Scientists establish how first flowering plants were pollinated 140 million years ago

Scientists have wound back the clock to learn how the world’s first flower was pollinated, but the answer isn’t so surprising.

Insects, which account for most flower pollination today, were almost certainly responsible for facilitating the first event, rather than wind, water or cross-fertilisation performed by larger animals.

To confirm this, Sydney-based scientists reconstructed the evolutionary history of angiosperms – flowering plants – to pinpoint the way pollen was distributed for Earth’s first blossom 140 million years ago.

These data for about 1,160 species and their known method of pollination was effectively run backwards over a 140 million-year simulation, to the point of a single common ancestor.

“As we’ve gotten more DNA evidence [of species], we’ve got more ability to put a lot of data together to try and work out some very tricky relationships between all of those species and all of the different families of flowers,” explains lead researcher Ruby Stephens from Macquarie University.

That ancestral angiosperm likely looked different to most flowers we know today. A 2017 study published in Nature Communications predicted the first flower was probably bisexual – containing both male and female reproductive organs.

Hypothetical model for the reconstructed ancestral flower.
Hypothetical model for the reconstructed ancestral flower. Credit: Catherine Wardrop (redrawn from Sauquet et al. (2017)

The flower likely had tepals – as distinct from petals and sepals – a structure seen today in species like tulips and magnolias.

Its descendants would have continued to evolve over millions of years, surviving multiple extinction events.

Today, angiosperms are the most diverse and abundant clade of plants, accounting for nearly 80% of all species.

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Angiosperm diversity is marked by multiple pollination methods, says Stephens’ supervisor Dr Hervé Sauquet, head of plant discovery and evolution research at the Botanic Gardens of Sydney, who also led the 2017 research into the ancestral angiosperm.

While the new research refines the role of insects as the first pollinators, it also charts the role of other forms of flower reproduction.

“Pollination from vertebrate animals like birds, bats, small mammals, even lizards, has evolved and reverted numerous times throughout history,” says Dr Sauquet. “Wind pollination has also evolved many times, but it is harder to reverse – once plants go pollination by wind, they rarely go back.”

The research also suggests wind pollination is more likely to occur at higher latitudes on the planet among open habitats, whereas flowers that prefer animal-based pollination are more likely to inhabit forested regions closer to the equator.

Stephens says these pollination mechanisms are visible in the structures of modern flowering plants.

“Having an understanding of those evolutionary patterns gives us a bit more depth when we look around us today and say, ‘This is how things are today, and this is where they’ve come from’, so it gives a bit of an idea of where things might go [in future] as well.”

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