Invalidity of Gasterosteus gymnurus (Cuvier, 1829) (Actinopterygii, Gasterosteidae) according to integrative taxonomy

The three-spined stickleback Gasterosteus spp. is a model organism largely used in biology. Four species have been described in Europe: G. aculeatus, G. gymnurus, G. islandicus and the extinct G. crenobion- tus. Our integrative taxonomy study, including 194 specimens, demonstrates that these taxa are distinguishable neither with the mitochondrial COI marker nor the morphological characters like lateral plates, supposed to dif- ferentiate them. Thus, we invalidate Gasterosteus gymnurus, and we consider it as junior synonym of Gasteros- teus aculeatus. The taxonomical status of Gasterosteus islandicus still needs to be clarified