WELCOME!
Imagine a world without nature’s astonishing diversity. Fortunately, we don’t have to. But how did this diversity arise, what maintains it, and why isn’t there even more of it in some cases? As an evolutionary biologist currently working at the University of Bern (Switzerland), these and related questions are what drives my research.
I am intrigued by the processes that generate biological diversity, particularly adaptation and speciation. My research examines how ecological differences shape selection and how populations respond – both phenotypically and genetically – to these pressures. I am especially interested in addressing conceptual challenges and approach them with a combination of methods, including field and laboratory experiments, phenotypic analyses, high-throughput genomic sequencing, and computational modeling.
A longstanding challenge in evolutionary biology is that we often try to infer past processes from present-day patterns. To address this, I focus on systems where evolutionary change can be observed on ecological timescales. More recently, I have also placed particular emphasis on manipulative field experiments, together with comparative genomic and phenotypic analyses, to provide direct evidence of selection in natural populations.
My main study system is the threespine stickleback, a small fish that has rapidly adapted to diverse freshwater habitats across the Northern Hemisphere since the last ice age (< 12,000 years). Thanks to their rich genomic resources and their suitability for both field and laboratory studies, sticklebacks provide an outstanding system for uncovering the ecological and genetic factors that drive, sustain, or constrain evolutionary change. In addition to sticklebacks, my research has also explored diversification in other systems, including cichlids, icefish, lampreys, sculpins, and Daphnia crustaceans.
My ongoing research includes the following topics:
Recombination: Genetic recombination is key to evolution, yet its rate varies across genomes. I study why this happens and how it shapes adaptation and diversification. I’m also interested in chromosomal inversions due to their impact on recombination. To explore these processes, I use simulations, genetics, population genomics, and meta-analyses. See e.g.: Roesti et al. 2012, Roesti et al. 2013, Berner & Roesti 2017, Haenel et al. 2018, Roesti 2018, Liu et al. 2022, Roesti et al. 2022
Genetics & genomics of adaptation: How does rapid adaptation of a population work at the genomic level? How many loci are involved, where are they within the genome, and what is their effect? And, what genomic signatures does parallel and divergent adaptation leave? See e.g.: Roesti et al. 2012, Roesti et al. 2014, Roesti et al. 2015, Haenel et al. 2019, Laurentino et al. 2020, Poore et al. 2022, Roesti et al. 2022
Species interactions: What is the role of species interactions in evolutionary diversification? I tackle this question by asking whether the presence or absence of a single species can trigger rapid change and reproductive isolation in another. Specifically, I study two ecologically similar fish species found in both allopatry and sympatry with respect to one another. See e.g.: Miller et al. 2019, Roesti et al. 2020, Roesti et al. 2023
Predictability of evolution: The topic of the predictability of evolution has a long history in evolutionary biology. Besides being of empirical interest, the “predictability problem” is also of fundamental conceptual and philosophical relevance: what is the value and function of predictions in evolutionary biology (and science in general), and how do we go about making predictions? And, what are the factors that constrain predictability? See e.g.: Roesti 2021, Roesti et al. 2024
Habitat selection: Organisms adapt to their environment through natural selection or – a possibility that is arguably much less considered – by choosing habitats that suit them best. I study the role of habitat selection in population divergence using a complementary set of approaches, including mark-recapture experiments, fitness assays, population genomics, genetic mapping, and phenotypic analyses.
In doing all this work, I would like to acknowledge the many great mentors, colleagues and students I am fortunate to work with, as well as my friends who believe in me as a scientist. For more information on my past or ongoing work – or anything else really – please do not hesitate to contact me!