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The extinction of the dinosaurs caused fruit to grow massive
When species die, you can count on plants to move in on their turf.
We know that our ability to genetically engineer living organisms has not yet reached the point where we could resurrect dinosaurs — we can barely resurrect animals which went extinct in living memory — but even if we could, it’s incredibly likely they wouldn’t be able to live in the world as it exists today.
Any successful Jurassic Park or Jurassic World would require that park engineers recreate the habitats of those extinct species as closely as possible, including characteristics like temperature, climate, atmospheric composition, and vegetation, all of which have changed significantly over the intervening tens of millions of years.
As soon as the dinosaurs exited the building, their prior home began changing around their still fossilizing bones. A new paper published in Proceedings of the Royal Society, authored by Renske Onstein from the German Centre for Integrative Biodiversity Research, and colleagues, used genetic reconstructions to peer back in time, and found that plant species changed dramatically in the wake of the K-Pg extinction.
“We used genetic data to reconstruct past relationships. Based on that information, we saw splitting and speciation happening,” Onstein told SYFY WIRE.
The common wisdom is that species thrive and evolutionary booms happen in the wake of extinction events, as old niches open up to new biological tenants. Strangely, perhaps, that’s not what researchers found. Instead, speciation — the process by which existing species branch off into new ones — slowed down, on average. At present, it’s unclear why that happened.
“That’s the next question. Why did speciation slow down? I’m not sure, to be honest. We saw some groups where speciation actually increased, because other species went extinct and there was less competition, so they could really flourish. Other groups went down in speciation. We still need to get our heads around that,” Onstein said.
Those plant species which persisted through the 25-million-years following the extinction of the non-avian dinosaurs underwent significant changes in their morphology, losing some of their defense mechanisms and growing much larger fruit.
Scientists broke ancient fruiting plants into two groups, based on the size of their fruit. The first group produced fruit four centimeters in diameter and smaller. The second group was everything larger than four centimeters, ranging up to 45 centimeters in length. Looking back through the evolutionary record of these plants, Onstein and the team found that fruit sizes increased in the 25-million-years after the dinosaurs vanished. That finding goes against previously held notions that large fruiting plants are dependent on megafauna for the dispersal of seeds.
“These large fruits probably still depended on large animals, but maybe not as large as these megaherbivores which were over 1,000 kilograms. The fruits could probably also be dispersed by animals comparable to tapirs, 100 or 200 kilograms. Those kinds of animals were evolving during that time,” Onstein said.
Sustained by smaller seed dispersers but lacking the megaherbivores, these species spread over larger regions of the globe, and they had a little help from a shifting climate. Around the same time that the dinosaurs were wiped out, the Earth’s climate underwent a shift, with temperatures becoming much warmer. As a result, tropical forests which were previously isolated to equatorial regions were stretching into higher latitudes. While the forests were getting larger in terms of overall surface area, they were also growing denser.
“In part, that could be related to the lack of herbivores. They create open systems by browsing and walking around, like elephants trampling things. Forests have less of a chance of developing when they’re around,” Onstein said.
Those spreading tropical forests were a veritable plant paradise for fruiting flora. In the wake of a vertebrate tragedy 66-million-years ago, everything was coming up fruit plant. The climate was shifting in their favor and the animals who usually snacked on them were dead. The only thing left to do was to get comfortable and let their guard down, and that’s exactly what they did. The prevalence of defensive features like spines declined as the adaptive cost of keeping them outweighed their benefit.
“Some species evolve spines to help them climb in dense forests. The forest was expanding so you’d think those spines would evolve more to facilitate climbing into the trees, but we saw they were lost. That’s strong evidence that they were related to defense from animals trying to feed on them,” Onstein said.
In essence, the death of the dinosaurs was a sort of vacation for large fruiting plants and they took full advantage of it, allowing themselves to get fat and vulnerable. Then we showed up and started using their fruits for our toast and to make alternative milks. You can have a stegosaurus, or you can you have oat milk, but you can’t have both.
