Summary1. Revegetation can provide major environmental benefits in degraded landscapes, but there is also potential for negative impacts from genetic change in local native populations. Broad areas of revegetation may provide a large source of foreign genes in landscapes where small remnant native populations act as a sink. Genetic change from hybridisation can threaten population persistence and contribute to species extinction through genetic assimilation or demographic swamping. 2. Implementation of revegetation within a risk management framework allows identification of risk factors, analysis and evaluation of risk to inform decision-making and management to minimise and mitigate the risk. Informed analysis and evaluation of genetic risk is important in revegetation because it will be difficult to control or reverse the impacts in natural ecosystems and they are often not expressed until the second generation or later. 3. A risk assessment protocol is presented based on evaluation of factors that influence the likelihood and consequences of adverse genetic change from revegetation arising through pollen dispersal. 4. The assessment is applicable to a broad range of revegetation activities and contributes to the development of informed decision-making processes in implementation of revegetation systems and land use practices that protect and enhance biodiversity in degraded landscapes. 5. Synthesis and applications. Implementation of revegetation programmes within a risk management framework will help to ensure that significant environmental benefits are captured with minimal concomitant negative impacts on the surrounding biodiversity. A genetic risk protocol provides a tool for evaluation of potential adverse genetic impacts on native populations from revegetation and can be implemented in conjunction with weed risk assessment. Risk assessment as an integral part of evaluation of environmental impact for large-scale revegetation programmes will contribute to the development of informed decision-making processes in the implementation of revegetation systems, and ultimately, it will aid in the development of land uses that protect and enhance biodiversity in degraded landscapes.

No abstract

Many plant species with agronomic potential have been introduced for livestock forage and have subsequently become weeds of natural ecosystems, or ‘environmental weeds’. Stringent border quarantine procedures introduced by Australia in 1997 ensure few high weed risk species are now imported into the country; however, there are no protocols for assessing and managing weed risk in use on a national scale ‘post-border’ (i.e. once a plant species is in the country). Environmental weed risk management in forage improvement programs aims to minimise the risk that new species and cultivar introductions will be invasive in natural ecosystems. We describe an environmental weed risk assessment (EWRA) model specifically aimed at assessing the weed potential of exotic and native forage species. The EWRA model predicts and ranks species for weed risk by assessing invasiveness, impacts and potential distribution. Assessments are based on published evidence, experimental observations and intuitive responses from experienced pasture researchers, in collaboration with weed experts. This model specifically addresses the need for environmental weed risk management in forage improvement programs.

No abstract

It is proposed that, for Conospermum, initial pollen tube wall constituents are manufactured and stored prior to pollen germination, and that tube extension occurs as described in the literature for other species, but at an exceptionally fast rate.

Blue-flowered Conospermum species are endemic to Western Australia, and are highly sought after in the horticulture industry. Aspects of the reproductive biology of several species were investigated. The paniculate inflorescences of Conospermum eatoniae E.Pritz. contain 6-10 florets; however, the uppermost two or three florets never open and only the basal one or two florets in an inflorescence set seed. When insect pollinators are excluded, flowers do not self-pollinate and set seed. Stigma receptivity occurred for up to 6 days following triggering of the style and was variable between C. eatoniae, C. amoenum Meisn. subsp. amoenum, C. caeruleum R.Br. and C. brownii Meisn. Hand-pollination with 10 pollen genotypes and two maternal C. eatoniae parents showed that although pollen tubes were observed in the style, no seed was set. Genetic analysis of open-set seed progeny showed that C. eatoniae outcrossed infrequently when grown in clonal rows in a plantation, but outcrossing was common in wild plants. This study demonstrates that the reproductive biology of blue-flowered Conospermum is complex and requires further investigation if the species are to be widely cultivated for horticulture.

No abstract