Galaxiidae, , Frankenberg, 1969

Raadik, Tarmo A., 2014, 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, Zootaxa 3898 (1), pp. 1-198 : 158-162

The Galaxiidae (revised)

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, 2001 a, 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 ( Waters et al. 2000 a, Li et al. 2010, Burridge et al. 2012). There is also debate about higher level relationships ( Johnson & Patterson 1996, Waters et al. 2000a, Waters & McDowall 2005, Li et al. 2010). Based on morphological analyses, galaxiids have been historically placed in the order Salmoniformes (Northern Hemisphere salmons, trouts, chars, etc.), and more recently, based on molecular analyses, to the order Osmeriformes (Northern Hemisphere smelts) ( Johnson & Patterson 1996, Waters et al. 2000a, Hoese et al. 2006, Nelson 2006, Burridge et al. 2012). Higher level relationships have been further refined with more detailed and broader genetic analysis suggesting that galaxiids comprise the distinctive Order Galaxiiformes , which is basal to the Osmeriformes and Salmoniformes ( Li et al. 2010, Burridge et al. 2012).

Following the revision of Galaxias olidus s.l. (this study), the Galaxiidae , or ‘galaxiids’ (incorrectly referred to as ‘minnows’ or ‘jollytails’), remain a moderately small freshwater family of seven genera but with 64 extant species in two subfamilies ( Galaxiinae and Aplochitoninae ) ( Table 41). Eight species have so far been described from fossil remains in New Zealand, extending the known age of the family to the Miocene ( Stokell 1945, Whitley 1956a, Lee et al. 2007, Schwarzhans et al. 2012).

The subfamily Galaxiinae is the larger and now contains 61 extant species in five genera, with Galaxias the most speciose, with 46 extant species. The greatest diversity of the Galaxiinae is found in Australia and New Zealand, which have 33 and 28 endemic species each respectively, and share two ( Galaxias brevipinnis and Galaxias maculatus ) ( Table 41). Galaxias is the most geographically widespread and diverse genus, with 45 extant, valid species recognised worldwide. Australia also has a high degree of endemism within this family with 34 species not found elsewhere ( Table 42). Nineteen of these are endemic to the mainland and 11 are endemic to Tasmania, which also has the endemic genus Paragalaxias .

Salmonid impacts on the Galaxias olidus complex

The ongoing impact on the Galaxiidae by predatory, alien trout ( Salmo trutta and Oncorhynchus mykiss ) has been recognised globally ( McDowall 2006a), with many nonmigratory galaxiid species reduced in abundance and populations highly fragmented and reduced in geographical range. Prior to the current study, salmonids were conclusively known to negatively impact Galaxias fuscus ( Raadik et al. 2010) and were implicated in the general decline in range and/or fragmentation of Galaxias olidus s.l., though the degree of impact or specific process of interaction was unclear ( Tilzey1976, Cadwallader 1996, Lintermans 2000a). Consequently the impact on nonmigratory galaxiids by salmonids in Australia has been considered to be moderate at most ( Jackson et al. 2004), only seriously affecting one species ( G. fuscus ) in a very small proportion of the range of G. olidus s.l. in southeastern Australia.

This study demonstrates the degree of salmonid impact on biodiversity in Australian non-migratory galaxiids has been seriously under-estimated due to the lack of taxonomic resolution in the Galaxias olidus complex. Significantly, trout are implicated in the decline and/or fragmentation in range of 10 of the 15 species within the complex (with at least regional/localised impacts documented/predicted in the remaining five), all of which occur in habitats which are now considered to have highly modified biotas which reflect relictual distributions as a result of recent and local extirpations. Significantly this is often in otherwise pristine or little modified upland habitat. Surviving populations of many of these new species are small and found above instream barriers that have prevented the upstream colonisation of trout (e.g. Galaxias gunaikurnai sp. nov., Galaxias mcdowalli sp. nov., Galaxias mungadhan sp. nov and Galaxias tantangara sp. nov.). These are at high risk of extinction from the genetic consequences of reduced population size and stochastic events such as drought (dewatering) or floods (extensive post-fire sedimentation or facilitation of further salmonid expansion) and the general effects of catchment and climate change (increasing water temperature, altered seasonality of flows, salinity etc.). Other species occur in multiple rivers but occupy specific habitat niches in streams with predators (e.g. Galaxias arcanus sp. nov., Galaxias terenasus sp. nov.), and loss of genetic diversity within these, and more widespread species (e.g. G. olidus , Galaxias oliros sp. nov.), may be occurring through reduction or elimination of local populations by salmonids singly or in concert with other threatening processes such as flow regulation and riparian habitat loss. These new species provide additional opportunities to investigate the specifics of trout-galaxiid interactions in Australia at multiple scales across the landscape, and to refine and implement appropriate scale conservation management strategies to further protect or expand galaxiid populations and build resistance and resilience to cope with stochastic change.

Of great significance is the possibility that additional lineages, sufficiently diverged to have similarly warranted recognition as candidate species, and therefore probably representing valid species, may have already been extirpated by salmonids. For example, phenotypically different populations of Galaxias olidus s.l., previously recorded from the headwaters of the Buchan River (Snowy River system) and Pieman Creek (Mitchell River system) ( Frankenberg 1969, McDowall & Frankenberg 1981), have been replaced by salmonids in the past 30 years and are now presumed extinct (T.A. Raadik, unpublished data). Other areas which may have similarly lost valid species are the Mount Baw Baw Plateau, the upper Snowy, Thredbo and Murrumbidgee river systems, and widespread reaches in the mid to upper portions of the La Trobe, Macalister, Mitchell and Tambo river catchments.

This historically unrecorded potential loss, and the continuing threat of rapid loss, of species-level diversity in non-migratory galaxiids in south-eastern Australia will prevent true levels of global species diversity in the Galaxiidae being defined; species probably have, and will continue to be lost before they are discovered. This reduces the overall success of global freshwater fish conservation efforts as the impact of salmonid predation on non-migratory galaxiids is widespread in the Southern Hemisphere and is currently being poorly addressed ( McDowall 2006a). Locally, it also confounds our knowledge of true levels of species diversity in upland regions of Australian freshwater environments. Now that the breadth of salmonid impacts has been redefined in the galaxiids of south-eastern Australia this should drive the acceptance of salmonid predation as a credible and major risk, where urgent implementation of effective conservation management strategies is required.