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3 páginas, 1 tabla. ; The recovery potential of decimated populations of sponges will largely hinge on their populations' size retrieval and their connectivity with conspecifics in unaffected locations. Here, we report on the development of microsatellite markers for estimation of the population connectivity and bottleneck and inbreeding signals in a Mediterranean sponge suffering from disease outbreaks, Ircinia fasciculata. From the 220,876 sequences obtained by genomic pyrosequencing, we isolated 14 polymorphic microsatellite loci and assessed the allelic variation of loci in 24 individuals from 2 populations in the Northwestern Mediterranean. The allele number per locus ranged from 3 to 11, observed heterozygosity from 0.68 to 0.73, and expected heterozygosity from 0.667 to 0.68. No significant linkage disequilibrium between pairs of loci was detected. The 14 markers developed here will be valuable tools for conservation strategies across the distributional range of this species allowing the detection of populations with large genetic diversity loss and high levels of inbreeding. ; This study was funded by the Spanish Government project SOLID CTM2010-17755, and the Catalan Government Grant 2009SGR-484 for Consolidated Research Groups and Juan de la Cierva contracts to AR and RPP. ; Peer reviewed

Este artículo contiene 13 páginas, 6 figuras, 4 tablas. ; Recent episodes of mass mortalities in the Mediterranean Sea have been reported for the closely related marine sponges Ircinia fasciculata and Ircinia variabilis that live in sympatry. In this context, the assessment of the genetic diversity, bottlenecks and connectivity of these sponges has become urgent in order to evaluate the potential effects of mass mortalities on their latitudinal range. Our study aims to establish (1) the genetic structure, connectivity and signs of bottlenecks across the populations of I. fasciculata and (2) the hybridization levels between I. fasciculata and I. variabilis. To accomplish the first objective, 194 individuals of I. fasciculata from 12 locations across the Mediterranean were genotyped at 14 microsatellite loci. For the second objective, mitochondrial cytochrome c oxidase subunit I sequences of 16 individuals from both species were analyzed along with genotypes at 12 microsatellite loci of 40 individuals coexisting in 3 Mediterranean populations. We detected strong genetic structure along the Mediterranean for I. fasciculata, with high levels of inbreeding in all locations and bottleneck signs in most locations. Oceanographic barriers like the Almeria-Oran front, North-Balearic front and the Ligurian-Thyrrenian barrier seem to be impeding gene flow for I. fasciculata, adding population divergence to the pattern of isolation by distance derived from the low dispersal abilities of sponge larvae. Hybridization between both species occurred in some populations that might be increasing genetic diversity and somewhat palliating the genetic loss caused by population decimation in I. fasciculata. ; This research was funded by the Spanish Government project MARSYMBIOMICS CTM2013-43287-P and the Catalan Government Grant 2014SGR-336 for Consolidated Research Groups. ; Peer reviewed

ABSTRACT Background: Knowledge about the distribution of the genetic variation of marine species is fundamental to address species conservation and management strategies, especially in scenarios with mass mortalities. In the Mediterranean Sea, Petrosia ficiformis is one of the species most affected by temperature-related diseases. Our study aimed to assess its genetic structure, connectivity, and bottleneck signatures to understand its evolutionary history and to provide information to help design conservation strategies of sessile marine invertebrates. Results: We genotyped 280 individuals from 19 locations across the entire distribution range of P. ficiformis in the Atlanto-Mediterranean region at 10 microsatellite loci. High levels of inbreeding were detected in most locations (especially in the Macaronesia and the Western Mediterranean) and bottleneck signatures were only detected in Mediterranean populations, although not coinciding entirely with those with reported die-offs. We detected strong significant population differentiation, with the Atlantic populations being the most genetically isolated, and show that six clusters explained the genetic structure along the distribution range of this sponge. Although we detected a pattern of isolation by distance in P. ficiformis when all locations were analyzed together, stratified Mantel tests revealed that other factors could be playing a more prominent role than isolation by distance. Indeed, we detected a strong effect of oceanographic barriers impeding the gene flow among certain areas, the strongest one being the Almeria-Oran front, hampering gene flow between the Atlantic Ocean and the Mediterranean Sea. Finally, migration and genetic diversity distribution analyses suggest a Mediterranean origin for the species. Conclusions: In our study Petrosia ficiformis showed extreme levels of inbreeding and population differentiation, which could all be linked to the poor swimming abilities of the larva. However, the observed moderate migration patterns are highly ...