Cryptic MHC Polymorphism Revealed but Not Explained by Selection on the Class IIB Peptide-Binding Region

The immune genes of the major histocompatibility complex (MHC) are characterized by extraordinarily high levels of nucleotide and haplotype diversity. This variation is maintained by pathogen-mediated balancing selection that is operating on the peptide-binding region (PBR). Several recent studies have found, however, that some populations possess large clusters of alleles that are translated into virtually identical proteins. Here, we address the question of how this nucleotide polymorphism is maintained with little or no functional variation for selection to operate on. We investigate circa 750–850 bp of MHC class II DAB genes in four wild populations of the guppy Poecilia reticulata. By sequencing an extended region, we uncovered 40.9% more sequences (alleles), which would have been missed if we had amplified the exon 2 alone. We found evidence of several gene conversion events that may have homogenized sequence variation. This reduces the visible copy number variation (CNV) and can result in a systematic underestimation of the CNV in studies of the MHC and perhaps other multigene families. We then focus on a single cluster, which comprises 27 (of a total of 66) sequences. These sequences are virtually identical and show no signal of selection. We use microsatellites to reconstruct the populations' demography and employ simulations to examine whether so many similar nucleotide sequences can be maintained in the populations. Simulations show that this variation does not behave neutrally. We propose that selection operates outside the PBR, for example, on linked immune genes or on the “sheltered load” that is thought to be associated to the MHC. Future studies on the MHC would benefit from extending the amplicon size to include polymorphisms outside the exon with the PBR. This may capture otherwise cryptic haplotype variation and CNV, and it may help detect other regions in the MHC that are under selection

Adaptive evolution of butterfly wing shape: from morphology to behaviour

International audienceButterflies display extreme variation in wing shape associated with tremendous ecological diversity. Disentangling the role of neutral versus adaptive processes in wing shape diversification remains a challenge for evolutionary biologists. Ascertaining how natural selection influences wing shape evolution requires both functional studies linking morphology to flight performance, and ecological investigations linking performance in the wild with fitness. However, direct links between morphological variation and fitness have rarely been established. The functional morphology of butterfly flight has been investigated but selective forces acting on flight behaviour and associated wing shape have received less attention. Here, we attempt to estimate the ecological relevance of morpho-functional links established through biomechanical studies in order to understand the evolution of butterfly wing morphology. We survey the evidence for natural and sexual selection driving wing shape evolution in butterflies, and discuss how our functional knowledge may allow identification of the selective forces involved, at both the macro-and micro-evolutionary scales. Our review shows that although correlations between wing shape variation and ecological factors have been established at the macro-evolutionary level, the underlying selective pressures often remain unclear. We identify the need to investigate flight behaviour in relevant ecological contexts to detect variation in fitness-related traits. Identifying the selective regime then should guide experimental studies towards the relevant estimates of flight performance. Habitat, predators and sex-specific behaviours are likely to be major selective forces acting on wing shape evolution in butterflies. Some striking cases of morphological divergence driven by contrasting ecology involve both wing and body morphology, indicating that their interactions should be included in future studies investigating co-evolution between morphology and flight behaviour

Itinéraires de graveurs néerlandais à Paris au début du XVIIe siècle : Theodoor Matham, Cornelis Danckerts et les autres.

Cet article revient sur la migration de graveurs venus des Pays-Bas septentrionaux à Paris durant la première moitié du xviie siècle. Originaires de différentes villes des Provinces-Unies telles que Haarlem, Amsterdam, Rotterdam ou Utrecht où ils firent leur apprentissage, leur séjour parisien constitue une étape cruciale dans la construction de leur carrière. À travers l’analyse attentive de plusieurs cas d’étude, nous chercherons à souligner les motivations de départ de ces graveurs. Nous étudierons ensuite les différents modes de diffusion de leurs œuvres et leurs choix éditoriaux pour finalement aborder les stratégies mises à l’œuvre pour intégrer le marché parisien.This article seeks to shed new light on the migration of Dutch printmakers to Paris during the first half of the seventeenth century. While the movement of Flemish printmakers has been relatively well studied, Dutch artists’ journeys to France remain little researched. Hailing from Dutch cities such as Haarlem, Amsterdam or Utrecht where they completed their apprenticeship, their stay in Paris was a crucial step in the construction of their career. Through the study of the most significant cases, this article aims first to give new insights into their motivations to settle in Paris. I will then focus on their artistic choices made in France by studying the modality of diffusion of their works, while the last paragraph will deal with their strategies to integrate the print market by analyzing the way they tried to meet the local demand

Hans Jakob Meier, avec une contribution de Jeremy Wood, Die Kunst der Interpretation. Rubens und die Druckgraphik

Prenant part à une trilogie sur le thème de la gravure de reproduction, ce troisième volume propose une étude monographique visant à mettre en valeur le rôle singulier que joua Rubens dans le développement de la gravure d’interprétation à l’époque moderne. Dès les premières années du XVIIe siècle, Rubens donne en effet une réelle impulsion à cette industrie, cherchant à explorer l’ensemble des potentialités interprétatives de la gravure. S’il se tourne en partie vers ce medium à des fins mer..

The diversification of Heliconius butterflies: what have we learned in 150 years?

Research into Heliconius butterflies has made a significant contribution to evolutionary biology. Here, we review our understanding of the diversification of these butterflies, covering recent advances and a vast foundation of earlier work. Whereas no single group of organisms can be sufficient for understanding life's diversity, after years of intensive study, research into Heliconius has addressed a wide variety of evolutionary questions. We first discuss evidence for widespread gene flow between Heliconius species and what this reveals about the nature of species. We then address the evolution and diversity of warning patterns, both as the target of selection and with respect to their underlying genetic basis. The identification of major genes involved in mimetic shifts, and homology at these loci between distantly related taxa, has revealed a surprising predictability in the genetic basis of evolution. In the final sections, we consider the evolution of warning patterns, and Heliconius diversity more generally, within a broader context of ecological and sexual selection. We consider how different traits and modes of selection can interact and influence the evolution of reproductive isolation.RMM is funded by a Junior Research Fellowship at King’s College, Cambridge. KMK is supported by the Balfour Studentship, University of Cambridge, SHMa by a Research Fellowship at St John's College, Cambridge, and SHMo by a Research Fellowship from the Royal Commission for the Exhibition of 1851. Our work on Heliconius has been additionally supported by the Agence Nationale de la Recherche (France), the Biology and Biotechnology Research Council (UK), the British Ecological Society, the European Research Council, the Natural Environment Research Council (UK), and the Smithsonian Tropical Research Institute.This is the author accepted manuscript. The final version is available from Wiley via http://dx.doi.org/10.1111/jeb.1267

Evolutionary genetics of immunological supertypes reveals two faces of the Red Queen

Red Queen host-parasite co-evolution can drive adaptations of immune-genes by positive selection that erodes genetic variation (Red Queen Arms Race), or result in a balanced polymorphism (Red Queen Dynamics) and the long-term preservation of genetic variation (trans-species polymorphism). These two Red Queen processes are opposite extremes of the co-evolutionary spectrum. Here we show that both Red Queen processes can operate simultaneously, analyzing the Major Histocompatibility Complex (MHC) in guppies (Poecilia reticulata and P. obscura), and swamp guppies (Micropoecilia picta). Sub-functionalization of MHC alleles into “supertypes” explains how polymorphisms persist during rapid host-parasite co-evolution. Simulations show the maintenance of supertypes as balanced polymorphisms, consistent with Red Queen Dynamics, whereas alleles within supertypes are subject to positive selection in a Red Queen Arms Race. Building on the Divergent Allele Advantage hypothesis, we show that functional aspects of allelic diversity help to elucidate the evolution of polymorphic genes involved in Red Queen co-evolution

Proposta per fomentar la sostenibilitat i compromís social i pensament crític a l'educació secundària obligatòria a través de metodologies innovadores

Aquest treball fa una recerca teòrica de tres estratègies docents innovadores per tal de fomentar a les aules de l'Educació Secundària Obligatòria dues competències transversals diferents, la sostenibilitat i compromís social i el pensament crític a l'aula. En concret, a través d'una recerca acadèmica es proposa, utilitzant l'aprenentatge basat en problemes, la tècnica puzle i la classe invertida, diferents activitats per fomentar les competències transversals ja esmentades. En primer lloc, es presenta una per una les estratègies innovadores protagonistes. Un cop presentades, es justifica el perquè de la necessitat de treballar amb elles per aconseguir els objectius suggerits, i es descriu pas per pas com portar a terme de manera satisfactòria l'estratègia. A més, s'especifica quin és el rol que ha de portar el docent i quin és el rol esperat de l'alumnat. Tot això es demostra a través de la recerca acadèmica de diferents tesis i documents acadèmics oficials. Un cop explicats els diferents passos a seguir per tal de complementar les diferents estratègies, es recomana una activitat per metodologia a realitzar seguint el pas per pas cercat i reflectit al treball amb anterioritat, amb un total de tres activitats proposades