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Introduction: Seagrass roots harbour diverse assemblages of microorganisms that likely benefit the growth and survival of meadows. Yet, restoration efforts rarely consider their effect on developing seagrass seedlings. Sediment origin should determine the types of rhizosphere and root-colonising (rhizoplane) microorganisms and thus the performance of seedlings during restoration, particularly for slow growing climax species like Posidonia. Recent Posidonia restoration attempts in South Australia used commercially sourced 'play pit sand' for seedling propagation and planting, but have been impacted by high mortality. More natural substrates like seagrass meadow sediment have not been previously investigated for suitability over conventional substrates with regard to seedling growth and survival. Methods: To assess the relevance of seagrass associated microorganisms in the growth of Posidonia angustifolia seedlings, we investigated the bacterial communities from tank-raised seedlings propagated in autoclave treated and untreated 'play pit sand' and meadow mix (comprising a 1:3 ratio of natural meadow sediment and beach sand) over a 12-week period. Autoclave treatment was adopted in order to diminish the bacterial load prior to planting and thus inform their contribution (if any) on early seedling growth. Samples for bacterial community analysis and seedling growth measurements (numbers and total length of roots/leaves, root diameter, seedling weight, starch reserves) were taken at 4 and 12 weeks. Bacterial assemblages were surveyed from DNA extracts from bulk and rhizosphere sediments and root tissues, as well as from swabs of P. angustifolia fruit, established meadow sediment and water samples prior to seedling propagation, by constructing Illumina 16S rRNA gene libraries. Results: While most growth measurements did not vary significantly between sediment type or treatment, proportional growth of roots versus leaves (as expressed as a pseudo root:shoot ratio) was significantly related to treatment, sediment type and seed length. Seedlings from meadow mix invested more in leaves, regardless of treatment, when compared to play sand. Autoclave treatment increased investment in roots for play sand but increased the investment in leaves for meadow mix. Bacterial communities differed significantly between sediments and between sample types (bulk, rhizosphere and roots), with the roots from meadow mix seedlings containing an increased abundance of various potentially beneficial bacterial taxa. Discussion: While such changes appear to affect the early development of seedlings, bacterial community dynamics are also likely coupled to changes in nutrient availability. Further research is thus required to disentangle host seedling growth-nutrient-bacterial community dynamics with the view to identifying microbes that may support the growth and vigour of seedlings under different nutrient conditions as part of future restoration efforts. [ABSTRACT FROM AUTHOR]

A disjunct population of red stringybark (Eucalyptus macrorhyncha) trees in South Australia is experiencing increasing amounts of dieback. Because the population is considered vulnerable to extinction, we investigated spatiotemporal vegetation changes, quantified the extent of dieback, and determined how topography influences dieback using aerial and satellite imagery. Classification of vegetation health status using hyperspectral aerial imagery indicated that 37% (accuracy = 0.87 Kappa) of the population was unhealthy and potentially experiencing dieback. When correlating this classification with a digital terrain model (DTM), the aspect and amount of solar radiation had the strongest relationship with the presence of unhealthy vegetation. PlanetScope satellite-derived, and spectral index-based analysis indicated that 7% of the red stringybark population experienced negative vegetation health changes during a five-year period (2017–2022), with positive vegetation health changes (9.5%) noted on pole-facing slopes. Therefore, our integrated remote sensing approach documented the extent and spatiotemporal dynamics of dieback, suggesting it could be applied in other studies. Topographical aspects exposed to high-solar radiation were particularly vulnerable to dieback, and pole-facing aspects demonstrated some recovery between droughts. The influence of topography and maps of vegetation health can be used to guide future management and restoration of the population. [ABSTRACT FROM AUTHOR]

Litoria cyclorhyncha (Hylidae) is native to southern Western Australia, but a naturalised population has established on the Eyre Peninsula, South Australia. We investigated the diet of this exotic population to assess potential impacts on biodiversity and ecosystems. Seventy-six frogs were collected from three different habitats and their diet items assigned to parataxonomic units (PU) within orders. Stomach contents were diverse, containing 467 prey items from 19 orders and 135 PU, with extrapolation suggesting a diet of ~200 PU. Shannon diversity estimates of prey items consumed produced different rankings for the three habitats at the PU and order level. Therefore, estimates at the order level may not be representative of the actual diversity of prey items. L. cyclorhyncha consumed mainly arthropods and low numbers of conspecific young frogs, geckos and a juvenile house mouse. This generalist, indiscriminate predatory diet is similar to that of other hylids and implies that the species poses a risk to native biodiversity and ecosystem processes by predation and competition. Therefore, further spread of this species needs to be prevented. Our findings can inform effective policies and management actions to mitigate future impacts of L. cyclorhyncha. The spotted-thighed frog (Litoria cyclorhyncha) is native to southern Western Australia, but has established an introduced population in South Australia. To determine the potential effects of the frog on other species and ecosystems, we analysed stomach contents of frogs in the introduced population and found it to be feeding indiscriminately on diverse fauna, potentially impacting on other species by predation and competition. Therefore, the spotted-thighed frog constitutes a potential threat to the native biodiversity of south-eastern Australia. Photo by C. M. Taylor. [ABSTRACT FROM AUTHOR]

Refugia can facilitate the persistence of species under long-term environmental change, but it is not clear if Pleistocene refugia will remain functional as anthropogenic climate change progresses. Dieback in populations restricted to refugia therefore raises concerns about their long-term persistence. Using repeat field surveys, we investigate dieback in an isolated population of Eucalyptus macrorhyncha during two droughts and discuss prospects for its continued persistence in a Pleistocene refugium. We first confirm that the Clare Valley in South Australia has constituted a long-term refugium for the species, with the population being genetically highly distinct from other conspecific populations. However, the population lost >40 % of individuals and biomass through the droughts, with mortality being just below 20 % after the Millennium Drought (2000-2009) and almost 25 % after the Big Dry (2017-2019). The best predictors of mortality differed after each drought. While north-facing aspect of a sampling location was significant positive predictor after both droughts, biomass density and slope were significant negative predictors only after the Millennium Drought, and distance to the north-west corner of the population, which intercepts hot, dry winds, was a significant positive predictor after the Big Dry only. This suggests that more marginal sites with low biomass and sites located on flat plateaus were more vulnerable initially, but that heat-stress was an important driver of dieback during the Big Dry. Therefore, the causative drivers of dieback may change during population decline. Regeneration occurred predominantly on southern and eastern aspects, which would receive the least solar radiation. While this refugial population is experiencing severe decline, some gullies with lower solar radiation appear to support relatively healthy, regenerating stands of red stringybark, providing hope for persistence in small pockets. Monitoring and managing these pockets during future droughts will be essential to ensure the persistence of this isolated and genetically unique population., Competing Interests: Declaration of competing interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: Udo Sarnow reports financial support was provided by Royal Society of South Australia Incorporated., (Copyright © 2023 The Authors. Published by Elsevier B.V. All rights reserved.)