Felix Hernandez Nohr’s doctoral research sheds light on how different species of temperate grasses repeatedly evolve similar adaptations. The work reveals unexpected genome structures, gene sharing between species, and recurring evolutionary patterns.
Why do different species sometimes evolve similar traits? During his PhD project at BIOVIT, Felix Hernandez Nohr has gained valuable novel insights into these processes using temperate grasses.
The PhD project investigated different species of temperate grasses in the subfamily Pooideae. By comparing genomes across species, the aim was to understand how species evolved and how particular traits arose.
The Pooideae grasses are particularly useful for studying evolution because they have grown in – and adapted to – a wide variety of environments, and possess diverse genome structures. The thesis combined genomic comparisons at several levels, ranging from a single species to large groups of related grasses. These analyses overturned long-existing hypotheses on the genome structure of Nardus stricta, with important implications for future genomic studies involving this species.
Another central finding of Hernandez Nohr's research is that evolution within Pooideae is often surprisingly repeatable; that is, similar traits appear across multiple grass lineages. Similar adaptations can emerge repeatedly through the reuse of the same genes and gene families in different evolutionary lineages. At the same time, genes can occasionally move between species through a process known as horizontal gene transfer.
New insights into genome structure and genes that can cross species barriers
A major part of the research focused on N. stricta, an early-diverging lineage within Pooideae. The findings provide a new picture of how the genome is structured, including hexaploid organisation, meaning there are six copies of the basic chromosome set, compared, for example, to two copies found in some plants, and animal species such as humans.
These findings provide a stronger foundation for future genetic and evolutionary studies involving the species.
The thesis also investigated how temperate grasses acquired the ability to produce fructans, a type of carbohydrate involved in plant frost resistance and winter survival.
Previously, scientists could have interpreted the presence of fructan metabolism in different grass groups as independent evolutionary inventions. However, Hernandez Nohr’s doctoral work revealed a different explanation. The ability to synthesize fructans in the Pooideae tribes Meliceae and Brachypodieae appears to have originated through horizontal gene transfer from N. stricta. Rather than evolving the trait independently, these groups inherited key genetic material from another lineage.
The Genetics Behind Annual Life Cycles
Another focus of the thesis was the repeated evolution of ‘annuality’, which is the strategy of completing a one-year life cycle; from germination to growth, flowering, seed production, and death.
This is in contrast to perennial plants which have a life span spread over multiple years, and reflects a much more complex trait (controlled by many genes) compared to e.g. fructan metabolism.
The research found that independently evolved annual grass lineages often made use of the same genes and gene families to control this process. However, these shared genetic factors did not appear to trigger the original transition from perennial to annual growth. Instead, they were associated with traits that refine and optimize the annual lifestyle after the transition had already occurred.
Complexity of traits shapes the pattern of repeatable evolution
The study found that the repeatability of evolution differs depending on the complexity of a trait. Fructan metabolism appeared repeatedly across a broad range of Pooideae lineages through both independent evolution and horizontal gene transfer. The more complex annuality trait, by contrast, evolved repeatedly only within a more limited group of grasses through independent evolution in lineages that repeatedly reused the same genes/gene families.
Taken together, the thesis findings contribute to a better understanding of repeated evolution in temperate grasses, and how genome structure and horizontal gene transfer shape the adaptive evolution of plants.
Felix Hernandez Nohr will defend his doctoral thesis, "Genome evolution in temperate grasses" at Norwegian University of Life Sciences 6th November 2026.
Professor Siri Fjellheim has been the principal supervisor. Co-supervisors have been Professor Simen Rød Sandve, and Dr. Marian Schubert.