Purification and characterisation of a DNA helicase, dheI I, from Drosophila melanogaster embryos.

We have purified a DNA helicase (dhel l) from early Drosophila embryos. dhel l co-purifies with the single-stranded DNA binding protein dRP-A over two purification steps, however, the proteins can be separated by their different native molecular weight, with dhel l activity co-sedimenting with a polypeptide of approximately 200 kDa and a sedimentation coefficient of 8.6 S. The enzyme needs ATP hydrolysis and divalent cations for displacement activity. It is very salt sensitive, having a Mg2+ optimum of 0.5 mM and being inhibited by NaCl concentration > 10 mM. Dhel l moves 5'-->3' on the DNA strand to which it is bound. Unwinding activity decreases with increasing length of the double-stranded region suggesting a distributive mode of action. However, addition of dRP-A to the displacement reaction stimulates the activity on substrates with >300 nucleotides double-stranded region suggesting a specific interaction between these two proteins.     

Enigmatic variations: divergent modes of regulating eukaryotic DNA replication

Proteins involved in DNA replication are conserved from yeast to mammals, suggesting that the mechanism was established at an early stage of eukaryotic evolution. In spite of this common origin, recent findings have revealed surprising variations in how replication initiation is controlled, implying that a conserved mechanism has not necessarily resulted in regulatory conservation.     

Species definitions and conservation: a review and case studies from African mammals

The nature of species, especially as applied to large mammals, is of major concern in conservation. Here, we briefly comment on recent thinking in alpha taxonomy, and assert that species are in essence evolutionary lineages, and that the most effective way of recognising them is by their diagnosability, i.e. the so-called Phylogenetic Species Concept. We further assert that the amount of genetic distance is not a relevant datum for distinguishing species, and that the ability to interbreed is not relevant. We consider a few case studies, especially that of the Northern White Rhinoceros Ceratotherium cottoni, and also species in Loxodonta, Giraffa and Oreotragus.     

Influence of grass proportion in stands of burr medic and subterranean clover on legume re-establishment and productivity following wheat

A field-plot experiment investigated the re-establishment and productivity in 1987 (following wheat (Triticum aestivum) in 1986) of burr medic (Medicago polymorpha) and subterranean (sub-) clover (Trifolium subterraneum), which were each sown with 0, 20, 40, 60, 80, or 100% grass in 1985. There was no difference in the amount of dry matter production by medic or sub-clover over the whole growing season but medic was more productive earlier and sub-clover more productive later. Grass generally had little effect on legume or total dry matter production at proportions <40%, though medic productivity was slightly more vulnerable to the effect of grass-infestation than sub-clover.     

A pervasive denigration of natural history misconstrues how biodiversity inventories and taxonomy underpin scientific knowledge

Embracing comparative biology, natural history encompasses those sciences that discover, decipher and classify unique (idiographic) details of landscapes, and extinct and extant biodiversity. Intrinsic to these multifarious roles in expanding and consolidating research and knowledge, natural history endows keystone support to the veracity of law-like (nomothetic) generalizations in science. What science knows about the natural world is governed by an inherent function of idiographic discovery; characteristic of natural history, this relationship is exemplified wherever an idiographic discovery overturns established wisdom. This nature of natural history explicates why inventories are of such epistemological importance. Unfortunately, a Denigration of Natural History weakens contemporary science from within. It expresses in the prevalent, pervasive failure to appreciate this pivotal role of idiographic research: a widespread disrespect for how natural history undergirds scientific knowledge. Symptoms of this Denigration of Natural History present in negative impacts on scientific research and knowledge. One symptom is the failure to appreciate and support the inventory and monitoring of biodiversity. Another resides in failures of scientiometrics to quantify how taxonomic publications sustain and improve knowledge. Their relevance in contemporary science characteristically persists and grows; so the temporal eminence of these idiographic publications extends over decades. This is because they propagate a succession of derived scientific statements, findings and/or conclusions - inherently shorter-lived, nomothetic publications. Widespread neglect of natural science collections is equally pernicious, allied with disregard for epistemological functions of specimens, whose preservation maintains the veracity of knowledge. Last, but not least, the decline in taxonomic expertise weakens research capacity; there are insufficient skills to study organismal diversity in all of its intricacies. Beyond weakening research capacities and outputs across comparative biology, this Denigration of Natural History impacts on the integrity of knowledge itself, undermining progress and pedagogy throughout science. Unprecedented advances in knowledge are set to follow on consummate inventories of biodiversity, including the protists. These opportunities challenge us to survey biodiversity representatively—detailing the natural history of species. Research strategies cannot continue to ignore arguments for such an unprecedented investment in idiographic natural history. Idiographic shortcuts to general (nomothetic) insights simply do not exist. The biodiversity sciences face a stark choice. No matter how charismatic its portrayed species, an incomplete ‘Brochure of Life’ cannot match the scientific integrity of the ‘Encyclopedia of Life’.     

Optimising two-stage independent culling selection in tree and animal breeding

Summary Theory is given for a simple practical method of predicting gain from two-stage independent culling, where stage 1 of selection is for individual performance and stage 2 is for either progeny performance only, or an index combining individual and progeny performance. Expected gain is determined as a direct function of heritabilities, genetic correlations, selection intensities and progeny-testing capacity. Results show the effect these parameters can have on proportions selected at each stage and, if multiple selection criteria are used, traits selected for first. Methods are discussed in the context of tree and animal breeding, with an example taken from forestry.     

Nothobranchius cooperi (Teleostei: Cyprinodontiformes): a new species of annual killifish from the Luapula River drainage,northern Zambia

Nothobranchius cooperi, Nagy, Watters and Bellstedt, new species, is described from seasonal streams and ephemeral pools associated with the upper Mansa River system in the middle Luapula drainage and systems draining into the low-lying area marginal to the southwestern part of Lake Bangweulu, in the Luapula province of northern Zambia. It belongs to the N. brieni species group. Males of Nothobranchius cooperi are distinguished from congeners by the following unique combination of characters: body scales with broad orange posterior margin, forming a highly irregular cross-barred pattern; anal fin fairly uniform orange-red with irregular to regular, light blue-green zone close to the base; caudal peduncle length 1.2–1.3 times its depth; prepelvic length 48.8–51.9% SL; and head depth 75–77% of head length. Genetic divergence of the mitochondrial COI and ND2 genes and nuclear S7 gene support the distinction of the new species from its closest known relative, N. rosenstocki and confirms its position in the N. brieni species group.