A BOTANICAL GORDIAN KNOT: THE CASE OF ATERAMNUS AND GYMNANTHES (EUPHORBIACEAE)

The taxa of the Euphorbiaceous tribe Hippomaneae (sensu Webster, 1975) still present notoriously difficult problems in generic delimitation, despite the revisionary efforts of Mueller (1866), Baillon (1874), Bentham (1880), Pax and Hoffmann (1912), and others. This is especially true of the complex of taxa with highly reduced flowers which Baillon (1874) reduced to the single genus Excoecaria. Although Rogers (1951) achieved an acceptable differentiation between Sapium and Stillingia, the demarcation lines between Actinostemon, Gymnanthes, Sebastiania, and some smaller genera remain uncertain. This problem in classification is exacerbated by some nomenclatural difficulties, among which the status of Gymnanthes is most critical. Rothmaler (1944) initiated a still unresolved nomenclatural crisis by resurrecting the generic name Ateramnus P. Browne (1756), based on a Jamaican plant that Rothmaler identified with Gymnanthes lucida Sw. Since Ateramnus is a validly published earlier name, Rothmaler argued that it should be adapted for the genus currently known as Gymnanthes Sw. (1788). Recently, this suggestion of Rothmaler's has been taken up by Adams (1970, 1972) and by Gillis (1974), who apply names under Ateramnus to species heretofore treated under Gymnanthes. Gillis avowedly follows the lead of Dandy (1967), who in his index of generic names published between 1753 and 1774 listed Ateramnus in such a manner as to imply that it has priority over Gymnanthes. This has created a confusing situation in the current literature, because some botanists have followed Adams and Gillis in adopting Ateramnus (Correll, 1979; Tomlinson, 1980), whereas others continue to use Gymnanthes (Foumet, 1978; Elias, 1980). Little (1979), in his most recent index to the names of North American trees, judiciously declines to accept Ateramnus in place of Gymnanthes until this nomenclatural conflict is resolved. One solution to this problem might be to propose Gymnanthes for conservation. However, as noted by Gillis (1974), conservation of Swartz's generic name has already been rejected once by the Special Committee for Pteridophyta and Phanerogamae (Taxon 3: 241. 1954). The deciding factor in that vote may have been doubt that Ateramnus and Gymnanthes are synonyms. Long before Rothmaler's article, Hallier (1918) concluded that it is highly doubtful that Ateramnus was based on the plant Swartz called Gymnanthes lucida. This may be seen clearly by comparing the characteristics of Swartz's species with the brief description of Browne (1756: 339):