Mount Kinabalu, (Sabah, Malaysia) is the youngest (ca. 1.5 million yrs old) and highest (4,095 m) mountain between the Himalayas and Irian Jaya, Indonesia. Because of this combination of youth and isolation, considerable mystery surrounds the origins of its high elevation endemics. We chose a group of high-elevation species from Dendrochilum subgen. Platyclinis sect. Eurybrachium to begin an investigation of the origin(s) of endemicity on Mount Kinabalu. We tested biogeographic hypotheses that the Kinabalu endemics arose from ancestors in: 1) the high mountains of Sumatra, 2) the high mountains of Mindanao, Philippines, and 3) lower elevations on Mount Kinabalu or elsewhere in Borneo. Using phylogenetic patterns predicted by the three competing hypotheses, we evaluated which had the highest support in a likelihood framework. Based on analyses of ITS 1 and ITS 2 sequence variation in Dendrochilum, we rejected hypotheses that the Kinabalu high-elevation endemics arose from ancestors in other high mountains of southeast Asia (Sumatra or the Philippines), and tentatively accepted their origin from lower elevation ancestors in Borneo. The origin of high-elevation endemics from lower elevation Bornean ancestors appears to be a general mode of evolution for many species on Mount Kinabalu.

Communicating Editor: Kathleen A. Kron