Are Archaea inherently less diverse than Bacteria in the same environments?

Like Bacteria, Archaea occur in a wide variety of environments, only some of which can be considered 'extreme'. We compare archaeal diversity, as represented by 173 16S rRNA gene libraries described in published reports, to bacterial diversity in 79 libraries from the same source environments. An objective assessment indicated that 114 archaeal libraries and 45 bacterial libraries were large enough to yield stable estimates of total phylotype richness. Archaeal libraries were seldom as large or diverse as bacterial libraries from the same environments. However, a relatively larger proportion of libraries were large enough to effectively capture rare as well as dominant phylotypes in archaeal communities. In contrast to bacterial libraries, the number of phylotypes did not correlate with library size; thus, 'larger' may not necessarily be 'better' for determining diversity in archaeal libraries. Differences in diversity suggest possible differences in ecological roles of Archaea and Bacteria; however, information is lacking on relative abundances and metabolic activities within the sampled communities, as well as the possible existence of microhabitats. The significance of phylogenetic diversity as opposed to functional diversity remains unclear, and should be a high priority for continuing research.     

Are bark beetle outbreaks less synchronous than forest Lepidoptera outbreaks?

Comparisons of intraspecific spatial synchrony across multiple epidemic insect species can be useful for generating hypotheses about major determinants of population patterns at larger scales. The present study compares patterns of spatial synchrony in outbreaks of six epidemic bark beetle species in North America and Europe. Spatial synchrony among populations of the Eurasian spruce bark beetle Ips typographus was significantly higher than for the other bark beetle species. The spatial synchrony observed in epidemic bark beetles was also compared with previously published patterns of synchrony in outbreaks of defoliating forest Lepidoptera, revealing a marked difference between these two major insect groups. The bark beetles exhibited a generally lower degree of spatial synchrony than the Lepidoptera, possibly because bark beetles are synchronized by different weather variables that are acting on a smaller scale than those affecting the Lepidoptera, or because inherent differences in their dynamics leads to more cyclic oscillations and more synchronous spatial dynamics in the Lepidoptera.     

Can antimicrobial peptides scavenge around a cell in less than a second?

Antimicrobial peptides, which play multiple host-defense roles, have garnered increased experimental focus because of their potential applications in the pharmaceutical and food production industries. While their mechanisms of action are richly debated, models that have been advanced share modes of peptide-lipid interactions that require peptide dynamics. Before the highly cooperative and specific events suggested in these models take place, peptides must undergo an important process of migration along the membrane surface and delivery from their site of binding on the membrane to the actual site of functional performance. This phenomenon, which contributes significantly to antimicrobial function, is poorly understood, largely due to a lack of experimental and computational tools needed to assess it. Here, we use ¹⁵N solid-state nuclear magnetic resonance to obtain molecular level data on the motions of piscidin's amphipathic helices on the surface of phospholipid bilayers. The studies presented here may help contribute to a better understanding of the speed at which the events that lead to antimicrobial response take place. Specifically, from the perspective of the kinetics of cellular processes, we discuss the possibility that piscidins and perhaps many other amphipathic antimicrobial peptides active on the membrane surface may represent a class of fast scavengers rather than static polypeptides attached to the water-lipid interface.     

Taxonomic distinctness along nutrient gradients: More diverse,less diverse or not different from random?

Taxonomic distinctness indices are a family of anthropogenic stress indicators that have been used widely in marine ecosystems; however, their utility in freshwater ecosystems is still unclear. We used two taxonomic distinctness indices and species richness to assess relationships between nutrient gradients and three freshwater taxonomic groups, including diatoms, macrophytes and invertebrates. We found that the indices based on the three organismal groups showed generally rather clear relationships with the nutrient levels, indicating that these indices may bring useful additional information for the purposes of bioassessment. However, the two indices describing taxonomic distinctness showed opposite patterns in relation to nutrient levels. The indices for the three groups of organisms were generally poorly correlated with each other, showing that different organismal groups react differently to anthropogenic stress. Accordingly, taxonomic distinctness indices likely tell us about various aspects of nutrient enrichment of freshwater ecosystems. Our findings also emphasized that the value of these indices may be largely dependent on the organismal group used.     

Are men more promiscuous than women?

In spite of the unassailable logic that every new coital partner a man has is also a new partner for the woman concerned, men typically claim more sexual partners than women. If these claims are correct, can prostitutes and other hypersexual women account for this slippage? The present study examines whether the incidence of such women is sufficient to explain the discrepancy in number of lifetime partners claimed by men and women.     

Are Chaoborus larvae more abundant in acidified than in non-acidified lakes in Central Canada?

Eriksson et al (1980) hypothesized that the abundance of certain macroinvertebrate predators, such as larvae of the phantom midge Chaoborus , should increase in acidified lakes because of the elimination of fish. To examine the influence of pH and presence of fish on Chaoborus abundance, we surveyed Chaoborus populations in 33 lakes in Ontario, Canada which ranged in pH from 4.5 to 7.4. Chaoborus larvae were not more abundant in the acidified lakes that were devoid of fish than in the remaining lakes. Therefore, we concluded that pH and presence of fish are not prime determinants of total Chaoborus abundance in Canadian Shield lakes. We hypothesized that significant increases in Chaoborus abundance should only be anticipated when fish populations are eliminated by acidification of relatively nutrient rich lakes.     

Are inbred offspring less fit? Survival in a natural population of Mexican jays

The importance of inbreeding avoidance for the fitness of individualsis currently undergoing reevahation. Especially when the frequencyof inbreeding is low, it may be difficult to accumulate sufficientinformation. In a long-term study of the Mexican jay (Aphelocomaultamarina) in Arizona, we found inbreeding, as determined bypedigree, to be rare even though this species exhibits strongnatal philopatry and commonly lives in social groups of closerelatives. Brood sizes of inbred pairs were significantly lowerthan those of outbred pairs, suggesting hatching failure; butthere was no difference in die probability that one or moreyoung would fledge from a nest. Survival of inbred nestlingsto die next year was significantly lower than that of outbrednestlings.     

Are more diverse parts of the mammalian skull more?labile?

Morphological variation is unevenly distributed within the mammalian skull; some of its parts have diversified more than others. It is commonly thought that this pattern of variation is mainly the result of the structural organization of the skull, as defined by the pattern and magnitude of trait covariation. Patterns of trait covariation can facilitate morphological diversification if they are aligned in the direction of selection, or these patterns can constrain diversification if oriented in a different direction. Within this theoretical framework, it is thought that more variable parts possess patterns of trait covariation that made them more capable of evolutionary change, that is, are more labile. However, differences in the degree of morphological variation among skull traits could arise despite variation in trait lability if, for example, some traits have evolved at a different rate and/or undergone stabilizing selection. Here, we test these hypotheses in the mammalian skull using 2D geometric morphometrics to quantify skull shape and estimating constraint, rates of evolution, and lability. Contrary to the expectations, more variable parts of the skull across mammalian species are less capable of evolutionary change than are less variable skull parts. Our results suggest that patterns of morphological variation in the skull could result from differences in rate of evolution and stabilizing selection.     

Why do arms extract less oxygen than legs during exercise?

To determine whether conditions for O2 utilization and O2 off-loading from the hemoglobin are different in exercising arms and legs, six cross-country skiers participated in this study. Femoral and subclavian vein blood flow and gases were determined during skiing on a treadmill at approximately 76% maximal O2 uptake (V(O2)max) and at V(O2)max with different techniques: diagonal stride (combined arm and leg exercise), double poling (predominantly arm exercise), and leg skiing (predominantly leg exercise). The percentage of O2 extraction was always higher for the legs than for the arms. At maximal exercise (diagonal stride), the corresponding mean values were 93 and 85% (n = 3; P < 0.05). During exercise, mean arm O2 extraction correlated with the P(O2) value that causes hemoglobin to be 50% saturated (P50: r = 0.93, P < 0.05), but for a given value of P50, O2 extraction was always higher in the legs than in the arms. Mean capillary muscle O2 conductance of the arm during double poling was 14.5 (SD 2.6) ml.min(-1).mmHg(-1), and mean capillary P(O2) was 47.7 (SD 2.6) mmHg. Corresponding values for the legs during maximal exercise were 48.3 (SD 13.0) ml.min(-1).mmHg(-1) and 33.8 (SD 2.6) mmHg, respectively. Because conditions for O2 off-loading from the hemoglobin are similar in leg and arm muscles, the observed differences in maximal arm and leg O2 extraction should be attributed to other factors, such as a higher heterogeneity in blood flow distribution, shorter mean transit time, smaller diffusing area, and larger diffusing distance, in arms than in legs.     

What to do in marine biotechnology?

During the symposium "Marine Biotechnology: Basics and Applications", held 25 February-1 March, 2003 in Matalasca?as, Spain, a special brainstorm session was organized. Two questions were addressed: 1, "What is the most desirable development in marine biotechnology"?; 2, "What is the most spectacular development in this field in your 'wildest' dreams"? The outcome of this session is reported in this paper. From the more than 250 ideas generated, concern for the environment and human health emerged as the most significant issues.     

Are male rhesus monkeys more aggressive than females?

The justification for the “generalization that primate males are more aggressive than females” (Fedigan & Baxter, 1984) was tested in a troop of 24 captive rhesus monkeys. Males (N=9) were more dominant than females (N=15), i.e., they had more subordinate partners ( _m=17.0 vs. _f=6.6;p<0.01); hence, their aggression rate was higher ( _m=77.6 vs. _m=38.1;p<0.05). However, adjusting the rate of aggression according to the number of subordinate targets revealed no gender difference and males directed numbers of aggressive acts against individual subordinate partners that were not higher than those of females ( _m=4.4 vs. _f=5.4;p>0.1). It was concluded that aggressiveness is an individual attribute that is (1) independent of dominance status, and (2) independent of sex.     

Are desmosomes more than tethers for intermediate filaments?

Desmosomes are intercellular adhesive junctions that anchor intermediate filaments at membrane-associated plaques in adjoining cells, thereby forming a three-dimensional supracellular scaffolding that provides tissues with mechanical strength. But desmosomes have also recently been recognized as sensors that respond to environmental and cellular cues by modulating their assembly state and, possibly, their signalling functions.