My research spans a wide variety of questions, all related to sex-specific selection, sex-chromosome evolution, and major evolutionary transitions in flowering plants. Here, I give a brief description of the three main branches of my research program. I am actively recruiting post-docs to work with me, and the Genetics of Sex Differences Research Group here at Lund University, of which I am a member.

Angiosperm evolutionary demography

Compared to animals, flowering plants exhibit a staggering diversity of reproductive form and function, from combined to separate sexes (and nearly everything between), outcrossing to self-fertilization, and a bewildering array of floral architectures to achieve pollination by animal or abiotic vectors. The purpose of this 4-5 year Swedish Research Council funded research project is to develop a theoretical frame- work to understand how this tremendous reproductive diversity influences the demography of populations, and how demographic processes feedback to influence the evolution of plant reproductive and life-history traits. This work will push the boundaries of evolutionary demography theory by combining mendelian genetics with demographic matrix models that correctly take into account critical features of angiosperm mating systems and sexual reproduction by pollination. In particular, the models will rigorously explore the eco-evolutionary consequences of the joint contributions of male and female fertility to individual fitness. A major strength of the approach is that the models can be easily parameterized using empirically estimated demographic rates, allowing theoretical predictions to be grounded in the biology of real populations.

This project is a major extension of my recent work with Dr. Lotte DeVries combining population genetics theory with demographic matrix models that correctly deal with the intricacies of pollination and mixed mating systems that are so common among hermaphrodite flowering plants. We are looking for a highly motivated and qualified post-doc to work with myself and Dr. DeVries on this project. Please send an email to express your interest.

Genomics of Sex Determination in the Hawaiian Wikstroemia

Despite intense study for over 100 years, understanding how and why genes determining sex evolve – and the consequences for the chromosomes harboring them – remains an open problem in evolutionary biology. One obstacle is that most previous work has focused on ancient sex chromosome systems, like those found in mammals, where recombination suppression and genetic degeneration has obliterated any signs or signals of how genetic sex-determination evolved in the first place. The goal of this project is to understand the genomic changes giving rise to at least two and possibly three parallel transitions from hermaphroditism to dioecy via the evolution of new sex chromosomes within an endemic Hawaiian radiation of the flowering plant genus Wikstroemia (Thymelaeaceae; 12 spp.). Using a combination of genomics, bioinformatics, gene expression, and greenhouse experiments, we are aiming to: (1) locate and fully annotate sex-linked regions of the genome associated with each form of dioecy; (2) clarify the systematics of this radiation and study the biogeography of sex-linked genes, and the relative times of origin and whether/how recombination suppression has evolved for each form; and (3) determine what genes/developmental pathways are involved in sex-determination in these closely related lineages. This fascinating radiation offers a unique snapshot of repeated evolution of genetic sex- determination from a common genetic starting point, shedding new light on how and why evolutionary transitions to separate sexes occur.

My collaborator Bengt Hansson and I are actively recruiting M.Sc. students and a post-doctoral researcher with bioinformatics experience to join this project. Please email me if you are interested!

Population Genetics Theory

The humming engine of my research is theoretical population genetics. I am interested in a wide variety of questions related to the maintenance of genetic variation in systems involving sex-specific selection, evolution and adaptation in partially selfing populations, sex chromosome and genome structural evolution, frequency dependent selection, and the consequences of evolutionary transitions in mating/ploidy/reproductive systems. I am increasingly interested in developing theory that makes testable predictions that can be addressed by modern genomic methods.

M.Sc. students and post-docs who might be interested in these or other questions in evolutionary and population genetics are encouraged to contact me to discuss possible projects and funding opportunities!

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