Eating fruit increases biodiversity

By scattering plant seeds, fruit-eating animals contribute to an increase in plant speciation and hence biodiversity. These are the results of a new study led by Renske E. Onstein and W. Daniel Kiessling, researchers at the Institute for Biodiversity and Ecosystem Dynamics (IBED), Amsterdam. The results were published in the journal Nature Ecology & Evolution.

Rainforests are juicy fruit supermarkets: more than 70% of woody, tropical plant species bear fruit and rely on animals such as chimpanzees, elephants or cattle to plant their seeds. By spreading plant seeds over long distances, these animals contribute to the possibility of plant speciation. An international team of researchers from the Netherlands, the United Kingdom, France, Sweden and Denmark studied more than 2,000 species of palms with edible fruits (such as the date palm) to understand how the ecology of the species, their distribution and interaction with potential fruit-eating animals could affect their speciation. This was done by creating large databases of phylogenetic, functional characteristics and species distribution data for these palms.

Long before humans invaded tropical rainforests, there were many other animals, such as giant sloths and gomphotoria, that enjoyed fruit snacks and thus served as seed distributors. “These large animals, called megafaunas, are now largely extinct,” says Renske Onstein, lead researcher. "But they probably contributed to the dispersal of palms with very large 'megafaunal' fruits from 4 to 12 cm long over long distances."

These megafaunal fruits are too large to be swallowed by any other species, such as birds or bats, and currently only a few animals, such as tapirs, are large enough to swallow and disperse these seeds. “The goal of our study was to compare the speciation of palms with very large fruits and palms with smaller fruits,” Onstein says. "We expected that the historical interaction of these mafaunal palms with megafaunal animals would likely reduce their rate of speciation compared to palms with smaller fruits, due to increased gene flow between populations and therefore reduce the chances of geographic speciation."

The preconditions for speciation are limited gene flow and isolation of populations. These populations can then evolve into new species over millions of years. "We were surprised to see that not only fruit size is important in explaining palm speciation, but also the interaction between fruit size, island colonization and shape." Indeed, palms whose seeds are scattered by flying animals such as pigeons and bats that can colonize isolated Asian and Pacific islands have shown the highest rate of speciation compared to Latin American palms growing in the undergrowth of rainforests, which rely on sedentary, limited by the range of movement of animals.

These results provide important information about the future of biodiversity. “We are currently witnessing a massive wave of species extinction around the world, fueled by our human dominance in Earth's ecosystems,” says Daniel Kissling, who pioneered the study. Many species are disappearing from our planet due to hunting, habitat fragmentation and other human influences.This so-called defaunization is one of the main drivers of global environmental change and has serious consequences for the functioning of ecosystems and human well-being.

“Our research shows that interactions between species, such as between animal seed carriers and the plants they feed on, are critical to biodiversity and the benefits that nature provides to humans,” explains Daniel Kiessling. “Therefore, we must not only protect individual species, but also provide enough space and a suitable habitat for animals to live. We also need to focus on restoring important interactions between species where they were lost. ” Without it, the future biodiversity will look like a supermarket with empty shelves.

Kordopolova M. Yu.