Cytotaxonomy of seven species of Galaxias (Pisces: Galaxiidae) in Tasmania

Karyotypes of 7 species of the genus Galaxias in Tasmania are compared and a phylogenetic interpretation of these data offered. Species fall into 3 distinct groups, viz. those with 2n=44 (G. brevipinnis, G. johnstoni and G. fontanus), those with 2n=32 (G. truttaceus, G. tanycephalus and G. auratus), and G. maculatus with 2n=22. Land-locking appears to have been a major evolutionary force. G. johnstoni and G. fontanus are most likely land-locked derivatives of the ancestral G. brevipinnis. G. tanycephalus and G. auratus are almost certainly land-locked derivatives of the ancestral G. truttaceus. G. maculatus has a specialized karyotype which may have been derived from a G. truttaceus-like complement by 5 Robertsonian centric fusions. It is postulated that the original stock ancestral to the 7 species examined was G. brevipinnis-like. Species relationships suggested from previous classical morphological investigations are supported by the present study.