Evidence of a latitudinal gradient in spider diversity in Australian cotton |
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Authors: | MARY E. A. WHITEHOUSE SCOTT HARDWICK BRAD C. G. SCHOLZ AMANDA J. ANNELLS ANDREW WARD PAUL R. GRUNDY STEVEN HARDEN |
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Affiliation: | 1. CSIRO Entomology, ACRI, Narrabri, (Email: Mary.Whitehouse@csiro.au),;2. CSIRO Entomology, Hillston, New South Wales,;3. Present address: Biocontrol, Biosecurity and Bioprocessing Group, Agresearch, Lincoln Research Centre, Canterbury, New Zealand.;4. DPI Queensland, Toowoomba, Queensland,;5. Present address: Department of State Development, Trade and Innovation, City East, Queensland, Australia.;6. Department of Agriculture, Kununurra, Western Australia,;7. Present address: Department of Agriculture, Carnarvon, Western Australia, Australia.;8. Katherine Research Station, Stuart Highway, Katherine, Northern Territory,;9. Present address: DPI plant science, Darling heights Queensland, Australia.;10. Department of Primary Industries and Fisheries, LMB 1, Biloela, Queensland,;11. Present address: Department of Primary Industries & Fisheries, Ayr, Queensland, Australia.;12. NSW DPI, Tamworth Centre for Crop Improvement, Calala Lane, Tamworth, New South Wales, Australia |
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Abstract: | The most common explanation for species diversity increasing towards the tropics is the corresponding increase in habitats (spatial heterogeneity). Consequently, a monoculture (like cotton in Australia) which is grown along a latitudinal gradient, should have the same degree of species diversity throughout its range. We tested to see if diversity in a dominant cotton community (spiders) changed with latitude, and if the community was structurally identical in different parts of Australia. We sampled seven sites extending over 20° of latitude. At each site we sampled 1–3 fields 3–5 times during the cotton growing season using pitfall traps and beatsheets, recording all the spiders collected to family. We found that spider communities in cotton are diverse, including a large range of foraging guilds, making them suitable for a conservation biological control programme. We also found that spider diversity increased from high to low latitudes, and the communities were different, even though the spiders were in the same monocultural habitat. Spider beatsheet communities around Australia were dominated by different families, and responded differently to seasonal changes, indicating that different pest groups would be targeted at different locations. These results show that diversity can increase from high to low latitudes, even if spatial heterogeneity is held constant, and that other factors external to the cotton crop are influencing spider species composition. Other models which may account for the latitudinal gradient, such as non‐equilibrium regional processes, are discussed. |
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Keywords: | Araneae Bt community conservation biological control habitat hetrogenity insecticide rarefaction curve |
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