Vegetation classification in a floristically complex area: the Agulhas Plain

The vegetation of the Agulhas Plain was classified and described using Campbell’s (1985) approach. Data collected included a subset of Campbell’s structural and higher taxon characters, as well as dominant (10% cover) species, which would enable the recognition of communities to at least the sub-series level in his hierarchy. The classification was produced using the Braun–Blanquet method of table sorting. Nine zonal communities, at various hierarchical levels, were recognized and mapped. Non-fynbos communities included Forest & Thicket, and Renoster Shrubland. Fynbos communities, which covered most of the study area, were Mesotrophic Asteraceous Fynbos, Dune Asteraceous Fynbos, Dry Restioid Fynbos, Protea repens Proteoid Fynbos, Protea obtusifolia–Leucadendron meridianum/P. susannae–L. coniferum Proteoid Fynbos, L. platyspermum–P. compacta–L. xanthoconus Proteoid Fynbos and Mesic Ericaceous Fynbos. It was not possible to classify Forest & Thicket below the group level while a new concept (Dune Asteraceous Fynbos) was developed at the sub-series level. In all other respects the largely lowland vegetation of the Agulhas Plain could be integrated with Campbell’s Fynbos Biome mountain vegetation concepts. This study therefore demolished any justification for retaining a lowland fynbos vegetation concept. Since we utilized the skills of a number of trained botanists in collecting easily recognizable structural, and limited floristic data, the entire study was completed in under 18months. The mapped communities are adequate for conservation planning and comprise an essential descriptive basis for future studies on the evolution and maintenance of species diversity on the Agulhas Plain. The efficiency and effectiveness of our approach makes it suitable as a model for rapid vegetation classification of the much-threatened vegetation of the fynbos biome lowlands

Whole-genome sequencing reveals host factors underlying critical COVID-19

Critical COVID-19 is caused by immune-mediated inflammatory lung injury. Host genetic variation influences the development of illness requiring critical care1 or hospitalization2,3,4 after infection with SARS-CoV-2. The GenOMICC (Genetics of Mortality in Critical Care) study enables the comparison of genomes from individuals who are critically ill with those of population controls to find underlying disease mechanisms. Here we use whole-genome sequencing in 7,491 critically ill individuals compared with 48,400 controls to discover and replicate 23 independent variants that significantly predispose to critical COVID-19. We identify 16 new independent associations, including variants within genes that are involved in interferon signalling (IL10RB and PLSCR1), leucocyte differentiation (BCL11A) and blood-type antigen secretor status (FUT2). Using transcriptome-wide association and colocalization to infer the effect of gene expression on disease severity, we find evidence that implicates multiple genes—including reduced expression of a membrane flippase (ATP11A), and increased expression of a mucin (MUC1)—in critical disease. Mendelian randomization provides evidence in support of causal roles for myeloid cell adhesion molecules (SELE, ICAM5 and CD209) and the coagulation factor F8, all of which are potentially druggable targets. Our results are broadly consistent with a multi-component model of COVID-19 pathophysiology, in which at least two distinct mechanisms can predispose to life-threatening disease: failure to control viral replication; or an enhanced tendency towards pulmonary inflammation and intravascular coagulation. We show that comparison between cases of critical illness and population controls is highly efficient for the detection of therapeutically relevant mechanisms of disease

Competitive interactions between the perennial shrub Leipoldtia constricta and an annual forb, Gorteria diffusa

Competitive interactions were studied between individuals of the perennial shrub, Leipoldtia constricta L. Bol., and an annual forb, Gorteria diffusa Thunb. in the winter rainfall region of the Karoo using nearest-neighbour analysis. Strong competitive interactions were measured between intraspecific and interspecific nearest-neighbour pairs. In particular, the size and reproductive potential of the annual forb was reduced whenever it established next to the perennial shrub. This reduction was greater than that occurring intraspecifically among individuals of the annual forb. Despite this effect, more annuals established close to the perennial shrub, presumably as the result of the latter’s multiple-stemmed growth habit which traps soil at its base providing a ‘safe site’ for germination and establishment

Angiotensin-converting-enzyme gene insertion/deletion polymorphism and response to physical training

Background The function of local renin-angiotensin systems in skeletal muscle and adipose tissue remains largely unknown. A polymorphism of the human angiotensin converting enzyme (ACE) gene has been identified in which the insertion (I) rather than deletion (D) allele is associated with lower ACE activity in body tissues and increased response to some aspects of physical training. We studied the association between the ACE gene insertion or deletion polymorphism and changes in body composition related to an intensive exercise programme, to investigate the metabolic effects of local human renin-angiotensin systems. Methods We used three independent methods (bioimpedance, multiple skinfold-thickness assessment of whole-body composition, magnetic resonance imaging of the mid-thigh) to study changes in body composition in young male army recruits over 10 weeks of intensive physical training. Findings Participants with the II genotype had a greater anabolic response than those with one or more D alleles for fat mass (0·55 vs −0·20 kg, p=0·04 by bioimpedance) and non-fat mass (1·31 vs −0·15 kg, p=0·01 by bioimpedance). Changes in body morphology with training measured by the other methods were also dependent on genotype. Interpretation II genotype, as a marker of low ACE activity in body tissues, may conserve a positive energy balance during rigorous training, which suggests enhanced metabolic efficiency. This finding may explain some of the survival and functional benefits of therapy with ACE inhibitors