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Systematics Section / ASPT

Cannon, Charles H. [1], Oh, Sang-Hun [2], Manos, Paul S. [2].

The history of SE Asian rainforest: a regional survey of chloroplast sequence variation in the SE Asian stone oaks.

We surveyed the DNA sequence variation in an intergenic spacer region on the chloroplast genome in 375 individuals of the genus Lithocarpus (Fagaceae) from 11 populations, >60 species, and 7 sections. Samples included both major centers of taxonomic diversity (Indochina and Borneo) and the entire range of morphological variation (particularly the two main fruit types present in the genus). Strong geographical, morphological, and ecological patterns are present in the results. A major geographic division was apparent in the genetic network reconstructing the historical relationships among haplotypes. The clade containing the ancestral type was found almost throughout the range of the stone oaks but was primarily concentrated in Indochina and north/central Borneo. The clade was only found in the Sundaland region, including Borneo and peninsular Malaysia. In general, few ancestral haplotypes were 'missing' from the dataset, indicating limited coalescence and extinction. Additionally, the ancestral type was also found in two individuals of Castanopsis and is only a base pair or two different from haplotypes found in numerous individuals of Castanopsis and Cyclobalanopsis. Few taxa were fixed on a particular haplotype and sympatric individuals were more likely to possess closely related haplotypes than conspecific individuals found in other populations. This is not to say that taxa were not 'cohesive' on the genetic network. These patterns are best explained by a combination of limited interspecific hybridization and 'stalled' lineage sorting of ancestral polymorphisms. Overall, the patterns seem to indicate that the main centers of diversity represent large ancient refugia, possibly dating back to the late Eocene when the three genera originally diverged. Populations in the western portion of Sundaland appear to have gone through a major bottleneck event, potentially related to climate change in the late Oligocene. This lineage seems to have diversified and reinvaded the central mountain range of Borneo.

1 - Texas Tech University, Department of Biological Sciences, Box 43131, Lubbock, Texas, 79409-3131
2 - Duke University, Department of Biology, 139 Biological Sciences Building, PO Box 90338, Durham, North Carolina, 27708-0338, USA

chloroplast DNA sequence
ITS sequence
species cohesion.

Presentation Type: Paper
Session: 43-14
Location: Cottonwood A (Snowbird Center)
Date: Wednesday, August 4th, 2004
Time: 11:30 AM
Abstract ID:589

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