Flowering plants may have originated between 149 and 256 million years ago, according to a study published today. Researchers found that flowering plants are neither as old as suggested by previous molecular studies, nor as young as a literal interpretation of their fossil record. The discrepancy between estimates of flowering plant evolution from molecular data and fossil records has caused much debate. Even English naturalist Charles Darwin described the origin of this group as an ‘abominable mystery'”, said Jose Barba-Montoya from University College London (UCL) in the UK. “To uncover the key to solving the mystery of when flowers originated, we carefully analysed the genetic make-up of flowering plants, and the rate at which mutations accumulate in their genomes,” said Barba-Montoya, lead author of the study published in the journal New Phytologist.
The researchers compiled a large collection of genetic data for many flowering plant groups including a dataset of 83 genes from 644 taxa, together with a comprehensive set of fossil evidence to address the timescale of flowering plant diversification. Through the lens of the fossil record, flowering plants appear to have diversified suddenly, precipitating a Cretaceous Terrestrial Revolution in which pollinators, herbivores and predators underwent explosive co-evolution.
Molecular-clock dating studies, however, have suggested a much older origin for flowering plants, implying a cryptic evolution of flowers that is not documented in the fossil record. “In large part, the discrepancy between these two approaches is an artifact of false precision on both palaeontological and molecular evolutionary timescales,” said Professor Philip Donoghue from the University of Bristol in the UK.
Palaeontological timescales calibrate the family tree of plants to geological time based on the oldest fossil evidence for its component branches. Molecular timescales build on this approach, using additional evidence from genomes for the genetic distances between species, aiming to overcome gaps in the fossil record.