PHYLOGENETIC-RELATIONSHIPS AND ECOMORPHOLOGICAL DIVERGENCE IN SYMPATRIC AND ALLOPATRIC SPECIES OF PARAGALAXIAS (TELEOSTEI, GALAXIIDAE) IN HIGH-ELEVATION TASMANIAN LAKES

Four species of Paragalaxias (Galaxiidae) inhabit lakes of submontane Tasmania. P. dissimilis and P. eleotroides are sympatric in Great Lake and Shannon Lagoon; P. mesotes occurs in Arthurs and Woods lakes; P. julianus is found in lakes of the Western Plateau. Phylogenetic analys is shows the genus to be monophyletic, and indicates that P. julianus is the sister-species of the other three species, and that P. dissimil is is the sister-species of P. mesotes and P. eleotroides. Morphologic al comparisons show that the two sympatric species have diverged from the others, with P. dissimilis becoming limnetic/pelagic (terminal mou th, eyes more lateral with convex interorbital, symmetrical paddle-sha ped pectoral fins with rays divided once, forked tail, many, long gill rakers, large swimbladder), while P. eleotroides has become benthic ( downturned mouth, eyes high on head with interorbital convex, rhomboid al pectoral fins with upper rays longest, rays divided twice, truncate d tail, few, short gill rakers, small swim bladder). This character di vergence is consistent with the tenets of character displacement excep t that it remains unproved that it has been driven by resource competi tion. The ecomorphological divergence parallels that described for spe cies pairs in northern cool temperate lakes with fish faunas of low sp ecies richness, particularly in threespine stickleback, Gasterosteus a culeatus.