Gammarus orinos n. sp. from the Massif Central (France): its genetic and morphological distinction from Gammarus ibericus Margalef, 1951 (Crustacea, Amphipoda)

Until 1974 Gammarus ibericus was known only from the type-locality in Spain. In that year, Goedmakers recorded the species from many localities in the Massif Central, France. Indeed, these populations show a great morphological resemblance to the Spanish ones. These French populations were used in cross-breeding experiments with other populations from southern France, without result. Attempts to hybridize these populations with the G. ibericus from the type-locality also failed to produce any offspring. Electrophoretic studies showed that the French and Spanish populations are very different from a biochemical point of view; these differences are much greater than between any of the known freshwater species (or populations) from western Europe. It is therefore decided that the populations from the Massif Central belong to a separate species: G. orinos n. sp. Careful examination of hundreds of specimens from both Spain and France showed that minor but constant morphological differences exist between the two species.