Most living angiosperms (flowering plants) are pollinated by insects, and the new reconstruction of the ancestral pollination mode of angiosperms suggests that their most recent common ancestor was also insect pollinated.
Macroevolution of pollination modes across angiosperms, showing the proportional marginal likelihood of pollination mode at the ancestral nodes for each angiosperm order. Image credit: Stephens et al., doi: 10.1111/nph.18993.
“Pollination is a fundamental ecological process that has influenced the diversification of many seed plant families throughout evolutionary history,” said Macquarie University Ph.D. student Ruby Stephens and colleagues.
“Both gymnosperms and angiosperms depend on pollination to reproduce sexually, with pollen transfer effected by insects, vertebrates, wind or water as vectors.”
“Shifts between different pollinators or pollination modes are often implicated in the speciation of closely related plants, and in the angiosperms pollination shifts have driven the evolution of the vast array of floral forms present today.”
“Precisely how the first angiosperms were pollinated, and how pollination modes have evolved through time, remains a key question in angiosperm macroevolution,” they added.
“The majority of angiosperms are pollinated by animals, especially insects (e.g. bees, flies, wasps, moths, butterflies, beetles and thrips) but also vertebrates (e.g. birds, bats, lizards and small mammals).”
“Indeed, although some flowers self-pollinate, up to a third of angiosperms set no seed at all without animal pollination.”
“However, abiotic pollination by wind or water also occurs in many diverse plant lineages, and wind pollination is estimated to have evolved at least 65 times across the angiosperms.”
3D model of the ancestral flower reconstructed by the eFLOWER team. Image credit: Sauquet et al, doi: 10.1038/ncomms16047.
In their research, the scientists used a state-of-the-art evolutionary tree of all angiosperms, unveiling data on what pollinates 1,160 species across all major angiosperm families.
“The evolutionary tree shows us what plant families evolved when,” Stephens said.
“By running different models, we can map backwards from what pollinates a plant in the present, to what might have pollinated the ancestor of that plant in the past.”
“This is a significant discovery, revealing a key aspect of the origin of almost all plants on Earth today.”
“Plants are the lifeblood of our planet, and our study highlights the importance of insects to plant reproduction throughout Earth’s history.”
“Our research uncovered insights into the evolution of other forms of pollination,” said Botanic Gardens of Sydney researcher Hervé Sauquet.
“Pollination from vertebrate animals like birds, bats, small mammals, even lizards, has evolved and reverted numerous times throughout history.”
“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 reveals wind pollination is more likely to evolve in open habitats towards the poles, while animal pollination is more likely to occur in closed rainforests near the equator.
“Some 90% of the estimated 330,000 species of angiosperm today depend on animals for pollination,” said Washington University’s Professor Susanne Renner, who was not involved in the study.
“The new findings confirm that insects have pollinated angiosperms for the most of this plant lineage’s history.”
“This underscores the need for the conservation of insects — their role as pollinators is essential for the continued existence of plants.”
The results appear in the journal New Phytologist.
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Ruby E. Stephens et al. Insect pollination for most of angiosperm evolutionary history. New Phytologist, published online June 5, 2023; doi: 10.1111/nph.18993
