Implications for management and conservation of the population genetic structure of the wedge clam Donax trunculus across two biogeographic boundaries

Abstract

In a resource management perspective, the understanding of the relative influence of the physical factors on species connectivity remains a major challenge and is also of great ecological and conservation biology interest. Despite the overfishing threat on the wedge clam Donax trunculus in Europe, relatively little information is known about its population genetic structure and connectivity and their consequences on conservation policies. We employed 16 microsatellite loci to characterise the genetic diversity and population structure of D. trunculus. A total of 514 samples from seven different localities along the Atlantic-Mediterranean transition, from the Atlantic (Gulf of Cádiz) to the north-western Mediterranean were genotyped. The analysis of the population genetic structure displayed a clear distinction along the Atlantic-Mediterranean transition with different clusters in the Atlantic Ocean, the Alboran Sea and the northwestern Mediterranean. Consequently, we recommend that these three areas should be considered as different management units. We showed that all populations seem to be at high long-term risk of extinction with the exception of the protected Doñana National Park population which still seems to have evolutionary potential. Therefore, our results emphasized the necessity of protection of this economic resource and the validity of molecular tools to evaluate the population dynamics.

Mitochondrial DNA analyses of Donax trunculus (Mollusca: Bivalvia) population structure in the Iberian Peninsula, a bivalve with high commercial importance

“…Globally, both markers analysed revealed high genetic diversity in D. trunculus in line with previous studies based on microsatellites (Marie et al, ; Nantón et al, ). Based on the 16S gene, the F type revealed abundant haplotype diversity (0.679) and low levels of nucleotide diversity (0.0046).…”

“…However, pairwise F ST using the M combined sequences displayed three groups: the Mediterranean group (GA, DE, MA), the Atlantic group (all localities on the coast of the Atlantic Ocean), and the Alboran group (FU). The population structure proposed in this study (three groups: Atlantic, Mediterranean, and Alboran) was observed previously using microsatellite markers (Marie et al, ; Nantón et al, ). The existence of two independently evolving mitochondrial lineages should be considered when population structure studies are carried out in species with DUI.…”

“…In fact, the level of captures has decreased within the last 16 years from ~17 t (2001) to 557.20 kg (2016) (Consellería do Mar, Xunta de Galicia, http://www.pescadegalicia.gal/estadisticas), and the exploitation of this species is now concentrated at one single locality, Vilarrube. Furthermore, in some southern areas of the Iberian Peninsula, natural beds of D. trunculus seem to be at great, long‐term risk of extinction (Marie et al, ). Since wild stocks in some areas have decreased greatly, it is necessary to use different strategies to increase the production of exhausted natural banks.…”

“…To date, population genetic analyses based on microsatellite markers have provided evidence that, in the Iberian Peninsula, D. trunculus displays a genetic differentiation along the Atlantic–Mediterranean transition with three distinct groups: the Atlantic Ocean, the Alboran Sea, and the Mediterranean Sea (Marie et al, ; Nantón et al, ; Rico et al, ). However, the use of different marker types has shown discrepancies in diversity patterns in other species (Brito, ; Ferchaud et al, ; Hoffman et al, ; Johnson, Toepfer, & Dunn, ; Martínez, Freire, Arias‐Pérez, Méndez, & Insua, ; Toews & Brelsford, ).…”

“…The objectives of the study were to characterize the genetic diversity within localities and to verify the population structure and demographic patterns previously inferred based on nuclear markers (Marie et al, ; Nantón et al, ). The results can aid in the design of fishery management and conservation strategies for D. trunculus inhabiting the Atlantic and Mediterranean coasts, and the recovery of the natural beds in the north‐western Atlantic area.…”