Natures wonders: fungus helps pine beetles attack (Introduction)

by David Turell , Friday, February 24, 2023, 15:06 (421 days ago) @ David Turell

Complex research shows the relationship:

https://www.sciencealert.com/creepy-study-shows-how-fungi-lure-tree-killing-beetles-to-...

"Millions of conifers have been destroyed across Europe due to infestations of the Eurasian spruce bark beetle (Ips typographus), and fungi may be helping the tree-killing critters by manipulating the tree's natural defenses.

"According to a new study, the tiny beetles can sniff out aromatic compounds produced by their symbiotic partners – fungi – breaking down tree resin, making it easier for the beetles to find suitable trees to eat and have babies in.

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"The authors showed in previous research that I. typographus could identify its fungal symbionts of the genera Grosmannia, Endoconidiophora, and Ophiostoma by their chemical compounds.

"Now they have shown that Grosmannia penicillata and other fungal symbionts metabolize spruce resin compounds from the Norway spruce (Picea abies), which is the beetle's host tree, altering the aroma into an attractive blend of oxygenated derivatives.

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"The team of researchers from Europe and South Africa performed a series of tests in the lab with bark beetles and samples of bark from Norway spruce trees to find out what chemical signals the beetles use to find trees infected with the fungus.

"They found that G. penicillata fungus breaks down chemicals in the bark resin, known as monoterpenes, into new compounds and that 12 days after fungal infection, these compounds made up most of the chemicals that the bark samples gave off.

"Specific pheromones in the bark attracted the beetles, and female beetles, in particular, were more interested in the pheromones on the spruce bark when symbiotic fungi were present.

"Researchers also found that I. typographus have dedicated olfactory neurons sensitive to these oxygenated compounds. Another type of fungus called Trichoderma sp., which is harmful to bark beetles, was also tested, and it produced oxygenated metabolites too, but I. typographus wasn't interested in them.

"Kandasamy and colleagues were surprised to find that when fungal symbionts grew on the spruce bark, beetles were drawn to the bark and made tunnels in it.

"The results suggest that bark beetles can smell mixtures of compounds produced by fungi and follow the scent depending on whether those fungi are their symbiotic partners or a danger to them.

"The oxygenated metabolites may help beetles determine if a fungus is present, how well the host tree protects itself, or if the fungi are overwhelming it, and locate potential feeding and breeding sites."

Comment: a very complex mechanism developed by adaptation or by design?