Abstract
The rockpool shrimp Palaemon elegans is an ecologically important crustacean species within the European coastline fauna. In the present study, genetic diversity and population structure and connectivity were assessed by examining 21 polymorphic microsatellite loci at 13 sampling sites located along the natural distribution range. All localities showed similar levels of genetic variability. Significant deficits of heterozygosity were recorded, most likely due to the presence of null alleles. Genetic structure analyses revealed two clearly genetically distinct groups within P. elegans but without following any geographical or oceanographic basis. Thus, our results provided nuclear evidence for the existence of a Mediterranean cryptic species within P. elegans, highlighting the need to revise its taxonomic status. Regarding P. elegans sensu stricto, population structuring was reported across the Atlantic–Mediterranean transition area, where the Almería-Orán Front restricts the gene flow between the Atlantic and the Mediterranean population. Moreover, while population connectivity was suggested between all Mediterranean localities, some substructure was found within the Atlantic group. Canary Islands exhibited a weak but significant genetic differentiation from all Atlantic mainland localities, consistent with the isolation-by-distance pattern detected throughout the Atlantic population. Overall, all these findings provided new insights into the population biology of P. elegans complex.
Highlights
The rockpool shrimp Palaemon elegans is an ecologically important crustacean species within the European coastline fauna
Taking into account that the smaller cluster was exclusively formed by Mediterranean individuals, coupled with the findings reported by Reuschel et al.[8], we considered that this group is the putative cryptic species suggested to exist within P. elegans with mitochondrial DNA (mtDNA) markers
Microsatellite markers were used for the analysis of the genetic diversity and population structure of the shrimp P. elegans
Summary
The rockpool shrimp Palaemon elegans is an ecologically important crustacean species within the European coastline fauna. It has been proved that historical and oceanographic processes could drive genetic differentiation between marine populations, even in species with high dispersal abilities[11] This is the case of the shrimp P. elegans since Reuschel et al.[8] carried out a phylogeographic analysis using two mitochondrial DNA (mtDNA) markers, revealing the existence of three haplogroups, one of them in the Atlantic localities (type I) and two from the Mediterranean localities (types II and III). Cryptic speciation is not considered an uncommon phenomenon in the Mediterranean Sea and molecular markers have indicated the presence of cryptic species in several taxa including shrimps[16,17] Given these findings in P. elegans, the need for further genetic studies using polymorphic nuclear markers, such as microsatellites, to clarify its phylogeography was highlighted
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