Identifier

etd-07132007-112813

Degree

Master of Science (MS)

Department

Biological Sciences

Document Type

Thesis

Abstract

Because of a dearth of modern quantitative studies of the ecology and evolution of birds, our understanding of the biogeography of the Bornean avifauna is rudimentary. Although paleogeographic evidence provides a well known mechanism for speciation in the lowlands of Borneo (i.e., repeated colonization and isolation of populations on Sunda islands caused by sea level changes), the process of speciation in montane areas is less easily explained. Knowledge about the processes responsible for montane speciation in Borneo is desirable because mountains clearly have played a key role in the evolution of the island’s avifauna, as evidenced by the relatively large number of montane endemics (25 of Borneo’s 39 endemic bird species are montane). To provide insight into the dynamics of montane speciation in Borneo, I examined the phylogeographic relationships of selected populations of four species across five sites in the mountains of Sabah, Malaysian Borneo. To determine the connectivity of bird populations among these sites, I compared DNA sequences of the second and third subunits of the mitochondrial nicotinamide adenine dinucleotide dehydrogenase gene of four species that have populations at all the sites: Streaky-breasted Spiderhunter (Arachnothera affinis), Temminck’s Babbler (Pellorneum pyrrogenys), Grey-throated Babbler (Stachyris nigriceps), and Ochraceous Bulbul (Alophoixus ochraceus). Divergence among populations at the five sites was very low, but interesting genetic patterns were still evident. The spiderhunter, which is distributed in both lowland and highland areas, showed no phylogenetic structure among its populations, as would be expected of a vagile species that is not restricted montane areas. For P. pyrrogenys and S. nigriceps, the most geographically distant population was phylogenetically distinct from all others. This isolation-by-distance pattern is reasonable for these small babblers, which are restricted to high elevations and assumed to be poor dispersers. The bulbul displayed the most interesting pattern. Its population in western Sabah near the Sarawak border was distinct from all others. Because this bulbul is presumed to be a good disperser and thus capable of moving among all the localities, this result suggests that the Lumaku birds represents a group with closer genetic ties to Sarawakian mountain populations than to Sabahan populations.

Date

2007

Document Availability at the Time of Submission

Release the entire work immediately for access worldwide.

Committee Chair

Frederick Sheldon

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