By analyzing DNA sequences from thousands of specimens, researchers have conducted a huge evolutionary study of all the animals, plants, and fungi living on a tropical mountain in Malaysian Borneo. Most of the unique biodiversity in the region is younger than the mountain itself, and they’re a mix of distant immigrants as well as descendants from local lowland ancestors, according to the work published in Nature this week.
Tropical mountainous areas are biodiversity hotspots and home to many one-of-a-kind endemic species – those that aren’t found anywhere else on the planet. Mountains are thought to be evolutionary “cradles” where new species are born and nurtured. But researchers didn’t know if their ancestors were low-altitude species that adapted to life higher up or immigrants that drifted in from other mountains.
To investigate the evolutionary routes to endemism, Leiden University’s Vincent Merckx and colleagues (including a 47-member Malaysian-Dutch expedition) sampled the entire tropical mountain biota of Mount Kinabalu in Sabah, East Malaysia, in 2012. That includes 33 endemic species, from mosses and mushrooms to leeches and frogs. At 4,095 meters (13,435 feet) high, Kinabalu is the highest point on the Southeast Asian island and the tallest mountain between the Himalayas and New Guinea. The team conducted genetic analyses on the 1,852 specimens (or their tissues) that were collected, as well as 3.7 million fungi DNA sequences obtained from soil cores.
Euphaea basalis is a rare damselfly that only occurs along four streams in montane forest on Mount Kinabalu. Jan van Tol/Naturalis Biodiversity Center, Leiden
The team discovered that most of Kinabalu’s unique species originated about 6 million years ago. That’s after the mountain reached its current elevation. Only two endemics – the frog Kalophrynus baluensis and the flowering plant Ilex kinabaluensis – are much older than the mountain itself. That this biodiversity hotspot has a pretty recent origin supports the idea of mountains as evolutionary cradles.
Furthermore, Kinabalu’s endemic species are the relatives and descendants of both lowland species that adapted to higher altitudes and immigrants from faraway high-altitude habitats. These immigrants were already pre-adapted for life in a cool environment, so they only had to make small adjustments.
This new work provides “a textbook example of how biodiversity originates from the interplay between long-distance dispersal and local recruitment, followed by adaptation and speciation through interaction with changes in the landscape, climate and environment,” University of Gothenburg’s Alexandre Antonelli writes in an accompanying News & Views article. The findings may help us protect not only species but also “the habitats that provide the stage for speciation.”
Video Credit: Naturalis Biodiversity Center