Stable karyotypes: a general rule for the fish of the family Prochilodontidae?

Cytogenetic studies involving the family Prochilodontidae have shown that these fish can be characterized by a constant diploid number and a conserved karyotypic macrostructure. This study focused on comparative physical chromosomal mapping using 18S and 5S rDNA to compare the species Semaprochilodus insignis and S. taeniurus. Our results indicated the conservation of large number of conventional chromosomal markers. The molecular cytogenetic analyses of the location of the 18S rDNA indicated the maintenance of a chromosome pair bearing these sites in both species analyzed, and it appears to be a conserved character among the majority of the species of this family. The stability of the number of 5S ribosomal DNA sites and their chromosomal localization as has been reported for the Prochilodontidae was not, however, confirmed for S. insignis and S. taeniurus, as these species showed multiple specific rDNA 5S sites. As such, and in spite of the fact that a number of studies indicate that the family Prochilodontidae has a conserved karyotypic structure, the utilization of molecular tools that use chromosomal segments as markers revealed that this presumed stability cannot be extended to the genome level for the species S. insignis and S. taeniurus.     

Optimization of two-joint arm movements: a model technique or a result of natural selection?

The fossil record of early hominids suggests that their Arm length, and presumably stature and weight, had a tendency to increase. Using the minimum jerk principle and a related formulation of averaged specific power, ASP, with regard to selected two-joint Arm movements, the current paper explores relationships between ASP, hand trajectory length (or Arm length, or body mass) and mean movement speed, deriving relationships which indicate that ASP is proportional to cubic mean movement speed, but inversely proportional to hand trajectory length (or Arm length, or 1/3 power of body mass). Accordingly, an `ecological niche’ is modeled in a three-parameter space. Either ASP maximization for fixed movement time, or ASP minimization for fixed mean movement speed, taken as selective optimization criterion, allows the increasing of human Arm length during evolution, regardless of the arm-to-forearm length ratio.     

Does natural selection organize ecosystems for the maintenance of high productivity and diversity?

Three types of evidence suggest that natural ecosystems are organized for high productivity and diversity: (i) changes not previously experienced by a natural ecosystem, such as novel human disturbances, tend to diminish its productivity and/or diversity, just as 'random' changes in a machine designed for a function usually impair its execution of that function; (ii) humans strive to recreate properties of natural ecosystems to enhance productivity of artificial ones, as farmers try to recreate properties of natural soils in their fields; and (iii) productivity and diversity have increased during the Earth's history as a whole, and after every major biotic crisis. Natural selection results in ecosystems organized to maintain high productivity of organic matter and diversity of species, just as competition among individuals in Adam Smith's ideal economy favours high production of wealth and diversity of occupations. In nature, poorly exploited energy attracts more efficient users. This circumstance favours the opening of new ways of life and more efficient recycling of resources, and eliminates most productivity-reducing 'ecological monopolies'. Ecological dominants tend to be replaced by successors with higher metabolism, which respond to more stimuli and engage in more varied interactions. Finally, increasingly efficient predators and herbivores favour faster turnover of resources.     

Humans act against the natural process of breeder selection: A modern sickness for animal populations?

We present a new idea about the possible effects of human-induced mortality on different age cohorts (i.e., breeders vs. juveniles) in long-lived animals. Our hypothesis is based on Curios idea on the effect of natural selective processes on cohorts to explain age-related increases in fecundity (selection hypothesis). We believe that negative human pressure may modify such contribution to reproduction of good versus low quality phenotypes, altering the genetic structure of the population. Ecologists and environmental managers in general should be aware of how stochastic events provoked by humans may induce changes in the genetic structure of populations.     

Long-term effects of ionising radiation on the brain: cause for concern?

There is no clear evidence proving or disproving that ionising radiation is causally linked with neurodegenerative diseases such as Parkinson’s and Alzheimer’s. However, it is known that high doses of ionising radiation to the head (20–50 Gy) lead to severe learning and memory impairment which is characteristical for Alzheimer’s. The cumulative doses of ionising radiation to the Western population are accruing, mostly due to the explosive growth of medical imaging procedures. Children are in particular prone to ionising radiation as the molecular processes within the brain are not completely finished. Furthermore, they have a long lifespan under risk. We wish to open a debate if such low doses of radiation exposure may lead to delayed long-term cognitive and other defects, albeit at a lower frequency than those observed during application of high doses. Further, we want to sensitise the society towards the risks of ionising radiation. To achieve these aims, we will recapitulate the known symptoms of Parkinson’s and Alzheimer’s on the molecular level and incorporate data of mainly low- and moderate-ionising radiation (<5 Gy). Thus, we want to highlight in general the potential similarities of both the neurodegenerative and radiation-induced pathways. We will propose a mechanistic model for radiation-induced neurodegeneration pointing out mitochondria as a key element. This includes effects of oxidative stress and neuroinflammation—all fundamental players of neurodegenerative diseases.     

Flowering phenology: An example of relaxation of natural selection?

Flowering phenology has normally been viewed as fundamental to a plant species' reproductive ecology. Researchers in the field have emphasized the adaptive importance of flowering at a particular time relative to other individuals in the population, or other species in the community. An alternative view, however, is that flowering phenology is a trait that may not be under strong selection, and this may have allowed some variation to appear in populations by chance.     

Critical-like self-organization and natural selection: Two facets of a single evolutionary process?

We argue that critical-like dynamics self-organize relatively easily in non-equilibrium systems, and that in biological systems such dynamics serve as templates upon which natural selection builds further elaborations. These critical-like states can be modified by natural selection in two fundamental ways, reflecting the selective advantage (if any) of heritable variations either among avalanche participants or among whole systems. First, reproducing (avalanching) units can differentiate, as units adopt systematic behavioural variations. Second, whole systems that are exposed to natural selection can become increasingly or decreasingly critical. We suggest that these interactions between SOC-like dynamics and natural selection have profound consequences for biological systems because they could have facilitated the evolution of division of labour, compartmentalization and computation, key features of biological systems. The logical conclusion of these ideas is that the fractal geometry of nature is anything but coincidental, and that natural selection is itself a fractal process, occurring on many temporal and spatial scales.     

The nature of natural: defining natural character for the New?Zealand context

New?Zealand has a long-standing statutory policy goal to preserve the natural character of the coastal environment and various freshwater environments and their margins. In the absence of an authoritative definition, it has not been possible to develop a method to measure natural character and its change, nor the outcomes of the long-standing national policy goal. Here we develop a definition of natural character that is relevant and useful in the New?Zealand environmental, cultural and legal/policy context. Literature-derived interpretations of natural character and equivalent concepts are evaluated as to their potential suitability for developing a biophysical definition of natural character. Using a set of carefully designed criteria a subset of interpretations are condensed into a definition of natural character. The application of this definition is qualified following consideration of the literature addressing human perception and experiences of natural character. Appropriate reference conditions and baselines for evaluating natural character in different contexts are discussed.     

Resistance to oomycetes: a general role for the hypersensitive response?

Oomycete plant pathogens, such as Phytophthora, downy mildews and Pythium, have devastating disease effects on numerous crop and ornamental plants. Various types of genetic resistance to oomycetes occur in plants, and can be determined at the subspecific or varietal level (race or cultivar-specific resistance), or at the species or genus level (nonhost resistance). In addition, resistance might be a quantitative phenotype (partial resistance). Resistance reactions are often associated with the hypersensitive response – a programed cell death pathway. Recent advances in the genetic, biochemical and cytological characterization of disease resistance suggests that the hypersensitive response is associated with all forms of resistance to Phytophthora and downy mildews. Identification of the resistance genes involved in nonhost and partial resistance to oomycetes remains an important challenge.     

Understanding reversals in the relative strength of sexual selection on males and females: a role for sperm competition?

Sperm competition affects sexual selection intensity on males, but models suggest it cannot affect the relative intensity of sexual selection on males compared to females. However, if sperm competition depresses the payoff for male multiple mating, it could affect the relative intensity of sexual selection and even cause sexual selection to be more intense on females than males (reversal of typical pattern). To evaluate how sperm competition, energy availability, and parental investment affect the intensity of sexual selection on each sex, I constructed a simulation model using the relationship between fecundity and number of mates to estimate sexual selection gradients. Unlike earlier models, I include a trade-off between paternal investment and sperm competition ability. The amount of energy available for reproduction affects the sexual selection gradient for each sex. Reversals in the sex experiencing stronger sexual selection do occur when additional paternal investment reduces a male's ability to compete for fertilizations within females. The shape of the distribution of mates for each sex (determined by mate competition) is also important. Output from the model is qualitatively similar to empirical data from insects with paternal investment. This model challenges previous thinking about the role of sperm competition in sex-role reversal.     

Does natural selection favour taller stature among the tallest people on earth?

The Dutch are the tallest people on earth. Over the last 200 years, they have grown 20 cm in height: a rapid rate of increase that points to environmental causes. This secular trend in height is echoed across all Western populations, but came to an end, or at least levelled off, much earlier than in The Netherlands. One possibility, then, is that natural selection acted congruently with these environmentally induced changes to further promote tall stature among the people of the lowlands. Using data from the LifeLines study, which follows a large sample of the population of the north of The Netherlands (n = 94 516), we examined how height was related to measures of reproductive success (as a proxy for fitness). Across three decades (1935–1967), height was consistently related to reproductive output (number of children born and number of surviving children), favouring taller men and average height women. This was despite a later age at first birth for taller individuals. Furthermore, even in this low-mortality population, taller women experienced higher child survival, which contributed positively to their increased reproductive success. Thus, natural selection in addition to good environmental conditions may help explain why the Dutch are so tall.     

Evolution of the additive genetic variance–covariance matrix under continuous directional selection on a complex behavioural phenotype

Given the pace at which human-induced environmental changes occur, a pressing challenge is to determine the speed with which selection can drive evolutionary change. A key determinant of adaptive response to multivariate phenotypic selection is the additive genetic variance–covariance matrix (G). Yet knowledge of G in a population experiencing new or altered selection is not sufficient to predict selection response because G itself evolves in ways that are poorly understood. We experimentally evaluated changes in G when closely related behavioural traits experience continuous directional selection. We applied the genetic covariance tensor approach to a large dataset (n = 17 328 individuals) from a replicated, 31-generation artificial selection experiment that bred mice for voluntary wheel running on days 5 and 6 of a 6-day test. Selection on this subset of G induced proportional changes across the matrix for all 6 days of running behaviour within the first four generations. The changes in G induced by selection resulted in a fourfold slower-than-predicted rate of response to selection. Thus, selection exacerbated constraints within G and limited future adaptive response, a phenomenon that could have profound consequences for populations facing rapid environmental change.     

Synchrony: a neuronal mechanism for attentional selection?

Attentional selection involves brain processes that select and control the flow of information into the mechanisms that underlie perception and consciousness. One theory proposes that the neural activity that represents the stimuli or events to be attended to is selected through modification of its synchrony. Recent experimental evidence supports this theory, by showing that changes in attentional focus increase the synchrony of neural firing in some neuron pairs and decrease it in others.     

Darwinian agriculture: when can humans find solutions beyond the reach of natural selection?

Progress in genetic improvement of crop yield potential has slowed since 1985. Simultaneously, more sustainable management of agricultural ecosystems is needed. A better understanding of natural selection can help solve both problems. We illustrate this point with two specific examples. First, the genetic legacy of crop plants has been refined by millions of years of natural selection, often driven by competition among plants. We therefore suggest that most simple, tradeoff-free options to increase competitiveness (e.g., increased gene expression, or minor modifications of existing plant genes) have already been tested by natural selection. Further genetic improvement of crop yield potential over the next decade will mainly involve tradeoffs, either between fitness in past versus present environments, or between individual competitiveness and the collective performance of plant communities. Eventually, we may develop the ability to predict the consequences of genetic alterations so radical that they have not yet been tested by natural selection. Second, natural selection acts mainly at the level of genes, individuals, and family groups, rather than ecosystems as a whole. Consequently, there is no reason to expect the structure of natural ecosystems (diversity, spatial, or temporal patterns) to be a reliable blueprint for agricultural ecosystems. Natural ecosystems are nonetheless an important source of information that could be used to improve agriculture.     

Fast methods of enantiopurity determination for the Soai reaction: Towards a general enantioenrichment detector?

The Soai reaction system possesses a remarkable combination of characteristics (enantioselective autocatalysis, strong positive nonlinearity leading to asymmetric amplification, ability to be triggered by wide variety of exogenous enantioenriched materials) that make it a potential starting point for a generalized detector for enantioenrichment. In this study we apply standard approaches used in pharmaceutical process research to the problem of developing a rapid method for analysis of the enantiopurity of the Soai reaction product. Several methods for rapid analysis (<1 min per sample) are described, including an approach using chiral supercritical fluid chromatography (SFC) and an approach using achiral chromatography with circular dichroism (CD) detection. Some thoughts on incorporation into a device for generalized enantioenrichment detection are presented.