Responses of savanna lawn and bunch grasses to water limitation

The grass layer of African savannas consists of two main vegetation types: grazing lawns, dominated by short, mostly clonally reproducing grasses, and bunch grasslands, dominated by tall bunch grasses. This patchy distribution of vegetation types is mostly created by large herbivores, which selectively feed on the more nutritious lawn grass species. Besides grazing, herbivores trample the soil, thereby causing soil compaction, with possible consequences for water infiltration. This raises two questions: (i) is water more limiting in grazing lawns than in bunch grasslands and (ii) are lawn grasses more drought tolerant than bunch grasses? To study these questions, we compared drought conditions in both lawn and bunch grasslands in a South African savanna. Additionally, in a climate room, we compared the performance of three lawn and three bunch grass species under a control and a water limitation treatment. Thirdly, we investigated whether there are differences between lawn and bunch grasses in traits related to drought tolerance. Our results show that despite large differences in water availability in the field, lawn and bunch grasses did not differ in their growth response to drought. Drought reduced growth of both growth forms equally. However, we found strong intrinsic trait differences between growth forms, with lawn grasses having higher specific root length and relative growth rate and bunch grasses having a higher root:shoot ratio. These results suggest that after drought-induced plant death, lawn grasses might be more capable of recolonizing patches of bare soil.     

The N-terminal -barrel domain of the Escherichia coli K88 periplasmic chaperone FaeE determines fimbrial subunit recognition and dimerization

The K88 periplasmic chaperone FaeE is a homodimer, whereas the K99 chaperone FanE is a monomer. The structural requirements for dimerization of the K88 fimbrial periplasmic chaperone and for fimbrial subunit-binding specificity were investigated by analysis of mutant chaperones. FaeE contains a C-terminal extension of 19 amino acid residues when compared to FanE and most other fimbrial chaperones. A C-terminal truncate of the K88 chaperone FaeE was constructed that lacked 19 C-terminal amino acid residues. Expression and complementation experiments revealed that this C-terminal shortened chaperone was still functional in binding the K88 major subunit FaeG and K88 biosynthesis. Two hybrid chaperones were constructed. Each hybrid protein contained one -barrel domain of FaeE and the other -barrel domain of FanE (Fae/FanE or Fan/FaeE, respectively). Expression and complementation experiments revealed that the Fae/FanE but not the Fan/FaeE hybrid chaperone was functional in the formation of K88 fimbriae. The Fan/FaeE hybrid chaperone was active in the biosynthesis of K99 fimbriae. The truncated FaeE mutant chaperone and the hybrid Fae/FanE chaperone were able to form stable periplasmic protein complexes with the K88 major fimbrial subunit FaeG. Cross-linking experiments suggested that the C-terminal shortened chaperone and the Fae/FanE hybrid chaperone were homodimers, as is the wild-type K88 chaperone. Altogether, the data suggested that the N-terminal -barrel domain of a fimbrial chaperone determines subunit specificity. In the case of the K88 periplasmic chaperone, this N-terminal domain also determines dimerization of the protein.     

Social competition as a driver of phenotype–environment correlations: implications for ecology and evolution

While it is universally recognised that environmental factors can cause phenotypic trait variation via phenotypic plasticity, the extent to which causal processes operate in the reverse direction has received less consideration. In fact individuals are often active agents in determining the environments, and hence the selective regimes, they experience. There are several important mechanisms by which this can occur, including habitat selection and niche construction, that are expected to result in phenotype–environment correlations (i.e. non-random assortment of phenotypes across heterogeneous environments). Here we highlight an additional mechanism – intraspecific competition for preferred environments – that may be widespread, and has implications for phenotypic evolution that are currently underappreciated. Under this mechanism, variation among individuals in traits determining their competitive ability leads to phenotype–environment correlation; more competitive phenotypes are able to acquire better patches. Based on a concise review of the empirical evidence we argue that competition-induced phenotype–environment correlations are likely to be common in natural populations before highlighting the major implications of this for studies of natural selection and microevolution. We focus particularly on two central issues. First, competition-induced phenotype–environment correlation leads to the expectation that positive feedback loops will amplify phenotypic and fitness variation among competing individuals. As a result of being able to acquire a better environment, winners gain more resources and even better phenotypes – at the expense of losers. The distinction between individual quality and environmental quality that is commonly made by researchers in evolutionary ecology thus becomes untenable. Second, if differences among individuals in competitive ability are underpinned by heritable traits, competition results in both genotype–environment correlations and an expectation of indirect genetic effects (IGEs) on resource-dependent life-history traits. Theory tells us that these IGEs will act as (partial) constraints, reducing the amount of genetic variance available to facilitate evolutionary adaptation. Failure to recognise this will lead to systematic overestimation of the adaptive potential of populations. To understand the importance of these issues for ecological and evolutionary processes in natural populations we therefore need to identify and quantify competition-induced phenotype–environment correlations in our study systems. We conclude that both fundamental and applied research will benefit from an improved understanding of when and how social competition causes non-random distribution of phenotypes, and genotypes, across heterogeneous environments.     

The National QAAMS Program – A Practical Example of PoCT Working in the Community

The Quality Assurance for Aboriginal and Torres Strait Islander Medical Services (QAAMS) Program is the largest and longest-standing national point-of-care testing (PoCT) program in Australia. With a focus on PoCT for diabetes management, it now operates in 115 Indigenous medical services and has been funded continuously by the Australian Government for 11 years. A recent independent evaluation of the QAAMS Program concluded that the program continues to meet best practice standards for Indigenous healthcare, diabetes management and PoCT.     

Aspects and altitudes modify the requirement of disturbance in oak (Quercus leucotrichophora A. Camus) belt of Garhwal Himalaya

Present study measures the impact of forest disturbance on population structure and regeneration status of a Himalayan banj oak (Qsuercus leucotrichophora A. Camus) forest at different aspects and altitudes. The whole study was carried out by placing 300 systematically selected sample plots in banj oak forest. The study revealed that moderately disturbed forest patches were present in all elevation ranges and both north and south facing aspects whereas most of the highly disturbed patches were situated near middle and lower stretches of forests or close to habitations. Density of primary diameter class (5–15 cm) was recorded highest in moderately disturbed zone in upper elevation ranges and north facing aspect and ‘fair’ category of regeneration was most frequent in all elevation ranges and aspects. The paper concludes a positive effect of mid-level disturbance on plant community for better regeneration and study recommends a minimum resource extraction and silvicultural practices in banj-oak belt of Himalaya for a minimum canopy opening which not only be able to provide biomass to local communities for their daily needs but also would be able to maintain and improve forest health.