Liocarcinus corrugatus (Pennant, 1777) (Crustacea: Brachyura: Portunidae): a cosmopolitan brachyuran species?

The swimming crab genus Liocarcinus is restricted to European marine ecosystems, except L. corrugatus (Pennant, 1777), which also occurs in the Indo-West Pacific. To ascertain if the two populations represent a cosmopolitan species or a species complex, we used a series of morphological, morphometric and molecular phylogenetic analyses on European and Asian material of L. corrugatus. We further investigated the phylogenetic context of the genus Liocarcinus with related portunid taxa to establish its monophyly. Liocarcinus is paraphyletic with respect to Polybius henslowii. We propose that P. henslowii is a valid species, most likely the result of a very recent speciation within L. holsatus. The first gonopods of Asian and European L. corrugatus are similar in shape, but the carapaces of the Asian specimens are significantly longer. While L. corrugatus is monophyletic, the European and Asian populations separate into two distinct clades with high support. Based on the consistent morphological difference and the deep genetic differentiation (p-distance of 4.5% for COX1), the European and Asian populations of L. corrugatus should be treated as two distinct species. An old name is available and the Asian population should now be recognised as Liocarcinus strigilis Stimpson, 1858.