Sleep and vigilance linked to melanism in wild barn owls.

Understanding the function of variation in sleep requires studies in the natural ecological conditions in which sleep evolved. Sleep has an impact on individual performance and hence may integrate the costs and benefits of investing in processes that are sensitive to sleep, such as immunity or coping with stress. Because dark and pale melanic animals differentially regulate energy homeostasis, immunity and stress hormone levels, the amount and/or organization of sleep may covary with melanin-based colour. We show here that wild, cross-fostered nestling barn owls (Tyto alba) born from mothers displaying more black spots had shorter non-REM (rapid eye movement) sleep bouts, a shorter latency until the occurrence of REM sleep after a bout of wakefulness and more wakefulness bouts. In male nestlings, the same sleep traits also correlated with their own level of spotting. Because heavily spotted male nestlings and the offspring of heavily spotted biological mothers switched sleep-wakefulness states more frequently, we propose the hypothesis that they could be also behaviourally more vigilant. Accordingly, nestlings from mothers displaying many black spots looked more often towards the nest entrance where their parents bring food and towards their sibling against whom they compete. Owlets from heavily spotted mothers might invest more in vigilance, thereby possibly increasing associated costs due to sleep fragmentation. We conclude that different strategies of the regulation of brain activity have evolved and are correlated with melanin-based coloration.

Clinal variation in a brown lemur (Eulemur spp.) hybrid zone: Combining morphological, genetic and climatic data to examine stability.

Studies of hybrid zones can inform our understanding of reproductive isolation and speciation. Two species of brown lemur (Eulemur rufifrons and E. cinereiceps) form an apparently stable hybrid zone in the Andringitra region of south-eastern Madagascar. The aim of this study was to identify factors that contribute to this stability. We sampled animals at 11 sites along a 90-km transect through the hybrid zone and examined variation in 26 microsatellites, the D-loop region of mitochondrial DNA, six pelage and nine morphological traits; we also included samples collected in more distant allopatric sites. Clines in these traits were noncoincident, and there was no increase in either inbreeding coefficients or linkage disequilibrium at the centre of the zone. These results could suggest that the hybrid zone is maintained by weak selection against hybrids, conforming to either the tension zone or geographical selection-gradient model. However, a closer examination of clines in pelage and microsatellites indicates that these clines are not sigmoid or stepped in shape but instead plateau at their centre. Sites within the hybrid zone also occur in a distinct habitat, characterized by greater seasonality in precipitation and lower seasonality in temperature. Together, these findings suggest that the hybrid zone may follow the bounded superiority model, with exogenous selection favouring hybrids within the transitional zone. These findings are noteworthy, as examples supporting the bounded superiority model are rare and may indicate a process of ecologically driven speciation without geographical isolation.

Introduction

Although increasing our knowledge of the properties of networks of cities is essential, these properties can be measured at the city level, and must be assessed by analyzing actor networks. The present volume focuses less on individual characteristics and more on the interactions of actors and institutions that create functional territories in which the structure of existing links constrains emerging links. Rather than basing explanations on external factors, the goal is to determine the extent to which network properties reflect spatial distributions and create local synergies at the meso level that are incorporated into global networks at the macro level where different geographical scales occur. The paper introduces the way to use the graphs structure to identify empirically relevant groups and levels that explain dynamics. It defines what could be called âeurooemulti-levelâeuro, âeurooemulti-scaleâeuro, or âeurooemultidimensionalâeuro networks in the context of urban geography. It explains how the convergence of the network multi-territoriality paradigm collaboratively formulated, and manipulated by geographers and computer scientists produced the SPANGEO project, which is exposed in this volume.

A cryptic heterogametic transition revealed by sex-linked DNA markers in Palearctic green toads.

In sharp contrast to birds and mammals, most cold-blooded vertebrates have homomorphic (morphologically undifferentiated) sex chromosomes. This might result either from recurrent X-Y recombination (occurring e.g. during occasional events of sex reversal) or from frequent turnovers (during which sex-determining genes are overthrown by new autosomal mutations). Evidence for turnovers is indeed mounting in fish, but very few have so far been documented in amphibians, possibly because of practical difficulties in identifying sex chromosomes. Female heterogamety (ZW) has long been established in Bufo bufo, based on sex reversal and crossing experiments. Here, we investigate a sex-linked marker identified from a laboratory cross between Palearctic green toads (Bufo viridis subgroup). The F(1) offspring produced by a female Bufo balearicus and a male Bufo siculus were phenotypically sexed, displaying an even sex ratio. A sex-specific marker detected in highly reproducible AFLP genotypes was cloned. Sequencing revealed a noncoding, microsatellite-containing fragment. Reamplification and genotyping of families of this and a reciprocal cross showed B. siculus to be male heterogametic (XY) and suggested the same system for B. balearicus. Our results thus reveal a cryptic heterogametic transition within bufonid frogs and help explain patterns of hybrid fitness within the B. viridis subgroup. Turnovers of genetic sex-determination systems may be more frequent in amphibians than previously thought and thus contribute to the prevalence of homomorphic sex chromosomes in this group.

Social Evolution in ants

Review of the book . Social Evolution in Ants. Bourke, A. F. G. and Franks, N. R. 1995. Princeton University Press, Princeton, New Jersey, xiii + 529 pp. ISBN o-691-04427-9 (cl), O-691 -04426-o (pbk)

INdividual SUrveys in RAllies (INSURA), A new tool for exploring transnational activism?

Prior the middle of the 90', interviewing participants in protest events was quiet rare. INdividual SUrveys in RAllies (INSURA) did enter the social researcher's usual toolkit only in the following decade after Favre, Fillieule and Mayer (1997) conducted such a survey with as a primary ambition to build a solid methodological framework that could be subsequently applied by other researchers. After some years of intensive use of INSURA, one is entitled to wonder whether that technique has fulfilled social researchers' hopes or not. In that paper, results of a collective work on alter-global rallies in Evian and Saint- Denis are used to answer three interrelated questions. Firstly, some basic methodological questions about how to collect data on crowds are adressed. What are the specific constraints of interviewing people at the very moment they are "expressing" a political opinion? What specific constraints result from the morphology of the covered events, that is to say, how to build a valid sampling frame? The authors then turn to a more general point about the questions that can be solved, or not, using that technique. Secondly it is the strenghts and weaknesses of INSURA in exploring the transnational dimension of alter global protests that is adressed. The authors show that INSURA is certainly well suited to explore the demographics of alter-global events, as well as relational networks of individuals and multiple belongings. On the contrary, it is assumed that organization networks and movement's boundaries are far more difficult to explore through that method, a fact that seriously limits international cross comparisons of events and movements based on that tool.

Coevolutionary arms races: increased host immune defense promotes specialization by avian fleas.

We investigated the relationship between host defense and specialization by parasites in comparative analyses of bird fleas and T-cell mediated immune response of their avian hosts, showing that fleas with few main host species exploited hosts with weak or strong immune defenses, whereas flea species that parasitized a large number of host species only exploited hosts with weak immune responses. Hosts with strong immune responses were exploited by a larger number of flea species than hosts with weak responses. A path analysis model with an effect of T-cell response on the number of host species, or a model with host coloniality directly affecting host T-cell response, which in turn affected the number of host species used by fleas, best explained the data. Therefore, parasite specialization may have evolved in response to strong host defenses.

Machine learning for spatial environmental data. Theory, applications and software

The book presents the state of the art in machine learning algorithms (artificial neural networks of different architectures, support vector machines, etc.) as applied to the classification and mapping of spatially distributed environmental data. Basic geostatistical algorithms are presented as well. New trends in machine learning and their application to spatial data are given, and real case studies based on environmental and pollution data are carried out. The book provides a CD-ROM with the Machine Learning Office software, including sample sets of data, that will allow both students and researchers to put the concepts rapidly to practice.

Establishment success and resulting fitness consequences for vole dispersers

Dispersal is one of the most important, yet least understood phenomena of evolutionary ecology. Triggers and consequences of dispersal are difficult to study in natural populations since dispersers can typically only be identified a posteriori. Therefore, a lot of work on dispersal is either of a theoretical nature or based on anecdotal observation. This is especially true for cryptic species such as small mammals. We conducted an experiment on the common vole, Microtus arvalis, in semi-natural enclosures and investigated the spatial and genetic establishment success of residents and dispersers in their natal and new populations. Our study uses genetic data on the reproductive success of 1255 individuals to measure the fitness trajectories of the residents and dispersing individuals. In agreement with past studies, we found that dispersal was highly male-biased, and was most probably induced by the agonistic encounters with conspecifics, suggesting it could act as an inbreeding avoidance mechanism. There was low breeding success of dispersers into new populations. Although nearly 26% of identified dispersers reproduced in their natal populations, only seven percent reproduced in the new populations. Settlement appeared to be a pre-requisite for reproduction in both sexes, and animals that did not spatially settle into a new population dispersed again, usually on the same day of immigration. In the event that dispersers reproduced in the new population, they did so at relatively low population densities. We also found age-related differences between the sexes in breeding success, and male dispersers that subsequently established in the new population were young individuals that had not reproduced in their natal population, whereas successful females had already reproduced in their natal population. In conclusion, with our detailed field data on establishment and substantial parentage assignments to understand breeding success, we were able to gain an insight into the fitness of dispersers, and how the two sexes optimise their fitness. Taken together, our results help to further understand the relative advantages and costs of dispersal in the common vole.

Temporal variation in glucocorticoid levels during the resting phase is associated in opposite way with maternal and paternal melanic coloration.

Sex-dependent selection can help maintain sexual dimorphism. When the magnitude of selection exerted on a heritable sex trait differs between the sexes, it may prevent each sex to reach its phenotypic optimum. As a consequence, the benefit of expressing a sex trait to a given value may differ between males and females favouring sex-specific adaptations associated with different values of a sex trait. The level of metabolites regulated by genes that are under sex-dependent selection may therefore covary with the degree of ornamentation differently in the two sexes. We investigated this prediction in the barn owl, a species in which females display on average larger black spots on the plumage than males, a heritable ornament. This melanin-based colour trait is strongly selected in females and weakly counter-selected in males indicating sex-dependent selection. In nestling barn owls, we found that daily variation in baseline corticosterone levels, a key hormone that mediates life history trade-offs, covaries with spot diameter displayed by their biological parents. When their mother displayed larger spots, nestlings had lower corticosterone levels in the morning and higher levels in the evening, whereas the opposite pattern was found with the size of paternal spots. Our study suggests a link between daily regulation of glucocorticoids and sex-dependent selection exerted on sexually dimorphic melanin-based ornaments.

La Formación de la imagen turística inducida: un modelo conceptual

Teniendo en cuenta que la imagen turística ha sido reconocida como uno de los elementos más influyentes para la competitividad de los destinos turísticos, el principal objetivo de este artículo es construir un marco conceptual que muestre la influencia de la red relacional del destino en su imagen emitida. En este contexto, se asume que la imagen tu rística es una construcción social resultante de lainteracción de los distintos agentes que intervienen en el destino turístico (administraciones públicas, instituciones locales, empresas turísticas, etc.); y se propone un modelo teórico para mostrar los efectos de la red relacional del destino turístico en la calidad de la imagen turística creada en términos de conocimiento generado y, por tanto, en su competitividad

On an asymptotic formula for the maximum voltage drop in a on-chip power distribution network

We present a new asymptotic formula for the maximum static voltage in a simplified model for on-chip power distribution networks of array bonded integrated circuits. In this model the voltage is the solution of a Poisson equation in an infinite planar domain whose boundary is an array of circular pads of radius ", and we deal with the singular limit Ɛ → 0 case. In comparison with approximations that appear in the electronic engineering literature, our formula is more complete since we have obtained terms up to order Ɛ15. A procedure will be presented to compute all the successive terms, which can be interpreted as using multipole solutions of equations involving spatial derivatives of functions. To deduce the formula we use the method of matched asymptotic expansions. Our results are completely analytical and we make an extensive use of special functions and of the Gauss constant G

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Summary: New forms of learning develop within the learning networks of polytechnics

Supergenes and complex phenotypes.

Understanding the molecular underpinnings of evolutionary adaptations is a central focus of modern evolutionary biology. Recent studies have uncovered a panoply of complex phenotypes, including locally adapted ecotypes and cryptic morphs, divergent social behaviours in birds and insects, as well as alternative metabolic pathways in plants and fungi, that are regulated by clusters of tightly linked loci. These 'supergenes' segregate as stable polymorphisms within or between natural populations and influence ecologically relevant traits. Some supergenes may span entire chromosomes, because selection for reduced recombination between a supergene and a nearby locus providing additional benefits can lead to locus expansions with dynamics similar to those known for sex chromosomes. In addition to allowing for the co-segregation of adaptive variation within species, supergenes may facilitate the spread of complex phenotypes across species boundaries. Application of new genomic methods is likely to lead to the discovery of many additional supergenes in a broad range of organisms and reveal similar genetic architectures for convergently evolved phenotypes.

Unicoloniality, recognition and genetic differentiation in a native Formica ant.

Some ants have an extraordinary form of social organization, called unicoloniality, whereby individuals mix freely among physically separated nests. This mode of social organization has been primarily studied in introduced and invasive ant species, so that the recognition ability and genetic structure of ants forming unicolonial populations in their native range remain poorly known. We investigated the pattern of aggression and the genetic structure of six unicolonial populations of the ant Formica paralugubris at four hierarchical levels: within nests, among nests within the same population, among nests of populations within the Alps or Jura Mountains and among nests of the two mountain ranges. Ants within populations showed no aggressive behaviour, but recognized nonnestmates as shown by longer antennation bouts. Overall, the level of aggression increased with geographic and genetic distance but was always considerably lower than between species. No distinct behavioural supercolony boundaries were found. Our study provides evidence that unicoloniality can be maintained in noninvasive ants despite significant genetic differentiation and the ability to discriminate between nestmates and nonnestmates.