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Systematics Section / ASPT

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

Cohesion of nuclear ITS sequences within rainforest tree species (Lithocarpus: Fagaceae) across different geographic scales.

The extent of species cohesion, based on either morphological or genealogical criteria, in diverse tropical tree genera is largely unknown due to poorly developed taxonomic schemes, prevalence of sterile collections, and lack of genetic data. In the paleotropical genus Lithocarpus (ca. 300 spp.) taxonomic information is well-developed and often associated with characteristics of the acorn and cupule, features that are well-represented in herbarium collections and in the field. We sampled over 300 individual trees from mixed communities of the genus within areas that contain as many as 20 species. We emphasized W Malaysian and Bornean populations, two areas that were geologically connected during the Tertiary. Using phylogenetic analysis of ITS sequences, widespread species and lineages, especially those with distinct fruit types, were treated as test cases for addressing questions of species cohesion within and among populations at several geographic scales. Previous notions of infrageneric groupings were supported in only two cases, one clade spanning the entire range of the genus (sect. Pasania s.s.), the other clade linking the areas of W Malaysian and Bornean (sect. Synaedrys s.s.). Using conspecific samples from widely separated populations, we found evidence for numerous examples of cohesion or clades at the species level. A few clades were admixtures of species, perhaps indicative of hybridization. Individuals of several species were unresolved, and their ITS sequences will be examined more closely for evidence of recombination with reference to other sequences obtained from the same populations. Overall, we can infer that reproductive barriers exist in tropical species of Fagaceae, and that by concentrating on specialized fruit types, salient features of the infrageneric taxonomy of Lithocarpus, we have evidence for the polyphyly of traditional infrageneric groups, and specific hypotheses for multiple origins of particular fruit types from less specialized types.

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

ITS sequence
species cohesion
tropical species.

Presentation Type: Paper
Session: 43-15
Location: Cottonwood A (Snowbird Center)
Date: Wednesday, August 4th, 2004
Time: 11:45 AM
Abstract ID:593

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