Genetic variation and diadromy in some native New Zealand galaxiids (Teleostei: Galaxiidae)

We examined genetic variation at 13 isozyme loci in three diadromous and two non-diadromous species of galaxiid fish from streams in South and Stewart Islands of New Zealand. Analysis of allele frequency data revealed higher F_s7 and Nei's D values among conspecific populations of the non-diadromous species. We propose that the genetic structurings of these species are affected by their migratory behaviours. We suggest that the derived condition of non-diadromous behaviour may increase scope for speciation, but also the probability of extinction. This is exacerbated by population fragmentation over the last century.