Graduate position: UFribourg.TheoreticalEvolutionaryBiology PhD position in Theoretical Evolutionary Biology: "The evolution of monoecy in flowering plants" A 4-year PhD position is available to start September 1st, 2026 in the Department of Biology at the University of Fribourg (Switzerland) as part of an SNSF-funded Ambizione research project led by Dr. Thomas Lesaffre (https://thomas-lesaffre.github.io/). Short scientific description: The way flowering plants distribute their reproductive resources between their male and female function is diverse. Most species are cosexual, meaning that individuals produce both pollen and ovules, but vary widely in how much they allocate to each function. Others have evolved polymorphic sexual systems where individuals specialise to varying degrees into their male or female function, so that essentially any combination of cosexual and unisexual male and female individuals may coexist in a single population. This great diversity of ways in which male and female function are distributed amongst individuals has attracted much attention from evolutionary biologists. As a result, the mechanisms driving its evolution are now thought to be fairly well-understood. However, plant sexual strategies do not only vary between individuals, but also within individuals, as sexual reproduction in flowering plants occurs through the production of many flowers that may each contain different amounts of pollen and ovules. This is most striking in the case of monoecy, where male and female function are carried by different flowers on the same individual. Monoecy is the second most frequent sexual system in Angiosperms after hermaphroditism (where flowers are bisexual), but the mechanisms driving evolutionary transitions to and from this system remain poorly understood. This is in part because theoretical models on sexual system evolution have focused on explaining variation at the individual level, leaving within-individual patterns of allocation largely unaccounted for. In this project, the PhD student will work together with Dr. Lesaffre to develop new theory exploring the evolutionary mechanisms underlying the diversity of within-plant patterns of allocation. Consider applying if you: * Hold (or will soon obtain) a Master's degree in biology, mathematics or physics. * Are interested in evolutionary ecology, especially that of plants and flowers. * Have a keen interest for mathematical modelling and conceptual thinking. * Enjoy problem solving and coding. The position is open to applicants worldwide. We welcome applications from individuals of all backgrounds and encourage candidates from underrepresented groups to apply. Applications should be addressed to Dr. Lesaffre (thomas.lesaffre@unil.ch) before the end of the day on April 24th, 2026. Your application should include the following elements: * A personal motivation letter (one or two pages). * Your CV with the contact details of two references. * Your Master's thesis if available, or a short description of it in the form of an abstract. * Your academic transcripts. More practical information: The PhD position is funded for four years from September 1st, 2026. During that time period, the student will be registered at the doctoral school and will benefit from two fixed-term work contracts: an initial one-year contract followed by a three-year one. The gross annual salary is around 53'000 CHF per year (exact amount may be vary according to SNSF and institutional guidelines). Funding is available for conference, course and workshop attendance. Because Dr. Lesaffre does not currently hold a tenured position, the PhD student will be co-supervised by Prof. Thomas Flatt, who will be their official supervisor for the duration of their studies. Fribourg is vibrant medieval university town with a large student population situated close to the beautiful Alps and well-connected by train. It is a bilingual French/Swiss German part of Switzerland, with a French-speaking majority. Though research will be conducted in English and knowledge of local languages is not expected, learning a few words of French might prove useful in everyday life. Contact for further information: For informal enquiries, please contact Dr. Lesaffre directly at thomas.lesaffre@unil.ch Thomas LESAFFRE (to subscribe/unsubscribe the EvolDir send mail to golding@mcmaster.ca)