Bioclimatic prediction of the potential distribution of Solanum elaeagnifolium in New Zealand
Species which invade New Zealand often do not arrive directly from their centre of origin, but migrate via other countries, especially United Kingdom and Australia. According to estimates, 56% of New Zealand naturalised flora had entered as contaminants of seed consignments intended for sowing. The countries from which New Zealand has received the most imports, in particular those with similar agricultural practices, have donated the greatest number of weedy species. The Australian weed flora is likely to include a significant proportion of the species which will invade New Zealand in the future, since Australia is an important source of agricultural products. While such plants may not be excluded indefinitely, it is the task of the New Zealand quarantine service to prevent invasions in the short term by ensuring that species whose entry is restricted or prohibited do not exceed specified tolerances in imports.
An analysis was undertaken to estimate the potential distribution of Solanum elaeagnifolium on the basis of climatic parameters. The Bioclimate Prediction System computer program (BIOCLIM) was used to generate a ‘climate profile’ of the species. In order to broaden the basis for climatic comparison, the computer-based system CLIMEX was employed.
The study showed that very few locations were suitable for S. elaeagnifolium in New Zealand. At most locations, the climate was too cool in summer and too wet on an annual basis. Molnar & McKenzie (1976) considered that this species is adapted to semi-arid regions with 300-600 mm annual rainfall. Except for a marginal suitability of some locations in the central Hawkes Bay Region, this species appears unlikely to be a problem in New Zealand. The plant has consequently been removed from the quarantine list. The report also gives data on temperature and rainfall tolerances for the plant.
Sources
Panetta F D, Mitchell N D (1991) Bioclimatic prediction of the potential distributions of some weed species prohibited entry to New Zealand. New Zealand Journal of Agricultural Research, 34,341-350.
Molnar V M, McKenzie D N (1976) Progress report on silver-leaf nightshade research. Vermin and Noxious Weeds Destruction Board of Victoria pamphlet no. 61. Melbourne, Department of Crown Lands and Survey.
New Zealand Plant Conservation Network
http://www.nzpcn.org.nz/exotic_plant_life_and_weeds/