An electron microscopy study of the outer pericarp surface of achenes (fruits) of Rhynchospora (Cyperaceae) in the Guianas, South America, bearing on the delimitation of species and sections, and to clarify the taxonomy and distribution of species occurring in the Guianas.

摘要

Seventy-seven taxa and 3 infraspecific taxa of Rhynchospora (Cyperaceae) were found to occur in the Guianas (Guyana, Surinam, and French Guiana), South America. A new section, Stipitatae is proposed, seven taxa are new (two of which described provisionally), and one elevated to the species level. The species were taxonomically evaluated and circumscribed based on laboratory studies of micromorphological achene characters utilizing SEM, morphological herbarium studies of dried specimen collections, information on relationships between species from other studies published in the literature, habitat characterization, and distribution patterns. Label data was obtained from 2,206 specimens represented in major herbaria worldwide that are known to have extensive collections of Guiana specimens. A database from this label information was used to produce habitat profiles and plot distribution maps for each species using a GIS software program (ARCMAP) utilizing base maps available from the Biodiversity of the Guianas Program, Smithsonian Institution. SEM micrographs are provided for all 80 taxa (including infraspecific taxa). These micrographs include images of the whole achene (fruit) and detail of the pericarp. The infrageneric classification of Rhynchospora is discussed. Morphological characteristics of the genus and recent cytological advances including chromosome counts for each species are reviewed. Habitat and distribution including range maps for each species within the Guianas are presented. A taxonomic treatment is provided for all the taxa including a key to species, full detailed descriptions, habitat, distribution, nomenclatural notes, and discussion on distinguishing features.