The fire ecology of spiders: investigating the effects of fire on spiders at the individual and community level.

Author: Jessica Marsh

Marsh, Jessica, 2017 The fire ecology of spiders: investigating the effects of fire on spiders at the individual and community level., Flinders University, School of Biological Sciences

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Fire is a major disturbance event that can have profound effects on ecosystems and on the biota within. The increasing use of anthropogenic fire in Australia, as a means to control fuel loads and provide asset protection, coupled with predictions for larger and more frequent wildfires has meant that the need to understand, and make predictions about how these events affect ecosystems, and the biota within them, is high. This need is especially potent where burning is being conducted in areas of high conservation status or environmental concern, such as the Eucalyptus cneorifolia vegetation communities on Kangaroo Island, which are listed as Critically Endangered under the Environment Protection and Biodiversity Conservation Act 1999. The chapters of this thesis are dedicated to increasing the understanding of how fire affects spiders, both at an individual and community level, and is focussed on spiders occupying fragmented patches of threatened E. cneorifolia vegetation communities.

The first empirical chapter of this thesis used a controlled and replicated experimental design to show how burning small fragments of native vegetation affected the composition and diversity of spider communities within. We found burn temperature, burn treatment and vegetation structure to significantly affect the composition and diversity of spider communities. The second chapter expanded on these findings by analysing a functional response of spiders to fire, utilising two novel guild systems. In support of the findings from the analysis of a taxonomic response in Chapter One, we found burning to significantly affect the diversity and composition of functional guilds.

In order to accurately record and analyse patterns of spider community change following burning it is crucial to understand the implications of the method used to categorise the data and the effect it has on patterns of community response to environmental variables. We investigated this in the third empirical chapter. In order to do so we used multivariate techniques to analyse changes in the community composition and diversity of family, morphospecies and guild assemblages in response to environmental variables associated with burning. Ordinations revealed significant differences in the response of these three assemblages to burning.

The fourth chapter used a novel approach and experimental design to investigate the responses of individual spiders to exposure to smoke. We detected significant increases in the rate of movement following exposure to a smoke stimulus. These findings are novel and suggest a potential mechanism for emigration of spiders away from fire, however they require further testing.

This thesis covers diverse elements of spider fire ecology that link together, building on the findings of previous studies and adding new and novel insights. In it we cover aspects of spider community fire ecology with recommendations for management techniques, methodological suggestions for improving the use of spider data in ecological research and experimental analyses of behavioural responses by spiders to fire related stimuli.

Keywords: Spiders, fire, ecology, remnant vegetation, traits, guilds, fourth corner

Subject: Biological Sciences thesis

Thesis type: Doctor of Philosophy
Completed: 2017
School: School of Biological Sciences
Supervisor: Assoc Prof Duncan Mackay