Genetic and morphological differences between populations of the western minnow, Galaxias occidentalis, from two river systems in south-western Australia

Abstract

Allozyme electrophoresis was used to examine patterns of genetic differentiation in the western minnow, Galaxias occidentalis, from the North Dandalup and Canning Rivers in south-westem Australia. Two distinct genetic forms of this species were identified in these rivers and both forms occur sympatrically in samples from two sites. A significant deficit of heterozygotes and a non-random association of alleles among loci was observed in these two samples. The distribution of one of the genetic forms extended from the headwater streams in the Darling Range to the transition zone between the ranges and the Swan Coastal Plain. With the exception of one population, the distribution of the other form extended from the transition zone to the Swan Coastal Plain. The exception was a population that was caught from a site in the ranges but grouped with the populations from the coastal plain. Discriminant analyses of meristic and morphological data were undertaken to determine if morphological differences exist between the two identified genetic groups. All individuals were correctly classified by the analyses of samples from each catchment separately and of the two sympatric populations separately. However, the discriminant analysis of individuals from all sites correctly classified only 85.7% of the Darling Range genetic group and 79.4% of the Swan Coastal Plain genetic group. Further research is required to clarify the taxonomic status of these two genetic forms of G. occidentalis.

Extreme Intraspecific Mitochondrial DNA Sequence Divergence inGalaxias maculatus(Osteichthys: Galaxiidae), One of the World's Most Widespread Freshwater Fish

“…As noted by McDowall (1972), geographically and genetically isolated populations are not necessarily reproductively isolated. Taxonomic decisions are further complicated by the sympatric occurrence of distinct but closely related genetic types (e.g., Watts et al, 1995;Allibone et al, 1996). With its wide but disjunct distribution, and sympatric ''diadromous'' and ''landlocked'' types, G. maculatus typifies the problems inherent in the taxonomy of freshwater species.…”

Genetic and morphological study of the Black-stripe minnow, Galaxiella nigrostriata (Salmoniformes: Galaxiidae), including a disjunct population near Perth, Western Australia

“…For example, the Galaxias genotype has been shown capable of quite rapid evolution as a result of landlocking behind hydro-electric impoundments (Fulton 1978) and segregation in different river systems (Watts et al 1995). Indeed, small levels of environmental heterogeneity were regarded by Wallis et al, (2001) to be a sufficient reason explaining genetic divergence in populations of Galaxias vulgaris Stokell in the South Island of New Zealand.…”

“…(Nevo 1978). For example, Watts et al (1995), recorded 20% of loci polymorphic in G. occidentalis, a relatively widespread galaxiid endemic to southwestern Australia. While genetic similarity between fish from the three different locations sampled is very high and does not reflect geographic distance, the northern population, in contrast to the main population is entirely monomorphic, indicating that reproductive isolation and small population size at EPP 173 has possibly resulted in inbreeding effects.…”

Fifteen from one: a revision of the Galaxias olidus Günther, 1866 complex (Teleostei, Galaxiidae) in south-eastern Australia recognises three previously described taxa and describes 12 new species

“…149): Western Galaxias, Galaxias occidentalis Ogilby, 1899 (Watts et al 1995, Morgan et al 2010, Murphy 2010, and Dwarf Galaxias, Galaxiella pusilla (Mack, 1935) (Coleman et al 2010, Unmack et al 2012. More recently, significant levels of genetic diversity were discovered in the Mountain Galaxias, Galaxias olidus Günther, 1866 in which 15 deeply divergent, distinctive, genetically defined candidate species (sensu Vences et al 2005) were diagnosed (Raadik 2011.…”

“…The taxonomy and systematics of the Galaxiidae is undergoing revision with a number of recent and ongoing studies on Australian, New Zealand and South African species (Watts et al 1995, Waters & Cambray 1997, Waters & Wallis 2000, Coleman et al 2010. There is also continuing debate whether the Western Australian Salamanderfish, Lepidogalaxias salamandroides Mees, 1961, is distinct or part of this family , Li et al 2010, Burridge et al 2012.…”