The Systematics and Reproduction Of Bluetongue Lizards of the Genus Tiliqua (Squamata: Scincidae)

Abstract

This is a transcribed version of the thesis, created as part of the SETIS project. For a digitsed version of the original hard copy thesis, see version 2 at the bottom of the page (https://hdl.handle.net/2123/27611.2). Thesis abstract: The systematics of the genus Tiliqua are explored using univariate and multivariate analyses of morphological characters. Within each species and subspecies, adult size, the seasonality of reproduction, fecundity and offspring size are assessed from morphological variation in the reproductive tracts of both males and females. A suite of 19 synapomorphies, including both external and osteological characters, identifies a restricted genus Tiliqua and its sister-genus, Cyclodomorphus, together forming the Tiliqua lineage. The relationships of this lineage are probably with the genus Egernia. The genus Trachydosaurus is placed in the synonymy of Tiliqua, and the genera Hemisphaeriodon and Omolepida placed in the synonymy of Cyclodomorphus. Within the restricted genus Tiliqua, seven Recent species are identified on the basis of external characters. Each species is formally redescribed, and geographic variation in morphology is examined. Tiliqua adelaidensis is a small species, probably recently extinct, known only from a restricted area around Adelaide. Tiliqua multifasciata is a moderate-sized species largely restricted to Triodia grasslands in arid parts of northern and central Australia. It shows little geographic variation in morphology compared to other species. Tiliqua nigrolutea is a moderate to very large species restricted to cool climates in Tasmania and south-eastern Australia. Although there is much geographic variation, with both size and coloration suggesting a division into a southern lowland morph and a northern highland morph, patterns of variation in different characters are not concordant, and formal taxonomic division is not recommended. Tiliqua occipitalis is a large species inhabiting semi-arid habitats, particularly mallee habitats, in southern Australia, and showing relatively little geographic variation. Tiliqua rugosa is a highly apomorphic, moderate to large species inhabiting open semi-arid habitats. Geographic variation in morphology is extensive, and concordant patterns of variation in different characters, including scalation, adult size and coloration identify four subspecies: T. r. rugosa in south-western Australia, T. r. asper in south-eastern and eastern Australia, T. r. konowi on Rottnest I. and a newly-described race, T. r. palarra, in the Shark Bay region. Limited hybrid zones are identified between the southern mainland taxa towards the western side of the Hampton Tableland, and between the north-western and south-western subspecies in the Murchison River district. The Tiliqua with elongate temporal scales are divided into two allopatric species, T. scincoides and T. gigas, each of which is further divided into three subspecies. Within T. scincoides, the nominate race is distributed through open grassland and woodland habitats of south-eastern and eastern Australia, as far north as Cape York Peninsula. T. s. intermedia is distributed through savannah habitats of northern Australia, west of north-central Queensland. A new subspecies, T. s. chimaerea, is described to accomodate populations from the Babber and Tenimbar Islands in Indonesia that were formerly referred to T. gigas. Within T. gigas, the nominate race is restricted to the Moluccas and north coastal New Guinea east to the Huon Peninsula, and T. g. keyensis is restricted to the Kei and Aru Islands. A new subspecies, T. g. evanescens, is erected for other New Guinean populations. Zones of sympatry between Australian Tiliqua species were studied to provide evidence for species status. Hybridisation was limited, and confined to three taxa: T. nigrolutea, T. rugosa and T. scincoides. A detailed account of the osteology of T. s. scincoides and comparative data for other Tiliqua are provided. A set of apomorphic osteological and external characters was analysed cladistically, and the following scheme of intrageneric relationships hypothesised: ((gigas, scincoides) (adelaidensis ((nigrolutea, rugosa) (multifasciata, occipitalis)))). On the basis of this hypothesis, a model of speciation in Tiliqua is developed. All Tiliqua species and subspecies for which data on reproduction are available appear to be seasonal breeders, with the possible exception of T. g. gigas. Mating occurs in late spring for southern species, and earlier in northern taxa. Only T. nigrolutea appears to normally breed less frequently than annually. Litter size and offspring size are unusually variable for skinks. The hypothesis of cladistic relationships suggests that large litters have evolved twice in Tiliqua, in T. multifasciata and T. scincoides, while small litters, and correspondingly large young, have evolved once, in T. rugosa. The pattern of variation in litter size in Tiliqua does not unequivocally support either density-based or demographic-based models for the evolution of litter size. An annotated bibliography of the genera Tiliqua and Cyclodomorphus is appended.