Charles Darwin’s abominable mystery

Associate Professor Sean Graham

Associate Professor Sean Graham

Associate Professor Sean Graham has been using DNA evidence to understand the explosive evolutionary radiation of the flowering plants, a question that has frustrated biologists since the time of Charles Darwin, who famously called it “an abominable mystery.” Graham was involved in a key discovery in 1999 that helped turn our understanding of flowering-plant genealogical relationships (or phylogeny) on its head, by showing that a handful of families are modern-day survivors of this earliest radiation.

Additional research just published in the journal Nature by Graham and his graduate students broadens our understanding of flowering-plant origins. This work reveals that a family of Southern Hemisphere aquatic plants called Hydatellaceae evolved near the origin of flowering-plant history. The diminutive aquatic Hydatellaceae are relatives of the water-lily family (Nympaeaceae), a favourite subject of Impressionist paintings, and familiar inhabitants of freshwater habitats in British Columbia.

“The relationship between these two families was totally unexpected. This helps us re-evaluate our understanding of early flowering-plant evolution. For a botanist this is like discovering that something you thought was a rather uninteresting lizard is actually a living dinosaur!” said Graham.

These two families have diverged considerably from each other. For example, a few dozen plants of Hydatellaceae can easily fit into the palm of a hand. In contrast to water lilies, mature individuals of Hydatellaceae have dozens of tiny flowers in compact flowering heads—and some species regularly flower under water.

“The new findings fundamentally strengthen our understanding of the very roots of plant biology,” he added.

Solving Darwin’s abominable mystery has considerable consequences for the molecular biology revolution that underpins much of agricultural research today. This new understanding of plant phylogeny provides a more robust framework for understanding the structure and function of all plant genomes.

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