Systematics of the golden trapdoor spiders (Araneae: Idiopidae: Euoplini) of eastern Australia

Abstract

The spider infraorder Mygalomorphae includes the funnel-web spiders, tarantulas, trapdoor spiders and their kin. Because of their particular life history characteristics, systematic revisions of mygalomorph taxa are fundamentally informative and of broader biological interest, but also a matter of conservation priority. Mygalomorph spiders are relatively long-lived, usually with limited dispersal abilities, high habitat specificity, and a long historical presence in areas relative to landscape processes. These characteristics lead to high levels of speciation and local endemism in many mygalomorph lineages, and a build-up of genetic structure between and within species at fine spatial scales. From the perspective of a researcher, high levels of genetic structure and speciation make mygalomorph lineages ideal for investigating biogeographic history and speciation processes. From a conservation perspective, local endemism, habitat specificity and low dispersal ability mean that mygalomorph populations (and potentially species) are sensitive to habitat modification, and have little ability to disperse from, or recolonise, affected areas. In the context of a biodiversity crisis, and hindered by ‘impediments’ to systematics and taxonomy, systematists must allocate their time and efforts carefully. Given their inherent vulnerability and the value of research on mygalomorph taxa, revisions of poorly known elements of this fauna are both urgent and of evolutionary importance. Intergeneric relationships within the spiny trapdoor spiders of Australasia (Idiopidae: Arbanitinae) were recently stabilised. This provided a foundation for targeted work into genera within the subfamily, many of which had never received substantial systematic attention. Prior to my project, only seven species of golden trapdoor spider (tribe Euoplini, previously all in the genus Euoplos) had been described from eastern Australia, despite the genus spanning the length and breadth of the eastern mesic zone. The genus was seen as a conservation priority because it is highly diverse in south-eastern Queensland, Australia, a region where urban development (sub-coastal) and agricultural development (inland) threaten to encroach on the natural remnants where undescribed species occur. Furthermore, undocumented variability in morphology and burrow entrance structure in the genus presented a valuable opportunity to study morphology and behavioural evolution in mygalomorph spiders. In this thesis, I compare and integrate morphological data, behavioural data (burrow entrance type) and molecular data in order to: infer the first robust phylogeny of the genus Euoplos; investigate the phylogenetic signal of morphology and burrow entrance architecture to generate evolutionary hypotheses of broader relevance to mygalomorph systematics; and revise select lineages in the genus based on their conservation priority. In Chapter 2, I use morphological data to guide targeted sampling of Euoplos from eastern Australia, before generating the first comprehensive molecular phylogeny for the genus. Male morphology and burrow entrance architecture are then compared with the molecular phylogeny to reveal the existence of two widespread, sympatric lineages which differ in their burrow entrance structure and male morphology: the ‘wafer-door’ lineage and the ‘plug-door/palisade’ lineage. I also identify a taxonomic error in the literature, where males belonging to a wafer-door species were incorrectly linked with females belonging to a sympatric species in the plug-door/palisade lineage. In chapter 3, I present a systematic revision of a group of Euoplos which were recovered as a clade in Chapter 2, and which construct remarkable ‘palisade’ type burrow entrances. Revision of the group was seen as urgent because all species have very small natural ranges and occur in remnant rainforest habitats within heavily modified landscapes. This revision results in the description of four new species, and I was also able to identify species-specific differences in burrow entrance architecture, providing a means of non-intrusive species identification. In Chapter 4, all available data are integrated into a total-evidence phylogenetic analysis of the entire tribe Euoplini. Ancestral state reconstruction is used to demonstrate how morphological and behavioural (burrow entrance architecture) characters relate to topology. This chapter results in the reclassification of the tribe, with two new genera erected: Cryptoforis (wafer-door lineage) and Narellea (a single, divergent species). This chapter also highlights the utility of both male and female morphology for phylogenetic and taxonomic studies on mygalomorph spiders, and provides morphological characters and a phylogenetic framework for future integrative phylogenetics/taxonomy on the Idiopidae and other mygalomorph groups. Chapter 5 consists of a complete taxonomic synopsis of the newly-recognised genus Cryptoforis. Revision of this new genus was seen as a priority due to the cryptic nature of the wafer-door burrows they create, and due to the fact that they were previously undocumented from mainland Australia. Numerous species also appear to be short-range endemics, restricted to remnant or relictual habitats in eastern Australia. In total, 16 species are described in the genus. In summary, my project is a comprehensive systematic treatment of the golden trapdoor spiders (tribe Euoplini) of Australia, revealing a diverse assemblage of mygalomorph spiders in multiple evolutionary lineages. It presents new data on phylogenetic relationships, morphology, and behaviour in the tribe. Immediate practical outcomes include a new generic classification of the tribe which more accurately represents the diversity contained within it, a full revision of the new genus Cryptoforis, and a targeted revision of the short-range endemic palisade-building Euoplos from south-eastern Queensland. My thesis demonstrates the strength of a ‘holistic’ total-evidence systematic approach, whereby different data types are iteratively compared and integrated, and in particular, the utility of this approach to understanding the taxonomy and evolution of poorly known mygalomorph taxa.