The Pattern of Protein Accumulation in Relation to DNA Replication in Jerusalem Artichoke Callus Cultures

While the synchronous first division cycle in cultured explantsfrom Jerusalem artichoke tubers may vary in duration from oneto two days the length of the ‘S’ phase of thiscycle remains approximately constant at 14 h. A study of thepattern of protein accumulation in relation to this ‘S’phase shows the development of three different populations ofcells in an initially uniform explant. Cells from the centreof the explant accumulate neither DNA or protein while cellsin the peripheral layers accumulate protein according to thesame pattern irrespective of whether they synthesize DNA ornot. This similarity between dividing and nondividing cellsis of interest in considering cellular events leading to celldivision.     

A cost‐effective method of assessing thermal habitat quality for endotherms

The conservation of many endothermic species depends critically on the availability of suitable retreat sites, yet we know little about the variation in thermal quality of such microhabitats. Studies of thermal habitat suitability for birds and mammals must account for the effect of endothermic heat production on their microclimates. For example, endotherms may significantly raise the air temperature in their retreat sites and this effect must be considered when assessing retreat site quality. We devised an inexpensive means by which to construct pseudo‐endothermic ‘environmental temperature’ models with the use of disposable heat pads. We applied this technique to investigate thermal aspects of nest box design, illustrating the potential positive and negative effects of nest box insulation depending on the environmental context. We suggest that, from a thermal perspective, the avoidance of heat stress is an important and underappreciated issue in the retreat site selection of endotherms.     

Evolutionary and ecological genomics of non‐model plants

Abstract Dissecting evolutionary dynamics of ecologically important traits is a long‐term challenge for biologists. Attempts to understand natural variation and molecular mechanisms have motivated a move from laboratory model systems to non‐model systems in diverse natural environments. Next generation sequencing methods, along with an expansion of genomic resources and tools, have fostered new links between diverse disciplines, including molecular biology, evolution, ecology, and genomics. Great progress has been made in a few non‐model wild plants, such as Arabidopsis relatives, monkey flowers, and wild sunflowers. Until recently, the lack of comprehensive genomic information has limited evolutionary and ecological studies to larger QTL (quantitative trait locus) regions rather than single gene resolution, and has hindered recognition of general patterns of natural variation and local adaptation. Further efforts in accumulating genomic data and developing bioinformatic and biostatistical tools are now poised to move this field forward. Integrative national and international collaborations and research communities are needed to facilitate development in the field of evolutionary and ecological genomics.     

On the occurrence, causes and potential consequences of low zooplankton to phytoplankton ratios in New Zealand lakes

SUMMARY. 1. New Zealand lakes are shown to have lower average zooplankton biomasses than north-temperate lakes of similar average phytoplankton biomass, expressed as cell volume or chlorophyll a , or similar average total phosphorus concentration, typically by a factor of 5 or more.
2. Evidence suggests that the relatively low zooplankton biomasses of New Zealand lakes may be related to a tendency for them to be dominated by large algae that are not directly available as food for zooplankton, with oligotrophy lakes in particular differing from north-temperate lakes in this respect.
3. This difference in turn may be related largely to their mixing regimes. All of the New Zealand lakes are polymietic or monomietic, whereas the northern lakes used for comparison are mostly dimietic. Also, hetero-cystous cyanobacteria are favoured by the low inorganic nitrogen concentrations that are typical of New Zealand lakes.
4. Poor nutritional quality of the phytoplankton, relating to nitrogen limitation in many New Zealand lakes, might supplement the effects of cell size.
5. Low exploitation of phytoplankton by zooplankton can be expected to produce a shift in the metabolism of New Zealand lakes towards the sediments. Among the potential consequences of this effect are increased hypolimnetic oxygen demand with increased susceptibility to development of large internal loads of nutrients, and consequently, increased sensitivity to accelerated eutrophication from any increase in external nutrient loads.     

Evolution of Eukaryotic Microorganisms and Their Small Subunit Ribosomal RNAs

Traditional views about the origin of eukaryotes and relationshipsbetween major "kingdoms" reflect interpretations of the fossilrecord and comparisons of phenotypic characters. This perspectiveis challenged by phylogenetic frameworks inferred from comparisonsof macromolecular sequences which share a common ancestry. Similaritiesbetween ribosomal RNA genes demonstrate that instead of beingrelatively recent biological inventions, eukaryotes representa discrete lineage that may be as old as the archaebacterialand eubacterial lines of descent. The diversity of protistansmall subunit rRNA sequences exceeds that seen within the entireprokaryotic world. The earliest branching lineages include diplomonads,microsporidians, and tritrichomonads. Yet, other major protistangroups diverged relatively late in the evolutionary historyof nucleated cells. Rather than being a concise evolutionaryassemblage, the Protista should be regarded as a collectionof paraphyletic lineages. In contrast, the Fungi, Plantae, andAnimalia are independent monophyletic groupings. They originatednearly simultaneously during a relatively recent period characterizedby a massive diversification of forms. This novel view of eukaryoticevolution suggests that a reliance upon large phenotypic differencesin delineating kingdoms can obscure true genealogical relationships.Instead of dividing eukaryotes into four or more major divisions,they should be considered as a single kingdom that encompassesa progression of independently diverging lineages.