Systematics Section / ASPT
Daniel, Thomas F. , McDade, Lucinda A. .
Floral Resupination in Acanthaceae: Taxonomic and Geographic Distributions, Expression, and Possible Functions.
Floral resupination (rotation of flowers, usually resulting in an upside down orientation) is infrequent among flowering plants and has rarely been associated with Acanthaceae. Although best known among Orchidaceae, resupination has been reported in diverse families including: Alstroemeriaceae, Balsaminaceae, Campanulaceae, Fumariaceae, and Gesneriaceae. Resupination takes place by various means in different taxa (e.g., torsion of pedicels, inferior ovaries, or corollas). Among Acanthaceae, resupination has been reported in three major lineages (tribes) of subfamily Acanthoideae: Acantheae (Streptosiphon), Justicieae (Dicliptera, Hypoestes, Peristrophe), and Ruellieae (Stenosiphonium, Strobilanthes s.l.). Because taxa with rotated corollas are distally nested among diverse lineages of Acanthoideae, resupination appears to be homoplastic in the subfamily. In spite of numerous independent origins, all Acanthaceae with resupinate flowers achieve rotation via torsion of the corolla tube relatively late in the floral bud's development. Rotation of corollas is usually 180º, which results in the ventral lip becoming oriented dorsally. Resupination appears to have been lost secondarily in some Neotropical Dicliptera. In other New World Dicliptera, the corolla is resupinate 360º; in these plants, the corolla appears to be normally oriented (i.e., with ventral lip in ventral position), but this orientation is achieved via exceptional torsion of the corolla tube. Presence of resupination has been used to characterize taxa; its occurrence is constant in some genera (e.g., Hypoestes) but not in others (e.g., Dicliptera). No species is known to have both resupinate and non-resupinate individuals. The incidence of resupination among Old World Acanthaceae is greater than among New World Acanthaceae. An obvious consequence of resupination is alteration in presentation of the flower (e.g., nototribal to stenotribal in Dicliptera). Observations of contrasting floral visitors to resupinate vs. nonresupinate New World Dicliptera suggest that selection for pollinator specificity accounts for the floral difference. Additional occurrences of resupination should be sought among Acanthaceae.
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1 - California Academy of Sciences, Department of Botany, 875 Howard Street, San Francisco, California, 94103-3009, USA
2 - Academy of Natural Sciences, Department of Botany, 1900 Benjamin Franklin Parkway, Philadelphia, Pennsylvania, 19103, USA
Presentation Type: Poster
Location: Salon C, D & E - Gov Ballroom/Hilton
Date: Tuesday, August 16th, 2005
Time: 12:30 PM