Southern Hemisphere Freshwater Salmoniforms: Development 



and Relationships 



R. M. McDowALL 



SEVERAL family-level groups of diadromous salmoniform 

 fishes are found in cool-temperate southern hemisphere 

 fresh waters, forming an obvious ecological counterpart to the 

 northern cool-temperate Salmonidae, Osmeridae, Plecoglossi- 

 dae, Salangidae, etc. With the exception of a single species, in 

 a high elevation lake in New Caledonia, they are all south of 

 about latitude 28°S. They occupy all of the main land masses 

 (Australia, New Zealand, South America, South Africa) and 

 some of the more distant southern islands (Lord Howe. Chat- 

 hams, Aucklands, Campbell, Falklands). Diagnostic familial and 

 generic characters are listed in Table 36. 



Familial arrangement of these fish varies from including all 

 in a single purportedly monophyletic family Galaxiidae (Nelson, 

 1972), through two families in separate sub-orders (Rosen, 1974) 

 to four families in one or two suborders. There are two obvious 

 and widely accepted familial groupings: Galaxiidae— Aplochi- 

 tonidae and Retropinnidae — Prototroctidae (McDowall, 1969). 

 The most recent view (Fink and Weitzman, 1982) suggests that 

 these four family level taxa are possibly all of osmeroid deri- 

 vation agreeing with my own evaluation (McDowall, 1 969), and 

 in contrast with Rosen (1974 — he links galaxiids and aplochi- 

 tonids with salmonoids; retropinnids and prototroctids with 

 osmeroids). The southern taxa are all clearly primitive prota- 

 canthopterygians of salmoniform type. Beyond that little can 

 be said other than that a further search of additional character 

 complexes is needed to clarify relationships. 



Within-family relationships are little studied. Three of the 

 southern families (Retropinnidae, Prototroctidae, Aplochiton- 

 idae) can be dealt with more simply than the fourth (Galaxiidae). 



Retropinnidae (Australia and New Zealand— see McDowall, 

 1979). — four species in two genera: Present state of knowledge 

 does not permit explicit recognition of affinities. Elongation of 

 the alveolar process in the premaxilla of Stokellia anisodon is 

 an advanced character which leaves three species of Retropinna 

 with the primitive condition (alveolar process short, maxilla 

 sometimes toothed). Stokellia also has unossified gill rakers (an 

 "advanced" but "loss" condition) and high scale count (100 

 compared with 70 or less in Retropinna— which is the derived 

 condition?) 



Prototroctidae (Australia and New Zealand— see McDowall. 

 1976).— Two species in one genus. Two congeneric species pose 

 no phylogenetic problems. The only significant question to ask 

 is "How do these species relate to the Retropinnidae?" Answers 

 to this question have not yet been sought. 



Aplochitonidae (Tasmania and South America— see McDowall. 

 197 la).— Three (perhaps four) species in two genera. Mono- 

 phyly of the Aplochitonidae (Aplochiton and Lovettia) should 

 not be assumed. Inclusion of Lovettia in the Gala.xias-Aplo- 

 chiton assemblage is supported by characters in Table 36 but 

 Lovettia has such reduced osteology that a search for characters 



in other structural systems is needed before its relationships can 

 be clarified. Inclusion oi Lovettia in the Aplochitonidae is based, 

 in part, on history (it has always been there!) and in part, on 

 the fact that it is a "galaxioid" with the dorsal fin over the pelvics 

 and an adipose fin present (like Aplochiton and unlike Gala.xias). 



Galaxiidae (.Australia. New Caledonia, Lord Howe. New Zea- 

 land. South America. South Africa). S'w genera with 37 species 

 distributed as follows: Gala.xias, 24— all areas but New Cale- 

 donia; Paragala.xias, 4— Tasmania; Neochanna, 3 — New Zea- 

 land; Gala.xiella, 3 — Australia; Brachygala.xias, 2 — South 

 America; NesogalcLxias. 1 —New Caledonia. This larger and more 

 complex family offers scope for phylogenetic analysis that has 

 had little attention. 



Relationships 



Previous studies of within-family relationships have been 

 based on morphological similarity (McDowall, 1 970), phenetics 

 based on muscle myogens (Mitchell and Scott, 1979), or den- 

 drograms derived from cluster analysis of morphometric or me- 

 ristic data (Campos, 1979). Johnson et al. (1981, 1983) have 

 sought to establish relationship on the basis of karyotypes and 

 multivariate analysis of morphometric and meristic characters 

 in the diverse Tasmanian fauna. 



The only attempt at a "strictly phylogenetic" interpretation 

 of within-family relationships, by Rosen (1978), was based on 

 misinterpretation of character states and a limited perception 

 of variation in the family, and achieved nothing (McDowall, 

 1980). A broad and strictly phylogenetic analysis of galaxiid 

 inter-relationships is not yet available and probably depends on 

 examination of additional character complexes. 



On the basis of out-group comparisons (all salmonoid— os- 

 meroid— galaxioid families have members that are diadromous) 

 it is my view that diadromy in the Galaxiidae is a primitive 

 character. It is represented in at least six species. 



Diadromous species tend to be large and generalised in char- 

 acter, but with specific adaptations to habitats occupied during 

 freshwater life. Vertebral numbers are high (> 60) and ray counts 

 in pelvic (7) and caudal (16) fins very stable. 



There are indications of close relationships with diadromous 

 stocks, e.g., Gala.xias maculatus seems likely to be a neotenous 

 derivative of some other diadromous galaxiid; distinctive ju- 

 venile colour patterns may relate G. argenteus to G. fasciatus 

 and perhaps G. truttaceus. 



There are numerous landlocked populations of diadromous 

 species, and present interpretations are that several species are 

 derived by isolation following landlocking, e.g., G. auratus 

 (landlocked) derived from G. truttaceus (diadromous) in Tas- 

 mania; G. gracilis from G. maculatus in New Zealand. 



Wholly freshwater species tend to be the more specialised 

 members, in which there is often dwarfing, reduced vertebral 

 counts, greater meristic instability, as well as the loss of the 

 distinctive marine juvenile stage. Some freshwater groups have 



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