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New Zealand’s South Island was once covered with dense forest, with trees breaking like a deep green wave on the grassy mountaintops. After the arrival of Māori settlers about 750 years ago, some slopes were cleared of their trees by people using fire, and the leaves did not return. For organisms living in these forests, their habitats changed almost overnight from sheltered woodlands to open, windswept grasslands.
The researchers found that since the forests burned, tiny winged insects called stoneflies have also changed. On one kind of evolutionary axis for just a few centuries, stoneflies that lived above the tree line lost their ability to fly, suggesting that man-made changes in an ecosystem such as deforestation could radically reshape their bodies. residents. This discovery was published in the journal Biology Letters on Wednesday.
Charles Darwin noticed that insects on the islands have a peculiar tendency towards flightless, perhaps because flying is dangerous when they are small and the winds are strong. Author of the new paper and a professor at the University of Otago in New Zealand, Jon Waters, said that in New Zealand, scientists have found flightless stoneflies on many different mountains. Initially it was unclear why – whether or not there was something supporting a non-flying form at altitude.
To answer the question, he and his colleagues collected stone flies at five sites walking through the forests to the bald tops of the mountains. As they climbed the slopes, they caught insects and recorded their positions. When they looked at all the data, they were surprised to find a very clear trend.
Dr. “As we go up, we found an incredible transition from winged populations to flightless populations,” Waters said. “Wherever we looked, this correlation was not with a particular altitude, but with where the trees stood.”
Since the transition takes place at the tree line and not at a certain height, the exposed condition above the trees suggests that it supports flightlessness in stoneflies. Perhaps, as with Darwin’s island bugs, high winds make flying a liability.
In some places, it is possible that even before the forests burn, there are flightless stoneflies that expand their territory after fires. Genetic analysis of the stoneflies showed that three of the five populations the researchers examined were quite different from their lowland winged brethren, implying that they had evolved on their own for some time.
However, the other two had smaller differences, suggesting that the change might be imminent – new enough to have been since humans arrived on the island.
The obvious rapidity of change reminds pepper moth caseAs air pollution from the Industrial Revolution in England darkened the trees it lived on, the light-colored moths have of course become more visible to hunters in their changing environments – their colors shifting from light to dark. These cases show that it doesn’t take millennia for animal populations to be altered by natural selection.
“You go to the trees and suddenly you enter a different population. Dr. “It’s almost like magic that in some of these cases, evolution seems to work so clearly and effectively over a short distance and over a short period of time.”
Now researchers are looking deeper into the genetics of stoneflies to understand what changes as the insects lose their ability to fly. Details may reveal whether the stoneflies’ apparent flexibility is due to new mutations, or whether their flightlessness is due to variations already present in their ancestral populations, just waiting for the right moment.
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