About 165 million years ago, during the Jurassic Period, an insect visited a plant for a meal.
It had big, scaled wings and a tube-like mouthpart called a proboscis, which it probably used
to suck up sweet fluids made by the plant.
And during that visit, the insect got pollen grains stuck to the base of its mouthparts.
Sound familiar?
You’ve probably seen butterflies flitting from plant to plant on broad wings, sticking
their probosces into flowers to drink nectar and maybe picking up a clump of pollen in
the process.
Only this wasn’t a butterfly - it was a lacewing, an extinct member of an order of
insects that’s still around today.
And this ancient lacewing had not visited a flowering plant.
The pollen it picked up was from a gymnosperm – the group that includes pines, cycads,
and ginkgoes.
Which is weird, because today most gymnosperms are conifers - plants whose reproductive structures
often look like cones and are pollinated by wind, not by insects.
So, why was this butterfly-lookalike visiting a gymnosperm 165 million years ago?
Well, in some ways, the world of the Jurassic was a lot like ours - similar interactions
between plants and insects were happening, but the players have changed over time.
The lacewing fossilized with pollen on its mouthparts shows how pollination began between
ancient groups of insects and gymnosperm plants.
And while these lacewings went extinct long before butterflies arrived on the scene, they
pioneered the relationship that would shape the rise of flowering plants and, ultimately,
the world we live in today.
Because, it looks like pollination by insects actually got going twice.
These days, flowering plants called angiosperms dominate our planet.
They’re the most diverse group of land plants, with around 300,000 known species, while today’s
gymnosperms number around 1000 species.
But, for most of the history of land plants, gymnosperms were dominant.
And for their first hundred million years, they were pollinated by wind or water blowing
or washing their winged seeds on their way.
So when did insects get in on the action?
The stage for insect pollination was set possibly as far back as the Permian Period, when insects
are thought to have started feeding on gymnosperm plant fluids.
Gymnosperms don’t make nectar, but they do make nutritious pollination drops that
are used for trapping airborne pollen.
And while it’s hard to catch an insect in the act of pollinating, the fossil record
gives us several lines of indirect evidence of pollination, like specialized plant structures,
specialized insect mouthparts, and pollen grains.
These specialized structures of early gymnosperms weren’t big cones like you’d see on a
pine tree today.
Instead, their reproductive structures were low profile or even recessed, in the form
of funnels, tubes, vents, and channels.
And some insects had mouthparts that seemed to be adapted to reach down into these reproductive
structures to get the pollination drops.
For example, there’s a fossil scorpionfly found in Russia that dates to about 250 million
years ago.
Although it wasn’t preserved carrying pollen, its long proboscis shows that it was feeding
on plant fluids.
And those butterfly-like lacewings with their tube-like mouthparts appeared about 180 million
years ago.
The fossil record even shows that some true flies were interacting with plants, too.
One family of flies with long probosces lived from about 125 million years ago to
100 million years ago.
Their relatively rigid mouthparts must’ve been awkward in flight, but were useful for
feeding.
Their fossils have been found in South America, Europe, and Asia.
And one of these flies found in Spanish amber dating to 105 million years ago actually had
a clump of pollen grains in the hairs on its back -- from an extinct gymnosperm plant.
Like the scorpionflies and lacewings, these true flies were thriving on the reproductive
structures of gymnosperms, not angiosperms.
So, by the Cretaceous Period, long, tube-like mouthparts adapted to reach into gymnosperms
had appeared in scorpionflies, lacewings, and true flies, evolving multiple times across
these groups.
And pollen that got stuck on legs, wings, heads, and bodies would’ve been carried
to other plants of the same species, kicking off the first round of insect pollination.
But insects without long probosces were getting in on the pollination game, too.
One of these groups were the false blister beetles.
A single individual was found fossilized in 105 million-year-old amber from northern Spain
with gymnosperm pollen dusted on its mouthparts, legs, and back.
And it was insects like these that would go on to be the crossover stars of the second
pollination revolution - the rise of flowering plants.
But when did flowering plants become the main attraction for pollinators?
Well, while there’s a lot of debate about when flowering plants - the angiosperms - first
arose, we’ve got fossil evidence that they were around by 140 million years ago.
And by about 100 million years ago, flowering plants had spread and diversified into the
major lineages that define our ecosystems today.
For the angiosperms to take over, they had to develop relationships with pollinators.
And it looks like it wasn’t the lacewings, scorpionflies, or true flies that would become
their first partners.
It was beetles!
Pieces of 99 million-year-old amber found in Myanmar contained short-winged flower beetles
surrounded by pollen.
Analysis of the pollen showed that it was mostly from a mix of gymnosperm plants, including
cycads and ginkgos.
But, one piece also contained pollen from a flowering plant - a water lily, which belonged
to an early group of flowering plants.
Now, these beetles didn’t have long, tubular mouthparts.
But early angiosperms didn’t have the reproductive structures that made a long proboscis necessary.
The ovaries of these flowers were bowl-shaped - a better fit for something like a beetle
that feeds with short, chewing mandibles.
So, beetles may have been the insects that were best able to shift from their relationships
with gymnosperms to the new resources offered up by angiosperms.
And as they were making the switch, flowers acquired a bunch of traits to attract pollinators
and allow pollination to happen.
Like, organs called nectaries evolved, which delivered tasty nectar rewards to pollinators
- these were a new take on the old pollination drops of gymnosperms.
And then relatives of today’s busiest pollinators – the bees – took up the job.
One fossil stinging wasp from 99 million-year-old Burmese amber was found with a mouth full
of pollen from a flowering plant.
As the angiosperms got their foothold and attracted crossover pollinators like beetles,
some pollinators still remained loyal to the gymnosperms.
But, ultimately, many of the specialized gymnosperm pollinators would go extinct, including the
ancient lacewings around 100 million years ago, and that group of true flies and certain
groups of scorpionflies about 94 million years ago.
And some of their plant hosts went extinct along with them.
So over the course of the Cretaceous, flowering plants, with the help of their new pollinators,
took over and became dominant.
They spread into many ecological niches and replaced the gymnosperms.
And then finally at around 46 million years ago, bees got into the game in a big way.
A group of bee fossils found in Germany were associated with 23 types of angiosperm pollen.
And many flowering plants would go on to echo the path that gymnosperms had taken long before,
developing tubular flowers shaped to pollinator mouthparts.
Today, there are four groups of insects with long probosces: butterflies and moths, certain
true flies, some beetles, and some caddisflies.
And they all pollinate flowering plants.
There are more than 77,000 species of beetles, the original crossover insects, that pollinate
flowers.
And true flies of different kinds pollinate an estimated 72% percent of crops, second
only to bees in helping the flowering plants we depend on for food reproduce.
As for the gymnosperms, most of them are back to being wind-pollinated, with airborne pollen
that gets stuck in pollen drops.
The wind pollination we see now is a newer strategy – one that has also evolved a bunch
of times.
But the gymnosperms haven’t been totally abandoned by their pollinators.
The sweet pollen drops of some modern gymnosperms still attract pollinating flies and moths.
So, pollination has really undergone two revolutions since its origins.
The relationships that took root between insects and gymnosperm plants transformed pollination
the first time - and some of those relationships have continued to this day, while others ended
in extinction.
And then, as some insects shifted their loyalty to flowering plants and kicked off the second
pollinator revolution, the relationships between plants and their pollinators that define the
world we live in today were born.
For a lot of these insect pollinators, like the lacewings, the ability to fly had to evolve
first.
So to find out when insects took to the skys, check out our episode, “When Insects First
Flew”.
And thanks to this month’s Eontologists for helping us flourish: Sean Dennis, Jake
Hart, Annie & Eric Higgins, John Davison Ng, and Patrick Seifert!
Become an Eonite at patreon.com/eons, and you can get fun perks like submitting a joke
for us to read, like this one from Matty
What fish lives at the bottom of the ocean?
Shale fish.
Shale fish...
Shell fish...
sh--because shale is a rock?
shell fish?
And as always thanks for joining me in the Konstantin Haase studio.
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