Unlocking the fossil record of plant genome size evolution: proxy development and validation

• Applicant: Phillip Jardine, Ph.D.
• Subject Area: Palaeontology
• Term: since 2025
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 558185540

Genome size – the amount of DNA in a cell nucleus – varies by five orders of magnitude across the land plants. Although genome size differences among taxa have been linked to variations in growth form, range size, plant functioning, stress tolerance and extinction selectivity, the patterns and processes of genome size evolution remain unclear. This is in large part due to the challenges of measuring genome size in the past, and in particular generating genome size estimates from fossil plant specimens. A correlation between genome size and cell size has led to the suggestion that stomatal guard cell length, measured from fossil leaves and cuticles, can be used as a genome size proxy. However, there are considerable uncertainties regarding how well guard cell length captures genome size, whether the relationship varies across plant clades or is modified by evolutionary adaptations to different habitats, and the magnitude of within-species variation in guard cell size. This project will address these issues by analysing the relationship between genome size and guard cell length across different plant clades, growth forms and habitats, and temporal trends within species. It will use a combination of data compiled from the literature, and new measurements from botanical garden and herbarium specimens. Finally, a new genome size – guard cell length calibration will be used to estimate genome size from plant fossils from the Middle Eocene Grube Messel oil shale (near Darmstadt, Germany). These estimates will be used to assess the precision of this genome size proxy, and will be compared to extant representatives of the same genera and families to test for genome downsizing within these lineages. The results of this project will provide a robust assessment of the palaeobotanical genome size proxy, including evaluations of the accuracy and precision of genome size estimates, and identifying the next steps for further development. It will also provide novel data on the relationship between genome size and stomatal traits in extant taxa, and is expected to stimulate further research into integrating extant and fossil genome size data.

• DFG Programme: Research Grants
• Co-Investigator: Professor Dr. Benjamin Bomfleur