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Chris Jiggins
University of Cambridge
Dept Zoology
United Kingdom

Defining the regulatory regions that control Heliconius butterfly colour pattern mimicry

talk 

Author(s): Jiggins, CD, Baxter, SW, Wallbank, R, Martin, S, Nadeau, N

Summary:

Genomic studies of natural populations are offering novel insights into adaptation and diversification. In particular, recent studies of parallel evolution of similar phenotypes in divergent lineages have commonly shown the utilization of shared genetic variation. Heliconius butterflies represent a recently documented example of shared allelic variation across species boundaries.

Heliconius display bright wing patterns that warn predators of distastefulness and also act as mating cues. The diversity of patterns displayed within and between the hundreds of forms is remarkable, as is the convergence between species onto near-perfect mimetic patterns. Recent field studies have identified a group of populations along the eastern slopes of the Andes that are allied to H. timareta and share wing phenotypes with sympatric H. melpomene. Genomic studies have shown that the populations with similar phenotypes also share allelic variation at wing patterning loci, with adaptive introgression across the species boundary providing the most likely explanation for this pattern.

We sequenced a 600 Kb genomic region that regulates diverse red wing pattern phenotypes, using 80 Heliconius samples. Genomic intervals associated with at least three independent red colour pattern phenotypes were resolved using sequence comparisons that grouped similar wing phenotypes, irrespective of species. By comparing the level of nucleotide variation within each colour pattern interval, we estimate the time in generations when introgression events occurred between H. melpomene and H. timareta. Gene exchange after speciation has resulted in the adaptive spread of colour pattern alleles. Here we have identified narrow genomic regions that must act through cis-regulatory control of the transcription factor optix, in order to control complex phenotypes.

Erik Svensson
Faculty of Science, Lund University
Evolutionary Ecology Unit, Department of Biology
Sweden

Ecology and mating interactions: temperature influences male-female conflict in a colour polymorphic damselfly

talk 

Author(s): Svensson, E

Summary:

Heritable and conspicuous colour polymorphisms have a long research tradition in ecological genetics, and these systems have been used to investigate issues such as negative-frequency-dependent selection (NFDS), maintenance of genetic variation, sexual selection and sexual conflict. Here I will present long-term field observational data and experiments on the evolutionary dynamics of a sexually selected colour polymorphism in the damselfly Ischnura elegans. Three female morphs exist in this species, one of them being a male mimic ("androchrome females"). Androchrome have lower mating rates than other female morphs, suggesting that male mimicry is a female defence against excessive and costly male mating harassment that is detrimental to female fitness. I will present long-term field data from a longitudinal study across multiple populations that show the stability of this female polymorphism and the results of experiments where we have manipulated morph frequencies and densities and evaluated the effects on morph and population fitnesses. I will also present data showing that the male-female mating interactions are environment-dependent and moulded by ambient temperatures, resulting in geographic variation in morph frequencies. Thus, sexual conflict in this system and the benefits of male mimicry is highly context-dependent upon local ecology and the thermal environment.

Sofia Seabra
Faculdade de Ciências da Universidade de Lisboa
Centro de Biologia Ambiental
Portugal

Experimental and genomic approaches in the study of the balanced colour-polymorphism of the meadow spittlebug (Philaenus spumarius)

talk 

Author(s): Seabra, SG, Rodrigues, AS, Silva, SE, Silva, J, Marabuto, E, Pina-Martins, F, Gharbi, K, Blaxter, M, Borges, PAV, Jiggins, C, Quartau, JA, Paulo, OS

Summary:

Philaenus spumarius (Insecta, Hemiptera, Aphrophoridae) has for long been a subject of interest of evolutionary biologists due to its heritable colour polymorphism that shows evidence of balancing selection and of clinal variation in the colour mophs frequencies. We are studying the adaptive significance of this polymorphism, particularly to understand if the melanic morphs (e.g. “marginellus” morph) have any advantage/disadvantage in terms of survival and reproductive success, efficiency of egg maturation and resistance to desiccation compared to non-melanic morphs (“typicus” and “trilineatus”). Results so far indicate a higher survival, higher number of eggs clutches and higher number of eggs laid by the “trilineatus” females than “typicus” or “marginellus” females. We are also taking a genomic approach for a) the identification of genetic basis of the colour polymorphism and b) for detecting signatures of balancing and directional selection in the genome of P. spumarius. For this purpose we are applying RAD sequencing in a) a set of samples from the three different morphs referred above, using a high frequency cutter enzyme (PstI) and in b) another set of samples from 8 populations across the distribution range of the species representing the main mitochondrial haplogroups, using a lower frequency cutter enzyme (SbfI). We are also assembling a draft of the genome that will aid in the identification of homologous regions to available references, although the very large genome size of this insect constitutes an extra challenge.

Kang-Wook Kim
University of Sheffield
Department of Animal and Plant Sciences
United Kingdom

Genetic and genomic insights into a colour polymorphism of the Gouldian finch (Erythrura gouldiae)

talk 

Author(s): Kim, K, Pryke, SR, Griffith, SC, Burke, T

Summary:

The Red locus of the Gouldian finch Erythrura gouldiae is a pigmentation switch that determines black (melanin) and red (carotenoid) morphs. This locus offers a unique opportunity to investigate the genetic basis and evolutionary history of a sympatric polymorphism for colour that has also been found to be associated with multiple physiological and behavioural differences. We used classical linkage mapping combined with RAD (Restriction site Associated DNA) sequencing and association analysis to localize the locus to a small (65-kb) genomic region. The pattern of nucleotide diversity at the Red locus is characterized as a genomic island that shows significant differentiation and divergence between the black and red haplotypes. Evolutionary theory suggests two distinct hypotheses to explain this pattern. First, sequence divergence may have accumulated within the species due to reduced gene flow between morphs, supported by the observed high degree of pre- and post-zygotic incompatibility, or due to a genomic rearrangement. Second, the sequences may have diverged in isolated lineages, prior to population merger or introgression. We examined the two alternative possibilities by using genetic and genomic tools and assess the evidence for balancing selection.

Frederico Henning
University of Konstanz
Department of Biology
Germany

King Midas meets Mendel: unraveling the genetic basis of an evolutionarily relevant color polymorphism

talk 

Author(s): Henning, F, Fukamachi, S, Meyer, A

Summary:

Color polymorphisms are tractable traits that are directly related to various crucial evolutionary processes including adaptation and speciation. The genetic basis of coloration has been the focus for genetic and evolutionary research for over a century. Despite this interest, few studies have successfully unraveled the genetic basis of color polymorphisms in natural populations; and the processes governing the origin, spread and maintenance of polychromatism are still poorly understood. The Midas cichlids of the crater lakes in Nicaragua are an excellent system to investigate the maintenance of a conspicuous color polymorphism and its role in speciation-with-gene flow. Midas cichlids are characterized by a conspicuous polychromatism: most individuals are grayish with dark bars, while some exhibit a gold coloration. The color morphs mate assortatively and have been suggested to be undergoing divergence in sympatry. Here, we explore the genetics of this trait using a combination of genetic mapping and next-generation sequencing technologies. The results show that a simple mendelian genetic architecture can underlie sympatric divergence, and might even constitute evidence for one-gene models of speciation. We further show that the onset of the phenotype is variable and dosage dependent (i.e homozygotes have earlier onset). This observation is of interest to understanding the fitness landscapes under predation pressure in the wild. The genomic region that harbors the gold locus is genomically unstable and characterized by the presence of tandem duplications and innumerous indels. The genes in the region are related to immune function, coloration and social affiliation. Patterns of association found in population-based fine-mapping using SNP genotyping and targeted-enrichment NGS are complex and compatible with multiple origins. These results indicate a role of mutation rate, hitch-hiking and pleiotropy in the maintenance of this conspicuous color polymorphism.

Jonathan Whitney
University of Hawaii
Department of Biology
United States

Natural selection drives incipient divergence despite continuous gene flow in sympatric color morphs of a coral reef fish

talk 

Author(s): Whitney, JL, Karl, SA

Summary:

The role that natural selection plays in initiating divergence-with-gene-flow remains controversial. Color polymorphisms offer rich opportunities to explore how selection can drive the evolution of reproductive isolation even in the face of gene flow. We integrate genetics, ecology, and behavior to outline how disruptive selection on color pattern in combination with assortative mating is driving divergence in sympatric color morphs of the arceye hawkfish (Paracirrhites arcatus) in Hawaii. First, ecological surveys show a strong correlation between phenotype & environment. Fine-scale microhabitat variation in visual backgrounds creates distinct niches that appear to favor alternative color patterns. Experimental tests are ongoing, but preliminary evidence shows reduced fitness in morphs found in contrasting habitats. Second, field observations of mating pairs indicate that, even in zones of overlap, fish are 10x more likely to pair with like morphs. Lab-based experiments of captive fish are currently being used to further explore the strength of assortative mating and its impact on reproductive isolation. Third, genome scans using 30 microsatellite loci show divergent patterns of genetic variation across morphs indicative of divergence-with-gene-flow; and outlier detection methods confirm three loci as candidates for positive selection. The strong association between genetic variants, color pattern, and ecological gradients all suggest that P. arcatus has evolved genetically-based alternative phenotypes that are adapting to spatially heterogeneous habitats despite continuous gene flow. We are currently using comparative genomics to discover regions showing signatures of natural selection and identify the underlying genetic basis of adaptive color pattern and correlated traits. This research outlines one of the few case studies of ongoing sympatric divergence in any marine fish and will help elucidate the role color polymorphism plays in promoting speciation.

David Field
Institute of Science and Technology
Evolutionary genetics
Austria

Selection on flower colour genes in a snapdragron hybrid zone

talk 

Author(s): Field, DL, Tavares, H, Couchman, M, Copsey, L, Bradley, D, Ellis, T, Boell, L, Rebocho, X, Coen, E, Barton, N

Summary:

A major goal of evolutionary biology is to understand how diverging populations become distinct species. Although much progress has been made in identifying genes that contribute towards population divergence and speciation, direct measurements of their effect on fitness in nature are often difficult to obtain. We are studying the evolutionary dynamics of speciation between two subspecies of Antirrhinum (snapdragons) with different flower colours (yellow and magenta). In this system, two major loci control flower colour and give rise to six colour phenotypes across a narrow hybrid zone. Surprisingly, these species are visited by the same array of pollinators (large bees). This raises the question of how these genes initially arose and spread and how populations are currently maintained in the face of gene flow. To better understand the role of flower colour genes in speciation we are using an integrated approach to examine the role of selection, epistasis, drift and gene flow over multiple time scales. To examine short and long-term evolutionary processes we are using SSR and SNP markers for individuals sampled across the hybrid zone as well as sequence variation with Restriction-Associated DNA sequencing (RAD) data from allopatric populations. The existence of a steep cline (~280m wide) for flower colour and diagnostic markers linked to the underlying genes, suggests selection is acting against some of the hybrid colour phenotypes. Significant heterozygote deficit at small spatial scales (<30m) and an excess of parental phenotypes also suggests assortative mating may play a role in maintaining the hybrid zone. Initial results from RAD tags indicate that the highest regions of divergence (Fst) between allopatric populations are located near the genes that control flower colour. Taken together, these results suggest that selection is acting on the flower colour genes, likely through pollinators discriminating among the flower colour phenotypes within the hybrid zone.

Nagarjun Vijay
Evolutionary Biology center, Uppsala University
Department of Evolutionary Biology
Sweden

Speciation genomics in the European crow: a magic hybrid zone where sexual selection and few major effect loci may promote speciation

talk 

Author(s): Vijay, N, Poelstra, J, Bossu, C, Baglione, V, Grabherr, M, Kruszewicz, A, Lantz, H, Müller, I, Wikelski, M, Wolf, J

Summary:

Plumage colour differences within and between species are characteristic of many organisms and are particularly conspicuous in birds. The evolution of such colour polymorphisms, their contribution to prezygotic isolation and their general role in speciation has been a central theme in the evolutionary sciences. The hybrid zone between carrion and hooded crows (Corvus [c.] corone and C. [c.] cornix) is a prime example. The zone appears to have been maintained by strong assortative mating mediated by plumage colour for at least a century. The discrete segregation in colouration strongly contrasts with a surprising lack of genetic differentiation. Here, we aim at identifying the genetic basis of this colour polymorphism and assess its role in the speciation process. To achieve this goal, we generated an annotated draft reference sequence of one Hooded crow individual which we then used a backbone for population genomic analyses. We further conducted an extensive (RNAseq) gene expression experiment under common garden conditions focusing on differential gene expression of genes expressed in active feather follicles. The combination of the population genomic data and detailed information from the gene expression experiment provides a powerful approach to identify the genetic cause of colouration differences and its consequence for local genomic divergence between this pair of incipient species.

Jon Slate
University of Sheffield
Department of Animal & Plant Sciences
United Kingdom

The origins of two colour polymorphisms in a wild mammal population

talk 

Author(s): Slate, J, Feulner, PGD, Gratten, J, Pemberton, JM

Summary:

In a wild population of Soay sheep, that has been the focus of a >25 year field study, two coat colour polymorphisms are segregating as single locus Mendelian traits. Previously, the underlying mutations have been discovered, and it has been shown that both genes are under selection. However, the age and origins of the polymorphisms were unknown. In this talk, we show that Soay Sheep underwent admixture with more modern breeds in the 1800s, and that both polymorphisms arose through the introgression of domesticated genetic variants into the Soay population. Therefore, the current field site can be regarded as a ‘natural laboratory’ in which wild type and domesticated variants have been competing with one another for over 100 years. It is shown that domesticated variants are not necessarily less fit in the wild. More generally, admixture between domesticated and wild populations may be a common source of genetic variation, capable of providing the material required for evolutionary change and adaptation.

Rosemary Gillespie
University of California Berkeley
Environmental Science
United States

The role of transient versus balanced color polymorphism In adaptive radiation: spiders in the Hawaiian Islands

talk 

Author(s): Gillespie, RG, Brewer, MS, Croucher, PJP, Oxford, GS

Summary:

Color variation, when genetically determined, provides a visual tool for examining selection. Moreover, variation is a key to rapid adaptive response, which in turn forms the basis for adaptive radiation. Our work focuses on different genera of spiders in the Hawaiian Islands, in particular: (1) Long jawed spiders in the genus Tetragnatha (Tetragnathidae) that are characterized by exuberant adaptive radiation. This genus has colonized the islands an estimated 5mya and shows evolutionary progression from older to younger islands. One lineage, the “spiny leg clade”, is represented throughout the archipelago by four distinct color ecomorphs and molecular phylogenetic analyses indicate that each ecomorph has evolved repeatedly. However, species on the older islands (Kauai and Oahu) show a developmental switch between two ecomorphs – Green and Maroon. More derived species on the younger islands exhibit a single ecomorph, Green or Maroon, at all life stages, though species formation is associated with multiple shifts between ecomorphs. We are currently using a genomic approach to understand how the color-switching characteristic of species on the older islands has translated into diversification of species representing different ecomorphs on the younger islands. This system contrasts with (2) the exuberantly patterned Hawaiian Happy Face spider, Theridion grallator, a single species which displays a visible and balanced genetic color polymorphism. The happy face spider retains variability between individuals within a population (as compared to within individuals or between species in Tetragnatha). Moreover, while the frequency of color morphs is similar in different populations of happy face spiders, the mode of inheritance of the color polymorphism has changed between islands in the Hawaiian chain. Together, these studies provide insights into how, and under what circumstances, variability can translate into diversity.

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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