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Tatiana Dimitriu
Université Paris-Descartes
Faculté de Médecine

Bacterial sex can enhance cooperation


Author(s): Dimitriu, T, Julien, B, Ariel, L, François, T


Mobile genetic elements, such as plasmids, are the most prominent mechanism of bacterial sex and play a large role in bacterial adaptation. Plasmids move between bacteria by conjugation, an active, unidirectional horizontal transfer of genetic material from donor to recipient cells. Since conjugation is costly for donors and is primarily controlled by the plasmid itself, horizontal transfer is usually seen as parasitism of the bacterial hosts. However, chromosomal genes can also influence horizontal transfer. Transferring plasmids could benefit the donor host by generating a specific behavior in recipients. Using both modeling and experimental work we show that if cooperation genes are located on the plasmid, conjugation can benefit the host bacteria by facilitating the maintenance of cooperation. We modeled populations of donor and recipients and showed that horizontal transfer increases the selection for cooperation by increasing relatedness and the overall amount of public good secreted in the population. This effect in turn allows for the selection of transfer: when cooperation is needed, genes increasing donor and recipient abilities can be selected both on the plasmid and on the chromosome. Our results could explain the high frequency of genes related to cooperation that are located on plasmids. In addition to the models, we used a synthetic system with independent control of cooperation and conjugation to experimentally test their relationship in Escherichia coli. We introduced multiple fluorescent proteins into bacterial strains and were able to measure the frequency of different types of bacteria, plasmids, as well as transfer events, by flow cytometry. We show that plasmid transfer indeed increases the selection for cooperation. Based on our models and experiments, we can conclude that the role that bacterial sex plays in evolution is strongly linked to the presence of and interaction with cooperation via public good secretion.

Stuart Wigby
University of Oxford
Department of Zoology
United Kingdom

Condition and molecular mating strategies in Drosophila melanogaster: large females get more, small males try harder


Author(s): Wigby, S, Sirot, L, Perry, J, Kim, Y


Theory predicts that males in good condition should produce larger sexually selected traits, such as ejaculates, but the allocation of ejaculates should also vary with the number of mating opportunities available to males. Fruit flies, Drosophila melanogaster, who develop under crowded larval conditions have reduced body size, and these small males posses fewer ejaculate resources. We show, however, that these small males transfer relatively higher proportion of their reserves of a key seminal protein, sex peptide, at mating, and manage to match large males in the quantity they transfer to females. Small males could potentially benefit form this strategy because they have fewer mating opportunities: thus they are predicted to invest relatively more in each mating opportunity they get. Large females receive larger quantities of the receptivity-inhibiting sex peptide from males of all sizes, but unexpectedly these large females remate sooner than small females. Thus, female mating frequency is strongly dependent on the female developmental environment. Future work should aim to uncover to what extent female condition and male influences interact to regulate female remating rate.

Luke McNally
University of Edinburgh
Centre for Immunity, Infection and Evolution
United Kingdom

Cooperative niche construction facilitates zoonosis in pathogenic bacteria


Author(s): McNally, L, Viana, M, Brown, SP


The majority of emergent human pathogens are zoonotic in origin. Understanding the factors underlying the evolution of pathogen host range is therefore of critical importance in protecting human health. Classical evolutionary theory predicts that the evolution of generalism in pathogens will be subject to trade-offs, and hence reduced within-host fitness compared to specialists, as pathogens evolve to tolerate multiple host environments. Here we show that rather than passively reacting to host environments, bacteria can use niche construction via cooperative secretions to achieve host generalism. We use an epidemiological framework to show that cooperative niche construction strategies can outcompete both specialists and classical generalists under a wide range of realistic conditions. We then use a phylogenetic comparative analysis of 191 bacterial pathogens to show that larger secretome sizes are associated with a greater probability of zoonosis, in agreement with our theoretical predictions. Our results suggest that cooperative behaviour is a key factor in the evolution of generalism in bacteria, and that monitoring programmes focusing on the horizontal transfer of secreted proteins could help identify future emerging human pathogens.

Lutz Becks
Max Planck Institute for Evolutionary Biology

Eco-evolutionary dynamics and the evolution of sex


Author(s): Becks, L


The evolution of sexual reproduction is one of the most important and controversial problems in evolutionary biology because sexual reproduction is almost universal while its inherent costs have made its maintenance difficult to explain. Major hypotheses on the evolution of sex predict sex to be advantageous when the environment changes frequently over time. Recurrent change can occur as a result of eco-evolutionary feedback dynamics but has not been considered in the context of the evolution of sex. An eco-evolutionary feedback loop occurs when environmental change causes natural selection in a population within a few generations, and the resulting trait evolution then modifies the environment, causing further selection and evolution, and so on. An example for this eco-evolutionary feedback comes from a predator-prey system where the algal prey evolves a defence against predation when grazing by rotifer is intense, and loses the defence, but gains competitive ability when the predators (rotifers) are scarce and prey are abundant. I present experimental results showing that the rate of sex evolved to higher rates in the rotifer when eco-evolutionary feedback dynamics occur. In contrast, the rate of sex evolved to lower rates in control populations where the trait evolution in the algae and thus the eco-evolutionary feedback was prohibited. Thus the changes driven by the interplay of ecological and evolutionary change on one time scale can provide conditions allowing for a more globally relevant explanation for the evolution of sex.

Deborah Dawson
University of Sheffield
Animal and Plant Sciences
United Kingdom

Engineering microsatellite markers to study and compare a wide range of species


Author(s): Dawson, DA


We have developed a set of conserved avian markers with high cross-species utility in order to save resources and enable new comparisons between species. These markers will not only reduce the necessity and expense of microsatellite isolation for a wide range of genetic studies, including avian parentage and population analyses, but will also now enable comparisons of genetic diversity among different species (and populations) at the same set of loci, with no or reduced bias. No other marker type enables such comparisons. Additionally, these markers (i.e. microsatellites), in contrast to single nucleotide polymorphism (SNP) and genotyping-by-sequencing methods, are readily typed in samples of low DNA quality or concentration (e.g. non-invasive samples or museum specimens), and enable the quick cheap identification of species, hybrids, clones and ploidy. We selected zebra finch (Taeniopygia guttata) sequences that possessed a repeat region and that displayed high sequence similarity to chicken (Gallus gallus). Each primer sequence was a complete match to zebra finch and, after accounting for degenerate bases, at least 86% similar to chicken. These markers are of especially high utility in passerines, but also show utility in non-passerine species. The approach used here can be applied to other taxa in which appropriate genome sequences are available.

Katie Duryea
Dartmouth College
United States

Females bite back: sexual conflict and the evolution of venom proteins in the reproductive tract of female anole lizards


Author(s): Duryea, K, Calsbeek, R, Kern, A


Reproductive proteins evolve rapidly in many species, yet the ecological significance of these proteins remains largely unknown. In this study, we investigate reproductive proteins in Anolis lizards, a system in which the ecological basis for a fertilization bias has been established. When female A. sagrei mate with multiple males, they preferentially use the sperm from larger sires to produce sons. Field experiments reveal that this bias may be adaptive, based on patterns of offspring survival. Using Next Generation Sequencing, we investigate genes that are expressed in the reproductive tract of female anoles. Comparisons with Drosophila, the system in which female reproductive gene expression has been best studied, reveal broad similarities in the genetic response to mating across these distantly related taxa. Additionally, we investigated the molecular evolution of a group of serine proteases that are differentially expressed after mating in the reproductive tract of female anoles. Of these serine proteases, some appear closely related to snake venom proteins. Due to the deep origin of venom toxin in squamates and the hypothesized origin of Drosophila reproductive serine proteases from digestive proteases, our results suggest that Anolis reproductive serine proteases and venom serine proteases could share a common phylogenetic origin. This would imply that digestive enzymes have been involved in the evolution of cryptic aspects of female choice in multiple mating systems.

Hannah Dugdale
University of Sheffield
Animal and Plant Sciences
United Kingdom

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


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.

Cristian Cañestro
Universitat de Barcelona

Functional impact of gene loss in genome evolution and animal diversity: the chordate Oikopleura dioica as a case study


Author(s): Cañestro, C, Martí-Solans, J, Badia-Ramentol, J, Godoy-Marin, H, Albalat, R


What is the impact of gene losses in the generation of biodiversity is a crucial question in Evolutionary Biology that still remains largely unknown. Until now, gene losses have been often neglected because the proof for gene loss is negative and difficult to detect, especially in complex genomes outside bacteria and yeast. The state-of-the-art sequencing technology offers us for the first time the exciting opportunity to perform exhaustive genome-wide analyses to detect unambiguous cases of gene losses in animals with complex genomes. Our group has started an ambitious project with two main aims. First, we will sequence full genomes of a several individuals from many populations and species of the larvacean class to gain novel insights into the dynamics of gene losses, to understand the correlation of gene loss with phenotypic traits, and to test for evolutionary gene dispensability (EGD), a new concept that we have developed in this project. Second, we will perform systematic knockdown experiments and RNA–seq analyses to provide functional evidence for the impact of gene loss, and test for adaptive and neutral events of gene loss in the context of genetic robustness and gene network connectivity. In this project, we use the urochordate Oikopleura dioica (and other related larvacean species) as case study, because the recent genome-sequencing project, in which we participated, revealed that this organism exhibits the smallest genome and the largest genomic plasticity of all metazoans known to date, including an extraordinary amount of gene losses. Preliminary results show the feasibility to identify actual genes that are in the process of being lost in different populations, which appear as potential candidates of losses that can be adaptive.

Kay Lucek
University of Bern
Institute of Ecology and Evolution

Historical contingency and parallel parapatric divergence between lake and stream stickleback pairs of variable age


Author(s): Lucek, K, Sivasundar, A, Kristjánsson, BK, Skúlason, S, Seehausen, O


When genetic constraints restrict phenotypic evolution, diversification is predicted to evolve along the so-called line of least resistance, the leading axis of the underlying G matrix. To address the importance of such constraints and their resolutions, empirical studies on parallel cases of phenotypic divergence of different age are valuable. However such studies are very rare. Here we study the parapatric evolution of six independently evolved lake and stream stickleback systems from Iceland and Switzerland, ranging in age from a few decades to several millennia. Using phenotypic data, we test to which degree parallel evolution occurs among independent lake-stream freshwater systems as well as during the marine-freshwater transition. We furthermore investigate in both cases how the underlying evolutionary trajectories diverge through time. We find that strong and consistent phenotypic divergence occurred independent of time for both the parapatric lake-stream systems and for the marine-freshwater transition. The extent of phenotypic divergence differs however between the two countries studied here. This indicates that historical contingency partially shapes the phenotypic outcome of divergent selection in lake-stream environments. Moreover, our results suggest that parapatric phenotypic divergence can evolve along a common evolutionary trajectory for some trait combinations, independently of their evolutionary age. The directionality of change in these traits may however differ due to historical contingency or environmental constraints. Other trait combinations differ rather between the two investigated countries but less within, suggesting that the underlying G matrix of each country could be differentially constrained. Thus phenotypic plasticity may play an important role during the colonization of novel habitats, where adaptive peak shifts may be readily achieved.

Sascha Krenek
Faculty of Environmental Sciences of Technische Universität Dresden
Institute of Hydrobiology

Hsp70 gene family evolution and differential expression in microbial eukaryotes


Author(s): Krenek, S, Schlegel, M, Berendonk, TU


In eukaryotes, members of the 70 kDa heat-shock protein family (Hsp70) are separated into four subfamilies according to their sub-cellular localisation and function. While in metazoans multiple cytosolic Hsp70s can be found, which are either constitutively expressed and/or stress-inducible, information about the copy number and diversity as well as differential expression of hsp70 genes in microbial eukaryotes is scarce. In this study, we have characterised the hsp70 gene family of the ciliate Paramecium caudatum to gain insight into the evolution and differential response to temperature stress of the distinct Hsp70 family members in protists. We further focused on the evolution of heat-inducibility in cytosolic hsp70s and investigated intraspecific differences in hsp70 gene expression to evaluate its potential use as biomarkers for temperature adaptation studies in Paramecium. Phylogenetic analyses disclosed five homologous groups, each with a closer relationship to orthologous hsp70s of Paramecium tetraurelia than to another P. caudatum Hsp70-group, indicating duplication events preceding Paramecium speciation. Furthermore, heat-shock expression studies and comparative EST analyses revealed one cytosolic group as the major heat inducible hsp70s in both P. caudatum and P. tetraurelia, suggesting a functionally conserved evolution of this gene family in Paramecium. In addition, the herein developed RT-qPCR assay unveiled different expression patterns between diverse thermal tolerant P. caudatum clones, demonstrating the potential use of Hsp70 as a biomarker for environmental stress studies in Paramecium. Interestingly, our analyses also suggest that heat-inducibility of cytosolic hsp70s evolved several times independently during the course of eukaryotic evolution, thereby indicating convergent evolution during Hsp70 subfunctionalization.


Chairman: Octávio S. Paulo
Tel: 00 351 217500614 direct
Tel: 00 351 217500000 ext22359
Fax: 00 351 217500028


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


Computational Biology & Population Genomics Group