Evolution of specialization in a spatially continuous environment

We study the evolution of specialization in a spatially continuous (one‐dimensional) environment divided into two habitats; we use a general trade‐off function relating fitnesses in the two habitats and illustrate our results with two classical trade‐off functions. We show that the population can either reach an intermediate value of the trait and be moderately adapted to both habitats (1 generalist), or split into two locally adapted subpopulations (2 specialists). We recover the qualitative results obtained with simpler metapopulation models with island migration: the evolutionary outcome depends on the concavity of the trade‐off, on the proportion of each habitat and on migration. Our quantitative prediction on migration, however, depends on isolation by distance. Our spatially explicit model may thus be particularly useful to describe the evolutionary dynamics of specialization in, perhaps, more realistic ecological scenarios.     

Fungal spores: dormancy, germination, chemical composition, and role in biotechnology (review)

This review is focused on one of the stages of ontogenesis distinctive by its particular tolerance to the action of unfavorable factors and ability to retain the genomic material for a long period of time, i.e., fungal spores. The major part is devoted to the characterization of the specific stage typical for spores, which is called dormancy. Data are presented characterizing the carbohydrate and lipid composition of spores, with special attention being paid to the role of carbohydrate protectors, in particular, trehalose and mannite, as well as to the role of rafts in the process of sporogenesis. The role of special compounds called autoinhibitors and autostimulators in the process of exit from dormancy is discussed. The final section deals with the role of spore seeding material in biotechnological processes. Data on the correlation between the chemical composition of spores, their ability to remain dormant, and the germination process are considered. Special biotechnological approaches are presented for the first; they allow for the preservation of the germinating ability of spores, intensification of sporogenesis, changes in the ratio of final fermentation products, and an increase in their yield.     

Cheap and Long‐Life Reusable Polymer for Asymmetric Organozinc Catalysis Based on Camphor‐Derived Hydroxyamides

Polystyrene grafted with a chiral zinc‐complexing camphor‐derived N,N‐disubstituted hydroxyamide is proposed as a new type of functional polymer of high reusability for the development of sustainable organozinc‐catalyzed asymmetric reactions. The main goal of this new functional polymer is the ease of the hydroxyamide‐moiety preparation (cheap chiral ligand obtained straightforwardly from an enantiopure starting material coming from the chiral pool), as well as its chemical robustness when compared with other related zinc‐complexing functional groups. The latter allows the polymer to be active after multiple applications, without significant loss of its catalytic activity. This fact is exemplified by the design and preparation of a polymer functionalized with a bis(hydroxyamide) proved previously as active in the homogeneous enantioselective addition of diethylzinc to aldehydes. The result is a cheap functional polymer with a very high reusability (the enantioselectivity and chemical yield are maintained practically constant after 20 applications). Additionally, a methodology for the multicycle use of these functional polymers is presented. Chirality, 2012. © 2012 Wiley Periodicals, Inc.     

Biophysical methods for biochip analysis. Use of wide field digital fluorescent microscopy

This paper discusses an issue on the development of biophysical methods for biochip analysis. A scheme and construction of a biochip analyzer based on wide-field digital fluorescence microscopy are described. The analyzer is designed to register images of biological microchips labeled with fluorescent dyes. The device developed is useful for high-sensitive throughput recording analyses by biochips after interaction of immobilized probes with fluorescently labeled sample molecules as well as it provides the higher rate of the analysis compared to laser scanning devices. With this analyzer a scope where biological microchips can be applied becomes wider, the development of new protocols of the analyses is possible and standard analyses run faster with the use of biochips, the expenses for the analysis performance can be reduced.     

The bite force of the largest fossil rodent (Hystricognathi,Caviomorpha, Dinomyidae)

Blanco R.E., Rinderknecht, A. & Lecuona, G. 2011: The bite force of the largest fossil rodent (Hystricognathi, Caviomorpha, Dinomyidae). Lethaia, Vol. 45, pp. 157–163. An exceptionally well‐preserved skull of the largest fossil rodent Josephoartigasia monesi allows the first analysis of the bite mechanics of this group of South American giant rodents. In this study, we reconstructed the main anatomical features of the skull of this Pliocene rodent, relating them to the bite force at incisors. Bite force was estimated using three different techniques. Two methods suggest that bite forces at incisors of around 1000 N were possible for these mammals. However, the incisors seem to be stronger than expected for this bite force implying that the bite forces may have been greater than 3000 N. We consider three hypotheses: allometric effects, teeth digging or defence against predators, to explain our results. □Bite force, Dinomyidae, incisors, largest rodent, Pliocene.     

Dynamics of induced EEG in the intervals between a target and trigger stimuli during formation of a set to emotionally negative facial expression

A visual set was used as a model to study the influence of the increased memory load on the recognition of facial expression in 70 healthy adults. In order to additionally load the working memory, we lengthened the time gap between target (faces) and trigger stimuli. Such a lengthening from 1 to 8 s resulted in an increase of set plasticity (fewer mistakes in facial expression recognition). It also led to a reduction of the reaction time and less number of contrast illusions in recognition. We analyzed theta- and alpha-band EEG changes during individual segments of the time gap and suggested that repeated trials with a certain fixed interval between stimuli formed an inner representation of the interval duration. This inner representation up-regulates the visual attention in case of anticipation of a relevant event (stimulus) and down-regulates the attention when the stimulus is not expected. In case of the plastic set, the induced EEG synchronization in the alpha band is stronger in the trials with correct recognition in the middle of the inter-stimulus time gap. We think this synchronization reflects the action of the top-down cognitive control that suppresses the influence of irrelevant information on the brain activity. Theta-band dynamics in the inter-stimulus time gap can be associated with the emotional strain caused by the fact that a person had to retain in memory (for several seconds) the result of facial expression recognition.     

Fungi are involved in the effects of litter mixtures on consumption by shredders

1. Decomposition of litter mixtures in both terrestrial and aquatic ecosystems often shows non‐additive diversity effects on decomposition rate, generally interpreted in streams as a result of the feeding activity of macroinvertebrates. The extent to which fungal assemblages on mixed litter may influence consumption by macroinvertebrates remains unknown. 2. We assessed the effect of litter mixing on all possible three‐species combinations drawn from four tree species (Alnus glutinosa, Betula pendula, Juglans regia and Quercus robur) on both fungal assemblages and the rate of litter consumption by a common shredder, Gammarus fossarum. After a 9‐week inoculation in a stream, batches of leaf discs were taken from all leaf species within litter mixture combinations. Ergosterol, an indicator of fungal biomass, and the composition of fungal assemblages, assessed from the conidia released, were determined, and incubated litter offered to G. fossarum in a laboratory‐feeding experiment. 3. Mixing leaf litter species enhanced both the Simpson’s index of the fungal assemblage and the consumption of litter by G. fossarum, but had no clear effect on mycelial biomass. Specifically, consumption rates of J. regia were consistently higher for mixed‐species litter packs than for single‐species litter. In contrast, the consumption rates of B. pendula were not affected by litter mixing, because of the occurrence of both positive and negative litter‐mixing effects in different litter species combinations that counteracted each other. 4. In some litter combinations, the greater development of some fungal species (e.g. Clavariopsis aquatica) as shown by higher sporulation rates coincided with increased leaf consumption, which may have resulted from feeding preferences by G. fossarum for these fungi. 5. Where litter mixture effects on decomposition rate are mediated via shredder feeding, this could be due to indirect effects of the fungal assemblage.     

Central but not systemic administration of ghrelin induces wakefulness in mice

Ghrelin is a brain-gut peptide hormone widely known for its orexigenic and growth hormone-releasing activities. Findings from our and other laboratories indicate a role of ghrelin in sleep regulation. The effects of exogenous ghrelin on sleep-wake activity in mice are, however, unknown. The aim of the present study was to determine the sleep-modulating effects of ghrelin after central and systemic administrations in mice. Sleep-wake activity after intracerebroventricular (i.c.v.) administration of 0.2, 1 and 5 μg ghrelin and intraperitoneal injections of 40, 100, and 400 μg/kg ghrelin prior to light onset were determined in C57BL/6 mice. In addition, body temperature, motor activity and 1-hour food intake was measured after the systemic injections. Sleep effects of systemic ghrelin (40 and 400 μg/kg) injected before dark onset were also determined. I.c.v. injection of ghrelin increased wakefulness and suppressed non-rapid-eye-movement sleep and electroencephalographic slow-wave activity in the first hour after injections. Rapid-eye-movement sleep was decreased for 2-4 hours after each dose of ghrelin. Sytemic administration of ghrelin did not induce changes in sleep-wake activity in mice at dark or light onset. Motor activity and body temperature remained unaltered and food intake was significantly increased after systemic injections of ghrelin given prior the light period. These findings indicate that the activation of central, but not peripheral, ghrelin-sensitive mechanisms elicits arousal in mice. The results are consistent with the hypothesis that the activation of the hypothalamic neuronal circuit formed by ghrelin, orexin, and neuropeptide Y neurons triggers behavioral sequence characterized by increased wakefulness, motor activity and feeding in nocturnal rodents.     

Predicting the environmental niche of the genus Phymaturus: Are palluma and patagonicus groups ecologically differentiated?

The genus Phymaturus (Reptilia: Liolaemidae) is distributed in the mountains and rocky plateaux of Argentina and Chile and comprises two groups of species, palluma and patagonicus. The two lineages have diverged early in the evolution of the genus and up to today, there is very little geographical overlap between them. We worked with records of localities from the literature, herpetological collections and field data to evaluate habitat suitability of the genus Phymaturus. We used 11 environmental variables to develop environmental niche models (ENMs) for each group within the genus using the Maxent software, and to determine those variables that best explain the distribution of each group. We also estimated measures of niche similarity using ENMTools to determine whether niche differentiation is real or apparent. The geographical overlap between the groups was very low considering the large geographical range of the genus. Some variables, such as mean annual temperature, soil type and bare soil cover, have a high contribution to the models for both groups. The current niche overlap between Phymaturus groups indicates that the environmental niches of the palluma and patagonicus groups are not equivalent. Based on background analysis, we cannot reject the hypothesis that similarity (or divergence) between groups of Phymaturus is no more than expected based on the availability of habitat. The results of this study are a first approximation to the knowledge of the environmental variables associated with the palluma and patagonicus groups, and reveal that the ecological differences found between these groups are more likely due to habitat availability in their respective regions than to differences in habitat preferences.