Dahlgrenodendron, a remarkable new genus of Lauraceae from Natal and Pondoland

Abstract

A reappraisal of the taxonomic relationships of the southern African tree, Beilschmiedia natalensis J.H. Ross, proved it to be wrongly placed in the genus Beilschmiedia Nees. Its mature fruit is completely covered by the accrescent hypanthium, whereas Beilschmiedia (and the tribe Perseeae) is characterized by a completely deciduous perianth. Since it does not fit well with any of the existing lauraceous genera, a new genus, Dahlgrenodendron J.J.M. v.d. Merwe & Van Wyk, and new combination, D. natalense (J.H. Ross) J.J.M. v.d. Merwe & Van Wyk, are proposed. The pollen is most distinctive and decidedly different from anything known in Lauraceae. Grains are free, radially symmetrical, para-isopolar, ± spindle-shaped prolate (when dry), atreme, with a wall ornamentation of striae alternating with prominent ± parallel ridges. Dahlgrenodendron is further characterized by opposite leaves, fruit with an endocarp consisting of a palisade of columnar sclereids which develop from the ovary wall, and 2-celled anthers. It is tentatively related to the tribe Cryptocaryeae, subtribe Cryptocaryineae and compared with Cryptocarya R. Br. and Ravensara Sonn. — the two genera currently constituting this subtribe. D. natalense is an exceedingly rare forest species confined mainly to the southern Natal/Pondoland sandstone region. With the total number of individuals probably not exceeding 200, it is considered an ancient relict on the brink of natural extinction.