Extinction of the dinosaurs allowed plants to grow huge fruits

(ORDO NEWS) — European ecologists, who used genetic reconstruction to look into the past, found that after the extinction of the dinosaurs 66 million years ago, drastic changes began to occur with many plant species.

An article about this, written by Renske Onstein of the German Center for Comprehensive Biodiversity Research in Leipzig and her colleagues, was published in Proceedings of the Royal Society B.

“We used genetic data to reconstruct the relationships of different species. Based on this information, we saw that their active diversification and new speciation was taking place,” explained Renske Onstein.

Previously, it was widely believed that after the events of extinction, an evolutionary boom inevitably occurs, when their neighbors occupy the place of the former, extinct species, occupying the vacant ecological niches.

However, in this case, things happened differently with plants, a different type of speciation took place, and the processes by which existing evolutionary branches split into new ones slowed down on average.

Plant species that persisted for 25 million years after the extinction of the non-avian dinosaurs underwent gradual changes in their morphology, losing some of their defense mechanisms and growing much larger fruits.

Scientists have divided ancient fruit plants into two groups depending on the size of their fruits. The first group gave fruits with a diameter of 4 cm or less. The second group included everything larger than 4 cm and sometimes reaching 45 cm in length.

By reviewing the evolutionary history of these plants, Onstein and her team found that fruit size increased markedly 25 million years after the extinction of the dinosaurs.

This conclusion runs counter to pre-existing notions that large fruit plants are directly dependent on megafauna for seed dispersal.

“These large fruits probably still depended on large animals, but perhaps not as large as the former megaherbivores, which weighed over a ton.

The fruits could also probably have been distributed by animals comparable in size to tapirs, weighing 100 or 200 kg. These animal species were actively evolving at that time,” Onstein says.

Supported by smaller seed dispersers in the absence of super-large herbivores, these plant species have spread across wider regions of the globe, aided by a changing climate as well.

Around the time the dinosaurs went extinct, Earth‘s climate changed dramatically and average temperatures rose. As a result, tropical forests that were previously isolated from equatorial regions have moved noticeably to higher latitudes.

At that time, forests not only occupied vast areas on land, but also became much denser, which could also be due to the absence of super-large herbivores.

In essence, the demise of the dinosaurs allowed fruit-bearing plants to grow larger fruits without having to spend additional resources to protect themselves.

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