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The molecular genetic techniques of allozyme electrophoresis and mitochondrial DNA sequencing were used to examine species boundaries, phylogenetic affinities, and population structure in wolf spiders associated with artesian springs of the Great Artesian Basin (GAB) in South Australia. These springs contain the only permanent water in this extremely arid region, and consequently are of great biological, economic, and sociological significance. Molecular diagnoses of species boundaries in nine lycosid species, involving 56 individuals genotyped at 37 putative allozyme loci and 21 individuals sequenced for a ~600-bp portion of nicotinamide adenine dinucleotide dehydrogenase 1 (NADH1), were largely concordant with those recently proposed on morphological criteria. They also identified a species not previously collected, and suggested that GAB and mesic forms of Venatrix arenaris (Hogg) may not be conspecific. As well as insights into the evolutionary relationships among species and genera, phylogenetic analysis demonstrated two distinct GAB lineages within Venatrix Roewer and Hogna Simon. Population structure analyses of the two most widespread species revealed contrasting patterns. For V. fontis Framenau & Vink, allozyme analyses of 300 individuals at 15 polymorphic loci plus NADH1 sequence analysis of 72 individuals revealed the presence of distinctive subpopulations at most sites, and a partial correlation with overall geographic proximity. In contrast, allozyme analysis of 191 V. arenaris specimens at 12 polymorphic loci demonstrated a comparative lack of both within-site variability and between-site differentiation in the GAB metapopulation.

Five species of the nephilid genus Nephila Leach are found in the Australasian region, which for the purposes of this study was defined as Australia and its dependencies (including Lord Howe I., Norfolk I., Christmas I., Cocos (Keeling) Is), New Guinea (including Papua New Guinea and the Indonesian province of West Papua), Solomon Is, Vanuatu, New Caledonia, Fiji, Tonga, Niue, New Zealand and other parts of the south-west Pacific region. All species are redescribed and illustrated. Nephila pilipes (Fabricius) occurs in the closed forests of eastern and northern Australia, New Guinea, Solomon Is and Vanuatu (through to South-East Asia); N. plumipes (Latreille) is found in Australia (including Lord Howe I. and Norfolk I.), New Guinea, Vanuatu, Solomon Is and New Caledonia; N. tetragnathoides (Walckenaer) inhabits Fiji, Tonga and Niue; N. antipodiana (Walckenaer) occurs in northern Australia (as well as Christmas I.), New Guinea and Solomon Is (through to South-East Asia); and N. edulis (Labillardière) is found in Australia (including Cocos (Keeling) Is), New Guinea, New Zealand and New Caledonia. Epeira (Nephila) walckenaeri Doleschall, E. (N.) hasseltii Doleschall, N. maculata var. annulipes Thorell, N. maculata jalorensis Simon, N. maculata var. novae-guineae Strand, N. pictithorax Kulczyński, N. maculata var. flavornata Merian, N. pictithorax Kulczyński, N. maculata var. flavornata Merian, N. maculata piscatorum de Vis, and N. (N.) maculata var. lauterbachi Dahl are proposed as new synonyms of N. pilipes. Nephila imperialis var. novaemecklenburgiae Strand, N. ambigua Kulczyński, N. sarasinorum Merian and N. celebesiana Strand are proposed as new synonyms of N. antipodiana. Meta aerea Hogg, N. meridionalis Hogg, N. adelaidensis Hogg and N. meridionalis hermitis Hogg are proposed as new synonyms of N. edulis. Nephila picta Rainbow is removed from the synonymy of N. plumipes and treated as a synonym of N. edulis, and N. nigritarsis insulicola Pocock is removed from the synonymy of N. plumipes and treated as a synonym of N. antipodiana. Allozyme data demonstrate that N. pilipes is distinct at the 80% FD level from N. edulis, N. plumipes and N. tetragnathoides. Nephila plumipes and N. tetragnathoides, deemed to represent sister-taxa owing to the shared presence of a triangular protrusion of the male pedipalpal conductor, were found to differ at 15% FD in the genetic study. No genetic differentiation was found between 10 populations of N. edulis sampled across mainland Australia. Species of the genus Nephila have been extensively used in ecological and behavioural studies, and the biology of Nephila species in the Australasian region is extensively reviewed and compared with studies on Nephila species from other regions of the world.

As part of an examination into the systematics of the freshwater crayfish genus Engaeus, an electrophoretic evaluation of specimens from a large number of collecting sites has been undertaken. From a total of 76 sample sets, a minimum of 30 distinct biological species have been delineated. Strong evidence from sites of both sympatry and allopatry suggests some further delineations of species but these must await additional discriminatory information. Sympatric species were detected on 11 separate occasions. In each case, fixed allelic differences were found, indicating an absence of interbreeding between each sympatric pair. Allopatric species were delineated where genetic differences between populations exceeded a threshold level determined from observed genetic differences between sympatric Engaeus species and between other (mainly decapod) species in the literature. The results of this analysis have confirmed low levels of heterozygosity in Engaeus species. Frequent isoIation of small populations of Engaeus species, and consequent loss of allelic variation, is suggested as a possible cause of these low levels. Some species have shown variation of allelic frequencies over their geographical range and, in some cases, this variation could be interpreted as showing clinal properties. Finally, the electrophoretic data have been interpreted to produce some information regarding the phylogenetic affinities of delineated species. Several groups of species were found which shared closer intra-group relationships than they did to the other species of Engaeus.

The Australian freshwater crayfish genus Gramastacus, previously consisting of two species known only from type localities, is revised utilising newly collected material ranging from The Grampians, Victoria, to the south-east, of South Australia. Morphological and biochemical studies demonstrate that Granzastacus is monotypic with G. insolitus Riek, 1972 the only species. Morphological comparisons between Granmstacus and Geocharax are also made, and although Gramastacus is similar to Geocharax, sufficient differences were found to uphold the generic status of Granlastacus. G. insolitus is a swamp-living species whose survival is threatened by further drainage of remaining known localities.