Heuristics or general learning processes?

The concept of heuristics implies that the rules governing choice behavior may vary with ecological constraints. Behavior analysis, in contrast, seeks general principles that transcend specific situations. To the extent that search is successful, the concept of heuristics is unlikely to play a significant role in the analysis of animal behavior.     

Do evolutionary processes minimize expected losses?

Evolution by variation and natural selection is often viewed as an optimization process that favors those organisms which are best adapted to their environment. This leaves open the issue of how to measure adaptation and what criterion is implied for optimization. This problem has been framed and analysed mathematically under the assumption that individuals compete to minimize expected losses across a series of decisions (e.g. choice of behavior), where each decision offers a stochastic payoff. But the fact that a particular analysis is tractable for a specified criterion does not imply the fidelity of that criterion. Computer simulations involving a version of the k -armed bandit problem can address the veracity of the hypothesis that individuals are selected to minimize expected losses. The results offered here do not support this hypothesis.     

Lotka–Volterra approximations for evolutionary trait-substitution processes

Journal of Mathematical Biology - A set of axioms is formulated characterizing ecologically plausible community dynamics. Using these axioms, it is proved that the transients following an invasion...     

Follicle cell processes: a shark thing?

Follicle cell processes (FCP) are identified in two species of carcharhinid shark (Selachii) but are absent in the little skate Leucoraja erinacea (Batoidea). This suggests that FCPs are either a unique structure that evolved in selachians or were lost by the batoids after their divergence, some 280 mya . The presence of FCPs in the selachians would be consistent with the evolution of large oocytes in this group of animals.     

What can observational data reveal about metacommunity processes?

A key challenge for community ecology is to understand to what extent observational data can be used to infer the underlying community assembly processes. As different processes can lead to similar or even identical patterns, statistical analyses of non‐manipulative observational data never yield undisputable causal inference on the underlying processes. Still, most empirical studies in community ecology are based on observational data, and hence understanding under which circumstances such data can shed light on assembly processes is a central concern for community ecologists. We simulated a spatial agent‐based model that generates variation in metacommunity dynamics across multiple axes, including the four classic metacommunity paradigms as special cases. We further simulated a virtual ecologist who analysed snapshot data sampled from the simulations using eighteen output metrics derived from beta‐diversity and habitat variation indices, variation partitioning and joint species distribution modelling. Our results indicated two main axes of variation in the output metrics. The first axis of variation described whether the landscape has patchy or continuous variation, and thus was essentially independent of the properties of the species community. The second axis of variation related to the level of predictability of the metacommunity. The most predictable communities were niche‐based metacommunities inhabiting static landscapes with marked environmental heterogeneity, such as metacommunities following the species sorting paradigm or the mass effects paradigm. The most unpredictable communities were neutral‐based metacommunities inhabiting dynamics landscapes with little spatial heterogeneity, such as metacommunities following the neutral or patch sorting paradigms. The output metrics from joint species distribution modelling yielded generally the highest resolution to disentangle among the simulated scenarios. Yet, the different types of statistical approaches utilized in this study carried complementary information, and thus our results suggest that the most comprehensive evaluation of metacommunity structure can be obtained by combining them.     

Ecological processes, remediation and regulation of contaminated soils

Land is used for agricultural production, industrial development, urban construction, and environmental beautiflcation, thus soil environment is an important component of living ecosystems for human survival. The contamination of soil ecosystems is harmful to human sustainability by inducing ground-water, surface water, and air pollution, which result from leaching, transportation and volatilization of soil pollutants. In addition, soil contamination results in a reduction in crop production, poor quality of agricultural products, and the spoilage of human health through consumption of these low-quality foods. Some new-type diseases such as SARS, AIDS, and en-dotoxin shock can abruptly take place on a large scale due to soil contamination under certain conditions.     

Glycerol: a neglected variable in metabolic processes?

Glycerol is a small and simple molecule produced in the breakdown of glucose, proteins, pyruvate, triacylglycerols and other glycerolipid, as well as release from dietary fats. An increasing number of observations show that glycerol is probably involved in a surprising variety of physiopathologic mechanisms. Glycerol has long been known to play fundamental roles in several vital physiological processes, in prokaryotes and eukaryotes, and is an important intermediate of energy metabolism. Despite some differences in the details of their operation, many of these mechanisms have been preserved throughout evolution, demonstrating their fundamental importance. In particular, glycerol can control osmotic activity and crystal formation and then act as a cryoprotective agent. Furthermore, its properties make it useful in numerous industrial, therapeutic and diagnostic applications. Few studies have focussed directly on glycerol, however, and while its metabolism is increasingly well documented, much of the details remain unknown. Considering the importance of glycerol in multiple vital physiological processes, its study could help unlock important physiopathological mechanisms.     

How many processes are responsible for phenotypic evolution?

SUMMARY In addressing phenotypic evolution, this article reconsiders natural selection, random drift, developmental constraints, and internal selection in the new extended context of evolutionary developmental biology. The change of perspective from the "evolution of phenotypes" toward an "evolution of ontogenies" (evo-devo perspective) affects the reciprocal relationships among these different processes. Random drift and natural selection are sibling processes: two forms of post-productional sorting among alternative developmental trajectories, the former random, the latter nonrandom. Developmental constraint is a compound concept; it contains even some forms of natural ("external" and "internal") selection. A narrower definition ("reproductive constraints") is proposed. Internal selection is not a selection caused by an internal agent. It is a form of environment-independent selection depending on the level of the organism's internal developmental or functional coordination. Selection and constraints are the main deterministic processes in phenotypic evolution but they are not opposing forces. Indeed, they are continuously interacting processes of evolutionary change, but with different roles that should not be confused.     

May random processes explain mating success in leks?

The object of this paper is to verify whether in specific cases the variance of mating success among lekking males may be due exclusively to a random mechanism, as opposed to the adaptive mechanisms of mate choice which are usually postulated in the literature in the framework of sexual selection theory. In fact, some studies attempted to compare observed distributions of male mating success with a Poisson ‘null’ distribution based on the conjecture of random mating; the conjecture is usually rejected. In this paper we construct a plausible model (the ‘null’ hypothesis) for a strictly random non-adaptive pattern of social behaviour of lekking males and females and we perform several simulations for reasonable choices of parameter values. It should be observed that some of the simulations based on our random model lead to a distribution of male mating success which is Poisson-like. However, contrary to predictions, in several simulations a random process of mate choice lead to non-Poissonian distributions. Accordingly, the fact that, when performing a statistical test on several sets of field data, we find both cases which are in agreement with Poisson distribution, or a normal one, and cases which are not, does not allow us to reject the assumption of random male reproductive success. Thus it is legitimate to conjecture that in many cases the inter-individual variability of male mating success might indeed be determined by random processes. If this conjecture were to be confirmed by further studies, the actual significance of sexual selection in the evolution of lekking species should be reassessed, and a novel approach in the analysis of field data would be called for.     

Algal biotechnology products and processes — matching science and economics

Several microalgae, such as species ofChlorella, Spirulina andDunaliella, are grown commercially and algal products such as -carotene and phycocyanin are available. The main focus of algal biotechnology continues to be on high value fine chemicals and on algae for use as aquaculture feeds. This paper provides the outline for a rational approach in evaluating which algae and which algal products are the most likely to be commercially viable. This approach involves some simple market analysis followed by economic modelling of the whole production process. It also permits an evaluation of which steps in the production process have the greatest effect on the final production cost of the alga or algal product, thus providing a guide as to what area the research and development effort should be directed to. An example of this approach is presented and compared with other models. The base model used here gives a production cost of microalgal biomass at about AS 14 to 15 kg^–1, excluding the costs of further processing, packaging and marketing. The model also shows that some of the key factors in microalgal production are productivity, labor costs and harvesting costs. Given the existing technology, high value products such as carotenoids and algal biomass for aquaculture feeds have the greatest commercial potential in the short term.This paper was presented at the Symposium on Applied Phycology at the Fourth International Phycological Congress, Duke University.     

What physiological processes permit insects to eat Eucalyptus leaves?

Many species of insects eat Eucalyptus foliage despite its relatively low nutritional value and the many plant secondary metabolites (PSMs) present, for example, terpenes, phenols and formylated phloroglucinols (FPGs). Formylated phloroglucinols are a new class of PSMs that act as antifeedants for possums and koalas. What physiological processes are present that permit insects to eat eucalypt foliage and how do PSMs influence insect feeding or digestion? Some trees seem to be repeatedly infested with eucalypt‐feeding insects, possibly as a result of previous chemosensory cues remaining from parental selection of a plant. Avoidance or storage of PSMs permit jarrah leafminers (Perthida glyphopa) and sawflies (Perga sp.) to consume eucalypt foliage without dealing with the majority of these compounds. Some PSMs can be metabolized by polysubstrate membrane oxidases as found in caterpillars or sawflies that feed on eucalypts. High midgut pH may be advantageous for nutrient extraction and PSM metabolism, and midgut pH ranges between 8.5 and 8.9 for caterpillars of Hyalarcta huebneri. Plant secondary metabolites may not be absorbed as a result of the combined presence of the peritrophic matrix and endogenous surfactants. Excretion of PSMs can be as metabolites or intact compounds. Both putative metabolites and sideroxylonal‐A, an FPG, are present in the faeces of larvae of the case moth, H. huebneri. The presence of sideroxylonal‐A in the food had an effect on the presence of 5‐hydroxytryptamine (5HT) in the central nervous system of caterpillars, as larvae fed leaves with a high concentration of sideroxylonal‐A had relatively more 5HT in the brain and central nervous system ganglia than larvae fed leaves containing a low concentration. Further work is necessary to clarify how PSMs are handled by eucalypt‐feeding insects and what effect FPGs have on feeding and digestion.     

Is Ap4A involved in DNA repair processes?

Hepatoma tissue culture (HTC) cells were incubated in the presence of the alkylating agent N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) to study the variations in the bisnucleosides polyphosphates (Ap4X) pool size. A transient but sensitive accumulation of these compounds is observed; if 3-aminobenzamide (3AB) which is a potent inhibitor of the ADP-ribosyltransferase (ADPRT) is added after the MNNG treatment, a more pronounced and persistent accumulation of Ap4X can be seen. A moderate heat-shock (30 min at 43 degrees C) results also in a small accumulation of Ap4X but the shape of the accumulation curve is quite different and the increase of the Ap4X pool is not sensitive to the presence of 3AB. However, both MNNG treatment and hyperthermia cause a marked inhibition of protein synthesis. On the other hand, the ADPRT activity is enhanced in the presence of MNNG whereas hyperthermia has little or a slightly inhibitory effect on this activity. These results suggest that MNNG treatment triggers an Ap4X accumulation in eukaryotic cells different from that observed after heat-shock and it seems likely that these compounds are involved in the DNA excision repair system in which the ADPRT enzyme is also implicated.     

Water deficit and growth. Co-ordinating processes without an orchestrator?

Water deficit affects plant growth via reduced carbon accumulation, cell number and tissue expansion. We review the ways in which these processes are co-ordinated. Tissue expansion and its sensitivity to water deficit may be the most crucial process, involving tight co-ordination between the mechanisms which govern cell wall mechanical properties and plant hydraulics. The analyses of sensitivities, time constants and genetic correlations suggest that tissue expansion is loosely co-ordinated with cell division and carbon accumulation which may have limited direct effects on growth under water deficit. We therefore argue for essentially uncoupled mechanisms with feedbacks between them, rather than for a co-ordinated re-programming of all processes. Consequences on plant modelling and plant breeding in dry environment are discussed.     

Cellular processes in the amygdala: gates to emotional memory?

The amygdala is considered a core structure of the so-called limbic system and has been implicated in a variety of functions, including emotional interpretation of sensory information, emotional arousal, emotional memory, fear and anxiety, and related clinical disorders. Despite the clinical and functional importance of the amygdala, it is only recently that some general principles of intra-amygdaloid mechanisms of signal processing that are relevant for fear behavior and memory have emerged from behavioral, anatomical, electrophysiological, and neurochemical studies performed in the amygdala of various mammalian species in vivo, in situ and in vitro.     

Are auxin and calcium movements in corn coleoptiles linked processes?

In this paper we present evidence for a tight linkage of calcium and auxin fluxes in corn coleoptile tissue. Imposed lateral gradients of auxin concentration induce a movement of calcium ions to the side of lower auxin concentration in the tissue. Imposing a lateral gradient of calcium concentration in turn leads to a movement of auxin to the side of lower calcium concentration. Whether these fluxes are using symplastic or apoplastic pathways or are transcellular cannot be decided from the results.Countercurrent fluxes of calcium ions and auxin could be demonstrated in polar transport experiments. This might be a further indication of a complex carrier system in the plasma membrane extruding auxin out of the cell with a concomitant calcium influx from the cell wall space into the cytoplasm.     

The ontology of organisms: Mechanistic modules or patterned processes?

Though the realm of biology has long been under the philosophical rule of the mechanistic magisterium, recent years have seen a surprisingly steady rise in the usurping prowess of process ontology. According to its proponents, theoretical advances in the contemporary science of evo-devo have afforded that ontology a particularly powerful claim to the throne: in that increasingly empirically confirmed discipline, emergently autonomous, higher-order entities are the reigning explanantia. If we are to accept the election of evo-devo as our best conceptualisation of the biological realm with metaphysical rigour, must we depose our mechanistic ontology for failing to properly “carve at the joints” of organisms? In this paper, I challenge the legitimacy of that claim: not only can the theoretical benefits offered by a process ontology be had without it, they cannot be sufficiently grounded without the metaphysical underpinning of the very mechanisms which processes purport to replace. The biological realm, I argue, remains one best understood as under the governance of mechanistic principles.     

Which evolutionary processes influence natural genetic variation for phenotypic traits?

Although many studies provide examples of evolutionary processes such as adaptive evolution, balancing selection, deleterious variation and genetic drift, the relative importance of these selective and stochastic processes for phenotypic variation within and among populations is unclear. Theoretical and empirical studies from humans as well as natural animal and plant populations have made progress in examining the role of these evolutionary forces within species. Tentative generalizations about evolutionary processes across species are beginning to emerge, as well as contrasting patterns that characterize different groups of organisms. Furthermore, recent technical advances now allow the combination of ecological measurements of selection in natural environments with population genetic analysis of cloned QTLs, promising advances in identifying the evolutionary processes that influence natural genetic variation.     

Do landscape processes predict phylogeographic patterns in the wood frog?

Understanding factors that influence population connectivity and the spatial distribution of genetic variation is a major goal in molecular ecology. Improvements in the availability of high-resolution geographic data have made it increasingly possible to quantify the effects of landscape features on dispersal and genetic structure. However, most studies examining such landscape effects have been conducted at very fine (e.g. landscape genetics) or broad (e.g. phylogeography) spatial scales. Thus, the extent to which processes operating at fine spatial scales are linked to patterns at larger scales remains unclear. Here, we test whether factors impacting wood frog dispersal at fine spatial scales are correlated with genetic structure at regional scales. Using recently developed methods borrowed from electrical circuit theory, we generated landscape resistance matrices among wood frog populations in eastern North America based on slope, a wetness index, land cover and absolute barriers to wood frog dispersal. We then determined whether these matrices are correlated with genetic structure based on six microsatellite markers and whether such correlations outperform a landscape-free model of isolation by resistance. We observed significant genetic structure at regional spatial scales. However, topography and landscape variables associated with the intervening habitat between sites provide little explanation for patterns of genetic structure. Instead, absolute dispersal barriers appear to be the best predictor of regional genetic structure in this species. Our results suggest that landscape variables that influence dispersal, microhabitat selection and population structure at fine spatial scales do not necessarily explain patterns of genetic structure at broader scales.