Dr Cathy G Rufaut
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Dip. Wildlife Management (Otago), MSc (Victoria), PhD (Otago) Research Fellow
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PhD title
Biodiversity in fragmented indigenous grasslands: Patterns of plant and invertebrate diversity in mid-altitude tall tussock grasslands, Eastern Otago, 2002
Supervisor
Assoc Prof Gerry Closs, Assoc Prof Kath Dickinson, Dr George Gibbs
Abstract
Habitat fragmentation causes a loss and change in condition of intact vegetation. Although habitat condition is often prime criteria for prioritising choice of reserves, it is not commonly examined in fragmentation studies. In New Zealand, a high diversity of native invertebrate species can still exist in semi-natural areas consisting of native and exotic plant mosaics. Because semi-natural areas are widespread, documenting the distribution and abundance of native invertebrates is highly important for biodiversity conservation and management, but there is little information currently available. This study documents plant-invertebrate diversity relationships in fragmented indigenous tall tussock grassland at two sites in the mid-altitude zone of the Rock and Pillar Range, eastern Central Otago, South Island. Specific emphasis was placed on examining the influence of tall tussock cover and ecological scale.
In Chapter One, vegetation data were collected in concentric circular plots around invertebrate trap sites to determine habitat patchiness at different spatial scales. High variability in plant assemblages was detected, particularly at the site-scale. Plant diversity patterns tended to be preserved among paired within-site scales. The amount of tall tussock canopy intactness related weakly overall to plant diversity patterns, except for a strong inverse increase in exotic plant cover. Inter-tussock heterogeneity was greatest at small scales where the tussock canopy was also patchy.
In Chapter Three, over 200 species of native terrestrial invertebrates were collected from a one-year period using pitfall and sticky traps. The resulting taxonomic inventory is one of very few available for grassland invertebrates. The fauna was dominated in richness and abundance by native invertebrates. Exotic species were detected at both study sites but formed a small proportion of taxon richness (< 5%). Community diversity and composition varied significantly between study sites and different seasons. High variability among local invertebrate assemblages was also detected.
In Chapter Four, the majority of invertebrate species were shown to utilise both tall tussock plants and the matrix. Invertebrate diversity at the tussock scale related weakly to amount of surrounding tussock cover along a tussock fragmentation gradient. Individual invertebrate species were both compatible and contrasting with community trends. Community diversity peaked in areas with a patchy tall tussock canopy. It is argued that small-scale loss of tall tussock cover and habitat condition did not isolate native invertebrate species, which instead used all areas of a local modified habitat. Retained native tussock plants are predicted to be important for this ubiquitous type of local invertebrate distribution.
In Chapter Five, analyses of higher taxonomic aggregations showed family level identifications to be a reliable surrogate for invertebrate species richness. This finding has some merit for asssessing habitat condition based on terrestrial invertebrate community composition. A restricted place for the higher taxon approach in community ecological studies was emphasised.
In Chapter Six, final conclusions emphasise that the distributions of native plant and invertebrate diversity were not identical along local tall tussock fragmentation gradients. The conservation and management implications of this finding are discussed.
Selected Publications
Journal
- Rufaut, C. G. & Gibbs, G. W. 2003. Response of a tree weta population (Hemideina crassidens) after eradication of the Polynesian rat from a New Zealand island. Restoration Ecology 11 (1), 13-19*.
- Barratt, B. I. P., Derraik, J. G. B., Rufaut, C. G. Goodman, A. J. & Dickinson, K. J. M. 2003. Morphospecies as a substitute for Coleoptera species identification, and the value of experience in improving accuracy. Journal of the Royal Society of New Zealand 33 (2), 583-590.
- Derraik J. G. B., Rufaut C. G., Closs G., Dickinson K. J. M (in press). Ground invertebrate fauna associated with native shrubs and exotic pasture in a modified rural landscape, Otago, New Zealand. New Zealand Journal of Ecology 29 (1).
- Schroeder, K., Rufaut, C. G., Smith, C., Mains, D. & Craw, D (in press). Rapid Plant Cover Establishment on Gold Mine Tailings in Southern New Zealand: Glasshouse Screening Trials. International Journal for Phytoremediation.
Internal Reports
- Rufaut, C. G. & Clearwater, S. G. 1998. Chetwode Islands Recovery: the response of lizards and invertebrates following eradication of kiore and weak from the Chetwode Islands. Department of Conservation Occasional Publication No. 41. 25 pp.
- Allen, R., Rufaut, C. G., Clearwater, S. G., Nunn, J. & Patrick, B. P. 2003. Ecological Assessment – Dunedin Coastal Reserves Management Plan. Wildland Consultants Ltd Contract Report for Dunedin City Council, Dunedin.
- Walker, S., Rogers, G., Lee, B., Rance, B., Ward, D., Rufaut, C., Conn, A., Simpson, N., Hall, G. & Larivière, M. C. 2004. Consequences to threatened plants and insects of fragmentation of alluvial floodplain podocarp forests. Landcare Research Contract Report: LC0304/166, Investigation No. 3482. 106 pp.
Conference Abstracts & Papers
- Rufaut, C. G., Dickinson, K. J. M., Closs, G. P. & Gibbs, G. W. 2001. Patterns in diversity: plant-invertebrates relationships in a modified tussock grassland. 5th Invertebrate Biodiversity & Conservation Conference, 1 – 4 December, Adelaide University, p 70.
- Rufaut, C. G., Hammit, S., Craw, D., Clearwater, S. G., Smith, C. 2004 What's driving natural revegetation patterns on overburden at Wangaloa coal mine? Australasian Institute of Mining and Metallurgy 29 August – 1 September, Nelson, 69 – 76.
Also See Publications