Damage to geological record papers – wissenschaft.de

Following the work of caterpillars, beetles, and their colleagues: The researchers report that plants have never been eaten by insects as they are today since the end of the Cretaceous period. This is suggested by comparing the damage that insects do to modern leaves from various forest ecosystems and fossil specimens from about 67 million years ago. Currently, severe infection can be age-related. However, it is still not clear to what extent rapid human-induced climate change, complex changes in the ecosystem or other factors play a role, the scientists say.

From time immemorial, insects attack the huge biomass consisting of terrestrial plants: in the course of evolution, herbivorous insects evolved in parallel with plants and feed on them in different ways. The basic plant and insect groups that characterize our nature today evolved before the end of the Cretaceous period. It is therefore assumed that the actors in the system have not changed radically at least in the past 67 million years. However, it is unclear how the level of plant infestation changed during this time period, which was marked by climatic changes.

At least as far as modern times are concerned, a noticeable trend is already emerging: grass samples from the early 2000s are more likely to show insect damage than samples collected in the early 20th century. This pattern has been linked to global warming. Because herbivores often reproduce better at higher temperatures and are also hungrier. However, increases in global temperatures have occurred occasionally during the past 67 million years. Among other things, researchers led by Lauren Azevedo-Schmidt of the University of Wyoming at Laramie are now investigating the extent to which it is possible to determine the increased prevalence of insects in plants during these times.

Leaves gnawing at the horizon

Azevedo Schmidt and colleagues examined the effects of insect damage on fossilized leaves from the late Cretaceous to the Pleistocene—hence the period from about 67 million years ago to 2 million years ago. They then compared the results of the assessment to similar leaf samples collected in three different forest ecosystems today. The researchers differentiate between different forms of damage associated with certain groups of insects: such as lateral gnawing, holes or mines in leaves. In addition, the basic characteristics of the plant biodiversity of the respective sample systems were recorded.

The results of the comprehensive analysis revealed: “The difference in insect damage between modern and fossil discoveries is astounding,” says Azevedo Schmidt, summarizing the central finding. Because scientists have found that all kinds of damage to today’s leaves are significantly more common. Compared to the level in the past 67 million years, they have reached an average about twice as high. Assessments showed that although the world had changed dramatically during this time period, the basic level of forest damage by insects seemed to fluctuate relatively little. The researchers report that even as the atmosphere has warmed in the past, only small increases have been recorded.

Human influence is supposed to be complex

Thus, the results prove that the change in plant-insect interaction is related to human age. However, the researchers stress that the exact reason behind this effect was not yet clear and may be complex. According to them, the increased damage to nutrition is not at least directly attributable to an increase in temperature as part of climate change. Because there could have been strong increases in the past. However, scientists warn that the current climate change is happening very quickly compared to past episodes. Azevedo-Schmidt and colleagues show that longer periods of change may once have given plants more opportunities to adapt to increased infestation by predatory insects through defensive strategies.

However, other human-made factors could play a decisive role: “It is possible that the extent to which humans influence plant-insect interactions is controlled not only by climate change, but by the way humans interact with the environment. Scientists say: “Terrestrial landscapes”. Because in nature, as it is known, many have mixed in a complex way. Researchers write that the increasing fragmentation of forests, loss of biodiversity among animal enemies of biting insects, and the spread of invasive species can play a defining role. However, according to them, according to them Further investigations should now clarify the exact causes of the damage caused by feeding on plants, which is apparently unprecedented from a geological point of view.

Source: University of Wyoming, magazine article, PNAS, doi: Proceedings of the National Academy of Sciences, doi: 10.1073/pnas.2202852119

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