Potential impacts of climatic change on southern African birds of fynbos and grassland biodiversity hotspots

Aim To examine potential impacts of climatic change on bird species richness of the fynbos and grassland biomes, especially on species of conservation concern, and to consider implications for biodiversity conservation strategy. Location Southern Africa, defined for this study as South Africa, Lesotho and Swaziland. Methods Climate response surfaces were fitted to model relationships between recorded distributions and reporting rates of 94 species and current bioclimatic variables. These models were used to project species’ potential ranges and reporting rates for future climatic scenarios derived from three general circulation models for 30‐year periods centred on 2025, 2055 and 2085. Results were summarized for species associated with each biome and examined in detail for 12 species of conservation concern. Results Species richness of fynbos and grassland bird assemblages will potentially decrease by an average of 30–40% by 2085 as a result of projected climatic changes. The areas of greatest richness are projected to decrease in extent and to shift in both cases. Attainment of projected shifts is likely to be limited by extent of untransformed habitat. Most species of conservation concern are projected to decrease in range extent, some by > 60%, and to decrease in reporting rate even where they persist, impacts upon their populations thus being greater than might be inferred from decreases in range extent alone. Two species may no longer have any areas of suitable climatic space by 2055; both already appear to be declining rapidly. Main conclusions Species losses are likely to be widespread with most species projected to decrease in range extent. Loss of key species, such as pollinators, may have far‐reaching implications for ecosystem function and composition. Conservation strategies, and identification of species of conservation concern, need to be informed by such results, notwithstanding the many uncertainties, because the certainties of climatic change make it essential that likely impacts not to be ignored.     

Fine mapping of 14q24.1 breast cancer susceptibility locus

In the National Cancer Institute Cancer Genetic Markers of Susceptibility (CGEMS) genome-wide association study of breast cancer, a single nucleotide polymorphism (SNP) marker, rs999737, in the 14q24.1 interval, was associated with breast cancer risk. In order to fine map this region, we imputed a 3.93?MB region flanking rs999737 for Stages 1 and 2 of the CGEMS study (5,692 cases, 5,576 controls) using the combined reference panels of the HapMap 3 and the 1000 Genomes Project. Single-marker association testing and variable-sized sliding-window haplotype analysis were performed, and for both analyses the initial tagging SNP rs999737 retained the strongest association with breast cancer risk. Investigation of contiguous regions did not reveal evidence for an additional independent signal. Therefore, we conclude that rs999737 is an optimal tag SNP for common variants in the 14q24.1 region and thus narrow the candidate variants that should be investigated in follow-up laboratory evaluation.     

Development of a chitosan-based nanoparticle formulation for delivery of a hydrophilic hexapeptide, dalargin

Nanoparticle based delivery systems can offer opportunities for targeting, controlled release, and enhanced stability of their drug, protein, or gene therapy payload. This study investigated the use of chitosan in combination with the ionic additives sulfobutyl-ether-7-beta-cyclodextrin (SB-CD) or SB-CD/dextran sulfate (SB-CD/DS) mixture in comparison with chitosan: DS in the formulation of nanoparticles incorporating the hexapeptide dalargin. The physical characteristics (particle size, zeta potential), entrapment and loading efficiency, and release of dalargin were quantified. It was demonstrated that anionic cyclodextrin, SB-CD, can be used in complex coacervation with chitosan, with and without the presence of DS, to form nanoparticles. The presence of SB-CD or DS in the nanoparticle formulation and the weight ratio of chitosan to anionic additive(s) influenced the physical properties of the nanoparticles and their ability to carry dalargin. In addition, the particle size of nanoparticles was also affected by the molecular weight of chitosan and DS. The use of either DS or SB-CD/DS mixture produced chitosan nanoparticles with small particle size, high dalargin entrapment efficiency, enhanced peptide stability, and sustained release characteristics.     

Cryo-EM structure of the DNA-dependent protein kinase catalytic subunit at subnanometer resolution reveals alpha helices and insight into DNA binding

The DNA-dependent protein kinase catalytic subunit (DNA-PKcs) regulates the nonhomologous end joining pathway for repair of double-stranded DNA (dsDNA) breaks. Here, we present a 7A resolution structure of DNA-PKcs determined by cryo-electron microscopy single-particle reconstruction. This structure is composed of density rods throughout the molecule that are indicative of alpha helices and reveals structural features not observed in lower resolution EM structures. Docking of homology models into the DNA-PKcs structure demonstrates that up to eight helical HEAT repeat motifs fit well within the density. Surprisingly, models for the kinase domain can be docked into either the crown or base of the molecule at this resolution, although real space refinement suggests that the base location is the best fit. We propose a model for the interaction of DNA with DNA-PKcs in which one turn of dsDNA enters the central channel and interacts with a resolved alpha-helical protrusion.     

Hot bird drinking patterns: drivers of water visitation in a fynbos bird community

Water affects distribution of many species, but climate change is set to change rainfall patterns and hence water availability. In South Africa, various global climate‐change models suggest a drier future for the winter rainfall regions with implications for survival of plant and animal species of the fynbos region. Most birds offload heat by evaporative water loss, and this increases exponentially from 25°C. Birds need to replenish their water loss to cope particularly at high temperatures, especially species that have little preformed water in the diet. We documented bird species drinking at five natural water sources at a semi‐arid fynbos site through time‐lapse cameras to explore which birds are drinking when. We modelled the total numbers of birds observed drinking as a function of diet, mass and relative abundance and found that species classified as granivores were predicted to drink most frequently, with the more common species most frequently recorded. A phylogenetically controlled trait‐based logistic regression indicated abundance as the best predictor of observation at the water sources. Daily drinking rates at the species level for the ten most frequently observed species were generally best explained by daily temperature, with higher drinking rates on hotter days. However, daily drinking patterns were poorly explained by diurnal temperature trends at the hourly level, and we were unable to document sufficient predators to comment on the influence of predator avoidance or other heat mitigation strategies. Finally, we discuss the implications of our observations for the set of fynbos endemic passerines.     

Species richness and floristic relationships between mesas and their surroundings in southern African Nama Karoo

Abstract. Floristic composition of 14 mesas (i.e. flat‐top mountains) in four different study areas was investigated in southern African Nama Karoo. The study areas were arranged along a latitude gradient. Two simple questions were asked: are mesas potential conservation islands (a) in terms of re‐colonization potential and (b) in terms of species richness? Detailed vegetation surveys along a transect from the plains to the top of each mesa were summarized to obtain species composition for the three main habitats: plain, slopes and plateau. Floristic similarities between plains and mesa habitats were used to answer question (a), and species richness was used to answer question (b). Geographic position, high within‐area variability and elevation were found to largely influence the findings, resulting in only few consistent trends. The main findings of this study were, however: (1) mesas can act as sources for re‐colonization as well as havens for species adapted to mountain habitats. (2) Considering total species richness, mesa habitats were richer in species than plains in the northern, but not the southernmost study area. (3) Scaled by area, mesa plateaus emerged as the most species‐rich in all study areas. (4) Smaller and medium‐sized mesas showed greater re‐colonization potential, i.e. shared more species with their surrounding plains. (5) Medium‐sized to larger mesas supported plant communities more distinct from the surrounding plains. (6) A cut‐off point of approximately 240 m above the surrounding plain was indicated for the shift from ‘re‐colonization’ to ‘remnant’ function. These findings stress the importance for the protection of mesa habitats in view of increasing human pressure on mountain habitats.     

成都斑竹园林分结构及鹭类集群栖息调查

１９９８年９月,我们先后两次对斑竹园林分结构和鹭类集群栖息情况进行了调查研究。现报告如下。１基本概况斑竹园距离成都３０５ｋｍ,距新津８５ｋｍ,位于川西平原南部,成都市新津县兴义镇兴场村羊马河边,地理位置在东经１０３°４８′２４″－１０３°４８′３...     

Rapid chondrocyte maturation by serum-free culture with BMP-2 and ascorbic acid

In serum-containing medium, ascorbic acid induces maturation of prehypertrophic chick embryo sternal chondrocytes. Recently, cultured chondrocytes have also been reported to undergo maturation in the presence of bone morphogenetic proteins or in serum-free medium supplemented with thyroxine. In the present study, we have examined the combined effect of ascorbic acid, BMP-2, and serum-free conditions on the induction of alkaline phosphatase and type X collagen in chick sternal chondrocytes. Addition of either ascorbate or rhBMP-2 to nonconfluent cephalic sternal chondrocytes produced elevated alkaline phosphatase levels within 24–72 h, and simultaneous exposure to both ascorbate and BMP yielded enzyme levels at least threefold those of either inducer alone. The effects of ascorbate and BMP were markedly potentiated by culture in serum-free medium, and alkaline phosphatase levels of preconfluent serum-free cultures treated for 48 h with BMP + ascorbate were equivalent to those reached in serum-containing medium only after confluence. While ascorbate addition was required for maximal alkaline phosphatase activity, it did not induce a rapid increase in type X collagen mRNA. In contrast, BMP added to serum-free medium induced a three- to fourfold increase in type X collagen mRNA within 24 h even in the presence of cyclohexamide, indicating that new protein synthesis was not required. Addition of thyroid hormone to serum-free medium was required for maximal ascorbate effects but not for BMP stimulation. Neither ascorbate nor BMP induced alkaline phosphatase activity in caudal sternal chondrocytes, which do not undergo hypertrophy during embryonic development. These results indicate that ascorbate + BMP in serum-free culture induces rapid chondrocyte maturation of prehypertrophic chondrocytes. The mechanisms for ascorbate and BMP action appear to be distinct, while BMP and thyroid hormone may share a similar mechanism for induction. J. Cell. Biochem. 66:394–403, 1997. © 1997 Wiley-Liss, Inc.