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West Perth, Australia

Stingemore J.A.,University of Western Australia | Krauss S.L.,Kings Park and Botanic Garden
Restoration Ecology

Restoration of diverse native plant communities typically requires the collection of large amounts of seed. Thus, practitioners often struggle to find adequate supplies near project sites and need to know from how far they can collect without compromising restoration success-how far does local provenance extend? We addressed this issue by assessing genetic variation within, and differentiation among, 12 potential seed source populations of Persoonia longifolia, a key component of the jarrah forest of Western Australia. An analysis of molecular variance of 66 polymorphic amplified fragment length polymorphism markers partitioned 92% of the total genetic variation within populations and 8% among populations, indicating relatively weak but statistically significant population genetic differentiation. Ordination of these genetic data showed marked west/east and north/south gradients. Pairwise population genetic dissimilarity was correlated with both geographic distance and environmental distance derived from five climate variables. However, partial Mantel tests showed that the relationship between genetic and geographic distance was not independent of environmental distance, suggesting a non-neutral signature in these markers. Bayesian outlier analysis identified two markers, and spatial analysis method tests identified highly significant associations between these two markers and three environmental variables. Frequency differences at these markers across populations suggested the possibility of climatically adapted provenances. The global significance value from analyses of similarities for these two markers correlated to a general provenance distance of 47 km, in contrast to a threshold of 60 km for the complete dataset. Guidelines for seed sourcing that consider these population genetic data should lead to more effective ecological restoration with this species. © 2012 Society for Ecological Restoration International. Source

Phillips R.D.,Australian National University | Phillips R.D.,University of Western Australia | Dixon K.W.,Kings Park and Botanic Garden | Dixon K.W.,University of Western Australia | Peakall R.,Australian National University
Molecular Ecology

A leading hypothesis for the immense diversity of the Orchidaceae is that skewed mating success and small, disjunct populations lead to strong genetic drift and switches between adaptive peaks. This mechanism is only possible under conditions of low gene flow that lead to high genetic differentiation among populations. We tested whether orchids typically exhibit high levels of population genetic differentiation by conducting a meta-analysis to compare mean levels of population genetic differentiation (FST) between orchids and other diverse families and between rare and common orchids. Compared with other families, the Orchidaceae is typically characterized by relatively low genetic differentiation among populations (mean FST = 0.146) at allozyme loci. Rare terrestrial orchids showed higher population genetic differentiation than common orchids, although this value was still lower than the mean for most plant families. All lines of evidence suggest that orchids are typically characterized by low levels of population genetic differentiation, even in species with naturally disjunct populations. As such, we found no strong evidence that genetic drift in isolated populations has played a major role in the diversification of the Orchidaceae. Further research into the diversification of the family needs to unravel the relative roles of biotic and environmental selective pressures in the speciation of orchids. © 2012 Blackwell Publishing Ltd. Source

Nelson D.C.,University of Georgia | Flematti G.R.,University of Western Australia | Ghisalberti E.L.,University of Western Australia | Dixon K.W.,Kings Park and Botanic Garden | And 2 more authors.
Annual Review of Plant Biology

It is well known that burning of vegetation stimulates new plant growth and landscape regeneration. The discovery that char and smoke from such fires promote seed germination in many species indicates the presence of chemical stimulants. Nitrogen oxides stimulate seed germination, but their importance in post-fire germination has been questioned. Cyanohydrins have been recently identified in aqueous smoke solutions and shown to stimulate germination of some species through the slow release of cyanide. However, the most information is available for karrikins, a family of butenolides related to 3-methyl-2H- furolsqb2,3-crsqbpyran-2-one. Karrikins stimulate seed germination and influence seedling growth. They are active in species not normally associated with fire, and in Arabidopsis they require the F-box protein MAX2, which also controls responses to strigolactone hormones. We hypothesize that chemical similarity between karrikins and strigolactones provided the opportunity for plants to employ a common signal transduction pathway to respond to both types of compound, while tailoring specific developmental responses to these distinct environmental signals. © 2012 by Annual Reviews. All rights reserved. Source

Walck J.L.,Middle Tennessee State University | Hidayati S.N.,Middle Tennessee State University | Dixon K.W.,Kings Park and Botanic Garden | Dixon K.W.,University of Western Australia | And 2 more authors.
Global Change Biology

At the core of plant regeneration, temperature and water supply are critical drivers for seed dormancy (initiation, break) and germination. Hence, global climate change is altering these environmental cues and will preclude, delay, or enhance regeneration from seeds, as already documented in some cases. Along with compromised seedling emergence and vigour, shifts in germination phenology will influence population dynamics, and thus, species composition and diversity of communities. Altered seed maturation (including consequences for dispersal) and seed mass will have ramifications on life history traits of plants. Predicted changes in temperature and precipitation, and thus in soil moisture, will affect many components of seed persistence in soil, e.g. seed longevity, dormancy release and germination, and soil pathogen activity. More/less equitable climate will alter geographic distribution for species, but restricted migratory capacity in some will greatly limit their response. Seed traits for weedy species could evolve relatively quickly to keep pace with climate change enhancing their negative environmental and economic impact. Thus, increased research in understudied ecosystems, on key issues related to seed ecology, and on evolution of seed traits in nonweedy species is needed to more fully comprehend and plan for plant responses to global warming. © 2011 Blackwell Publishing Ltd. Source

Bunn E.,Kings Park and Botanic Garden
Acta Horticulturae

While in vitro regeneration and propagation is integral to modern plant breeding and horticultural production many problems still remain with development of efficient commercial in vitro propagation systems. For example, in vitro root induction and development remains problematic with many woody species. Recent research indicates benefits may be gained by departing from conventional (albeit convenient) agar-based in vitro systems for the rooting phase of micropropagation. This study investigates agar medium pulse auxin treatments with root development in a non-agar medium with two critically endangered and difficult to root woody species. A single auxin pulse treatment using indolebutyric acid (IBA) at 20 μM was sufficient to produce 100% rooting in G. dryandroides ssp. hirsuta with >16 roots per rooted shoot in a sand/perlite/peat root development medium (RDM). The best result with H. rutilans was >70% rooting after seven weeks with a pulse treatment of 10 μM NAA + 20 μM IBA or 30 μM NAA + 20 μM IBA in RDM. Developing and optimising alternative rooting treatments has the potential to significantly improve in vitro rooting of rare and recalcitrant plant species for conservation and horticultural development. Source

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