Banksia Marginata Research Articles

Distinctive Arbutin-Containing Markers: Chemotaxonomic Significance and Insights into the Evolution of Proteaceae Phytochemistry.

Natural products isolation studies of eight endemic Tasmanian Proteaceae species - Agastachys odorata, Persoonia juniperina, Hakea megadenia, Hakea epiglottis, Orites diversifolius, Orites acicularis, Orites revolutus, and Telopea truncata - and three endemic Australian Proteaceae species Banksia serrata, Banksia praemorsa, and Banksia marginata were undertaken. Two previously unreported glycoside-derived natural products were identified, in addition to four other tremendously rare arbutin esters. The results of this study provide further evidence consistent with the proposal that these distinctive arbutin esters represent markers that can provide valuable insights into the chemical evolution of plant species within the family Proteaceae.

Time since fire shapes plant immaturity risk across fire severity classes

BackgroundWhen fire intervals are shorter than the time required for plants to reproduce, plant populations are threatened by “immaturity risk.” Therefore, understanding how the time between fires influences plants can inform ecosystem management. Quantifying periods of immaturity risk requires investigating the influence of fire intervals across plant life stages, but most studies are indiscriminate of maturity. As fire regimes are multidimensional, it is also important to consider other characteristics of fires such as severity. We conducted a field study in heathy woodland that investigated how fire severity and fire interval influence immaturity risk to serotinous resprouter species, by examining if fire severity interacts with the time since the fire to influence the occurrence of mature individuals and relative abundance of three species: silver banksia (Banksia marginata Cav.), prickly teatree (Leptospermum continentale Joy Thomps), and heath teatree (Leptospermum myrsinoides Schitdl).ResultsRegression modeling revealed a strong, positive influence of time since the last fire on the proportion of quadrats at a site with mature plants, for all three species. We only detected a small and uncertain influence of fire severity on the proportion of quadrats with mature heath and prickly teatree, and did not observe an effect of fire severity on the maturity of silver banksia. Interestingly, no relationships were observed between time since fire and the relative abundance of plants. That is, only when plant life stages were considered did we detect an effect of fire on plants. Populations of the three species were mostly immature in the first 7 years post-fire, suggesting if sites were uniformly burnt in this time frame, there could be increased risk of local extinctions.ConclusionsOur study highlights the importance of examining population processes, such as reproduction, in addition to plant relative abundance. Surprisingly, we did not detect strong differences in plant maturation across fire severity classes; low occurrence of mature plants in recently burnt areas indicated that immaturity risk was high, regardless of fire severity. Ecological studies that distinguish between plant life stages will help to predict the impacts of fire on populations and enhance decision-making. We recommend fire intervals of ≥ 8 years to protect serotinous resprouter plants in heathy woodland vegetation of southern Australia.

Contributions of phenotypic integration, plasticity and genetic adaptation to adaptive capacity relating to drought in Banksia marginata (Proteaceae).

The frequency and intensity of drought events are predicted to increase because of climate change, threatening biodiversity and terrestrial ecosystems in many parts of the world. Drought has already led to declines in functionally important tree species, which are documented in dieback events, shifts in species distributions, local extinctions, and compromised ecosystem function. Understanding whether tree species possess the capacity to adapt to future drought conditions is a major conservation challenge. In this study, we assess the capacity of a functionally important plant species from south-eastern Australia (Banksia marginata, Proteaceae) to adapt to water-limited environments. A water-manipulated common garden experiment was used to test for phenotypic plasticity and genetic adaptation in seedlings sourced from seven provenances of contrasting climate-origins (wet and dry). We found evidence of local adaptation relating to plant growth investment strategies with populations from drier climate-origins showing greater growth in well-watered conditions. The results also revealed that environment drives variation in physiological (stomatal conductance, predawn and midday water potential) and structural traits (wood density, leaf dry matter content). Finally, these results indicate that traits are coordinated to optimize conservation of water under water-limited conditions and that trait coordination (phenotypic integration) does not constrain phenotypic plasticity. Overall, this study provides evidence for adaptive capacity relating to drought conditions in B. marginata, and a basis for predicting the response to climate change in this functionally important plant species.

Pre-dispersal seed-predation affects fruit crop and seed fitness in a highly fragmented savanna tree

Context Silver banksia (Banksia marginata) savannas of south-eastern Australia were formerly widespread but are now largely cleared and fragmented, with small populations often showing recruitment limitation. Which may, in part, be due to seed predation by yellow-tailed black cockatoos (Zanda funerea), which have been observed foraging for seed. Aims The study aimed to investigate the impact of pre-dispersal seed predation by yellow-tailed black cockatoos on fruit crop between early development and seed release. Additionally, we wanted to assess seed fitness from partially damaged and discarded cones. Methods The study quantified silver banksia infructescence removal at four populations between early December and seed release in March. We also quantified seed mass and germinability of seeds from cones removed in December, February and March. Key results All populations experienced significant seed predation (>50%), with almost complete removal of cones from some populations. Early removal limits seed release from cones (only 18% of early removed follicles released seed). Further, early removal also significantly reduced seed mass and germination. Conclusions Pre-dispersal seed predation by cockatoos is likely to act as a strong filter for recruitment limitation in silver banksia, by negatively affecting annual seed crop size, seed fitness and germinability. Implications Our study showed the potential impact fragmentation can have on antagonistic plant–animal interactions. Small, isolated B. marginata populations are likely to continue to decline without active strategies to remedy seed predation such as large-scale restoration.

Preservation quality of plant macrofossils through a Quaternary cave sediment sequence at Naracoorte, South Australia: Implications for vegetation reconstruction

Plant macrofossils are an important source for detailed vegetation reconstructions, often at the species level, which usually cannot be achieved with other plant material such as pollen and spores. However, the preservation quality of plant macrofossils is not well understood, especially in cave settings. Here, we assess the preservation quality of Quaternary plant macrofossils of Casuarinaceae, Astroloma humifusum, Banksia marginata and Eucalyptus species for Robertson Cave, in the World Heritage listed Naracoorte Caves. We conclude that the level of preservation varies considerably among taxa and plant organs, which can influence the vegetation reconstruction. Woody endocarps and fruits preserved better as macrofossils than leaves and flowers. The age of the sediment did not always impact the preservation quality, although in some cases it led to clear deterioration. The impact of fire was evident and possibly influenced the preservation potential of some taxa. Therefore, care must be taken when reconstructing vegetation from plant macrofossils as preservational changes and floristic change are sometimes difficult to separate.

Managing Genetic Diversity and Representation in Banksia marginata (Proteaceae) Seed Production Areas Used for Conservation and Restoration

Landscape degradation is a major threat to global biodiversity that is being further exacerbated by climate change. Halting or reversing biodiversity decline using seed-based restoration requires tons of seed, most of which is sourced from wild populations. However, in regions where restoration is most urgent, wild seed sources are often fragmented, declining and producing seed with low genetic diversity. Seed production areas (SPAs) can help to reduce the burden of collecting native seed from remnant vegetation, improve genetic diversity in managed seed crops and contribute to species conservation. Banksia marginata (Proteaceae) is a key restoration species in south-eastern Australia but is highly fragmented and declining across much of its range. We evaluated genetic diversity, population genetic structure and relatedness in two B. marginata SPAs and the wild populations from which the SPA germplasm was sourced. We found high levels of relatedness within most remnants and that the population genetic structure was best described by three groups of trees. We suggest that SPAs are likely to be important to meet future native seed demand but that best practice protocols are required to assist land managers design and manage these resources including genetic analyses to guide the selection of germplasm.

How widespread are recruitment bottlenecks in fragmented populations of the savanna tree Banksia marginata (Proteaceae)?

Land clearing of habitat into smaller, isolated remnants is a major driver of plant and animal extinctions globally. In southeastern Australia, once widespread temperate savannas have been subjected to extensive land clearing since European settlement. Some small fragments have persisted, but declines in the dominant trees have been reported, with anecdotal observations of widespread recruitment bottlenecks and seed set failure. To test the hypothesis that populations of Banksia marginata are experiencing widespread recruitment bottlenecks, we examined tree size-class distribution and production of infructescences (cones) of 15 populations on the western plains of Victoria, Australia. We found no evidence of widespread recruitment bottlenecks or a failure to set seeds; most populations were recruiting, though we did find evidence of declining recruitment with population size, suggesting evidence of an Allee effect. The proportion of trees without cones varied between populations; three populations had large numbers of trees (> 40%) lacking mature fertile cones. Managers should focus on minimising threats to seedling survival and augment populations below 100 individuals to improve recruitment and maintain stand persistence in the landscape.

Genetic data and climate niche suitability models highlight the vulnerability of a functionally important plant species from south-eastern Australia.

Habitat fragmentation imperils the persistence of many functionally important species, with climate change a new threat to local persistence due to climate niche mismatching. Predicting the evolutionary trajectory of species essential to ecosystem function under future climates is challenging but necessary for prioritizing conservation investments. We use a combination of population genetics and niche suitability models to assess the trajectory of a functionally important, but highly fragmented, plant species from south‐eastern Australia (Banksia marginata, Proteaceae). We demonstrate significant genetic structuring among, and high level of relatedness within, fragmented remnant populations, highlighting imminent risks of inbreeding. Population simulations, controlling for effective population size (N e), suggest that many remnant populations will suffer rapid declines in genetic diversity due to drift in the absence of intervention. Simulations were used to demonstrate how inbreeding and drift processes might be suppressed by assisted migration and population mixing approaches that enhance the size and connectivity of remnant populations. These analyses were complemented by niche suitability models that predicted substantial reductions of suitable habitat by 2080; ~30% of the current distribution of the species climate niche overlaps with the projected distribution of the species climate niche in the geographic region by the 2080s. Our study highlights the importance of conserving remnant populations and establishing new populations in areas likely to support B. marginata in the future, and adopting seed sourcing strategies that can help populations overcome the risks of inbreeding and maladaptation. We also argue that ecological replacement of B. marginata using climatically suited plant species might be needed in the future to maintain ecosystem processes where B. marginata cannot persist. We recommend the need for progressive revegetation policies and practices to prevent further deterioration of species such as B. marginata and the ecosystems they support.

Genetic analysis of 'Banksia marginata' from Central Victoria

Genetic analysis of 'Banksia marginata' from Central Victoria

Can severe drought reverse woody plant encroachment in a temperate Australian woodland?

AbstractQuestionIncreases in the cover of woody plants have been documented in woodland, savanna and grassland ecosystems across the globe, commonly attributed to changes in land use or disturbance regimes. This is often thought to result in alternative stable states resistant to reversal. However, some multi‐decadal‐scale studies have found woody plant cover fluctuates according to variations in rainfall. After a decade‐long El Nino event, we ask: can severe drought reverse woody plant encroachment in a temperate Australian woodland?LocationTemperate coastal woodland in Victoria, SE Australia that has remained unburned for over a century.MethodsUsing data spanning 41 yr, changes in basal area and tree density were assessed for the major woody species in a eucalypt woodland. Data were used to determine whether a decade of severe drought (1997–2009) had reversed a previously identified phase of woody plant encroachment (1971–1996).ResultsAfter an increase in stand density between 1971 and 1996, attributed to an increase in the fire‐sensitive species Allocasuarina littoralis, total tree density then declined by 42% between 1996 and 2012. Changes in tree density differed across dominant woody species (A. littoralis −34%, Allocasuarina verticillata +26%, Acacia pycnantha −78%, Banksia marginata −73%, Eucalyptus spp. −97%), and seedling recruitment almost completely ceased for all species. However, the basal area of A. littoralis (having almost doubled between 1971 and 1996) had continued to increase by 75%, with increases highest in areas where initial basal area was lowest. Despite this increase, total stand basal area remained relatively stable, with an increase of 5%, because of a combined decline in basal area for all other species of 62%.ConclusionDespite the most severe drought on record, site occupancy – as measured by basal area – did not decline between 1996 and 2012. Thus, severe drought did not reverse woody plant encroachment. Rather, findings were consistent with the previous trend of increasing A. littoralis dominance at the expense of other tree species in the long‐term absence of fire.

Fungal Planet description sheets: 92-106.

Novel species of microfungi described in the present study include the following from Australia: Diaporthe ceratozamiae on Ceratozamia robusta, Seiridium banksiae on Banksia marginata, Phyllosticta hymenocallidicola on Hymenocallis littoralis, Phlogicylindrium uniforme on Eucalyptus cypellocarpa, Exosporium livistonae on Livistona benthamii and Coleophoma eucalyptorum on Eucalyptus piperita. Several species are also described from South Africa, namely: Phoma proteae, Pyrenochaeta protearum and Leptosphaeria proteicola on Protea spp., Phaeomoniella niveniae on Nivenia stokoei, Toxicocladosporium leucadendri on Leucadendron sp. and Scorias leucadendri on Leucadendron muirii. Other species include Myrmecridium phragmitis on Phragmites australis (Netherlands) and Camarographium carpini on Carpinus betulus (Russia). Furthermore, Pseudoidriella syzygii on Syzygium sp. represents a novel genus of hyphomycetes collected in Australia. Morphological and culture characteristics along with ITS DNA barcodes are provided for all taxa.

Influence of prescribed burning on fruit production in Proteaceae

Prescribed burning is applied worldwide as a forest management tool. It is broadly accepted that altered fire regimes can directly impact upon community structure and composition, but little is known about the indirect effects of altered fire regimes on the mechanisms that produce community-level changes such as changes to the reproductive output of individual plants, hence populations. We examined the reproductive output of four species of Proteaceae within a long term study site where disturbance histories for the last twenty years have been accurately recorded on 216 plots. Frequent fire was found to increase woody fruit production in Banksia marginata, but had no apparent effect on B. serrata, Hakea eriantha or H. sericea. Results of this study vary from a similar study which examined the effect of wildfires. The differences observed are likely to reflect the differing impacts of fire intensity on these species. Indirect changes in fruit production may result in changes in reproductive success of species which in turn may affect vegetation community structure and faunal habitat.

English

Banksia croajingolensis Molyneux & Forrester is described and illustrated. Its relationships with Banksia integrifolia, Banksia marginata and Banksia paludosa are discussed.

Use of growth characteristics for predicting plant age of three obligate-seeder Proteaceae species

We tested the ability to predict plant (and hence population) age for three fire-sensitive obligate-seeder Proteaceae species (Banksia ericifolia, Banksia marginata and Petrophile pulchella) in the heath and woodland vegetation of the Sydney region. To do this we sampled the number of growth whorls, as well as other growth characteristics (stem girth and height measurements, and canopy area and volume estimates), in areas of known time since last fire (TSLF). The average number of growth whorls was a very good predictor of plant age for both Banksia species (R2 = 98%, 99%), but this needed to be corrected for linear underestimation in P. pulchella (R2 = 92%). This technique could successfully be applied to these species in similar habitats across a large spatial scale, and so this information can be used to determine the age of a population in areas of unknown TSLF. A sample size of 15 plants was sufficient for accurate age estimates of all species; however, better estimates of TSLF for a particular plant community were obtained when estimates from two or more of the species were combined. We thus provide empirical evidence for the validity and accuracy of the growth-whorl technique for predicting plant age and hence TSLF. This information will assist in informing the development of appropriate management strategies for plants in relation to fire. Of the other growth characteristics studied, stem girth was the most reliable predictor; however, in general these other characteristics had wide confidence intervals on the predictions for sites greater than 10 years TSLF, owing to a non-linear relationship with age.

Effects of the fire retardant Phos-Chek on vegetation in eastern Australian heathlands

The effects of the fire retardant Phos-Chek D75R on species composition, survival and growth of eastern Australian heathland vegetation are described. Two sites in Victoria were selected, Victoria Valley in the Grampian Ranges and Marlo in East Gippsland. Both areas supported heathland vegetation that was long, unburnt and relatively undisturbed. Plots were subjected to single applications of increasing concentrations of retardant (0.5, 1.0 and 1.5 L fire retardant m−2) or no additional fire retardant (‘Control’ and ‘Water only’ treatments). A single application of Phos-Chek did not appear to significantly change species composition or projected foliage cover of the major life forms of native heathland vegetation. However, it did cause whole plant and shoot death of key species Allocasuarina paludosa, Banksia marginata, Leptospermum continentale and L. myrsinoides, and was observed to affect other species. The fertilising effect of the fire retardant generally increased shoot growth of the key species but did not significantly increase the overall height of these species. The application of fire retardant enhanced weed invasion, particularly when supplied at higher concentrations. A number of research recommendations are made from this preliminary investigation.

Characteristics and dynamics of the sand dune vegetation at North Bay, Tasmania

The vegetation of the coastal sand dunes at North Bay on the Forestier Peninsula was surveyed in 80 quadrats along seven transects. A total of six plant communities was identified; four from the back dunes and two from the fore dunes. The back dunes were dominated by Banksia marginata Cav. and the fore dunes by Spinifex sericeus R.Br. and Acacia sophorae (Labill.) R.Br. Size class analysis of age classes of the back dune vegetation indicated and eventual senescence of the dominant B. marginata and a replacement by closed canopy trees from wet euclypt forest, such as Notelaea ligustrina Vent. Two communities were found to be of high conservation significance: a S. sericeus grassland from the fore dune and a closed-forest community from the back dunes. Both communities are in a relatively undisturbed state, although the S. sericeus grassland has been invaded by exotic herbs. For these significant communities to remain intact, weeds and human activity must be controlled on the fore dunes and fire excluded from the back dunes.

Sources and consequences of seed mass variation in Banksia marginata (Proteaceae)

1 We examined the sources and consequences of seed mass variation in Banksia marginata occurring in fire‐prone heath on nutrient‐poor soils to determine factors influencing seed size and possible fitness benefits of large seeds. 2 Individual seed mass varied fivefold. Variation occurred among populations (29% of total), among years (10%) and among plants (plants, 6%; year × plants, 13%), but was most pronounced within plants (42%). Within plants, seed mass variation was greater within infructescences (35%) than among infructescences (7%). 3 Seed mass variation within infructescences was not related to whether follicles contained one or two seeds. Seed mass was also unaffected by ovule position within follicles and follicle position within infructescences. 4 Seed mass variation among infructescences and plants was related to the limited availability of nutrient resources during seed provisioning. Mean seed mass was negatively related to seed number per infructescence and per plant. When resources decreased late in the flowering season and after defoliation, seed mass declined by 7–10% and seed number by 31–45%. When resources increased after inflorescence removal, seed mass increased by 8% but seed number was unaffected. Plants thus had only a limited capacity to maintain seed mass by adjusting seed number when resources varied. 5 The N and P contents of seeds (mg seed−1) increased linearly with seed mass, indicating costs of producing larger seeds in terms of limited environmental nutrients. 6 Seedling size increased with seed mass, implying fitness benefits of larger seeds in terms of increased seedling establishment on nutrient‐poor soils. Seed mass had little or no effect on seed germination, relative growth rates and root:shoot ratios. 7 Although stabilizing selection should eliminate seed mass variation occurring within plants, such variation persists because resource constraints limit the ability of plants to control individual seed size.

Habitat Segregation by Serotinous Shrubs in Heaths: Post-fire Emergence and Seedling Survival

Seeds of two serotinous shrub species generally restricted to the drier edges, and two serotinous shrub species commonly confined to the wetter drainage channels of upland sedge–heaths were assessed for germinability and used in manipulative field experiments. In post-fire field experiments the effects of habitat and manipulated soil moisture were examined to test if the distribution of adult plants was influenced by soil moisture at seed germination. The effects of habitat on seedling survival for 11 months were also assessed. One species from the edge zone, Banksia marginata Cav., and one from the channel zone, Hakea microcarpa R.Br., had germination preferences corresponding to the distribution of adult plants. The other edge species, Hakea dactyloides (Gaertner) Cav., did not show a significant preference for either zone. The second channel species, Callistemon pityoides F.Muell., did not germinate in the field or in a laboratory germination trial. Some evidence for soil-stored dormancy related to temperature and or waterlogging was found in both Hakea species. Overall the results suggest that for two species habitat segregation occurs when seeds are incorporated into the seed-bed and germination occurs. No differential survival effects across habitats were found in the first year of growth.

An Examination of the Drought and Frost Tolerance of Banksia marginata (Proteaceae) as an Explanation of Its Current Widespread Occurrence in Tasmania

Populations of Banksia marginata Cavanilles from sea level to 1040 m above sea level near Hobart were examined for frost and drought tolerance to determine the extent of the inter-population variation and physiological plasticity of this species. This study was designed to give some insight into the reasons behind the successful occupation of a wide range of habitats by B. marginata in Tasmania today. All populations were highly frost tolerant, irrespective of season, with the peak tolerance usually occurring in summer, suggesting a link to some other physiological aspect such as drought tolerance. Water relations results were complex and highly variable among the populations. For the highest altitude population at least it is probable that cell elasticity and high apoplastic water contents, rather than osmotic adjustment, assist in frost and drought tolerance. It is likely that the physiological plasticity and apparent genetic diversity exhibited by these populations assisted the survival of B. marginata in pockets of refugia throughout Tasmania during past climatic upheavals during glacial and interglacial cycles.

Regeneration and Survival of Indigenous Dry Sclerophyll Species in the Brisbane Ranges, Victoria, After a Phytophthora cinnamomi Epidemic

Changes in the distribution of both pathogen and flora provided data on pathogen decline and on survival, colonisation and regeneration of plant species in defined plots in open dry sclerophyll forests of the Brisbane Ranges 23-30 years after invasion by Phytophthora cinnamomi. The density of the stringybark eucalypts (Eucalyptus informal subgenus Monocalyptus) which dominate the overstorey was halved on some plots. The survivors now show vigorous crown growth but few seedlings are present. Regeneration of the understorey occurred in three stages. Firstly, resistant sedges and then seedlings of resistant opportunists rapidly colonised ground left vacant by the destruction of the dominant understorey species, Xanthorrhoea australis. In the second stage, moderately susceptible species such as Banksia marginata and Grevillea steiglitziana resprouted from old stumps and prostrate legumes increased their ground cover. In the third stage some highly susceptible species, such as X. australis, Dillwynia glaberrima, Hibbertia stricta and Monotoca scoparia have regenerated from seed on sites previously badly affected by the pathogen. Some plants of these species have survived for 10 years, despite the continued presence of scattered pockets infected with of P. cinnamomi. However, Isopogon ceratophyllus, frequent in the understorey of the plot prior to disease, has not regenerated.