Essais d’hybridisation entre Gammarus aequicauda (Martynov, 1931) et Gammarus plumicornis Costa, 1853

Two morphologically and ecologically different forms within the genus Gammarus, known as G. plumicornis Costa, 1853 and G. aequicauda (Martynov, 1931), are interfertile in experiments and produce a vital F1. In nature, however, heterogeneous couples are rare, although not altogether absent. It is supposed that plumicornis and aequicauda are two former subspecies, which – owing to an overlap in their present distribution areas – have not developed sufficient isolating mechanisms to prevent hybridization.