Reinforcement of a population of chalky wattle on Eyre Peninsula, South Australia

Manfred Jusaiti

Herbicidal control of bridal creeper (Asparagus asparagoides) in an ecologically sensitive environment

Asparagus asparagoides (bridal creeper) is a highly invasive noxious environmental weed in southern Australia. It poses a severe threat to biodiversity and conservation in temperate natural ecosystems. Pterostylis arenicola, a threatened terrestrial orchid endemic to South Australia, is directly imperilled by this weed in most of its remnant populations. The coincident growth phenologies of orchid and weed make for an ecologically sensitive environment when considering methods of weed control or eradication. To minimise impact on the orchid and its ecosystem, this paper examines the efficacy of herbicide application for A. asparagoides control using the weed wiping technique, comparing it to the conventional spray application method. The most prolonged control of A. asparagoides was achieved after a single wipe-application of 1.5 g a.i. (active ingredient) L−1 metsulfuron methyl, either alone or in combination with 120 g a.i. L−1 glyphosate, both treatments giving significantly better weed control five years after treatment than comparable spray applications. An investigation of the effect of glyphosate on cultures of the mycorrhizal fungus isolated from P. arenicola indicated a significant decline in mycelial growth with increasing herbicide concentration over the range 0.5–3.0 kg a.i. ha−1. These results provide further incentive for the use of ecologically sensitive herbicide application techniques, such as weed wiping, in areas of high conservation concern.Manfred Jusaiti

Haloragis eyreana (Prickly Raspwort), Haloragaceae

Extensive surveys between 1997-1999 counted approximately 16,000 individuals with an area of occupancy of 0.8 km2 and an extent of occurrence of 711 km2 (Jusaitis and Freebairn 2011). Since 1999, plant numbers at five population monitoring points have been steadily declining. The species is listed as Endangered under the Australian Commonwealth Environment Protection and Biodiversity Conservation Act 1999 (EPBC Act), and assessed as Critically Endangered under IUCN criteria. Haloragis eyreana has rather specific habitat requirements, being found in low lying, disturbed areas subject to inundation or water runoff during winter. We wanted to examine the influence of planting-site proximity to the water table on translocation success. This case study describes a translocation trial that led to the serendipitous discovery of an ideal microsite for plant establishment and ongoing recruitment of this species.Manfred Jusaiti

Habitat manipulation stimulates natural regeneration of Prickly Raspwort (Haloragis eyreana) on Eyre Peninsula (South Australia)

Project summaryManfred Jusaitis and Anthony Freebair

Population structure, flowering and seed production in the endangered Whibley Wattle, Acacia whibleyana (Leguminosae: Mimosoideae)

Acacia whibleyana (Whibley wattle) is a nationally endangered wattle, endemic to the near-coastal region around Tumby Bay on the Eyre Peninsula in South Australia. Two distinct sub-populations, referred to as the Quarry and the Salt-lake populations, each contained plants growing on roadsides and in scrub fragments. Marked differences were observed in the population size structure between the two populations. The absence of juveniles on roadsides in both populations signaled potential limitations to natural recruitment. Studies of reproductive biology of scrub plants over two years (1996-1997) indicated that between 1.1% (Salt-lake) and 6.9% (Quarry) of A. whibleyana inflorescences produced fruit. Each infructescence produced an average of 1.2–1.8 pods, although up to 10 pods per infructescence were observed at the Quarry scrub in 1996. Each pod contained 4–6 seed on average, with a viability of 85%. Plants at the Salt-lake scrub generally set less fruit, produced fewer pods per infructescence, and had lower seed numbers per pod when compared with Quarry plants, differences attributable to the superior vigor of Quarry plants. A. whibleyana seeds were dispersed by ants attracted by the lipid-rich aril. The soil seed bank had a patchy distribution across both sites possibly due to seed concentrating in the vicinity of ant nests. We concluded that the reproductive attributes studied were unlikely to constrain natural recruitment of A. whibleyana as both populations were capable of producing viable seed over the two years of this study.Manfred Jusaitis, Birgitte Sorensen and Lesley Polomk

The influence of ethanol as a solvent on the gibberellic acid-induced germination of Brachyscome and Allittia (Asteraceae) seeds

Published online 16 February 2018Gibberellic acid (GA₃) is routinely used as a germination stimulant for seeds. However, the methods used to dissolve GA₃ powder – particularly if using organic solvents – have the potential to affect germination outcomes. In this study we examined the influence of the solvent ethanol, used to dissolve GA₃, on the seed germination of 14 species of Brachyscome and two species of Allittia. These species are important Australian native composites with potential for use in habitat restoration. Seeds of 11 of these species were found to be particularly responsive to GA₃. However, the use of a low concentration of ethanol (0.5%) to dissolve GA₃ affected subsequent germination outcomes, with four species responding positively and eight negatively to this solvent. The pure effect of GA₃ was therefore masked by the presence of small concentrations of ethanol, whose effects varied between the species examined. Because of these potentially confounding effects of ethanol, we recommend the use of pure water for dissolution of GA₃ when testing seed germination responses in these genera.Rina Aleman, Manfred Jusaitis, Joan Gibbs, Phil Ainsley and Fleur Tive

Germination of Veronica parnkalliana seeds in response to seasonal and fire cues

Veronica parnkalliana (Scrophulariaceae) is an endangered herb endemic to South Australia, with only six herbarium specimens recorded since its first collection in 1909. A targeted search of a fire scar in the Flinders Ranges during the spring of 2008 found prolific regeneration of the plant after a prescribed burn during the previous autumn. This post-fire discovery prompted an investigation into the seed germination requirements for this species. In vitro laboratory studies showed that germination was stimulated by gibberellic acid (GA3), heat or smoked water. A seed burial experiment suggested that an annual cycle of dormancy was present, as germination of seeds that were exhumed after spring and summer was stimulated by a combination of heat and smoked water, but this did not occur after autumn or winter. Seeds buried at different depths before a fire were later monitored for seedling emergence in situ, and germination of exhumed seeds was also assessed. The depth of seed burial was a critical factor affecting germination. Results indicated that V. parnkalliana is a fire-ephemeral species with morphophysiological dormancy. These findings will provide valuable direction for future conservation planning for this species.Jenny Guerin, Michael Thorpe, Dan Duval, Manfred Jusaitis and Phil Ainsle

Influence of seed dimorphism and provenance on seed morphology, dispersal, germination and seedling growth of Brachyscome ciliaris (Asteraceae)

Brachyscome ciliaris is a floriferous Australian native daisy, with potential for use as a horticultural species. The species is hardy and seeds are relatively easy to germinate, but it is unique within the Brachyscome genus in that seeds are distinctly dimorphic. Within a fruiting capitulum, ray seeds are smooth and narrow with a minute pappus, whereas disc seeds have broad flat wings with curled hairs and a longer pappus than that of ray seeds. Both seed morphs, collected from five populations of the species, were tested to determine differences in their morphology, germination speed and percentage, seedling growth and wind-dispersal characteristics. Ray seeds were generally lighter and smaller than disc seeds and their length varied significantly with provenance. Dormancy levels of the two seed morphs and growth of ray- and disc-derived seedlings did not differ significantly, but differences were significant among the five populations tested. Seeds germinated readily, and germination was optimal under winter or summer conditions and lower in spring or autumn. Seed production by plants raised from ray or disc seeds was identical, but Noora-sourced plants yielded more seed than did plants sourced from the other provenances tested. Seed size, germination and plant growth of B. ciliaris varied significantly among populations. Winged disc seeds were dispersed slightly further by wind than were wingless ray seeds. We concluded that dormancy, germination and seed-yield characteristics of B. ciliaris were all influenced more by seed provenance than by seed morph (ray or disc).Rina Aleman, Manfred Jusaitis, Joan Gibbs, Phillip Ainsley, Fleur Tiver and Sophie Peti

Species distribution models with field validation, a key approach for successful selection of receptor sites in conservation translocations

Original research articleConservation translocations of threatened species are being widely used to mitigate human impacts. However, their effects are surrounded by some controversy since these actions have often failed to meet planned objectives. Despite the limited number of published studies, existing evidence indicates that a main constraint for the long-term success of translocation actions is the selection of suitable receptor sites. In this study, we present a methodological approach to identify suitable receptor sites that combines the use of species distribution models (SDMs) and in situ field validation trials. This method was successfully applied to translocate a population of Critically Endangered Narcissus cavanillesii, which was going to be destroyed by the construction of the Alqueva dam (Portugal), the largest dam in Europe. The results of the SDM developed for the target species were biologically validated through in situ germination trials in sites with contrasting species suitability values. The population translocated to the site selected with this approach has experienced a stable demographic trend for more than ten years and established new mature plants outside the translocated patches. This methodology, which has proven to be a fast and reliable approach for the selection of appropriate receptor sites for conservation translocations, could be useful in other studiesinfo:eu-repo/semantics/publishedVersio