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Processes underlying the transition from sexual reproduction to asexuality

Titel Englisch Processes underlying the transition from sexual reproduction to asexuality
Gesuchsteller/in Schwander Tanja
Nummer 170627
Förderungsinstrument SNF-Förderungsprofessuren
Forschungseinrichtung Département d'Ecologie et d'Evolution Faculté de Biologie et de Médecine Université de Lausanne
Hochschule Universität Lausanne - LA
Hauptdisziplin Zoologie
Beginn/Ende 01.02.2017 - 31.01.2019
Bewilligter Betrag 798'074.00
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Alle Disziplinen (3)

Disziplin
Zoologie
Oekologie
Genetik

Keywords (4)

Insect; Parthenogenesis; Genetic systems; Reproduction

Lay Summary (Französisch)

Lead
Les méchanismes résponsables des transitions de la reproduction sexuée à la reproduction asexuée
Lay summary
La reproduction sexuée: A quoi est-ce que ça sert? Identifier les facteurs qui sont responsables pour le maintien de la reproduction sexuée dans les populations naturelles est un but central en biologie évolutive. La reproduction sexuée est associée avec de multiples coûts, surtout chez les animaux où les mâles contribuent souvent peu de ressources à la descendance. Les coûts associés avec la reproduction sexuée ont alors motivé des recherches pour identifier les bénéfices. Par contre, un aspect qui n’est souvent pas considéré est que les espèces asexuées dérivent d’ancêtres sexués et que de multiples contraintes génétiques et développementales peuvent empêcher une transition durable de la reproduction sexuée à la reproduction asexuée.  Comment de nouvelles espèces asexuées peuvent alors apparaitre reste largement inconnu. Le but de ce projet est donc de comprendre comment de nouvelles espèces asexuées évoluent, et quel type de changements génétique et développemental sont à la base de transitions de la reproduction sexuée à la reproduction asexuée. Différents insectes, notamment des phasmes et des guêpes, sont utilisés comme modèles d’étude.
Direktlink auf Lay Summary Letzte Aktualisierung: 03.01.2017

Verantw. Gesuchsteller/in und weitere Gesuchstellende

Mitarbeitende

Publikationen

Publikation
Effective purifying selection in ancient asexual oribatid mites
Brandt A Schaefer I Glanz J Schwander T Maraun M Scheu S Bast J (2017), Effective purifying selection in ancient asexual oribatid mites, in Nature Communications, 8, 873.
Evolution and comparative ecology of parthenogenesis in haplodiploid arthropods
van der Kooi C. J. Matthey-Doret C. and Schwander T. (2017), Evolution and comparative ecology of parthenogenesis in haplodiploid arthropods, in Evolution Letters, 1, 304.
Patterns and mechanisms in instances of endosymbiont-induced parthenogenesis
Ma W-J Schwander T (2017), Patterns and mechanisms in instances of endosymbiont-induced parthenogenesis, in Journal of Evolutionary Biology, 30, 868-888.

Zusammenarbeit

Gruppe / Person Land
Formen der Zusammenarbeit
Rocio Gomez lab/Universidad Autónoma de Madrid Spanien (Europa)
- vertiefter/weiterführender Austausch von Ansätzen, Methoden oder Resultaten
Vorburger lab/ EAWAG Schweiz (Europa)
- vertiefter/weiterführender Austausch von Ansätzen, Methoden oder Resultaten
- Forschungsinfrastrukturen

Wissenschaftliche Veranstaltungen

Aktiver Beitrag

Titel Art des Beitrags Titel des Artikels oder Beitrages Datum Ort Beteiligte Personen
Phylogenetics Symposium Berlin Vortrag im Rahmen einer Tagung Gene expression and evolutionary rate changes after parallel evolution of asexuality in stick insects 18.11.2017 Berlin, Deutschland Schwander Tanja;
Behavioural and Evolutionary Ecology Lecture Einzelvortrag Gene expression and evolutionary rate changes after parallel evolution of asexuality in stick insects 11.10.2017 Bern, Schweiz Schwander Tanja;
Departmental talk at IST Vienna Einzelvortrag Gene expression and evolutionary rate changes after parallel evolution of asexuality in stick insects 19.07.2017 Vienna, Österreich Schwander Tanja;
Departmental Talk, University of Oxford Einzelvortrag Gene expression and evolutionary rate changes after parallel evolution of asexuality in stick insects 24.04.2017 Oxford, Grossbritannien und Nordirland Schwander Tanja;
Genomics of asexual lineages workshop Vortrag im Rahmen einer Tagung Various (Different titles for talks of different contributors) 28.03.2017 Namur, Belgien Schwander Tanja; Bast Jens;


Verbundene Projekte

Nummer Titel Start Förderungsinstrument
139013 Processes underlying the transition from sexual reproduction to asexuality 01.02.2013 SNF-Förderungsprofessuren
115585 Evolution and genetic basis of pathenogenesis in Timema walking sticks 01.05.2007 Stipendien für angehende Forschende

Abstract

Sex: What is it good for? Identifying the factors that drive the maintenance of sexual reproduction in natural populations remains a central goal in evolutionary biology. Sexual reproduction is associated with many costs, especially in metazoans, where males often provide little or no resources to their offspring. Females then pay the full cost of reproduction, yet only contribute half of their genome to each offspring. This generates a transmission disadvantage relative to parthenogenesis, which is two-fold in species that invest equally in both sexes. The fact that sexual reproduction is very costly, but the most widespread form of reproduction, has motivated a scientific quest for identifying mechanisms and situations that can generate benefits for sex. One aspect that is typically overlooked however, is that current parthenogens derive from sexual ancestors and that several genetic and developmental constraints should present a severe barrier to transitions from sexual reproduction to parthenogenesis. How new parthenogenetic species evolve and overcome such constraints remains largely unknown. The purpose of this research project is to develop insights into how transitions from sexual reproduction to parthenogenesis occur, using different insect groups as model systems.In the first three years of the project, we have developed cytological and immunostaining assays in a group of stick insects (genus Timema) for which we described seven independent transitions from sexual reproduction to parthenogenesis. These assays allowed us to show that parthenogenesis in at least one Timema stick insect species occurs via endoduplication. In the extension of the running project we propose to apply the same methods to four additional Timema parthenogens to infer whether the independent evolution of parthenogenesis in related species occurs via convergent or divergent mechanisms. Convergent parthenogenesis modes in the independently derived Timema asexuals would be indicative of high constraint levels, even in this group characterized by an unusually high number of parthenogenetic species. In parallel, we have identified a genomic region associated with parthenogenesis in a parasitoid wasp (Lysiphlebus fabarum). We have introgressed ‘parthenogenesis alleles’ from a parthenogenetic into a sexual strain of the same wasp species, taking advantage of rare males occasionally produced by parthenogenetic females. Using a genotyping-by-sequencing approach based on RAD-seq, we have identified loci associated with parthenogenetic reproduction in the introgression lines. Strikingly, when placing these loci on a newly generated linkage map, we found that they all mapped to the same linkage group and appear to be organized into a supergene structure. Parthenogenetic females are homozygous for this ‘parthenogenesis supergene’ while females heterozygous for the parthenogenesis supergene (as well as non-carriers) reproduce sexually, confirming earlier reports of single-locus recessive inheritance of parthenogenesis in L. fabarum. Interestingly, the Lysiphlebus genus comprises extensive reproductive polymorphism, with several sexual and parthenogenetic species as well as species comprising sexual and parthenogenetic strains. In the project extension, we propose to test whether parthenogenesis in related species shares the same genetic basis as the one uncovered in L. fabarum. We will compare genome-wide divergence and polymorphism in pairs of Lysiphlebus species and lines with different reproductive modes to test whether increased levels of divergence (relative to the genome average) in pairs occur in genomic regions homologous to the ‘parthenogenesis supergene’ in L. fabarum. These comparisons will allow us to infer whether the parthenogenesis supergene represents an ancestral polymorphism that segregated prior to speciation in the Lysiphlebus genus, whether the supergene spread across species barriers via admixture, or whether different parthenogenetic strains and species evolved independently and via different molecular mechanisms in the genus Lysiphlebus. Understanding whether analogous genetic and developmental changes underlie asexuality in different lineages that evolved in parallel can shed light on the degree of evolutionary constraints in the transition from sexual reproduction to parthenogenesis and is therefore of prime importance to investigate the evolution of new asexual taxa and the outcome of competition between sexual and asexual lineages. Understanding the mechanisms favoring and constraining the transition from sexual reproduction to asexuality will allow us to gain novel insights into one of the major questions in evolutionary biology: why have sex?
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