Using a pheromone lure survey to establish the native and potential distribution of an invasive Lepidopteran, Uraba lugens.
Abstract
When invasive species are first detected in a new environment there is often a demand for information about the potential for the organism to spread and create impacts. Uraba lugens (Lepidoptera: Nolidae) is an Australian native moth that has invaded New Zealand in what are presumed to be two separate episodes. After U. lugens was found in Auckland in 2001 a CLIMEXTM model was prepared to gauge the potential for the moth to spread and inflict damage in New Zealand. Inconsistencies in fitting model parameters to the then known native distribution, indicated that the known native distribution was probably incomplete, and that the unknown part of its range was critical for defining its likely range limits in New Zealand. A synthetic sex pheromone trapping survey was used to ascertain the altitudinal and upper rainfall range limits of U. lugens in part of its native range in Australia. The survey extended the known range of U. lugens into higher-altitude and higher-rainfall zones of Tasmania. We used the expanded distribution information to refine a CLIMEX model, and to project the climate suitability for U. lugens with particular emphasis on New Zealand. The projected climatic suitability of New Zealand indicates that the area likely to be at risk of invasion by U. lugens is considerably more extensive than was indicated from its historical distribution records in Australia. It now includes all the eucalypt forestry areas. Similarly, the global potential distribution covers the major eucalypt forestry regions of the world. The minimum heat sum necessary to complete a generation for U. lugens that was associated with its range limits was considerably lower than that predicted by average development rates gained from constant temperature and daylength studies. Possible explanations for this anomaly are discussed. Synthesis and applications. The lack of suitable data on the distribution of organisms is perhaps the single most common challenge for ecological climate modellers. Trapping along climatic gradients with a synthetic pheromone lure offers a cheap, rapid means of ascertaining the climatic distribution of suitable high profile insects.