NEW YORK (GenomeWeb) – A new Nature study offers genetic evidence that endemic organisms found at different elevations on a tropical mountain in eastern Malaysia represent a mix of some species that arrived by local migration and others dropped off by long-distance dispersal.
Researchers from the Netherlands, Malaysia, and elsewhere used Sanger sequencing to scrutinize fast-evolving loci in plants, animals, and insects from 18 genera found on Mount Kinabalu. Together with fungal sequences found in soil samples, the data helped them come up with phylogenetic trees for retracing the origins of organisms that characterize different elevation zones.
The results pointed to a mix of so-called "centric" organisms that stemmed from nearby populations at lower altitudes, as well as "eccentric" species — particularly in higher subalpine and alpine zones — that more closely resemble those in similar environments from far-off locations.
Despite the plant, animal, and other diversity detected on the mountain, though, the team's analyses hint that many mountain-adapted species may have taken relatively small evolutionary steps to adapt to their given environments, with nearby species staying in vegetation zones that resemble those at lower elevation and dispersal-dropped species arriving from similar niches in other locations.
"It does seem that there is some niche conservatism going on. These new species have evolved without changing their niche too much," corresponding author Menno Schilthuizen, a biology, tropical biology, and conservation researcher affiliated with Leiden University, the Naturalis Biodiversity Center, and the Malaysian University of Sabah, told GenomeWeb.
If that's the case, he explained, it could have implications for predicting climate change consequences, suggesting some organisms may not be nimble enough to adapt to very rapidly changing environments.
"If the climate changes very quickly, we cannot expect that these endemic species will be able to be rescued by their own evolutionary adaptation," Schilthuizen said. "[M]any of them are probably going to shift up on the mountain summit as the climate gets warmer until there's no more space for them to survive and then you'd have some population collapses."
In an effort to start untangling how various mountain species evolved, where their ancestors lived, and the events or migrations that brought them to Mount Kinabalu, he and his colleagues generated barcoding sequences for 1,852 representatives from snail, slug, spider, worm, insect, vertebrate, and various plant genera.
They also sequenced internal transcribed spacer sequence 2 ribosomal DNA sequences from basidiomycete and glomeromycete fungi in soil core samples collected on the mountain.
The samples came from research stations established at increasing elevations on the 4,095-meter (13,400-foot) mountain, each focusing on as many endemic organisms as possible, Schilthuizen said.
Based on the barcodes they identified at various mountain sites, the researchers saw different types of endemic species. The first involved organisms that originated far afield, such as a shrub-like plant from the coffee family that is most closely related to mountain plants from New Guinea.
Another group of endemic mountain organisms resembled species living nearby at lower altitude. These so-called centric species, which included flowering plants, conifers, fungi, and a group of stalk-eyed flies, were related to species found in lower, tropical montane forests in Borneo and tended to remain at sites that were relatively low on the mountain.
The final — and least-frequently found — group of creatures were those whose ancestors arrived and radiated on the mountain to produce several new species. Just a few of the organisms sampled on Mount Kinabalu fell into this category, Schilthuizen explained, including a few plants and some types of fungi.
Moreover, the team's phylogenetic analysis indicated that most of the endemic species found on the mountain diversified relatively recently, with an estimated 75 percent or more of the species appearing over the past 6 million years.
The researchers suspect the patterns detected on Mount Kinabalu represent the sorts of species settlement and mechanisms of endemism at play on other young and/or isolated mountains, though species dispersal and diversification patterns may vary somewhat on mountains within larger ranges such as the Himalayas.
The team plans to continue doing taxonomic studies on the new and known species found on Mount Kinabalu. For his part, for example, Schilthuizen is interested in delving more deeply into some of the beetle species that reside on the tropical mountain using additional genetic markers and/or mitochondrial genome sequences.