The formation of status hierarchies in leaderless groups

Two studies examined the link between social dominance and male waist-to-hip ratio (WHR). Groups of four men interacted in a leaderless group discussion. In both studies, men with higher WHRs (associated with current and long-term health status) were rated by other group members as behaving more leader-like when an observer was present, and rated themselves as being more assertive. In Study 2, men with higher WHRs were rated by independent observers as behaving more dominantly, but only when the evaluator was present. These results are discussed in terms of evolutionary models of health, attraction, and intrasexual competition.     

Correlation of space-time ranges in ecological hierarchies of various nature

Relations between characteristic scales of time and space are analyzed for the hierarchical systems of a various nature. The available data fit well to the power relation: [T] = a[L]b, where [T] and [L] are characteristic ranges of time and space, b--scaling exponent, a--conversion coefficient. The spatio-temporal scales of ocean physical and biological (pelagic) processes are closely overlapped. Contrastingly, the scale for terrestrial and benthic ecosystems and their environments differ noticeably. For terrestrial and benthic ecological systems, and also for atmospheric phenomena, the b values significantly less than 1, that indicates a significant coherence of structure-generating processes integrating lower-level hierarchical units to a higher-level entity. For geomorphological structures, both terrestrial and oceanic, the scaling parameters has appeared close to 1 (a "direct transfer" type of generating processes). For plankton systems, which are related with water masses, the b values vary from 1 (processes of direct transfer) up to 2 (random dispersal or diffusion processes). The author attributes this difference to the principle distinctions in dynamic properties of the physical environments for terrestrial (and probably, benthic) and plankton organisms. Finally, for the units (structures or processes) of one and the same organization level, scaling exponents are significantly higher and close to 2 (diffusive dynamics) or more (rigid spatial limitation). Thus, the development of many ecological structures looks dynamically like diffusion or gradual growth, but their putting in the higher-level order (integrity) is a qualitative leap forward and demands appropriate cooperative organizational processes.     

Dominance hierarchies of male green swordtails (Xiphophorus helleri) in nature

Swordtail males formed dominance hierarchies at shallow sites in creeks or streams and invested much time in maintaining a high rank-order position (mean 11·1 chases per 5 min).     

A new perspective on size hierarchies in nature: patterns, causes, and consequences

Many plant and animal aggregations have size hierarchies within which a variety of sizes of individuals, from large to small, can be found. Size hierarchies are thought to indicate the existence of competition amongst individuals within the aggregation, but determining their exact cause is difficult. The key to understanding size hierarchies lies in first quantifying the pattern of size and growth of individuals. We conducted a quantitative investigation of pattern in the size hierarchy of the clown anemonefish Amphiprion percula, in Madang Lagoon, Papua New Guinea. Here, groups of A. percula occupy sea anemones (Heteractis magnifica) that provide protection from predators. Within each anemone there is a single group composed of a breeding pair and zero to four non-breeders. Within each group there is a single size hierarchy; the female is largest (rank 1), the male is second largest (rank 2), and the non-breeders get progressively smaller (ranks 3–6). We demonstrate that individuals adjacent in rank are separated by body size ratios whose distribution is significantly different from the distribution expected under a null model—the growth of individuals is regulated such that each dominant ends up being about 1.26 times the size of its immediate subordinate. We show that it is decisions about growth at the individual level that generate the size hierarchy at the group level, and thereby determine maximum group size and population size. This study provides a new perspective on the pattern, causes and consequences of size hierarchies.     

View from the top: hierarchies and reverse hierarchies in the visual system

We propose that explicit vision advances in reverse hierarchical direction, as shown for perceptual learning. Processing along the feedforward hierarchy of areas, leading to increasingly complex representations, is automatic and implicit, while conscious perception begins at the hierarchy's top, gradually returning downward as needed. Thus, our initial conscious percept--vision at a glance--matches a high-level, generalized, categorical scene interpretation, identifying "forest before trees." For later vision with scrutiny, reverse hierarchy routines focus attention to specific, active, low-level units, incorporating into conscious perception detailed information available there. Reverse Hierarchy Theory dissociates between early explicit perception and implicit low-level vision, explaining a variety of phenomena. Feature search "pop-out" is attributed to high areas, where large receptive fields underlie spread attention detecting categorical differences. Search for conjunctions or fine discriminations depends on reentry to low-level specific receptive fields using serial focused attention, consistent with recently reported primary visual cortex effects.     

Minor groove functional groups are critical for the B-form conformation of duplex DNA

Two analogue bases are described: 3-deazaadenine is a derivative of adenine from which N3 has been deleted and 3-methyl-2-pyridone is a C-nucleoside that mimics thymine but lacks the O2 carbonyl. The dc(3)A-dm(3)2P base pair is similar to dA-dT but eliminates the polar functional groups in the minor groove. The presence of this base pair in dA-dT rich sequences results in destabilized duplexes or conformational preferences for monomolecular hairpins rather than bimolecular duplexes. When present in dG-dC rich sequences, no significant differences in helix stability are observed. These differences are explained on the basis of hydration effects, most notably, the elimination of the minor groove spine of hydration normally present in dA-dT rich sequences. CD spectra suggest that sequences with a fully modified core (four analogue base pairs) are more A-like helices than B-like helices. Sequences containing two analogue base pairs can be transformed to A-like helices under conditions of high salt, or 65% trifluoroethanol. These conformational changes are also explained in terms of a loss of hydration in the minor groove that normally stabilizes the B-form conformation. In the absence of such hydration, the helices are conformationally mobile and adopt a more A-like helix form.     

Seagrass complexity hierarchies: Influence on fish groups around the coast of Jersey (English Channel)

Recent research has identified a need for seagrass habitat management plans to be based on landscape-level approaches as they offer a more appropriate scale for large mobile fauna than smaller scales. Also, conservation decisions are more likely to be a choice between different seagrass beds rather than parts of individual beds. The present study examined the spatial utilisation of subtidal seagrass beds by fish around the coast of Jersey, English Channel (49°N 02°W) with the aim of identifying influential scales of complexity. A hierarchical-scale of landscape configuration and habitat characteristics was measured for eight seagrass beds using aerial photographic analysis (e.g. core area, contiguity and other landscape metrics), digital echo-sounder data (e.g. depth, canopy height) and diver surveys (e.g. epiphyte load). The contributions of these variables as predictors of functional fish groups were explored using multiple linear regression models. Results indicated that more fragmented seagrass beds supported lower numbers of fish species than more homogenous seagrass landscapes (squared semi-partial correlation coefficient, sr² = − 0.3). Densities of juveniles of larger fish species showed a negative relationship with increased fragmentation of the seagrass (sr² = − 0.34). At smaller scales of structural complexity the densities of cryptic fish were related positively to canopy height (sr² = 0.46). At night, fewer patterns could be explained by the independent variables in the model, which was attributed to the greater movement of fish between the seagrass and adjacent habitats to forage, and a breakdown in the association with seagrass habitat as a refuge from predation.     

Effects of the minor groove pyrimidine nucleobase functional groups on the stability of duplex DNA: the impact of uncompensated minor groove amino groups

DNA sequences containing four types of analog nucleosides are described. All four are pyridine derivatives constructed as C-nucleosides so that they mimic the pyrimidine derivatives 2'-deoxyuridine, thymidine or 2'-deoxycytidine, but in all cases the analogs lack the corresponding O2-carbonyls that in duplex DNA are located in the minor groove. In place of the O2-carbonyl is a hydrogen atom, a polar fluorine atom, or a nonpolar methyl group. The described C-nucleosides have native-like bidentate Watson-Crick hydrogen-bonding faces and can form essentially normal W-C base pairs of varying stability with A or G. In each modified base pair, two inter-residue hydrogen bonds should be present. In spite of a common number of interstrand hydrogen bonds, the thermodynamic stabilities of the prepared duplexes, each containing two analog base pairs, vary dramatically. Most notably, base pairs containing uncompensated purine amino groups (those lacking a hydrogen-bonding partner) in the minor groove exhibit the most dramatic reductions in thermodynamic stability. Removal of such uncompensated amino groups results in increased duplex stability. Base pairs containing fluorine in the minor groove positioned adjacent to an amino group seem to enhance duplex stability marginally (relative to --H or --CH(3)), but there is little evidence to suggest that fluorine is an effective hydrogen-bonding partner in these systems. The presence of minor groove methyl groups results in the least stable duplexes in each series of sequences.     

Detection of Mycobacterium tuberculosis genotypic groups by a duplex real-time PCR targeting the katG and gyrA genes

A duplex real-time PCR assay was developed for the assignment of Mycobacterium tuberculosis isolates to the three genotypic groups based on the katG463/gyrA95 polymorphism. The assay was as sensitive and specific as nucleotide sequencing and proved also able to detect unambiguously the isolate genotype in clinical specimens.     

Reverse hierarchies and sensory learning

Revealing the relationships between perceptual representations in the brain and mechanisms of adult perceptual learning is of great importance, potentially leading to significantly improved training techniques both for improving skills in the general population and for ameliorating deficits in special populations. In this review, we summarize the essentials of reverse hierarchy theory for perceptual learning in the visual and auditory modalities and describe the theory's implications for designing improved training procedures, for a variety of goals and populations.     

The nature of functional groups regulating the catalytic activity of prostaglandin endoperoxide synthetase

The influence of some reagents modifying NH2-, SH-groups or imidazole moiety, on the prostaglandin endoperoxide synthetase activity was studied. Acetaldehyde, pyridoxal phosphate, dithiobis (nitrobenzoic) acid and iodoacetamide were found not to affect the enzyme activity. The activity was abolished as a result of the interaction with p-chloromercuribenzoic acid and diethyl pyrocarbonate. The hemin completely protected the apo-enzyme against the inactivation with diethyl pyrocarbonate. The assumption about the presence of imidazole moiety in the active site of the enzyme was made.     

Causal structure and hierarchies of models

Economics prefers complete explanations: general over partial equilibrium, microfoundational over aggregate. Similarly, probabilistic accounts of causation frequently prefer greater detail to less as in typical resolutions of Simpson’s paradox. Strategies of causal refinement equally aim to distinguish direct from indirect causes. Yet, there are countervailing practices in economics. Representative-agent models aim to capture economic motivation but not to reduce the level of aggregation. Small structural vector-autoregression and dynamic stochastic general-equilibrium models are practically preferred to larger ones. The distinction between exogenous and endogenous variables suggests partitioning the world into distinct subsystems. The tension in these practices is addressed within a structural account of causation inspired by the work of Herbert Simon’s, which defines cause with reference to complete systems adapted to deal with incomplete systems and piecemeal evidence. The focus is on understanding the constraints that a structural account of causation places on the freedom to model complex or lower-order systems as simpler or higher-order systems and on to what degree piecemeal evidence can be incorporated into a structural account.     

Chemical nature of functional cholinoreceptor groups of Lymnaea stagnalis neurons.

1. The effect of pH and the influence of some alkylating agents on the properties of the cholinoreceptive membrane of the mollusc Lymnaea stagnalis neurons have been studied using the microelectrode voltage clamp technique. 2. Lowering below 7.5 of the pH of the bathing solution had to decrease the neuronal responses to ACh. A twofold decrease in cholinoreceptive membrane conductivity was found at the pH 6.7 +/- 0.1 (n=10). Raising the pH to 10.6 did not influence the response to ACh. 3. The pH effect is not associated with the influence on the properties of ionic channels but appears to be due to reduction of a functional group at the ChR active site by proton. 4. No highly reactive SH-groups were found at the ChR active site, but some functionally important carboxyl groups have been discovered. 5. The effect of pH is probably connected with reduction of --COO-- or imidazol group with a pKa of about 6.7.     

Multiple breeding females in free-ranging groups ofCallithrix jacchus

We present observations on the breeding patterns in a free-ranging population of common marmosets, Callithrix jacchusWe found evidence of the simultaneous presence of two reproductively active females in all three monitored groups. We recorded at least one full reproductive cycle (conception-birth) for two females in each group, but other adult females did not breed. An overview of data from other callitrichid field studies indicates that the observed pattern may be an additional characteristic of the flexibility of the social organization of common marmosets. Comparisons with data from other sites where callithrixhas been studied indicate that the presence of a second breeding female in a group may be related to high population density, though the underlying mechanisms remain unclear.     

Multiple groups of novel retroviral genomes in pigs and related species

In view of the concern over potential infection hazards in the use of porcine tissues and organs for xenotransplantation to humans, we investigated the diversity of porcine endogenous retrovirus (PERV) genomes in the DNA of domestic pigs and related species. In addition to the three known envelope subgroups of infectious gamma retroviruses (PERV-A, -B, and -C), classed together here as PERV group gamma 1, four novel groups of gamma retrovirus (gamma 2 to gamma 5) and four novel groups of beta retrovirus (beta 1 to beta 4) genomes were detected in pig DNA using generic and specific PCR primers. PCR quantification indicated that the retroviral genome copy number in the Landrace x Duroc F(1) hybrid pig ranged from 2 (beta 2 and gamma 5) to approximately 50 (gamma 1). The gamma 1, gamma 2, and beta 4 genomes were transcribed into RNA in adult kidney tissue. Apart from gamma 1, the retroviral genomes are not known to be infectious, and sequencing of a small number of amplified genome fragments revealed stop codons in putative open reading frames in several cases. Analysis of DNA from wild boar and other species of Old World pigs (Suidae) and New World peccaries (Tayassuidae) showed that one retrovirus group, beta 2, was common to all species tested, while the others were present among all Old World species but absent from New World species. The PERV-C subgroup of gamma1 genomes segregated among domestic pigs and were absent from two African species (red river hog and warthog). Thus domestic swine and their phylogenetic relatives harbor multiple groups of hitherto undescribed PERV genomes.     

Winner and loser effects and the structure of dominance hierarchies

In the literature on dominance hierarchies, "winner" and "loser"effects usually are denned as an increased probability of winningat time T, bated on victories at time T-l, T-2, etc, and anincreased probability of losing at time T, based on losing atT-1, T-2, etc., respectively. Despite some early theoreticalwork on winner and loser effects, these factors and how theyaffect the structure of dominance hierarchies have not beenexamined in detail. I developed a computer simulation to examinewinner and loser effects when such effects are independent ofone another (as well as when they interact) and when combatantsassess each other's resource-holding power. When winner effectsalone were important, a hierarchy in which all individuals heldan unambiguous rank was found. When only loser effects wereimportant, a dear alpha individual always emerged, but the rankof others in the group was often unclear because of the scarcityof aggressive interactions. Increasing winner effects for agiven value of the loser effect increase the number of individualswith unambiguous positions in a hierarchy and the converse istrue for increasing the value of the loser effect for a givenwinner effect Although winner and loser effects have been documentedin a number of species, no study has documented both winnerand loser effects (using some controlled, pairwise testing system)and the detailed nature of behavioral interactions when individualsare in groups. I hope the results of this model will spur suchstudies in the future.