Daniel, Thomas F. .
Acanthaceae of São Tomé and Príncipe.
Recent phylogenetic studies of Acanthaceae, based primarily on DNA sequence data, reveal that Africa is the likely ancestral source area for major lineages and genera of the family. Therefore knowledge of the family in and around this continent is essential for understanding its phylogenetic and biogeographic histories. A taxonomic revision of Acanthaceae in the island nation of SÃ£o TomÃ© and PrÃncipe, which comprises two islands in the Gulf of Guinea off the western coast of Africa, reveals that 16 species in 13 genera are native there: Acanthus montanus, Asystasia gangetica, Avicennia germinans, Brachystephanus occidentalis, Brillantaisia lamium, B. owariensis, B. vogeliana, Dicliptera verticillata, Elytraria marginata, Heteradelphia paulowilhelmia, Justicia tenella, J. thomensis, Nelsonia smithii, Phaulopsis micrantha, Rhinacanthus virens, and Stenandriopsis thomensis. Three species (Brachystephanus occidentalis, Heteradelphia paulowilhelmia, and Justicia thomensis) are endemic to SÃ£o TomÃ©. Fourteen of the native species occur on SÃ£o TomÃ© and nine species occur on PrÃncipe. An additional species (Ruellia breviflora) from South America is naturalized on SÃ£o TomÃ©. The Gulf of Guinea island archipelago is unusual in consisting of both continental (Bioko) and oceanic islands (AnnabÃ³n, PrÃncipe, and SÃ£o TomÃ©). Differences in distance from/past connections to mainland Africa, size, elevation, and age result in unique floristic assemblages on each of the major islands. The three oceanic islands of this tropical archipelago show a richness of Acanthaceae that is positively correlated with relative size and elevational ranges of the islands. Except for Avicennia, which has embryos readily capable of oceanic dispersal, most Acanthaceae are commonly absent or rare on isolated oceanic islands. Because of their general lack of morphological characteristics that might promote long distance dispersal, rafting appears to be the most plausible explanation for dispersal of most Acanthaceae across significant water barriers. A scenario for dispersal of Acanthaceae from mainland Africa to the oceanic islands in the Gulf of Guinea is described.
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1 - California Academy of Sciences, Department of Botany, 55 Music Concourse Drive, Golden Gate Park, San Francisco, CA, 94118, USA
Gulf of Guinea
São Tomé and Príncipe.
Presentation Type: Poster:Posters for Topics
Location: Hall A/Convention Center
Date: Monday, August 2nd, 2010
Time: 5:30 PM