Phylogeny and biogeography of the Niphargus transitivus group of species (Crustacea, Amphipoda)

The Niphargus transitivus group includes 12 groundwaterdwelling species. It is defined by an upright body position during locomotion, a small, stout body with short appendages, except for long coxae and dactyli, coxae V-VI equilobate or posterolobate, accessory flagellum subject to reduction, and the body endowed with adaptations for volvation ( = ability to enroll into a ball). The biogeography of this southeastern European group of species is discussed and a cladistic analysis of the group is presented. Some cases of parallel character evolution in groundwater amphipods are mentioned. The inference of biogeographic and phylogenetic information in elucidating the evolutionary history of the group is hampered by inconsistency of the data. One of the hypotheses about the evolutionary history of the group is thought to be the most parsimonious.