Morphometric and molecular analyses for populations of Palaemon longirostris and Palaemon garciacidi (Crustacea, Palaemonidae): Evidence for a single species

• Prawns identified either as Palaemon longirostris and Palaemon garciacidi are investigated.
• Variation in morphology and mtDNA among several populations is analysed.
• The morphometric analyses do not support their separation into distinct species.
• The molecular data corroborates the morphological analyses.
• There is no reason to recognise P. longirostris and P. garciacidi as distinct species.

Authors have disagreed on the taxonomic status of the white prawns along the coasts of the Northeast Atlantic Ocean and the Mediterranean Sea. The present study compares variation in morphology and mtDNA in populations of white prawns, identified as Palaemon longirostris and P. garciacidi, from the United Kingdom, The Netherlands, France, Spain, Portugal, Morocco and Tunisia. Differences in morphology among populations were tested using a multiple discriminant analyses (DA) on morphometric data. In order to resolve variation in mtDNA, 16S and COI mitochondrial (mt) genes were used. The morphometric analyses do not support their separation into distinct species, since individual prawns could not be assigned unequivocally to one of the various studied populations and a geographic pattern could be detected only in females. Molecular data corroborate the morphological analyses, since no geographic structure was found and the levels of sequence divergence observed among haplotypes from distinct populations (0.1–0.8%) are consistent with other 16S and COI intraspecific divergences of decapod crustaceans. Therefore, findings from this study do not support the distinction of P. longirostris and P. garciacidi as different species.