Dissertation Research: Systematics of Palm Subtribe Oncospermatinae

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9902082Doyle and Lewis The palm family has been recognized as a distinct group of plants throughout recorded history, but taxonomic and phylogenetic relationships among the ca. 200 genera are still unclear and are the subject of continuing study by a small group of specialists worldwide. It has been particularly difficult to discern reationships among the 112 genera within the lineage containing tribes Areceae, Cocoeae, Geonomae, and Hyophorbeae. In collaboration with other researchers working on portions of this lineage, graduate student Carl Lewis, under the supervision of Dr. Jeff Doyle at Cornell University, is conducting a phylogenetic study of Areceae subtribe Oncospermatinae, a group of eight genera comprising an estimated 12 species distributed on islands and neighboring landmasses of the Indian Ocean. Morphological data and DNA sequences will be used to resolve relationships within the subtribe, and to evaluate different biogeographic hypotheses for the group. The phylogenetic position of subtribe Oncospermatinae will also be determined, and the findings will be integrated into emerging hypotheses of relationships within the entire lineage. Morphological observations were collected from herbarium specimens and from living palms in the field, and these data support the hypothesis that subtribe Oncospermatinae is a natural lineage. Sequence data were obtained from two different DNA regions within the chloroplast genome that are commonly used in phylogenetic research at low taxonomic levels. Unfortunately, these regions are not variable enough to provide information about relationships between palm genera. In a search for DNA data more suitable for this study, the investigators have developed primers for amplifying and sequencing a large intron of the nuclear gene encoding malate synthase (EC 4.1.3.2), which has not been used previously in phylogenetic research. Preliminary data show the malate synthase intron to be a good source of phylogenetic information in palms, with sufficient nucleotide substitutions to discriminate among genera. A more focused investigation will be conducted on the important genus Oncosperma, which contains five or more species occurring over a broad region of coastal and insular southeast Asia, with one goal being a comprehensive taxonomic monograph of the group.