A salt bath will keep you going? Euryhalinity tests and genetic structure of caridean shrimps from Iberian rivers.

We assessed the role of euryhalinity and life-history traits on the population genetic structure of the four main caridean shrimp species from the Iberian Peninsula (Atyaephyra desmarestii, Dugastella valentina, Palaemon varians and Palaemon zariquieyi) able to complete their life cycle in freshwater/oligohaline habitats. Seawater exposure experiments indicated that A. desmarestii, D. valentina and P. zariquieyi are more sensitive to high salinity waters than P. varians and confirm the relationship between osmolality regulation and spatial distribution of species. The limited or no survival in seawater could explain the restricted distributions observed in D. valentina and P. zariquieyi, whereas the current A. desmarestii distribution could be due to either past river dynamics and/or human-mediated water transfers. Conversely, the high tolerance of P. varians to a large salinity range (euryhalinity) could explain its capacity to colonize geographically distant estuaries. In agreement with osmoregulation results, the phylogeography patterns of the cytochrome oxidase 1 (Cox 1) gene fragment revealed significant genetic differentiation among river systems whatever the species considered. Atyidae species presented higher nucleotide diversity levels than Palaemonidae species, while isolation-by-distance patterns were only found for the latter. Our results have important implications for the management and conservation of freshwater species, since the inter-catchment connectivity may affect the speciation processes.