How much should reproduction cost?

The ultimate goal of investigating costs of reproduction isto see whether evolutionary tradeoffs are important determinantsof observed variation in fecundity. However, the current empiricalapproach to studying costs of reproduction, manipulation ofbrood size, is only capable of demonstrating the existence ofa cost of reproduction. Little attention has been paid to thebiological significance of a cost of reproduction, when oneis found. In this paper, I outline an analytical framework thatcan be used in conjunction with brood manipulation experimentsto determine whether an observed cost of reproduction is capableof limiting clutch sizes at observed levels. In addition, thisframework can be used to determine whether patterns of variationin fecundity within a population are caused by evolutionarytrade-offs between present and future reproduction. Two patternsused as examples are increase in clutch size with female ageand intraseasonal decline in clutch size in birds. Because increasingbrood size can have several effects on adults (e.g., decreasedadult survival, decreased future fecundity of surviving adults,decreased care given to offspring in the enlarged brood), thereis a need to understand how all these effects are interrelated.The analytical framework outlined in this paper allows one toexpress a cost of reproduction (i.e., a decrease in future fecundityof parents) and decreases in the rate of survival of offspringfrom the current nesting attempt in a common "currency." Thispaper also suggests how brood manipulation experiments can distinguishbetween variation in clutch size resulting from life-historytrade-offs and variation that results from differences in parentalability or territory quality. The analytical methods can bereadily applied to other taxa.     

How much do we know about the current extinction rate?

Since about J600, 486 animal species have been recorded extinct. This represents about 0.04% of all animal species so far described. In the same period, 600 plant species are known to have disappeared, about 0.25% of the total. These figures are much smaller than those of the Permian/ Triassic and Cretaceous/Tertiary mass extinctions. One might therefore conclude that at present life on earth is at comparatively little risk of extinction. However, there is a growing body of data to show that the converse is true.     

How much is a stabilizing bond worth?

It is commonly supposed that the contribution of a bond to protein or nucleic acid stability is equal to the in situ stability of the bond itself. This is not true for the noncovalent bonds that stabilize molecular folding. In general, a bonding interaction contributes a free energy increment to protein or nucleic acid stability that is larger, an enthalpy increment that is smaller, and entropy and heat capacity increments that are more positive than the corresponding bond parameter.     

Who should benefit financially from a good idea?

The need to publish ideas so that they can be explored, debated and extended by others before they are fully tested in the lab or the clinic is in conflict with the need to patent those ideas to provide a commercial incentive to apply them. I discuss why this conflict occurs, why it is important, and suggest three ways to get round it: root-and-branch reform of patent law (which seems impossible), extension of the US system's ‘grace period’ between publishing and filing a patent to longer times in the US and implementing the same system in other countries (which seems unlikely to happen), and binding readers of journals with a network of optional confidentiality agreements that allow publication but not citation without the authors’ permission. This latter appears too complex and conflicting an idea to work either, but while many conflicts with common scientific practice exist, the complexity of the system need not deter us, as at root the idea is simple and so it could be managed by software instead of patent lawyers.     

How much water does a river need?

1. This paper introduces a new approach for setting streamflow-based river ecosystem management targets and this method is called the 'Range of Variability Approach' (RVA). The proposed approach derives from aquatic ecology theory concerning the critical role of hydrological variability, and associated characteristics of timing, frequency, duration, and rates of change, in sustaining aquatic ecosystems. The method is intended for application on rivers wherein the conservation of native aquatic biodiversity and protection of natural ecosystem functions are primary river management objectives.
2. The RVA uses as its starting point either measured or synthesized daily streamflow values from a period during which human perturbations to the hydrological regime were negligible. This streamflow record is then characterized using thirty-two different hydrological parameters, using methods defined in Richter et al . (1996). Using the RVA, a range of variation in each of the thirty-two parameters, e.g. the values at ± 1 standard deviation from the mean or the twenty-fifth to seventy-fifth percentile range, are selected as initial flow management targets.
3. The RVA targets are intended to guide the design of river management strategies (e.g. reservoir operations rules, catchment restoration) that will lead to attainment of these targets on an annual basis. The RVA will enable river managers to define and adopt readily interim management targets before conclusive, long-term ecosystem research results are available. The RVA targets and management strategies should be adaptively refined as suggested by research results and as needed to sustain native aquatic ecosystem biodiversity and integrity.     

Reporter genes: too much of a good thing?

Advances in viral vector design and identification of new reporter genes have allowed the development of novel delivery systems. In the presence of reporter genes, cellular transduction frequency, expression of the gene of interest and phenotypic effects in cells expressing the gene under study can now be easily monitored both in vitro and in vivo. Moreover, the presence of unique cell markers allows for the enrichment of transduced cells for research studies or patient infusion. The ideal reporter gene product should be biologically inert and not influence the cell population under investigation. Recent reports suggest that reporter gene products may not be biologically benign.     

Meiotic recombination: too much of a good thing?

Proper chromosome segregation in meiosis requires the right number and distribution of crossovers. Recent work in budding yeast has revealed a meiosis-specific role for RecQ helicase in limiting crossovers, distinct from its known somatic role in maintaining genome stability.     

How much can we know about the causes of evolutionary trends?

One of the first questions that paleontologists ask when they identify a large-scale trend in the fossil record (e.g., size increase, complexity increase) is whether it is passive or driven. In this article, I explore two questions about driven trends: (1) what is the underlying cause or source of the directional bias? and (2) has the strength of the directional bias changed over time? I identify two underdetermination problems that prevent scientists from giving complete answers to these two questions.     

How much cytoplasm can a bacterial genome control?

In this perspective we discuss that bacterial genomes have optimized during evolution to control a range of cytoplasm, from immediately after cell division to a maximum amount/volume present just prior to DNA replication and subsequent cell division. The genetic expansion of bacteria via evolution may be limited to a genome size:cytoplasm amount/volume ratios and energetics that have been selected for during 3.6-4 billion years of evolution on the Earth. The optimal genome size is one that is relatively constant, but also has some plasticity for evolutionary change (via gene transfer) and mutational events, and can control a range of cytoplasm during the cell cycle.