A BIOGEOGRAPHIC ANALYSIS OF ORCHID DISTRIBUTIONS ON MOUNT KINABALU

TODD J. BARKMAN1, RIMI REPIN2, REED S. BEAMAN3 and JOHN H. BEAMAN4

1Department of Botany, University of Texas, Austin, TX,

2Park Botanist, Sabah Parks, Sabah, Malaysia,

3Department of Botany, University of Florida, Gainesville, FL,

4Department of Botany and Plant Pathology, Michigan State University, E. Lansing, MI.

Evidence presented in this paper suggests that inferred divergence of the present-day orchid flora at various delimited sites on Mount Kinabalu may be explained, in large part, through vicariant events resulting from historical geologic processes proposed by Collenette (1965). These processes include the initial uplift of the granitic pluton which produced the first high-elevation habitats. Final uplifting of the pluton in the mid- to late Pleistocene allowed recent colonisation of the highest elevation habitats. If the timing of Collenette's geological events are accurate for the formation of Mount Kinabalu, then much of the flora is quite young, particularly at the highest elevations. Results of this analysis also suggest that ultramafic sites, such as Marai Parai and Pig Hill, are habitat patches acting as islands with respect to plant colonisation. Indeed the occurrence of relatively high numbers of endemic species on these islands may be due to evolutionary processes analogous to those resulting in the formation of endemics on true oceanic islands. Because of their endemism as identified by our analyses, continued conservation efforts should focus on the high-elevation areas and ultramafic sites surrounding the mountain. Difficulty in distinguishing between ecological and historical factors is discussed with respect to the biogeographic patterns observed in this study.


Satellite imagery of Mount Kinabalu draped over a digital terrain model of the mountain