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..

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

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

How do predators generalize warning signals in simple and complex prey communities? Insights from a videogame

The persistence of distinct warning signals within and between sympatric mimetic communities is a puzzling evolutionary question because selection favours convergence of colour patterns among toxic species. Such convergence is partly shaped by predators' reaction to similar but not identical stimulus (i.e. generalization behaviour), and generalization by predators is likely to be shaped by the diversity of local prey. However, studying generalization behaviour is generally limited to simple variations of prey colour patterns. Here, we used a computer game played by humans as surrogate predators to investigate generalization behaviours in simple (4 morphs) and complex (10 morphs) communities of unprofitable (associated with a penalty) and profitable butterflies. Colour patterns used in the game are observed in the natural populations of unprofitable butterfly species such as Heliconius numata. Analyses of 449 game participants' behaviours show that players avoided unprofitable prey more readily in simple than in complex communities. However, generalization was observed only in players that faced complex communities, enhancing the protection of profitable prey that looked similar to at least one unprofitable morph. Additionally, similarity among unprofitable prey also reduced attack rates only in complex communities. These results are consistent with previous studies using avian predators but artificial colour patterns and suggest that mimicry is more likely to evolve in complex communities where increases in similarity are more likely to be advantageous

Variation of chemical compounds in wild Heliconiini reveals ecological factors involved in the evolution of chemical defenses in mimetic butterflies.

Evolutionary convergence of color pattern in mimetic species is tightly linked with the evolution of chemical defenses. Yet, the evolutionary forces involved in natural variations of chemical defenses in aposematic species are still understudied. Herein, we focus on the evolution of chemical defenses in the butterfly tribe Heliconiini. These neotropical butterflies contain large concentrations of cyanogenic glucosides, cyanide-releasing compounds acting as predator deterrent. These compounds are either de novo synthesized or sequestered from their Passiflora host plant, so that their concentrations may depend on host plant specialization and host plant availability. We sampled 375 wild Heliconiini butterflies across Central and South America, covering 43% species of this clade, and quantify individual variations in the different CGs using liquid chromatography coupled with tandem mass spectrometry. We detected new compounds and important variations in chemical defenses both within and among species. Based on the most recent and well-studied phylogeny of Heliconiini, we show that ecological factors such as mimetic interactions and host plant specialization have a significant association with chemical profiles, but these effects are largely explained by phylogenetic relationships. Our results therefore suggest that shared ancestries largely contribute to chemical defense variation, pointing out at the interaction between historical and ecological factors in the evolution of Müllerian mimicry