Conservation of spiders (Araneae) in the Western Australian rangelands, with particular reference to disturbance by fire

Peter Langlands

    Research output: ThesisDoctoral Thesis

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    Abstract

    [Truncated abstract] Fire is a common disturbance in many ecosystems and an integral part of arid Australia. However, there are many gaps in the current knowledge of how the fauna and flora of the arid zone respond to fire. This is particularly true for invertebrates, including spiders, where there are several obstacles to successful biodiversity conservation. Besides lack of knowledge of the response of spiders to fire, there is also a considerable taxonomic impediment. That is, a majority of species are described long ago or not at all. I set out to improve our knowledge for the conservation of spiders in arid Australia by removing part of this taxonomic impediment and examining the long-term response of spiders to fire. To help remove the taxonomic impediment and facilitate my investigations of the postfire response of spiders, I revise the taxonomy and systematics of a genus of wolf spiders. The Australian wolf spider genus Hoggicosa Roewer, 1960 with the type species Hoggicosa errans (Hogg, 1905), is revised to include ten species. Hoggicosa is comprised of burrowing lycosids, several constructing doors from sand or debris, and are predominantly found in semi-arid to arid regions of Australia. Of nine previously described species, three are synonymised with Hoggicosa castanea (Hogg, 1905) comb. nov., and four new species are described. A phylogenetic analysis including nine Hoggicosa species, 11 lycosine species from Australia and four from overseas, with Arctosa cinerea Fabricius, 1777 as outgroup, supported the monophyly of Hoggicosa. Proposed synapomorphies for Hoggicosa are a larger distance between the epigynum anterior pockets compared to the width of the posterior transverse part in females, and a large number of specialised setae on the tip of the cymbium in males. The analysis found that an unusual sexual dimorphism for wolf spiders (females more colourful than males), evident in four species of Hoggicosa, has evolved multiple times. To examine the post-fire changes in assemblages of spiders I established a chronosequence study in spinifex habitat of central Western Australia. Ground-active spiders were pitfall-trapped over nine months in 27 sites representing experimental fires (0 and 0.5 years) and wildfires (3, 5, 8 and 20 years post-fire). ... Changes in abundance with post-fire age were significant for three of the five emergent groups. The fourth-corner analysis yielded more detailed results, but overall the two approaches are considered complementary. These studies make a substantial contribution of new knowledge to assist with the conservation of spiders in the arid zone of Australia. I have removed the taxonomic impediment for a charismatic and common genus of wolf spiders. In addition, I have examined in detail the post-fire response of an assemblage of spiders in spinifex habitat. The high degree of determinism in this assemblage and the strong correlation between post-fire changes in the vegetation and spiders is promising for land managers. It suggests that managers can directly influence the conservation of the spider fauna by actively managing fire effects on habitat structure and floristics. The development of a traits-based approach, which may contribute to predicting post-fire responses of spiders in other habitats, was only moderately successful. However, the development of such a mechanistic approach is novel and deserves further attention.
    Original languageEnglish
    QualificationDoctor of Philosophy
    Publication statusUnpublished - 2010

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