Assessing the Risk Posed by Transgenic Virus-Resistant Trifolium Repens to Native Grasslands in Southeast Australia

In Australia, comprehensive environmental risk assessments must be performed on transgenic plants (GMOs) prior to their commercial release. A key element is the determination of whether the release of a particular GMO poses any weediness threat to the environment or other agricultural systems, which can occur by means of direct invasion or by introgression of transgenes into wild populations of the same or closely related species. For transgenic pasture plants this question could be of added importance because many of these species have been selected for traits encouraging long-term persistence and competitiveness in complex plant communities (Godfree et al., 2004a). In situations where native vegetation is of high conservation value, such as Australia, the potential for transgenic pasture plants to invade native plant communities must therefore be quantified and analysed within a rigorous risk assessment framework. Over the past three years we have investigated the level of risk posed by transgenic virus-resistant (VR) Trifolium repens (white clover) to native grasslands and woodlands in the subalpine and montane regions of southeastern Australia. We have focused on identifying the viruses present in white clover populations in the subalpine zone, on determining the floristic composition of the communities that are most at risk, and on quantifying the likely selective advantage of VR T. repens in these environments

Implications of the 2019–2020 megafires for the biogeography and conservation of Australian vegetation

Australia's 2019–2020 'Black Summer' bushfires burnt more than 8 million hectares of vegetation across the south-east of the continent, an event unprecedented in the last 200 years. Here we report the impacts of these fires on vascular plant species and communities. Using a map of the fires generated from remotely sensed hotspot data we show that, across 11 Australian bioregions, 17 major native vegetation groups were severely burnt, and up to 67–83% of globally significant rainforests and eucalypt forests and woodlands. Based on geocoded species occurrence data we estimate that >50% of known populations or ranges of 816 native vascular plant species were burnt during the fires, including more than 100 species with geographic ranges more than 500 km across. Habitat and fire response data show that most affected species are resilient to fire. However, the massive biogeographic, demographic and taxonomic breadth of impacts of the 2019–2020 fires may leave some ecosystems, particularly relictual Gondwanan rainforests, susceptible to regeneration failure and landscape-scale decline

The impacts of extreme climatic events on wild plant populations

Despite growing evidence that species and ecosystems are responding to broad climatic trends globally, relatively little is known about the role that extreme climatic or weather events (ECEs) play in driving population and ecosystem change. The objective of this chapter is to provide an overview of the nature of ECEs and their impacts on the demography of wild plant populations in both terrestrial and aquatic ecosystems. We do this by drawing out some of the main lessons that have been learned from the past and contemporary study of ECEs, focusing primarily on case studies involving Australian vegetation, and then use these to identify potential phytosociological and evolutionary roles of extreme events within the context of anthropogenic climate change. We then discuss the contribution that genomics can make to our understanding of the demographic and evolutionary impact of historical ECEs on plant populations, and propose four key questions that are likely to shape future research in this field.</p

Polyploidy affects the seed, dormancy and seedling characteristics of a perennial grass, conferring an advantage in stressful climates

Polyploidy (the state of having more than two genome copies) is widely distributed in flowering plants and can vary within species, with polyploid races often associated with broad ecological tolerances. Polyploidy may influence within‐species variation in seed development, germination and establishment. We hypothesized that interactions between polyploidy and the seed developmental environment would affect subsequent dormancy, germination and early growth traits, particularly in stressful environments. Using seeds developed in a common garden under ambient and warmed conditions, we conducted germination trials under drought and temperature stress, and monitored the subsequent growth of seedlings. The study species, Themeda triandra, is a widespread, keystone, Australian native grass and a known polyploid complex. Tetraploid plants produced heavier, more viable seeds than diploids. Tetraploids were significantly more dormant than diploids, regardless of seed developmental environment. Non‐dormant tetraploids were more sensitive to germination stress compared to non‐dormant diploids. Finally, tetraploid seedlings were larger and grew faster than diploids, usually when maternal plants were exposed to developmental temperatures atypical to the source environment. Seed and seedling traits suggest tetraploids are generally better adapted to stressful environments than diploids. Because tetraploid seeds of T. triandra are more dormant they are less likely to germinate under stress, and when they do germinate, seedling growth is rapid and independent of seed developmental environment. These novel results demonstrate that polyploidy, sometimes in interaction with developmental environment and possibly also asexuality, can have within‐species variation in seed and seedling traits that increase fitness in stressful environments

Appendix C. Potential plant hosts for alfalfa mosaic virus present in New South Wales, Australia.

Potential plant hosts for alfalfa mosaic virus present in New South Wales, Australia

Appendix B. Geographic location of sites with alfalfa mosaic virus, white clover mosaic virus, and clover yellow vein virus in the study region.

Geographic location of sites with alfalfa mosaic virus, white clover mosaic virus, and clover yellow vein virus in the study region

Appendix A. Key vegetation communities and habitats surveyed in the study region.

Key vegetation communities and habitats surveyed in the study region