The team also collected fresh leaves of the insects' host plants and placed the insects in feeding experiment bags with these leaves. They allowed adult insects to feed for two to three days and immature stages to feed until full maturity when possible.The researchers then classified the damage to the leaves into categories, in the same way they catalog fossil leaf- chewing damage.
"This is the first attempt to compare leaf-chewing damage inflicted by many kinds of living insects on many kinds of plants throughout a large forest area, both to the culprit insects and to the leaf damage we see in the fossil record," said Carvalho."We mounted 276 of the insects with their damaged leaves and deposited them in the STRI Insect Collection."
This collection is the only known vouchered collection of diverse, identified insects and their feeding damage on leaves of identified plant hosts.
The number of collected insect species correlated strongly with the number of damage types recorded in canopy leaves of 24 tree and liana species observed in the feeding experiments. This suggests that the number of types of damage seen in the fossil record is also related to the actual diversity of damage-making insects.
The researchers also compared the modern leaf data to fossil data from Colombia, Argentina, the Great Plains and the Rocky Mountains. They found that the distribution of chewing marks was the same across both modern and ancient settings, showing a striking consistency in how insects have divided up their leaf resources since at least the end of the age of dinosaurs.
"In the fossil record we frequently find a decrease in damage-type richness during cooling events and after extinctions and an increase in damage-type richness during warming events and post-extinction recovery," said Wilf. "Usually, insect body-fossils from these critical time intervals are absent or very rare, so we rely on the insect-damaged leaves to tell the story. These fossil studies have been considered tremendously important for understanding how ecosystems have responded, and will respond, to climate change and disturbance. We now have direct observational evidence that the fossil data represent changes in actual insect richness and no longer need to infer this through deduction alone."
"This work also unlocks the potential to use insect damage as a new way to assess living insect richness, as in the fossil record, in the context of climate change," said Carvalho. "We used fossils to frame a hypothesis about how the world works, today and through time, and discovered in the living tropical rainforest that the hypothesis is correct.More kinds of chewing marks means more kinds of insects."
Other researchers on this project were Héctor Barrios, Programa de Maestría en Entomología, Universidad de Panamá; Donald M. Windsor and Carlos A. Jaramillo, Smithsonian Tropical Research Institute, Panamá; Ellen Currano, assistant professor of geology and environmental earth science, Miami University of Ohio; Conrad C. Labandeira, department of paleobiology, Smithsonian Institution and department of entomology, University of Maryland.
The David and Lucile Packard Foundation and the National Science Foundation supported this research.