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Context: Bromus diandrus Roth is a serious weed of cereal-based cropping systems in South Australia. Its adaptation to local climate and production systems, prolific seed production and evolution of herbicide resistance have made this weed difficult to manage. Aims: Studies were undertaken to determine genetic variation in seed dormancy within B. diandrus populations and its association with genes involved with gibberellic acid and abscisic acid synthesis. Methodology: Seeds from five B. diandrus populations were sampled during 2017 from commercial fields and planted during 2018 in pots. Protracted seedling emergence in these populations allowed selection of low and high dormancy cohorts. Seeds produced by these cohorts from each population were evaluated for variation in seed dormancy in the following year. The process of cohort selection and seed dormancy evaluation was repeated. The mechanism regulating seed dormancy was investigated in 2020 by assessing seeds of low and high dormancy cohorts concurrently for dormancy and for expression of ABA1 and GA20ox genes, using quantitative real-time PCR. Results: There was at least a two-fold difference in seed dormancy among populations collected from different farms. Low and high dormancy cohorts within each population maintained consistent differences in seed dormancy in both years of assessment, suggesting genetic control over this trait. Differences in seed dormancy between low and high dormancy cohorts were significantly correlated with ABA1 and GA20ox gene expression. Conclusions: Large differences in seed dormancy exist between individuals in B. diandrus populations. The study has provided evidence of genetic variation for seed dormancy within B. diandrus populations, which was associated with ABA1 and GA20ox gene expression. Implications: Presence of genetic variation for seed dormancy could play an important role in adaptation to escape pre-sowing weed-control tactics, meaning that B. diandrus could become an even greater problem in field crops grown in this region. Bromus diandrus is a serious weed of cereal crops in South Australia and is responsible for significant yield decline in wheat. Seed dormancy of different B. diandrus populations analysed for 3 years revealed genetic variation, and genes responsible for the control of seed dormancy were identified. The findings improve understanding of the genes involved in regulating seed dormancy, their expression over time, and how loss of dormancy is associated with changes in the gene expression. [ABSTRACT FROM AUTHOR]

There are 11 species of genus Chydorus Leach, 1816 (Cladocera: Chydoridae) in Australia, including populations of Chydorus sphaericus (O.F. Müller, 1785) morphologically undistinguishable from European ones. Our genetic study of C. sphaericus from two large artificial water bodies in the Adelaide region of South Australia led us to conclude the taxon was introduced to Australia from Europe by human activity, at least in the two studied water bodies. To provide a comprehensive sister-taxa coverage and survey of intraspecific variation, our data were complemented by sequences on Chydorus sphaericus-group from GenBank and Barcode of Life Data Systems website. We speculate that it was related to a mass stocking of introduced species of fishes from Europe. To confirm whether C. sphaericus is an invasive species due to human-mediated introductions, or whether it is a native Australian taxon, further extensive molecular studies (involving nuclear genes) and detailed morphological comparisons are needed. This is a first report on the invasion of a non-daphniid species of Cladocera to Australia. Its significance for Australian ecosystems needs special future studies.

The Holocene calcareous mudstone successions of numerous shallow coastal lakes in the Coorong region of southeastern South Australia include prominent organic-rich intervals (0.01 - 1 m thick; total organic carbon >2%), herein termed sapropels. New radiocarbon dates (n = 25) on bulk organic matter in single cores from three such lakes indicate that these sapropels are older in North Stromatolite Lake, part of the Salt Creek lake chain, than 100 km further south in the Robe Range at Old Man Lake and Lake Amy. The onset of sapropel deposition in North Stromatolite Lake at ca 6400 cal y BP marked its isolation from the open Coorong Lagoon, whereas in Old Man Lake, the onset of sapropel formation at ca 4000 cal y BP coincided with the transition from lagoonal to perennial lacustrine conditions as the sea withdrew from the interdunal Robe - Woakwine corridor. In contrast, the depocentre at Lake Amy was never directly connected to the marine system. Here, organic matter from near the base of the lowermost sapropel, dated at ca 4100 cal y BP, provides a minimum age for the onset of lacustrine conditions. Sapropel deposition recorded thus far in these lacustrine sequences ceased earlier in North Stromatolite Lake (ca 5000 cal y BP) than in Old Man Lake (ca 2600 cal y BP) and Lake Amy (ca 1900 cal y BP). This may simply reflect a marked local climatic gradient (drier in the north, wetter in the south). Alternatively, it may indicate that these shallow lacustrine sapropels, unlike their marine and deep-lake counterparts, do not form only during times of high precipitation but may be triggered by other processes such as the enhanced aeolianite influx associated with aridification. [ABSTRACT FROM AUTHOR]

The partial melting processes of Al-rich and cordierlte-absent garnet-orthopyroxene-bearing leucosome assemblages in the reworked Archaean Sleaford Complex in southern Eyre Peninsula, South Austrolia are examined. The Kimban Orogeny produced a pervasive development of garnet-K-feldspar- dominated leucosome assemblages. The textural relationships suggest that the peak assemblage garnet-orthopyroxene-K-feldspar involved a melt phase and formed through the divariant partial melting reaction garnet + biotite = orthopyroxene + K-feldspar + liquid in the KFMASH system,during a prograde KD heating event. A cordierite-bearing metapeilte also preserves the peak KD assemblage of garnet-cordierite-orthopyroxene-K-feldspar and the textural relationships suggest that peak assemblages formed through the crossing of the univariant partial melting reaction garnet + biotite = orthopyroxene + cordierite + K-feldspar + liquid in the KFMASH system, during the KD prograde heating stage. It is suggested that peak metamorphic P-T conditions reached 850-900°C and 0,9-1,0 GPa, and that the preservation of peak assemblages means that some melt was lost near or during the metamorphic peak. The pervasive interstitial K-feldspar groins nucleated synchronously with decompression, and the second generation at small euhedrol garnets are interred to have formed through deoompression-generated partial melting during o KD2 high-strain shear event, The P-T conditions of 700-750°C and 0.5-0.6 GPa were attained during the KD2 high-grade shear event. The inferred clockwise P-T path from KD1 to KD2 is campatible with a coillsional tectonic model during the Kimbon Orogeny (ca 1730-1700 Ma), whereas syn-KD2 decompression-cooling was a result of rapid tectonic exhumation of the terrain. [ABSTRACT FROM AUTHOR]