Genetic diversity of structuring species in the sea : influence on the demographic response to anthropic disturbances

• Main Author: Becheler, Ronan
• Other Authors: Laboratoire Environnement Profond (LEP), Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER), Université de Bretagne occidentale - Brest, Sophie Arnaud-Haond, Christian Hily
• Format: Doctoral or Postdoctoral Thesis
• Language: French
• Published: HAL CCSD 2013
• Subjects: Cold-water corals; Connectivity; Clonality; Demographic dynamics; Population genetics; Génétique des populations; Dynamique démographique; Clonalité; Connectivité; Zostera marina; Coraux d'eau froide; [SDV.GEN.GPO]Life Sciences [q-bio]/Genetics/Populations and Evolution [q-bio.PE]; [SDV.BID]Life Sciences [q-bio]/Biodiversity; Lophelia pertusa
• Online Access: https://tel.archives-ouvertes.fr/tel-01065808; https://tel.archives-ouvertes.fr/tel-01065808/document; https://tel.archives-ouvertes.fr/tel-01065808/file/These-2013-EDSM-BECHELER_Ronan.pdf

The influence of genetic diversity on the demographic stability of populations constitutes a paradigm in evolutionary ecology. The complexity of this relationship within natural populations is enhanced by the reciprocal effect of stability on diversity, and the degree of interconnection among populations. This interaction was explored within the seagrass Zostera marina and the cold-water corals Lophelia pertusa and Madrepora oculata, three partially clonal species. This life history trait, deeply influencing the population dynamics and evolutionary trajectory of species, constituted the underlying theme of this work.The sampling in space (regional scale) and time (a three-years step) of eelgrass meadows allowed us to better understand the clonal dynamics of these plants. The clonal architecture and diversity may result from the equilibrium between dispersal/recruitment of collectively dispersed clouds of seeds, and the competition for space among clones. Perturbations locally affect the equilibrium of meadows. This original dynamic makes impossible the identification of population contours. Yet, our results suggest that the genetic diversity sensu stricto (heterozygosity and number of alleles) represents a factor of demographic stability, through its putative influence on resistance capacity for seasonal disturbances. Cold-water corals show biogeographic pattern in line with the hypothesis of glacial extinction, within the Bay of Biscay. The noticeable footprints of fishing activities question the capacity of resilience of these ecosystems, depending on dispersal potential of the structuring species, which showed low levels of clonality. The lack of genetic structure observed for L. pertusa suggest, at least for this species, a high degree of interconnection among reefs at large scale, while M. oculata revealed a stronger regional structure. Sensitivity of these two species to climatic variations and the pressures of human activities highlight the need of thorough studies for their conservation. Results obtained ...