Aim Our aims were to identify centres of endemism and to infer whether these areas have functioned as refugia for subtropical rain forest plants through historical climate fluctuations.Location Subtropical eastern Australia (23-33°S; 145-155°E).Methods We collated 25,000 records of 179 endemic rain forest plants to identify geographical areas with unusually high concentrations of endemic taxa and range-restricted endemics. We then tested whether centres of endemism coincide with other features indicating refugia, including habitat stability over 120,000 years, and we related dispersal patterns to past habitat stability using seed weight as a surrogate for dispersal ability of endemic plant taxa.Results We identified five main centres of endemism. Historical stability and other processes affecting diversity, including current rainfall, rain forest area, and topographic complexity, explained 58% of variation in plant-weighted endemism. Taxa with poor dispersal ability were concentrated in the areas that were most stable historically.Main conclusions Several lines of evidence suggest that centres of endemism have functioned as important refugia for subtropical rain forest taxa through historical climate fluctuations. The highest concentrations of range-restricted endemic species occur in locations that are predicted to have maintained stable rain forest habitat over at least the past 120,000 years. This association was independent from other factors that were expected to promote diversity (i.e. rain forest area and current environmental suitability). These locations have disproportionately high concentrations of species with poor dispersal ability (large-seeded species).
Knowledge of the structure and dynamics of the ligand channel(s) in heme-copper oxidases is critical for understanding how the protein environment modulates their functions. Using photolabile NO and O2 carriers, we recently found that NO and O2 binding in Thermus thermophilus ba3 (Tt ba3) is ~10-times faster than in the bovine enzyme, indicating inherent structural differences that affect ligand access in these enzymes. Using x-ray crystallography, time-resolved optical absorption measurements, and theoretical calculations, we investigated ligand access in the Tt ba3 mutants Y133W, T231F, and Y133W&T231F, in which tyrosine and/or threonine in the O2-channel of Tt ba3 are replaced by the corresponding bulkier tryptophan and phenylalanine present in the aa3 enzymes. NO binding in Y133W and Y133W&T231F is 5-times slower than in wild-type ba3 and the T231F mutant, and the results show that the Tt ba3 Y133W mutation and the bovine W126 residue physically impede NO access to the binuclear center. In the bovine enzyme there is a hydrophobic “way-station,” which may further slow ligand access to the active site. Classical simulations of Xe diffusion to the active sites in ba3 and bovine aa3 show conformational freedom of the bovine F238 and the F231 side chain of the Tt ba3 Y133W&T231F mutant, with both residues rotating out of the ligand channel, resulting in no effect on ligand access in either enzyme.
Australian rainforests have been fragmented due to past climatic changes and more recently landscape change as a result of clearing for agriculture and urban spread. The subtropical rainforests of South Eastern Queensland are significantly more fragmented than the tropical World Heritage listed northern rainforests and are subject to much greater human population pressures. The Australian rainforest flora is relatively taxonomically rich at the family level, but less so at the species level. Current methods to assess biodiversity based on species numbers fail to adequately capture this richness at higher taxonomic levels. We developed a DNA barcode library for the SE Queensland rainforest flora to support a methodology for biodiversity assessment that incorporates both taxonomic diversity and phylogenetic relationships. We placed our SE Queensland phylogeny based on a three marker DNA barcode within a larger international rainforest barcode library and used this to calculate phylogenetic diversity (PD). We compared phylo- diversity measures, species composition and richness and ecosystem diversity of the SE Queensland rainforest estate to identify which bio subregions contain the greatest rainforest biodiversity, subregion relationships and their level of protection. We identified areas of highest conservation priority. Diversity was not correlated with rainforest area in SE Queensland subregions but PD was correlated with both the percent of the subregion occupied by rainforest and the diversity of regional ecosystems (RE) present. The patterns of species diversity and phylogenetic diversity suggest a strong influence of historical biogeography. Some subregions contain significantly more PD than expected by chance, consistent with the concept of refugia, while others were significantly phylogenetically clustered, consistent with recent range expansions.
Aim To enhance our understanding of the evolutionary interactions between seed-dispersal syndromes, life-forms, seed size, and habitat characteristics by studying their association with the regional-scale distributions of subtropical rain-forest plants in the context of climatic gradients.Location South-east Queensland, subtropical eastern Australia (152°E, 26°S).Methods We classified 250 rain-forest sites into six floristic site-groups based on their woody plant composition. The resulting classification was strongly associated with variation in rainfall. The distribution of species across the floristic site-groups was used to assign 568 species to seven habitat classes (one class for 'widespread' species, with all other species classified according to the sitegroup within which they were most frequent). Species were also classified for three other categorical life-history factors: three dispersal syndromes based on diaspore morphology (fleshy, wind-assisted, and unadorned); four life-forms (trees, shrubs and small trees, tall climbers, and short and shrubby climbers); and four seed-diameter classes (< 3 mm, ‡ 3 and < 4.5 mm, ‡ 4.5 and < 7 mm, and ‡ 7 mm). We used a basic comparative approach augmented by simple phylogenetically constrained comparisons to assess association between dispersal syndrome, seed size, life-form, and habitat class.Results Across the rain forests of south-east Queensland, the proportion of species with fleshy diaspores or of large stature increases with rainfall. Highrainfall sites also have larger average seed sizes, but the difference in average seed size between high-and low-rainfall sites is small compared with variation within sites. Among species, those with fleshy fruit tend to have larger seeds and to favour high-rainfall sites. Very few small trees produce diaspores adapted for wind-assisted dispersal. On average, species with unadorned diaspores have smaller seeds than those with fleshy diaspores. However, within sites, species with unadorned and fleshy diaspores have similar average seed sizes, and some species with unadorned diaspores from high-rainfall habitats have extremely large seeds.Main conclusions Commonly observed associations between fleshy fruit, larger plants, larger seeds, and productive habitats are apparent within the rain-forest flora of south-east Queensland. However, these associations are generally weak and involve complex interactions. For example, the strong tendency for species with fleshy fruit to have larger seeds than those with unadorned diaspores concealed a significant group of species from wetter forests that produce extremely large seeds and unadorned diaspores. The most widespread species in this study tend to be large plants (particularly robust lianes) and to produce fleshy fruit, but they tend not to have relatively large seeds. The association between large seeds, large plants, fleshy fruit and productive habitats is discussed as part of an evolutionary strategy favouring fitness in populations close to carrying
Photolysis of α-diazo N-methoxy-N-methyl (Weinreb) β-ketoamides derived from enantiomerically pure (EP) α-amino acids affords the corresponding EP β-lactam via an intramolecular Wolff rearrangement. Photochemistry is promoted with either standard UV irradiation or through the use of a 100W compact fluorescent light (CFL); the latter affords a safe and environmentally friendly alternative to standard photolysis conditions. A continuous-flow photochemical reactor, made from inexpensive laboratory equipment, expedites reaction times and is amenable to scale-up. Diastereoselectivity (cis or trans) of the product β-lactams has been shown to vary from modest to nearly complete. An extremely facile, atom-economical method for the epimerization of the product mixture to the trans isomer, generally highly crystalline, has been developed. Evidence is presented for C-3 epimerization of Weinreb amide structures via a non-basic, purely thermal route. Subsequent transformations of both the Weinreb amide at C-3 (β-lactam numbering) and amino acid side chain at C-4 are well tolerated, allowing for a versatile approach to diverse β-lactam structures. The technology is showcased in the synthesis of a common intermediate used toward several carbapenem-derived structures starting from unfunctionalized aspartic acid.
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