Leaf-Mining Insects Destroyed with the Dinosaurs Reappeared Elsewhere

A massive asteroid impact at the end of the Cretaceous period helped trigger the extinction of the dinosaurs. Yet while most attention is granted to these large animals, smaller creatures also disappeared from the face of the planet during this event. It turns out that leaf-mining insects in the western United States completely disappeared during this period. Now, scientists have discovered traces from new leaf-mining insects that were now present during the Cretaceous at Mexican Hat in southeastern Montana.

"Our results indicate both that leaf-mining diversity at Mexican Hat is even higher than previously recognized, and equally importantly, that none of the Mexican Hat mines can be linked back to the local Cretaceous mining fauna," said Michael Donovan, one of the researchers, in a news release.

Leaf miners live in the leaves of plants and tunnel for food. This leaves distinctive feeding paths in the plants and patterns of droppings. By studying fossils of leaves, scientists can see what kind of leaf-mining insects were present in the past.

The researchers looked at 1,073 leaf fossils in all. Then they compared these with more than 9,000 leaves from the end of the Cretaceous. In the end, they found nine different leaf damage types attributable to the larvae of moths, wasps and flies. In addition, they found six damage types that were unique to Mexican Hat.

The findings reveal that there was incredible diversity of leaf miners at this site. Yet they're currently unsure why this was. With further research, though, they scientists found no evidence of the survival of any leaf miners of the Cretaceous-Paleocene boundary. This suggests that an even more total collapse of terrestrial food webs occurred than had been recognized previously.

"These results show that the high insect damage diversity at Mexican Hat represents an influx of novel insect herbivores during the early Paleocene and not a refugium for Cretaceous leaf miners," said Peter Wilf, one of the researchers.

The findings are published in the journal PLOS One.