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White E.,Cooperative Research Center for Australian Weed Management | Vivian-Smith G.,Cooperative Research Center for Australian Weed Management
Austral Ecology | Year: 2011

In subtropical Australia, many native and invasive plant species rely on a shared suite of frugivores, largely birds, for seed dispersal. Many native plants fruit during summer in this region, whereas most invasive plants fruit during winter, thus providing the opportunity for contagious dispersal of seeds beneath synchronously fruiting species. We sampled invasive and native seed rain beneath the canopy of a native summer-fruiting tree Guioa semiglauca and an invasive winter-fruiting tree Cinnamomum camphora, in three study sites over the course of a year. In July, during peak fruiting season for C. camphora and other invasive species, seed rain of invasive species was higher beneath C. camphora than G. semiglauca. This was partly due to the invasive tree Ligustrum lucidum, whose seed rain was three times higher beneath C. camphora than beneath the native tree. In February, seed rain of native species was more abundant beneath the canopy of G. semiglauca than beneath C. camphora, despite the fact that C. camphora was also fruiting at this time. This was probably due to the larger fruit crop produced by G. semiglauca at this time of year. Our study provides evidence that the presence of invasive bird-dispersed plants may facilitate contagious seed dispersal of other invaders, and likewise native species may facilitate seed spread of other native plants. © 2010 The Authors. Journal compilation © 2010 Ecological Society of Australia. Source


Macdonald M.J.,University of New England of Australia | Macdonald M.J.,Cooperative Research Center for Australian Weed Management | Whalley W.R.D.B.,University of New England of Australia | Julien M.H.,Cooperative Research Center for Australian Weed Management | And 4 more authors.
Rangeland Journal | Year: 2012

Phyla canescens (Kunth) Greene, lippia, (Verbenaceae) is an important invasive species in the MurrayDarling Basin, Australia. The general lack of quantitative information on aspects of the life-history of P. canescens is a substantial impediment to the sustainable management of this species and the communities it invades. Complementary laboratory and field experiments investigated P. canescens germination. A thermogradient plate was used to examine its germination response to a variety of temperature regimes. Recruitment in the field was investigated at four sites across two catchments following four season disturbances. In the laboratory trials, seeds required temperatures that alternated by at least 5C, light, and to be covered by a thin film of water. Field germination occurred only at the one site that experienced a flood, despite periods of high rainfall that stimulated germination of other species. In this site seedling density and survivorship were reduced in the presence of existing vegetation. A survey of P. canescens following flooding of a temporary billabong revealed recruitment from both seed and vegetative fragments. This recruitment was almost exclusively restricted to the area that had been flooded. The results suggest that P. canescens requires inundation for successful recruitment and that these germination requirements are typical of species from disturbance-prone environments. © Australian Rangeland Society 2012. Source


Manners A.G.,Cooperative Research Center for Australian Weed Management | Manners A.G.,University of Queensland | Palmer W.A.,Cooperative Research Center for Australian Weed Management | Palmer W.A.,Australian Department of Primary Industries and Fisheries | And 5 more authors.
Arthropod-Plant Interactions | Year: 2010

Weed biocontrol relies on host specificity testing, usually carried out under quarantine conditions to predict the future host range of candidate control agents. The predictive power of host testing can be scrutinised directly with Aconophora compressa, previously released against the weed Lantana camara L. (lantana) because its ecology in its new range (Australia) is known and includes the unanticipated use of several host species. Glasshouse based predictions of field host use from experiments designed a posteriori can therefore be compared against known field host use. Adult survival, reproductive output and egg maturation were quantified. Adult survival did not differ statistically across the four verbenaceous hosts used in Australia. Oviposition was significantly highest on fiddlewood (Citharexylum spinosum L.), followed by lantana, on which oviposition was significantly higher than on two varieties of Duranta erecta ("geisha girl" and "Sheena's gold"; all Verbenaceae). Oviposition rates across Duranta varieties were not significantly different from each other but were significantly higher than on the two non-verbenaceous hosts (Jacaranda mimosifolia D. Don: Bignoneaceae (jacaranda) and Myoporum acuminatum R. Br.: Myoporaceae (Myoporum)). Production of adult A. compressa was modelled across the hosts tested. The only major discrepancy between model output and their relative abundance across hosts in the field was that densities on lantana in the field were much lower than predicted by the model. The adults may, therefore, not locate lantana under field conditions and/or adults may find lantana but leave after laying relatively few eggs. Fiddlewood is the only primary host plant of A. compressa in Australia, whereas lantana and the others are used secondarily or incidentally. The distinction between primary, secondary and incidental hosts of a herbivore species helps to predict the intensity and regularity of host use by that herbivore. Populations of the primary host plants of a released biological control agent are most likely to be consistently impacted by the herbivore, whereas secondary and incidental host plant species are unlikely to be impacted consistently. As a consequence, potential biocontrol agents should be released only against hosts to which they have been shown to be primarily adapted. © Springer Science+Business Media B.V. 2009. Source

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