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The expression, selection and evolution of combined versus separate sexes in an annual plant

Titel Englisch The expression, selection and evolution of combined versus separate sexes in an annual plant
Gesuchsteller/in Pannell John Richard
Nummer 163384
Förderungsinstrument Projektförderung (Abt. I-III)
Forschungseinrichtung Département d'Ecologie et d'Evolution Faculté de Biologie et de Médecine Université de Lausanne
Hochschule Universität Lausanne - LA
Hauptdisziplin Botanik
Beginn/Ende 01.03.2016 - 30.06.2019
Bewilligter Betrag 756'000.00
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Alle Disziplinen (3)

Disziplin
Botanik
Genetik
Oekologie

Keywords (11)

Population genetics; Sexual system; Experimental evolution; Hermaphroditism; Life history; Sex allocation; Sex determination; Dioecy; Competition; Pollen dispersal; Natural selection

Lay Summary (Französisch)

Lead
Most plants are hermaphroditic, but separate sexes have evolved frequently. Less frequently, plants with separate sexes evolved back towards hermaphroditism. This project will use a number of approaches to understand why such transitions come about, and what their implications are for the investments made by individuals to reproduction and growth, and for the evolution of their genome.
Lay summary

La recherche inclura aussi bien du travail théorique qu'empirique et sera organisée en deux parties. La partie A traitera de l’évolution de la séparation des sexes à partir de l’hermaphrodisme et de leur maintenance ainsi que des conséquences de la séparation des sexes sur les différences clés entre mâle et femelle (dimorphisme sexuel). La partie B traitera de la perte de la séparation des sexes et de la réversion vers l'hermaphrodisme. Dans la partie empirique nous utiliserons comme organisme modèle la plante Mercurialis annua qui est remarquable de par son importante variation de systèmes sexuels mais aussi de part les connaissances que nous avons accumulées lors des dernières années sur son écologie, sa génétique des populations, sa génétique écologique et sur son génome et ses transcriptomes. Dans la partie A nous: évaluerons le rôle de la séparation des sexes sur l'évolution de l’isolement reproductif entre les différentes lignées du complexe Mercurialis annua; investiguerons la dynamique évolutive de la stérilité mâle chez M. annua, un sujet qui n'a pas encore été investigué pour des populations où ségrègue déjà une stérilité de la fonction femelle ; et considérerons l'évolution du dimorphisme sexuel dans des situations où les fonctions mâle et femelle sont limitées par différentes ressources acquises et utilisées par différents organes. Dans la partie B nous : étudierons la réponse génotypique et génomique à la réversion, depuis des sexes séparés à l'hermaphrodisme, observée lors d'une expérience de sélection effectuée dans notre laboratoire lors des 4 dernières années ; et modéliserons grâce à des simulations informatiques la perte de la séparation des sexes. Ensemble les deux sous-projets de ce plan de recherche contribuerons substantiellement à la compréhension de l'évolution de sexes séparés versus combinés chez les plantes et les implications génomique.

 

Direktlink auf Lay Summary Letzte Aktualisierung: 23.02.2016

Lay Summary (Englisch)

Lead
Most plants are hermaphroditic, but separate sexes have evolved frequently. Less frequently, plants with separate sexes evolved back towards hermaphroditism. This project will use a number of complementary approaches to understand why such transitions come about, and what their implications are for the investments made by individuals to reproduction and growth, and for the evolution of their genome.
Lay summary

The research will include both theoretical and empirical work and is organised into two themes. Theme A will deal with the evolution of separate sexes from hermaphroditism, their maintenance, and the consequences of separate sexes for key differences between males and females (sexual dimorphism). Theme B will deal with the breakdown of separate sexes and reversions back to hermaphroditism. The empirical work will be use as a model the plant Mercurialis annua, which is remarkable for its high variation in sexual systems and the knowledge we have accumulated over recent years about its ecology, its population and ecological genetics, and its genome and transcriptomes. In Theme A we will: assess evidence for the role of separate sexes in the evolution of reproductive isolation between lineages in the Mercurialis annua complex; investigate the evolutionary dynamics of male sterility in M. annua, a subject that has hitherto not been investigated for populations already segregating for female sterility; and consider the evolution of sexual dimorphism in situations where male and female function is limited by different resources, supplied by different organs, and used by different sinks. In Theme B: we will study the genotypic and genomic responses of a reversion from separate sexes to hermaphroditism brought about by experimental evolution in our lab over the last four years; and we will use computer simulations to model the breakdown of separate sexes. Together, the subprojects of this research proposal will make a substantial contribution to understanding of the evolution of combined versus separate sexes in plants, and their genomic implications. 

Direktlink auf Lay Summary Letzte Aktualisierung: 23.02.2016

Verantw. Gesuchsteller/in und weitere Gesuchstellende

Mitarbeitende

Verbundene Projekte

Nummer Titel Start Förderungsinstrument
141052 The expression, selection and evolution of combined versus separate sexes in an annual plant 01.11.2012 Projektförderung (Abt. I-III)
147625 The evolutionary genomics of recombining sex chromosomes 01.04.2014 Sinergia
141052 The expression, selection and evolution of combined versus separate sexes in an annual plant 01.11.2012 Projektförderung (Abt. I-III)

Abstract

The great majority of plant species are hermaphroditic, but separate sexes have evolved frequently and occur in about half of angiosperm families. How have these transitions come about, and what can they tell us about plant adaptation at the phenotypic and genetic levels? How is sex determined, and how do sex chromosomes evolve? What is the optimum allocation of resources by males and females to vegetative growth and reproduction? How do secondary sexual differences between males and females arise, and how do they affect the evolutionary stability of separate sexes? And indeed what might provoke the breakdown of separate sexes and reversions back to hermaphroditism, and what evolutionary path is followed when this occur? These questions, which are central to on-going attempts to understand plant sexual diversity, will be addressed by this project. The project continues a research program aimed at understanding the causes and consequences of the evolution of dioecy (separate sexes) in plants and its breakdown in reversions from back to hermaphroditism. It will build on an outstanding conceptual and empirical base by integrating data acquired from fieldwork, ecological experiments, the analysis of genomic and gene expression data, and theoretical modelling. The project will co-ordinate the activities of two PhD students and two postdoctoral researchers working on independent but mutually supporting sub-projects. The research planned falls into two themes. Theme A will deal with the evolution of separate sexes from hermaphroditism, their maintenance, and the consequences of separate sexes for sexual dimorphism. Theme B will deal with the breakdown of dioecy and its reversion back to hermaphroditism. All empirical work will be use the Mercurialis annua species complex as a model. This taxon is remarkable for its high variation in sexual systems among lineages, which allows a number of important hypotheses about plant sexual reproduction to be tested. It is also remarkable as a study system because of the knowledge we have accumulated over recent years about its ecology, its population and ecological genetics, and its genome and transcriptomes. Theme A will comprise three subprojects. The first, conducted by a PhD student, will assess evidence for Haldane’s Rule in the Mercurialis annua species complex. Haldane’s Rule states that if one sex in the progeny has lower fitness, or is even inviable or sterile, it will be the heterogametic sex (the males in species with an XY sex-determination system). The Rule applies almost universally in animals, and has only recently been confirmed in a single plant species. We have recently found patterns that are consistent with Haldane’s Rule in the M. annua complex (male inviability), but also those that seem to contradict it (female infertility). The system is ripe for a stimulating series of investigations to understand the scope of Haldane’s Rule. The second subproject in Theme A, conducted by the second PhD student, will investigate the evolutionary dynamics of male sterility in M. annua. This project is particularly novel, because it will address the dynamics of male sterility in populations already segregating for female sterility - and phenomenon long considered by models but never studied empirically. The third subproject in Theme A, conducted by a postdoc with modelling skills, will consider the evolution of sexual dimorphism in situations where male and female function is limited by different resources, supplied by different organs, and used by different sinks. Theme B will comprise two subprojects, both conducted by postdocs. The first will involve the continuation for two more generations of a selection experiment that is bringing about a transition, by experimental evolution, of populations from dioecy to monoecy as a result of severe mate limitation. In the first three generations, pollen production by ‘leaky’ females has increased by 1.6-, 22- and 31-fold. After two more generations, we will apply and ‘evolve-and-resequence’ (E&R) approach to assess the genomic architecture of this remarkable response to selection. The E&R approach will be complemented by a QTL analysis on genotypes produced by crossing extreme phentotypes between control and evolved lines. The second subproject, conducted by the theory postdoc, will use Monte Carlo simulations to model the breakdown of dioecy (as found in our selection experiment) under conditions of frequent extinctions and colonisations in a metapopulation. This modelling will extend work done in the lab on sex-ratio evolution in a metapopulation by incorporating quantitative genetic variation (with different genomic architectures) of hermaphroditic sex allocation.
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