Aspidostemon

Werff, Henk Van Der, 2006, A revision of the Malagasy endemic genus Aspidostemon Rohwer & Richter (Lauraceae), Adansonia (3) 28 (1), pp. 7-44 : 9-10

RELATIONSHIPS OF ASPIDOSTEMON

Kostermans (1957) obviously considered the species now placed in Aspidostemon as belonging to Cryptocarya . Rohwer & Richter (1987) reject- ed this idea; they noted the marked differences in wood anatomy between the two groups and thought that the similarity in fruit structure (in both Aspidostemon and Cryptocarya the fruit is enclosed in the enlarged hypanthium) might be a parallel development and not a signal of common ancestry. A representative of Aspidostemon , A. andohahelense Van der Werff , was included in a recent generic classification of Lauraceae based on DNA sequence data ( Chanderbali et al. 2001) and was found to be part of a strongly supported clade that also includes Beilschmiedia , Potameia Thouars , Endiandra R.Br. and Cryptocarya . The genera forming this clade share a unique paniculate inflorescence with the ultimate divisions that are not quite cymose; that is, the lateral flowers of what looks like a cyme are not strictly opposite, but tend to be subopposite, while in most genera of Lauraceae with paniculate inflorescences the lateral flowers in a cyme are strictly opposite (Van der Werff 2001). Most species of Aspidostemon have small, few-flowered inflorescences, but in a few species, such as A. glandulosum Rohwer , inflorescences are sufficiently large and branched that one can observe the inflorescence type is that found in the Beilschmiedia clade. Thus, it seems very likely that Aspidostemon is part of the Beilschmiedia clade and that, based on the presence of fruit included in the enlarged hypanthium, it is most closely related to Cryptocarya . The monotypic South African genus Dahlgrenodendron Van der Merwe & Van Dyk ( Van der Merwe et al. 1988), which was not included in Chanderbali et al. (2001), probably also belongs to the Beilschmiedia clade. It has opposite leaves, 2-locellate anthers and a fruit enclosed in the hypanthium with persistent floral remains in common with Aspidostemon , but differs from the latter in having 9 stamens instead of 3 or 6 and in its flower shape which is very similar to that of Cryptocarya . Dahlgrenodendron has longitudinally striate pollen grains, a unique feature in the Lauraceae . Straka & Friedrich (1988) included two species of Aspidostemon (as Cryptocarya perrieri Danguy and C. trianthera Kosterm. ; these collections are now placed in A. caudatum Rohwer and A. longipedicellatum Van der Werff ) in their pollen study and found that both species had round, spinulose pollen grains. Richter & Van Wyk (1990) found that wood and bark anatomy of Dahlgrenodendron did not agree with that of other known genera, including Aspidostemon , and concluded that Dahlgrenodendron was an isolated genus for which they did not find close relationships. I follow Rohwer & Richter (1987) and Richter & Van Wyk (1990) and accept Aspidostemon as a distinct genus largely defined by a floral character (number of stamens) and supported by vegetative characters (leaves opposite and wood anatomy).

Geographic coordinates indicated in square brackets were assigned post facto using available information on Malagasy place names and topographic maps, compiled as a gazetteer of botanical collecting localities in Madagascar (http://www.mobot. org/MOBOT/research/madagascar/gazetteer). The distribution of the Aspidostemon species is presented on maps showing the major bioclimatic zones of Madagascar (after Cornet 1974; see Schatz 2000).