Systematics Section / ASPT
McDade, Lucinda A. , Daniel, Thomas F. , Kiel, Carrie A. .
Phylogenetic patterns among New World Acantheae: Widespread polyphyly and poor resolution present a marked contrast with Old World Acantheae.
Acantheae are Acanthaceae s.s. (i.e., plants with seeds borne on retinacula) that are marked by the synapomorphy of monothecous anthers. The lineage includes 21 genera with a total of ca. 500 species, and is distributed primarily in the American and African tropics. We previously showed Acantheae to be monophyletic and to include two strongly supported lineages: (1) Old World (OW) plants that share the synapomorphy of a one-lipped corolla and (2) a lineage comprising both Old and New World plants that retain the plesiomorphic two-lipped corolla. We have now examined relationships among plants belonging to this second lineage using DNA sequence data from four loci (nr-ITS, cp trnL-F intron and spacer, trnG-S spacer, rps16 intron). The Malagasy genus Achyrocalyx, with two-lipped corollas, is placed with OW Stenandriopsis as the basal lineage of this otherwise New World (NW) clade. Achyrocalyx seems to have been derived from within Stenandriopsis as this last genus is paraphyletic and Malagasy species are more closely related to Achyrocalyx than to African Stenandriopsis. Among NW plants, there is support for clades comprised of (1) the Jamaican taxa Salpixantha and Neriacanthus purdieanus plus continental Stenandrium, Holographis and one Aphelandra species; (2) South American species of Aphelandra that are spiny to varying degrees; and (3) taxa that share a 21 bp deletion in nrITS-1 including many species of Aphelandra plus all sampled species of Geissomeria and Encephalosphaera. Several other species of Aphelandra, two species of Neriacanthus and monotypic Rhombochlamys cannot be placed with confidence in any of these lineages. NW Acantheae present a strong contrast with OW Acantheae in that traditional genera are not well supported as monophyletic and clear morphological synapomorphies are few. We discuss evolutionary processes that might be responsible for these differences.
1 - Academy of Natural Sciences, Botany, 1900 Ben Franklin Parkway, Philadelphia, Pennsylvania, 19103, USA
2 - California Academy of Sciences, Botany, Golden Gate Park, San Francisco, California, 94118, USA
New World tropics
Presentation Type: Paper
Location: Cottonwood A (Snowbird Center)
Date: Tuesday, August 3rd, 2004
Time: 9:30 AM