Natures wonders: hornet distribute Agarwood seeds (Introduction)

by David Turell , Wednesday, July 06, 2022, 19:01 (660 days ago) @ David Turell

Attracted by scents mimicking prey scents:

https://www.the-scientist.com/news-opinion/trees-scent-tricks-hornets-into-shuttling-se...

"Each year, the agarwood tree, a sought-after source of medicines and perfumes that grows in the rainforests of southwest China, needs to solve a problem. The tree’s fruits mature during the hottest time of the year. As temperatures climb, the fruits split and the seeds hang from the fruit, where they can dry out in a matter of hours.

"To meet their ultra-fast seed-dispersal needs, the trees have tricked a species of hornets (Vespa velutina) into becoming seed couriers, a new study suggests. The work, published today (June 30) in Current Biology, describes how the agarwood’s fruit mimic the odors released when the insects start feasting on agarwood leaves. The hornets are lured in by these odors to prey on the insects but encounter a seed instead.

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"In a series of field experiments performed on two agarwood tree (Aquilaria sinensis) plantations in Yunnan Province, China, researchers at the Chinese Academy of Sciences followed the fate of a total of 600 seeds on 420 just-opened fruit on four trees. They observed when and how often hornets (genus Vespa) visited the fruit. The hornets descended upon and attacked the hanging, protected seeds of the plant (called diaspores) as if they were prey just 13 minutes after the seeds emerged, on average. While three species of hornets visited the trees, V. velutina aided in dispersal of 84 percent of the seeds.

"Once the hornets tore off the diaspores, they carried them to other branches or to their nests, which they usually built on large, well-shaded branches near the trunk of the tree. The hornets only consume the fleshy, outside part of the seed, called the elastiome, leaving the rest intact and viable. Overall, the hornets aided in the dispersal of 96 percent of the seeds. In separate laboratory experiments, the researchers also found that the seeds germinated in the type of shady environments favored by the hornets, suggesting that the hornets’ leftovers could survive as a next generation of agarwood trees.

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"Suspecting that the fruit might be mimicking compounds released when leaves are damaged by leaf-eating insects (which happen to be hornet prey), the researchers placed caterpillars (Heortia vitessoides) on A. sinensis seedlings. They analyzed the composition of the volatile molecules released by the damaged leaves, as well as the electrophysiological activity of the hornets’ antennae in response to these chemicals. They found that damaged leaves emitted 14 out of 17 chemicals emitted by the ripe fruit, and eight of these elicited high electrical activity in the hornets’ antennae. The researchers concluded that the fruit must be sending out the same volatiles the leaves deploy when eaten by a hornet’s food."

Comment: using attractive scents to lure hornets to disperse the seeds is a neat trick, not likely to develop by chance mutations. It is not much different than birds eating seeds and dispersing them in their poop.