Australian Native Shrubs Research Articles

Size class, sex ratio, and spatial distribution of four populations of Pimelea microcephala subsp. microcephala under different long-term rainfall regimes

The separation of sexes in dioecious plants enables males and females to adopt different strategies to balance reproduction and growth, but can also lead to female susceptibility due to their high reproductive burden. Understanding if a dioecious species is susceptible or adaptable in the face of worsening abiotic conditions would be useful for revegetating habitats under climate change. Our study compared four populations of the Australian native shrub, Pimelea microcephala subsp. microcephala (n = 885) across an annual rainfall gradient of ∼250–400 mm to understand the impact of decreasing rainfall on size classes, growth metrics, sex ratio, the proportion of juveniles and spatial distributions. We found that irrespective of site rainfall, male and female plants achieved similar sizes. The populations exhibited four size classes, defined by height, diameter and sex, but not site rainfall (unpaired group method with arithmetic mean cluster analysis, p < .05). Spatially, populations reflected the clumped distribution of overlying canopy cover, and did not demonstrate niche partitioning between sexes. The lack of population variation with rainfall indicates that the species may be suitable for arid zone revegetation in arid regions with declining rainfall. Conservation management of the species should include maintaining canopy tree cover to encourage seed dispersal.

Sex-linked reproductive allocation in the dioecious shrub Pimelea microcephala subsp. microcephala (Thymelaeaceae) from four populations across a rainfall gradient

ABSTRACT Dioecy, the separation of sexes into different male and female plants, can enable sexes to independently develop optimal strategies for the sex-linked allocation of reproductive resources. Understanding how dioecious species vary as conditions become more or less favourable may affect conservation and revegetation efforts in arid environments. Our study investigated sex-related resource allocation in the Australian native shrub, Pimelea microcephala subsp. microcephala (Thymelaeaceae) at four sites across an annual rainfall gradient of 250–390 mm in semi-arid South Australia. The study measured 25 male and 25 female individuals for plant height, plant diameter, the number of inflorescences per plant, number of flowers per inflorescence and the ratio of reproductive to vegetative biomass. Significant differences in the ratio of biomass allocated to reproduction between sexes (p < 0.05) were detected at three of the four sites, with sex-related differences increasing with decreased annual rainfall. Female reproductive allocation was two to five times greater, and was less variable than males at all sites except the highest rainfall site (p < 0.05), while male reproductive allocation decreased with average annual rainfall (p < 0.05). Growth outcomes of males and females were equal and female reproductive traits were mostly consistent between sites and were not associated with rainfall, therefore population structure may remain stable for P. microcephala subsp. microcephala as habitats become drier, so long as pollen limitation does not occur.

Efficacy of 5% Tea Tree Oil Hydrogel on Healing Morbus Hansen's Chronic Plantar Ulcer

Background: The damage of the peripheral nerves that occurs in Morbus Hansen (MH) patients can cause disability due to loss of sensory, motor and autonomic functions can cause wounds, infections, ulcers and disability. Ulcers are the most common cause of disability complications in MH patients and requires a certain time of healing. As many as 10-20% of MH patients experience ulcers on the soles. Tea Tree Oil (TTO) is extracted from steam distillation of the leaves and twigs of the Australian native shrub Melaleuca Alternifolia. In ulcers, TTO can work as an antimicrobial, anti-inflammatory, and antioxidant. TTO preparation in the form of hydrogel is believed to help the wound healing process. Purpose: To investigate the effect of TTO hydrogel 5% on the healing of Chronic Plantar Ulcer of Leprosy (CPUL). Methods: Tea tree oil hydrogel 5% was applied every 3 days for up to 8 weeks in 22 subjects with chronic MH plantar ulcers. Ulcer size, side effects, and possible side effects are evaluated weekly. Result: There were significant clinical and statistical differences in ulcer size (p = 0.000) and in ulcer depth (p = 0.000) after TTO hydrogel 5%. No side effects occurred in this study. The ulcer healed was 59%, the ulcer improved by 36.4%, the persistent ulcer was 4.6%, and there was no ulcer that got worse. Conclusion: TTO hydrogel 5% is effective in the healing process of chronic MH plantar pedis ulcers.

Australian native shrubs: Delivering benefits to livestock, soil, plants and people

s / Journal of Nutrition & Intermediary Metabolism 1 (2014) 1e55 6 marine products, particularlyfishmeal andfish oil, to beingmainly based on terrestrial products. One of the most important on-going strategies for feeding aquaculture is continually refining feeds to ensure they remain sustainable. This is especially the case for intensive aquaculture systems that rely on formulated manufactured aquafeeds. Ingredient screening and development underpin this and sit alongside other strategies to improve animal performance and increase how efficiently feeds are used. Aquaculture has global reach and offers aquaculture systems that are appropriate in different regions depending on environmental, cultural and socio-economic factors. For Atlantic salmon, off-shore and land-based systems are being discussed. Location-specific integrated multi-trophic aquaculture provides one direction with great promise, it also reflects the 3000 year old history of aquaculture that achieved an elegant solution through integrated polyculture. Funding source(s): N/A.

Maintenance of strong morphological differentiation despite ongoing natural hybridization between sympatric species of Lomatia (Proteaceae)

When species cohesion is maintained despite ongoing natural hybridization, many questions are raised about the evolutionary processes operating in the species complex. This study examined the extensive natural hybridization between the Australian native shrubs Lomatia myricoides and L. silaifolia (Proteaceae). These species exhibit striking differences in morphology and ecological preferences, exceeding those found in most studies of hybridization to date. Nuclear microsatellite markers (nSSRs), genotyping methods and morphometric analyses were used to uncover patterns of hybridization and the role of gene flow in morphological differentiation between sympatric species. The complexity of hybridization patterns differed markedly between sites, however, signals of introgression were present at all sites. One site provided evidence of a large hybrid swarm and the likely presence of multiple hybrid generations and backcrosses, another site a handful of early generational hybrids and a third site only traces of admixture from a past hybridization event. The presence of cryptic hybrids and a pattern of morphological bimodality amongst hybrids often disguised the extent of underlying genetic admixture. Distinct parental habitats and phenotypes are expected to form barriers that contribute to the rapid reversion of hybrid populations to their parental character state, due to limited opportunities for hybrid/intermediate advantage. Furthermore, strong genomic filters may facilitate continued gene flow between species without the danger of assimilation. Stochastic fire events facilitate temporal phenological isolation between species and may partly explain the bi-directional and site-specific patterns of hybridization observed. Furthermore, the findings suggest that F1 hybrids are rare, and backcrosses may occur rapidly following these initial hybridization events.

Temperature influences stomatal density and maximum potential water loss through stomata of Dodonaea viscosa subsp. angustissima along a latitude gradient in southern Australia

It is well known that physical leaf traits influence leaf functions, and that these traits vary across environmental gradients. Stomata can influence leaf function, with changes in density and size affecting potential water loss, CO2 uptake, and also leaf cooling. Plasticity in stomatal traits occurs in response to environmental factors; however, identifying which factors have the greatest influence is often difficult. We investigated variation in leaf size, stomatal density and size, and potential water loss from open stomata (gwmax), in the Australian native shrub Dodonaea viscosa subsp. angustissima, across a range of environmental factors including temperature, rainfall and CO2. We used herbarium specimens collected across a latitudinal gradient, and also sampled along an elevation gradient in southern Australia. There were significant relationships between mean summer maximum temperature and stomatal density, and gwmax. We found no significant relationships between rainfall or CO2 and the leaf traits we studied. Increased stomatal density at warmer locations may result in an increase in the potential for transpiration, as a means for evaporative cooling. Alternatively, it may enable increased CO2 and nutrient uptake during the short, winter-growing season.

Floral visitation in the Australian native shrub genus Acrotriche R.Br (Ericaceae): an abundance of ants (Formicidae)

AbstractThe genus Acrotriche is a group of predominantly winter flowering Australian native plants with small flowers that use a unique method of secondary pollen presentation. The mating system of one species has been determined as requiring transfer of pollen from one plant to another to enable effective pollination and floral conformity in other species suggests similar breeding systems. Previous authors have suggested non‐flying mammal pollination for members of the genus based on floral traits and reports of floral consumption; however, this hypothesis does not stand up to scrutiny. Acrotriche floral traits can also be interpreted as indicative of crawling invertebrate pollination. The identification of floral visitors and their potential for pollination has not been conducted previously for any Acrotriche species. To identify potential pollinators, the floral visitors to six different species of Acrotriche were observed throughout an entire 24 h period at a range of sites throughout South Australia. Ants were identified as the most common and abundant floral visitors for all Acrotriche species. Ant pollination is considered rare due to the negative effects that ant secretions can have on pollen viability. To determine these effects in relation to Acrotriche, pollen germination experiments were undertaken after contact with the integument of several ant species. Reductions in pollen viability varied between plants and ant species but in all experiments viable pollen remained after ant contact. These results, along with observed behaviour of ant visitors, indicate that ants may contribute to pollination in Acrotriche.

Isolation and characterization of polymorphic microsatellite DNA markers for Banksia candolleana (Proteaceae)

We developed 11 polymorphic microsatellite DNA markers for the Australian native shrub Banksia candolleana (Proteaceae). For 39 sampled individuals, the number of alleles per locus varied from four to eleven, while observed and expected heterozygosities ranged from 0.233 to 0.872, and 0.305 to 0.856, respectively. Three loci (BC-B1, BC-B2, and BC-A6) showed significant deviation from Hardy-Weinberg equilibrium (P < 0.05), and null alleles may be present at BC-B1 and BC-A6. These loci were suitably polymorphic for future studies assessing metapopulation dispersal dynamics.

Comparison of in vivo organic matter digestion of native Australian shrubs by sheep to in vitro and in sacco predictions

There is increasing interest in selection of genotypes of Australian perennial shrubs such as saltbush ( Atriplex nummularia, Atriplex amnicola and Atriplex semibaccata), orange wattle ( Acacia saligna), small-leaved bluebush ( Maireana brevifolia) and rhagodia ( Rhagodia preissii) for extensive grazing systems with sheep or cattle. A major limitation to cultivar development is that determining the in vivo organic matter digestibility of forage is expensive, time consuming and requires substantial amounts of biomass. A number of in vitro and in sacco techniques are available to predict in vivo digestibility of grasses and legumes however none of these prediction methods have been calibrated to in vivo data for Australian native shrubs. The aim of this study was to determine the in vivo digestibility of native shrub forage and compare these data to predictions using in vitro and in sacco methodologies. The hypothesis tested was that there is a linear relationship between in vivo organic matter digestibility (OMD) of Australian perennial shrub forage and a number of commonly used prediction methods. Of all the methods used, in vitro gas production from microbial fermentation showed the best relationship with in vivo OMD ( r 2 = 0.904). This method appears to be suitable for broad screening and ranking of genotypes. The in vitro pepsin-cellulase technique did not provide a good first estimate of in vivo OMD across all plant species but may be suitable to rank genotypes if data are calibrated with internal standards to manage intrinsic assay variation (step 1) followed by a correction to account for the high salt content of some plants (step 2) and a final linear correction to account for systematic overestimation of OMD of native shrubs (step 3). Further testing and refining of this third calibration step is required. The prediction of in vivo OMD using a 72 h in sacco digestion was adequate for the saltbush species but not for the orange wattle and small-leaved bluebush accessions. Prediction of in vivo OMD using the Daisy II rumen fluid digestion system was not satisfactory and there was not a statistically significant relationship between the acid detergent fibre, neutral detergent fibre or the acid detergent lignin content of the shrubs and in vivo OMD. The differences between the various laboratory-based methods to predict in vivo OMD are discussed and we hypothesise that the presence of plant secondary compounds may interfere with rumen microbial fermentation.

Exploring the anthelmintic properties of Australian native shrubs with respect to their potential role in livestock grazing systems

We measured in vitro anthelmintic activity in extracts from 85 species of Australian native shrub, with a view to identifying species able to provide a degree of worm control in grazing systems. Approximately 40% of the species showed significant activity in inhibiting development of Haemonchus contortus larvae. The most active extracts showed IC50 values of 60-300 microg/ml. Pre-incubation with polyvinylpolypyrrolidine removed the activity from some extracts, implicating tannins as the bioactive agent, while in other cases the pre-incubation had no effect, indicating the presence of other anthelmintic compounds. Plant reproductive maturity (onset of flowering or fruiting) was associated with increasing anthelmintic activity in some species. Variability was observed between plants of the same species growing in different environments, while variation between individual plants of the same species within a single field suggests the existence of distinct chemotypes. Significant activity against adult H. contortus worms in vitro was also demonstrated in a limited number of extracts tested against this life stage. Our study indicates that there is potential for Australian native shrubs to play an anthelmintic role in grazing systems, and highlights some plant biology factors which will need to be considered in order to maximize any anthelmintic effects.

Polymorphic microsatellite DNA markers for Banksia hookeriana (Proteaceae)

We developed 11 polymorphic microsatellite DNA markers for an Australian native shrub Banksia hookeriana (Proteaceae). The number of alleles per locus in 37 individuals varied from three to 17, observed and expected heterozygosities ranged from 0.297 to 0.838 and from 0.279 to 0.900, respectively. Two loci (BH-B5 and BH-B107) showed significant deviation from Hardy-Weinberg equilibrium (P<0.05), and null alleles may be present at these two loci. All loci showed independent inheritance.

Polymorphic microsatellite DNA markers for Banksia attenuata (Proteaceae)

AbstractWe developed 11 polymorphic microsatellite DNA markers for an Australian native shrub Banksia attenuata. The number of alleles per locus in 50 individuals varied from five to 18, observed and expected heterozygosities ranged from 0.300 to 0.740 and from 0.537 to 0.918, respectively. Six loci showed no significant deviation from Hardy–Weinberg equilibrium (P &gt; 0.05), and null alleles appear to exist at locus BA‐B1. All loci showed independent inheritance.

Growth and competition of Cytisus scoparius, an invasive shrub, and Australian native shrubs

English broom (Cytisus scoparius) is an aggressive invasive shrub in native sclerophyll forests of South Australia. We studied its relative growth rate (RGR) and competitive ability in soils from invaded and uninvaded woodlands, in comparison to three native species it commonly displaces:Hakea rostrata, Acacia verniciflua, and A. myrtifolia. Hakea was the slowest growing species throughout the year. Both native species had their highest RGR during spring. The RGR of broom was higher than that of both hakea and acacia in the winter and spring. Despite losing its leaves in the summer, the RGR of broom through the year was higher than that of either of the native species. Soil from the invaded stands had higher organic C, N and soluble P than that from uninvaded sites. Broom and acacia grew better in the higher nutrient soil than in the lower nutrient soil. Competition did not decrease the final biomass of any of the species in low nutrient soil. In the higher nutrient soil the biomass of broom was reduced by competition with acacia, but not by competition with hakea. Competition by broom reduced the biomass of hakea but not that of acacia. Broom's earlier and higher RGR, high competitiveness in nutrient rich soils, and probably its ability to change nutrient availability could be important contributors to the mechanisms by which it invades native woodlands.