Abstracts (first author)

Talk Presidential Address

Reinforcement (and other modes of speciation)

Author(s): Butlin RK

Summary:

Reinforcement is often considered special among modes of speciation because natural selection favours the build-up of barriers to gene flow: reproductive isolation is not just an incidental consequence of divergence, it is a device to prevent maladaptive hybridization. The idea is controversial partly because the term ‘reinforcement’ is used in various different ways. More importantly, reinforcement is hard to demonstrate and so it remains uncertain how much it contributes to speciation. Like other processes, it is only ever part of the speciation story. I will discuss the role of reinforcement is association with various other elements of speciation, using evidence from some of my favourite organisms.



Abstracts (coauthor)

Summary:

When individuals from separate populations mate, the resulting hybrid offspring can experience fitness benefits (heterosis) or costs (outbreeding depression) relative to their parents. Understanding the distribution and extent of these genetic benefits and costs is essential for guiding conservation plans that seek to mix wildlife populations. We use meta-analysis to test the hypothesis that phenotypic responses to intraspecific outbreeding can be predicted by combining information on population demography, environmental and cytogenetic contexts. Our dataset comprised 510 effect sizes describing intrinsic outbreeding responses, from 98 studies on animals and plants (79 species). Our results indicate that information on population context can be used to predict both observed outbreeding depression and heterosis. Studies for which we predicted a risk of outbreeding depression showed a cost to fitness (viability, survival, reproduction) in the F2 generation, relative to mid-parent performance. In cases predicted to exhibit heterosis we observed a corresponding fitness benefit relative to the mid-parent. We discuss whether and how these results, and our approach to predicting outbreeding responses, might be useful in conservation practice.

Summary:

At the onset of ecological speciation with gene flow, an ancestral species splits into ecotypes with incomplete reproductive isolation. In multiple systems, ecotypes coexist in many geographical locations, raising the question whether the genetic basis of divergence is identical across the whole range. While some loci may be under divergent selection on large geographical scales (reflecting a spread of favourable alleles), others might be involved in divergence only locally (potentially causing “parallel evolution”). Geographically close locations with a shared colonization history may be expected to share more divergently selected loci than distant ones. Our project aims at estimating the relative contribution of globally and locally selected alleles to divergence between ecotypes of the marine snail Littorina saxatilis. Using snails from Spain, Sweden and the United Kingdom, we performed an RNA-sequencing experiment and analysed the resulting allele frequency data. Because Swedish and British locations probably have a shared postglacial colonization history, we expected them to share loci under divergent selection. We found a large number of single nucleotide polymorphisms (SNPs) which showed differentiation between ecotypes only locally, indicating parallel evolution. In Spain there were more SNPs with significant differentiation between ecotypes than in Sweden and the UK, potentially reflecting stronger divergence between ecotypes. While transcriptome-wide differentiation between Swedish and UK samples was lower than their differentiation from Spain, we did not find a higher number of shared loci under selection. However, we identified >1000 SNPs showing increased differentiation between ecotypes across all three countries, suggesting a shared origin of divergence. Our results contribute to the understanding of the genome as a mosaic of loci with partly independent evolutionary histories and demonstrate how genomic patterns of selection vary across space.

Fewer invited talks by women in evolutionary biology: men accept invitations to speak more often than women

Author(s): Dugdale, HL, Schroeder J, Radersma R, Hinsch M, Buehler DM, Saul J, Porter L, Liker A, De Cauwer I, Johnson PJ, Santure AW, Griffin AS, Bolund E, Ross L, Webb TJ, Feulner PGD, Winney I, Szulkin M, Komdeur J, Versteegh MA, Hemelrijk CK, Svensson EI, Edwards H, Karlsson M, West SA, Barrett ELB, Richardson DS, Van den Brink V, Wimpenny JH, Ellwood SA, Rees M, Matson KD, Charmantier A, Dos Remedios N, Schneider NA, Teplitsky C, Laurance WF, Butlin RK, Horrocks NP

Summary:

Lower ‘visibility’ of female scientists, compared to male scientists, is a potential reason for the under-representation of women among senior academic ranks. Visibility in the scientific community stems partly from presenting research as an invited speaker at organised meetings. We analysed the sex ratio of presenters at the European Society for Evolutionary Biology Congress 2011, where all abstract submissions were accepted for presentation. Women were under-represented among invited speakers at symposia (15% women) compared to all presenters (46%), regular oral presenters (41%) and plenary speakers (25%). At the ESEB congresses in 2001–2011, 8–23% of invited speakers were women. This under-representation of women is partly attributable to a larger proportion of women, than men, declining invitations: in 2011, 50% of women declined an invitation to speak compared to 26% of men. We expect invited speakers to be senior scientists or authors of recent papers in high-impact journals. Considering all invited speakers (including declined invitations), 23% were women. This was lower than the baseline sex ratios of early–mid career stage scientists, but was similar to senior scientists and authors published in high-impact journals. High-quality science by women therefore has low exposure at international meetings, which will constrain Evolutionary Biology from reaching its full potential. We wish to highlight the wider implications of turning down invitations to speak. In particular, under-representation of women among invited speakers reduces the number of female role models for evolutionary biology students and contributes to the leaky pipeline. We encourage conference organisers to implement steps to increase acceptance rates of invited talks.

Summary:

Ludovic DUvaux, Carole Smadja, Julia Ferrari, Within and between species, multigene families (MF) are known to be highly diverse in terms of both Copy Number Variation (CNV) and allelic diversity. Accordingly, within and between population diversities of MF have a strong potential to result from, or to fuel, local adaptation – and possibly speciation. However, these diversities have seldom been contrasted and their relative evolutionary dynamics remain poorly understood. The host-plant races of the pea aphid provide an excellent system to understand these dynamics in the context of speciation with gene flow. Notably, Chemosensory MF (CMF) – e.g. Olfactory Receptors (OR), Gustatory Receptors (GR), Odorant Binding Proteins (OBP) – are critically important for specific host plant recognition, i.e. putatively a main cause of reproductive isolation. We sequenced 120 individuals from 8 races using a target enrichment protocol and Solexa sequencing – guaranteeing a median coverage of 150X. In doing so, we assessed CNV and nucleotidic diversity at about 3000 exons (from CMF, other MF and control genes) and 650 promoters of CMF genes. Preliminary results show CNV is widespread, as it occurs in 65% of all exons (even surprisingly up to 57% for control exons). As with SNPs in single copy genes, most CNV in non CMF genes is shared among races. In contrast, for targets linked to chemosensory genes – notably GR exons and promoters – CNV tends to structure by race. Also, the rate of duplication appears higher for CMF: OR, OBP and promoters show significantly more CNV than other MF. Together, these results suggest that many CMF genes may evolve under positive selection and contribute to adaptation to host plants. In order to better understand the genetic basis of adaptation, work is ongoing to link patterns of CNV (i) to the history of gene flow between races; and (ii) to observed differences in gene expression within and between races across native and non-native host plants.

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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