A New Combination in Gabonese Synsepalum (Sapotaceae)

Abstract

Gambeya nyangensis is shown to have been based on a mixed collection. The name is lectotypified and the species, with an amended description, is transferred to Synsepalum. Gambeya nyangensis Pellegrin was recognized in 1924 and illustrated four years later (Pellegrin, 1928), based on Le Testu 1786, a collection from the Tchibanga region of southwestern Gabon. Included in this gathering were flower-bearing branchlets as well as detached seeds. Pellegrin's assumption that these two elements represented one species appears to have misled him in his generic placement of the species. He commented that in its general habit and reticulate foliar nervation, G. nyangensis approached G. africana (G. Don) Pierre, but offered no other justification for his recognition of the new species in Gambeya. However, the fact that the seeds of both G. africana and G. subnuda (Baker) Pierre (type species of Gambeya) resemble those assumed to belong to his new taxon in having a linear hilum may also have influenced his decision. That some doubt about it existed in his mind is suggested by his statement that the flowers of G. nyangensis are very similar to those of Chrysophyllum sect. Zeyherella, in particular those of C. longipedicellatum De Wildeman. Aubr6ville (1961) stated flatly that G. nyangensis is not really a Gambeya. Nevertheless, lacking the intact fruit, he felt it best to leave the species there, while echoing Pellegrin's thoughts on Zeyherella and adding Pachystela and Ecclinusa to the list of generic candidates. Aubr6ville correctly pointed out that the seed of Le Testu 1786 precludes the use of either Pachystela or Zeyherella. Recent collecting in central Gabon has yielded specimens that resolve this puzzle. In January 1983 researchers at the Station d'l~tudes des Gorilles et Chimpanz~s in the Lope Reserve found chimpanzee dung containing a Sapotaceae seed that did not correspond to any species illustrated by Aubr6ville (1961). Seeds of the same species were found several times over the years, during November-January, in both chimpanzee and gorilla dung (White & Abernethy, 1997: 186), but it was not until November 1990 that a fruiting specimen was located and collected. It proved impossible to identify this specimen, and a number of trees were monitored for flowering activity. In June 1996 flowering material was collected that matches very well the flowerbearing branchlets of the type of G. nyangensis. Since the recently collected seeds have a much wider hilum than do those of the type (>15 mm vs. ca. 3 mm), it is now evident that the type collection is a mixture, and the name is lectotypified below in accordance with Articles 9.9 and 9.10 of the Code (Greuter et al., 1994). In Aubraville's key to genera in the Flore du Gabon, the recent material would lead to Afrosersalisia, but that genus is now recognized as a synonym of an inclusive Synsepalum, based on the convincing work of Pennington (1991). Other Gabonese genera similarly now included in Synsepalum are Pachystela, Tulestea, and Vincentella. The necessary combination in Synsepalum is made below, and an amended description of the species is