What can be learned from the study of connectivity and demography of sessile organisms for the design of marine conservation measures? A case study of the Mediterranean red gorgonian

Abstract

Within the current context of global change, analyzing the connectivity has become a key conservation issue, because of its important role in population persistence and recovery from disturbances. In the Mediterranean Sea, the coralligenous assemblages, considered as one of the most important hot spots of biodiversity, are broadly affected by global change. The red gorgonian, Paramuricea clavata, is amongst the main structural components of these assemblages. An examination of the demographic and genetic processes of P. clavata is crucial to understand the resilience of the Mediterranean coralligenous in a changing world and to build-up conservation and management actions that contribute to the protection of these highly diverse assemblages. Here, we present a case study in which the demographic structure and genetic connectivity of P. clavata populations in an isolated area (i.e. W Ibiza Island, Balearic Islands, Spain), was assessed. About 30 apical tips of colonies from five locations, separated by distances ranging between 1 and 14 km, were collected and analyzed with microsatellite markers. Migration patterns and spatial genetic structure among populations were mainly examined by Bayesian assignment tests, genetic differentiation measures, kinship coefficients and Bayesian clustering analysis. Furthermore, in order to determine how genetic differentiation and diversity are linked to demographic and connectivity patterns, we explored relations between demographic and connectivity variables and genetic parameters, using generalized linear models and correlations. Significant levels of genetic differentiation corresponding to a pattern of isolation by distance among populations were found. Furthermore, the clustering analysis detected three genetic groups, with high levels of self-recruitment and small migration rates. Our results, which confirmed the limited dispersal capacity of P. clavata, demonstrate a significant influence of connectivity and demography on the genetic structure and diversity of this species. The relevance of our results will be discussed within the context of climate change and marine conservation. Our findings support the need to account for the ecology and dynamics of sessile organisms in the design of management and conservation measures, contrary to the predominant current trend of focusing marine conservation on the preservation of mainly fishes