux et al. 2023).
From a management perspective, the first objective will allow us to test for different evolutionary lineages and, potentially, to define evolutionary units. We will be able to provide estimates of current effective population size for the different locations, which could be used to adjust current fishing quotas. The second objective will provide a relevant example of the inputs of population genomics for the management of protected areas.
Text by Jean-Baptiste Ledoux (CIIMAR, Interdisciplinary Centre of Marine and Environmental Research, Portugal)
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