ISOZYME ANALYSIS OF GALAXIAS SPECIES (TELEOSTEI, GALAXIIDAE) FROM THETAIERI RIVER, SOUTH-ISLAND, NEW-ZEALAND - A SPECIES COMPLEX REVEALED

We examined genetic differentiation among 23 samples of non-migratory river galaxias from 17 streams in the Taieri River system, South Islan d, New Zealand. Four major genetic types were found, two of which occu r in narrow sympatry in one location. These were compared with topotyp ical material representing Galaxias anomalus from the Clutha system (O tago) and G. vulgaris, is from the Waimakariri system (Canterbury) in order to establish identity. Morphological examination of these four m ajor genetic types revealed consistent concomitant differences. The re sults suggest that there are at least three species of river galaxias in the Taieri system: G. anomalus, G. vulgaris and al least one previo usly undescribed species. We propose that the genetic structuring and subsequent speciation of this group has been promoted by the absence o f the marine juvenile phase that is found in five other members of the genus native to New Zealand. This structuring may be exacerbated by p opulation fragmentation over the last century owing to the negative in fluence of introduced trout. The phylogenetic diversity within the riv er system mirrors the diverse flora and invertebrate fauna of the regi on, and has conservation implications that parallel those resulting fr om our improved knowledge of the New Zealand herpetofauna through the application of genetic analysis. (C) 1996 The Linnean Society of Londo n