Preliminary genetic analysis of koaro (Galaxias brevipinnis) in New Zealand lakes: Evidence for allopatric differentiation among lakes but little population subdivision within lakes

Abstract

Lake systems are often notable for the diversification of freshwater fish species. This has yet to be documented in New Zealand, although a possible case has been described in Galaxias brevipinnis from Lake Okareka, where lake‐ and stream‐resident fish show morphological and ecological differences. Samples of G. brevipinnis collected from three New Zealand lakes (Wakatipu, Wanaka, and Okareka) were examined using microsatellite DNA analysis to look for evidence of genetic structuring among samples within lakes (possibly indicative of incipient sympatric speciation or natal stream loyalty). Comparison among lakes was made to provide a context for genetic structuring within lakes. There was evidence of genetic differentiation among lake populations, reflecting original founder effect and subsequent genetic drift. However, there was little evidence of restricted gene flow among samples from different parts of lakes and their tributaries. Namely, there is no genetic evidence of incipient speciation in Lake Okareka, and little or no evidence of stream loyalty in Lake Wakatipu. However, the situation in Lake Okareka warrants further analysis using more microsatellite loci and wider sampling.