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Bibiana Rojas
Centre of Excellence in Biological Interactions, University of Jyväskylä
Biology and Environmental Sciences
Finland

Being complex can be safe: testing predator avoidance of varying aposematic signals in a novel environment

poster 

Author(s): Rojas, B, Rautiala, P, Mappes, J

Summary:

Conspicuous colour patterns may function as interspecific signals in the context of predation by warning predators about prey unprofitability (aposematism). This strategy relies on the ability of predators to learn the association between colouration and unprofitability, and the subsequent avoidance of the unprofitable prey. Frequency-dependent selection is expected to favour uniformity and act against variability in aposematic signals. However, variation in aposematic species occurs in many taxa suggesting that signal variation may serve other purposes or be under variable selective pressures. Although the fundamental assumptions of aposematism have been well supported by mathematical models and experiments in controlled laboratory setups, their implications in the natural environment of both predators and prey have been until recently greatly overlooked. Predators are supposed to learn simpler patterns easier. Because variation in aposematic signals may imply morph-specific attack rates, aposematism as an anti-predator strategy could be overall less effective for individuals with complex colour patterns, especially when exposed to naïve predators or when invading novel environments, unless there were associated differences in detectability. We tested that hypothesis using wax models of the polymorphic, aposematic poison frog Dendrobates tinctorius placed in the wild, in a site where the actual frogs do not occur. We found that over time aposematic prey get less attacks than cryptic prey, but there were no differences in the attack rate between simple and complex morphs. However, complex morphs seemed to be more difficult to detect than simple ones. We suggest that wild predators are able to generalise aposematic colour patterns. Complex patterns may compensate being difficult to learn by being less detectable, which may contribute to the maintenance of the great intra-populational variation in colour patterns in this species.

Viviana Marri
Faculty of Science of the University of Bern
Department of Biology
Switzerland

Differential effects of pigmentary and non-pigmentary antioxidants on growth, plumage coloration and resistance to oxidative stress in wild great tits

poster 

Author(s): Marri, V, Richner, H

Summary:

Carotenoid-based colorations are thought to be honest signals of individual quality but the mechanism underlying their expression is still not clear. Since carotenoids act both as antioxidants and immunostimulants, it has been suggested that carotenoid-based coloration can signal an individual’s ability to resist oxidative stress and/or to mount an immune response. However, the antioxidant role of carotenoids in vivo has recently been debated. The "protection hypothesis" holds that carotenoids, which are minor antioxidants and are bleached by reactive oxygen species, can be used as signals to indicate the availability of non-pigmentary antioxidants (e.g. vitamins) that protect them from oxidation. Here, we evaluated this hypothesis by assessing the interactive effects of carotenoids and vitamins on plumage coloration, oxidative stress, growth and fledging success in nestling great tits. We supplemented nestlings with carotenoids (lutein and zeaxanthin) and/or vitamins (E and C) in a 2x2 full-factorial design, and subsequently measured plumage reflectance, antioxidant capacity, oxidative damage and body condition. Vitamins enhanced the expression of the carotenoid-based plumage coloration during the breeding season and improved antioxidant capacity. They did not influence oxidative damage, probably because supplied nestlings invested more in growth, which is a major cause of free-radical production, rather than in reducing oxidative damage. Moreover, vitamin-treated nestlings had a higher probability of fledging. In contrast, carotenoids did not influence any of these traits and did not show any synergistic effect when supplemented together with vitamins. Our results support the "protection hypothesis" and hence the idea that carotenoids are minor antioxidants in vivo. Furthermore, we could show the importance of antioxidants during growth, supporting the idea that oxidative stress may play a central role in life-history trade-offs.

Alexandre Roulin
University of Lausanne
Department of Ecology and Evolution
Switzerland

Expression levels of genes belonging to the melanocortin system are associated with melanin-based coloration in two colour polymorphic owl species

poster 

Author(s): Roulin, A, Ducrest, A

Summary:

The adaptive function of colour polymorphism is a long-standing debate, principally because of limited knowledge of the genetic mechanism underlying morph production. A recent genetic model suggested that the melanocortin system could account for covariations between melanin-based colour morphs, behaviour, morphology and physiology. This genetic system may therefore account for the observed morph-specific life history strategies. In two owl species we explored whether the expression levels of genes belonging to the melanocortin system (MC1R, POMC, PC1, PC2 and the antagonist ASIP) as well as 15 other melanogenic genes are associated with melanin-based coloration. We considered the tawny owl (Strix aluco) because individuals vary continuously from light to dark reddish. We measured gene expression in feather follicles collected in nestlings at the time of melanin production. Our results are consistent with a key role of the melanocortin system on the expression of colour morphs. We indeed found that the expression levels of convertases (that process melanocortin hormones) covary with melanin-based coloration, an effect that strongly depends on genetic polymorphism at the melanocortin-1-receptor (MC1R). We conclude that the melanocortin system may explain why dark and light melanic morphs adopt alternative life history strategies and differentially cope with stressful factors.

Tom Ellis
IST Austria
Austria

Floral pigmentation evolution and movement through genetic space in snapdragons (Antirrhineae)

poster 

Author(s): Ellis, T

Summary:

Floral pigmentation is a conspicuous and variable trait with an enormous effect on sexual selection, and the underlying genetic pathways are well-understood. As such, flower colour evolution has great potential to inform our understanding of the relationship between genes and phenotype. Previous work has found consistent patterns of irreversible transitions from purple to white, red and blue flowers, via single-locus loss-of-function mutations in regulatory genes of the flavonoid pathway. Since yellow pigmentation is typically controlled by a wholly different pathway, transitions to yellow must involve mutations at two loci. However, transitions involving yellow flowers, or at broader taxonomic scales have never been properly examined. I present results from an ongoing comparative study of floral evolution in a tribe of snapdragons (Antirrhineae, Plantaginaceae), which aims to assess patterns of evolution between yellow, white and purple flowered species in a phylogenetic context. Single locus transitions appear to dominate at short time scales, demonstrating the need to look beyond the genus level. Transitions also appear to be generally more reversible than in previously examined groups. I also examine the role of other floral traits that may be correlated with shifts in flower colour.

Branka Tucić
Siniša Stanković Institute for Biological Research, University of Belgrade
Department of Evolutionary Biology
Serbia

Flower colour morphs of Iris pumila differ in the amounts of Hsp90 and phenolic compounds

poster 

Author(s): Tucić, B, Manitašević Jovanović, S, Vuleta, A

Summary:

Natural populations of the dwarf bearded iris, Iris pumila, display a striking flower-colour polymorphism. It was noted that the combination of fluctuating temperatures and the varied attractiveness of diverse colour morphs promotes a stable coexistence of multiple colour variants in a population. We have quantified the amounts of Hsp90 and the antioxidants, anthocyanins and total phenolics, in I. pumila flowers. These molecules impact abiotic stress tolerance, ultimately influencing the fitness of individual plants. A total of 100 clones that were raised in a common garden and assessed to different colour classes (dark violet, violet, light violet, dark blue, light blue, yellow/white) were examined. The amounts of two Hsp90 forms, inducible (Hsp90a) and constitutively expressed (Hsp90b) proteins were lowest in yellow and white flowers as compared to other colour classes. In blue flowers, the concentration of Hsp90a was observed to decrease gradually when proceeding from light blue to dark blue variants, whereas an inverse trend was observed in violet-coloured flowers. The concentration of anthocyanins was notably low in white/yellow flowers and in the blue and violet colour classes it progressively increased from light to dark floral morphs. The amounts of total phenolics were highest in the white and yellow colour morphs; they were relatively high in all of the blue variants, and gradually increase from light to dark colour morphs in the violet class. These results suggest that each I. pumila colour genotype is responsible for the production of unique amounts of Hsp90 and phenolics that protect cellular homeostasis under fluctuating temperature conditions within populations.

Andreas Härer
Faculty of Biology of the University of Constance
Department of Biology
Germany

Genomic instability in the locus responsible for a conspicuous polychromatism in Nicaraguan Midas Cichlid Fish

poster 

Author(s): Härer, A, Henning, F, Meyer, A

Summary:

Body coloration is polymorphic in many species. It is subject to both natural selection (e.g. cryptic coloration) and sexual selection (e.g. male nuptial coloration). Two extraordinary features of Cichlids are their enormous diversity in coloration and their rapid rates of diversification. Sexual selection on coloration has been proposed to be one of the major forces driving their explosive speciation rates, which makes them an ideal system to study the effects of body coloration on speciation processes. Most of the Nicaraguan lakes are inhabited by two color morphs of Midas cichlids: a barred dark morph, which represents the majority of individuals (~90%), and a gold morph (7 - 10%). All individuals have the normal phenotype at early stages of their life but some lose their dark coloration and become gold. Gold and normal fish mate assortatively and genetic divergence of neutral markers occurs between the two morphs. All of which suggests a role of this trait in the process of incipient speciation. In this study, we characterize the architecture of the genomic region that harbors the causal gold polymorphism. The interval was reduced to approximately 60 kb and it, as well as the flanking regions, shows strong evidence of genomic instability. This includes several indels of various sizes, gene duplications and chromosomal rearrangements. Lineage-specific, tandemly duplicated genes have been identified, some of which show signs of pseudogenization and selection. Comparative genomic analysis of the region indicates the presence of cichlid-specific and perhaps even Midas-specific chromosomal rearrangements. Regions of genomic instability have been proposed to have an impact on speciation due to altered recombination and mutation rates. The present study illustrates the architecture of an unstable genomic region that might underlie incipient sympatric speciation in Nicaraguan Midas cichlids.

Violaine Llaurens
CNRS
Museum National D'Histoire Naturelle de Paris
France

Investigating the role of dominance in the polymorphism of wing colour patterns in the mimic butterfly Heliconius numata

poster 

Author(s): Llaurens, V, Le Poul, Y, Annabel, W, Joron, M

Summary:

Dominance is a widespread mechanism by which the phenotype of heterozygotes is determined. In polymorphic loci, dominance thus plays an important role in the dynamic of the phenotypic polymorphism because of the high number of heterozygotes. This talk focuses on dominance in a striking case of colour polymorphism caused by Müllerian mimicry. In the unpalatable butterfly species Heliconius numata, several wing colour patterns are co-existing and these patterns exhibit high resemblance with other unpalatable species. Colour patterns thus seem to act as a warning signal of toxicity for predators. In H. numata, this protective mimicry is adapted to the spatial variation in communities of unpalatable butterflies, leading to a stable polymorphism of wing colour patterns due to selection/migration equilibrium. These complex wing colour patterns are mainly controlled by a single locus, the supergene P, which contains about 18 co-segregating genes. Dominance relationships among the haplotypes at the supergene P are predicted to be under high selective constraint due to an increased predation risk for non-mimetic intermediate heterozygotes. Using an original morphological approach based on automatic detection of pattern variation, we quantify the coefficient of dominance between haplotypes at the supergene P. The study of controlled crosses between sympatric and allopatric morphs suggests a complete dominance among haplotypes occurring within populations whereas mosaic of dominance is mainly observed in allopatric haplotypes. This highlights the important role of dominance in the polymorphism of distinct wing colour patterns involved in mimicry relationships and allow us to open research on the possible mechanisms of dominance at the supergene P.

Hui Wang
Université Montpellier 2
Institut des Sciences de l'Évolution de Montpellier - UMR 5554 - ISE-M
France

Maintenance of flower color polymorphism in Iris lutescens Lam. (Iridaceae)

poster 

Author(s): Wang, H, Conchou, L, Bessiere, J, Cazals, G, Schatz, B, Imbert, E

Summary:

As pollinator visitation rate is generally correlated with plant fitness in entomogamous species, stabilizing selection mediated by associative learning is expected to occur on floral traits, leading to low intra-specific variation. Flower color is among the most important visual signals to attract pollinators. Consistently, previous studies suggested that flower color polymorphism could be maintained by pollinator-mediated selection. In addition, flavonoid/anthocyanin, carotenoid pigments, which are responsible for coloration in most plants, have pleiotropic effects for plant survival. Therefore selection pressures induced by a range of abiotic (precipitation, soil or temperature) /biotic (herbivores and pathogens) factors could also be involved. Herein, we investigated flower color polymorphism in a common species in the Mediterranean area, Iris lutescens Lam. (Iridaceae), which displays a tremendous purple-yellow flower color polymorphism within populations. We revealed that I. lutescens is a rewardless species displaying mainly different anthocyanin accumulation induced flower color difference, that is not associated with marked difference in odor emitted nor level of defense against abiotic/biotic factors. Results of pollinator/florivore observations and genetic analyses underlying flower color variation will also be presented in this talk. Pollinators are the most probable selective agent responsible for the maintenance of this polymorphism, suggesting that this species is a good candidate to investigate the maintenance of flower color polymorphism.

Verena Kottler
Max Planck Institute for Developmental Biology
Molecular Biology
Germany

Mapping of the guppy pigmentation gene blond using RAD-seq

poster 

Author(s): Kottler, VA, Künstner, A, Hoffmann, M, Weigel, D, Dreyer, C

Summary:

The guppy (Poecilia reticulata) is a long-standing model for the study of sex-linked inheritance of male ornamental traits. The species also offers excellent opportunities to observe ‘evolution in action,’ as its populations adapt rapidly to changing predator regimes. While numerous studies have investigated the delicate interplay between natural and sexual selection shaping male coloration in the wild, surprisingly little is known about the genes and developmental pathways underlying guppy coloration. We have shown previously that spontaneous mutations in kita and colony-stimulating factor 1 receptor a (csf1ra) significantly change the normal camouflage as well as the variable male ornaments of the guppy. Another spontaneous guppy mutant, blond, greatly reduces all black pigmentation and thereby dramatically changes male color patterns. To map this pigmentation gene, we used next-generation sequencing followed by a quantitative trait locus (QTL) analysis. A total of 141 F2 individuals from a cross between a wild-type female and a blond male were sequenced by representational analysis using the restriction-site associated DNA tag method (RAD-seq). RAD-seq reads were mapped to a draft version of the guppy genome and single-nucleotide polymorphisms (SNPs) between the individuals were identified. The resulting ~7,000 high quality SNPs were used to narrow down a major QTL spanning 118 kb on autosomal linkage group 2. The target region contains three genes, of which adenylate cyclase 5 (adcy5) is a promising candidate gene as preliminary analysis suggests that it contains a frameshift mutation in blond guppies. Our study demonstrates that RAD-seq is a powerful tool to identify genes of interest even in organisms for which only limited genomic information is available.

Paul Richards
University of Nottingham
School of Biology
United Kingdom

Mapping the Cepaea nemoralis shell colour and banding supergene using RAD-Seq

poster 

Author(s): Richards, PM, Liu, MM, Lowe, N, Davey, JW, Blaxter, ML, Davison, A

Summary:

The classic shell colour and banding polymorphism of the land snail Cepaea nemoralis played a crucial role in establishing the importance of natural selection in maintaining morphological variation. Cepaea is also a pre-eminent model for ecological genetics because the outward colour and banding phenotype is entirely genetically determined, primarily by a ‘supergene’ of at least five loci. Unfortunately, progress in understanding the evolution and maintenance of the Cepaea polymorphism stalled, partly because of a lack of genetic markers. However, high-throughput genotyping-by-sequencing technologies, such as Restriction Site Associated DNA sequencing (RAD-Seq), now enable systems with few existing genetic resources to be researched from new angles and in far greater detail than ever before. Consequently, with an ultimate view to identify and dissect the individual components of the Cepaea supergene, and to understand their evolution, we used RAD-Seq to construct a local map of markers linked to the shell ground colour (C) and banding presence (B) loci of the supergene. We have identified and validated 11 linked markers, with the closest being within ~0.6 cM (1 recombinant out of 168) of the C-B supergene linkage group, with the combined loci together forming a 35.8 cM linkage map of markers that flank both sides of the Cepaea C-B supergene. This initial set of linked markers should form the foundations of future work to re-establish Cepaea as a prominent model of molecular ecology.

Contacts

Chairman: Octávio S. Paulo
Tel: 00 351 217500614 direct
Tel: 00 351 217500000 ext22359
Fax: 00 351 217500028
email: mail@eseb2013.com

Address

XIV Congress of the European Society for Evolutionary Biology

Organization Team
Department of Animal Biology (DBA)
Faculty of Sciences of the University of Lisbon
P-1749-016 Lisbon
Portugal

Website

Computational Biology & Population Genomics Group 
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