Researchers scoured the wildlife-rich forests of Malaysia's Mount Kinabalu (pictured) for previously unrecorded animals, plants, and fungi. Split among Malaysia, Brunei, and Indonesia, Borneo is the world's third largest island.
The study team hopes to shed light on evolutionary relationships between isolated and endemic mountain species and their more widespread lowland counterparts.
Previously it had been thought that lowland species slowly migrate up the mountain before adapting to colder, more extreme living conditions, Schilthuizen said.
But in many cases, it seems, species take the opposite route.
"Some of the species that live on top of the mountain are actually ancestral—they are older than their relatives in the lowlands," Schilthuizen said.
"They aren't newly evolved species but rather relics."
(See pictures of Borneo's threatened forests in National Geographic magazine.)