Genetic structure and diversity of the endangered bath sponge Spongia lamella

15 páginas, 5 tablas, 4 figuras.

1.Natural populations of Mediterranean commercial sponges have declined substantially over recent decades. The present study explored the distribution of genetic diversity of the endangered bath sponge Spongia lamella along the western Mediterranean and the Portuguese coast. Seven microsatellite markers were used to genotype 231 individuals scattered over nine populations. Basic genetic descriptors and population genetic analyses based on FST test, analyses of the molecular variance (AMOVA), Bayesian clustering, dissimilarity analysis of principal components, and demographic analyses were performed. Genetic differentiation between populations was large and highly significant (global FST = 0.236, P < 0.001). AMOVA and Bayesian analyses showed genetic differentiation among the Atlantic, Balearic, and North Mediterranean areas (FCT = 0.129, P = 0.003). Restricted gene flow owing to short-distance larval dispersal and hydrographical barriers may be playing an important role in genetic differentiation. Recent bottlenecks were also detected for most populations of this sponge. The high levels of inbreeding, sub-structuring, and modest levels of genetic diversity that characterized populations of S. lamella (mean value of genetic diversity 0.512), may compromise its long-term survival. Only one population, from the Gibraltar Strait, presented high levels of genetic diversity (Ceuta, genetic diversity = 0.657), indicating a hotspot of genetic diversity for this species with special relevance for its conservation. Disease outbreaks and overexploitation may be the most important causes of genetic diversity impoverishment of S. lamella. Future conservation guidelines should focus on preserving genetic diversity within genetically impoverished populations by limiting exploitation, and increasing population size. Transplanting specimens from areas with high values of genetic diversity to areas with low diversity values or to areas that have recently experienced demographic declines could reverse the local and global recession of this species.

Research funded by grants from the Agence Nationale de la Recherche (ECIMAR), a ‘Beatriu de Pinós’ contract (Comissionat per a Universitats i Recerca from Departament d'Innovació, Universitats i Empresa, Generalitat de Catalunya) and a ‘Juan de la Cierva’ contract (Ministry of Science from the Spanish Government) to R. P-P. Spanish Ministry of Education and Science (projects BENTHOMICS: CTM2010-22218 and SOLID: CTM2010-17755), and the BIOCAPITAL project (MRTN-CT-2004-512301) of the European Union. This is a contribution of the Consolidated Research Group ‘Grupo de Ecología Bentónica’, SGR2009-655 of Generalitat de Catalunya.

Peer reviewed