The origin of endemic species
The montane environment of Mt. Kinabalu is very different from the surrounding lowland of Sabah. Endemic mountainous species are not well adapted for life in the lowlands, while they have an advantage at higher altitude. At some point in time each of these species must have arrived or evolved on the mountain. What are the hypothetical routes to the mountain for these species?
The first hypothesis is based on climate change. The observation that these species occur in a colder environment could imply that they are remnants from a period when the earth was colder. As temperature rose, these lowland species moved to the mountains. The mountain was the last refuge for species that prefer a colder climate.
Could the ancestors of the endemic species have arrived by travelling all the way from other cold regions, such as the Himalayas or northern countries? Arrival due to long distance dispersal would imply that the closest relatives of these species should be found in other colder environments, such as distant mountains or temperate regions. Also, the species must have arrived after the formation of Mt. Kinabalu started.
As the mountain rose to the present elevation over the past 6 million years, local lowland species which lived close to the mountain could have gradually adapted to the cold. As they became able to cope with the different climate, they moved up the slopes became isolated from their lowland relatives during this process. If this is the case, we should find that the closest relatives of these species live around the mountain and they time of divergence of these species should have been after the formation of Mt. Kinabalu started.