An anatomical survey of the leaflet margins of the genus Attalea (Arecaceae: Arecoideae: Cocoseae: Attaleinae)

Abstract

An anatomical survey of the leaflet margins of 24 species of Attalea revealed insights into the taxonomy of the genus. Examination of cross-sections of Attalea leaflets revealed that the proximal and distal margins are not identical. Proximal margins nearly always contain a region of expansion cells, which are usually absent on the distal margin. The abaxial side of proximal margins is nearly always protruded, angling the margin upwards. Conversely, the adaxial side of the distal margin is protruded, angling the margin downwards. Thus we have upward facing proximal margins meeting downward facing distal ones. The leaflet margins were used to collaborate or question the accepted species of a recent taxonomic revision of Attalea, which synonymized several species. The anatomy of the leaflet margins lent support to uniting some species, but remained inconclusive in uniting others. Finally, although Attalea palms formerly belonged to five genera based on differences in floral morphology, evidence from the leaflet margins supports the notion that all Attalea palms belong to a single genus. Leaflet anatomy also revealed intermediate characters between hybrids and their parental species.

Key words:
anatomy; distal margin; expansion tissues; proximal margin; species complexes