Welwitschia mirabilis (Welwitschiaceae), male cone characters and a new subspecies

Abstract

Leuenberger, B. E.: Welwitschia mirabilis (Welwitschiaceae), male cone characters and a new subspecies. — Willdenowia 357–381. — ISSN 0511-9618Based on the observation of male cones in plants of old stock of Welwitschia mirabilis cultivated in the Botanic Garden Berlin-Dahlem and documented in the garden herbarium, two groups can be distinguished. Plants of “group 1” are characterized by short peduncles and long, purplish brown male cones with widely overlapping bracts. Plants of “group 2” are regularly flowering about three weeks later and have usually longer peduncles but shorter male cones which are glaucous-green to salmon coloured and more “sculptured” due to different bract shape and less overlapping bracts. Tracking the incompletely documented origin of these accessions revealed that some of the over 50 years old plants were grown from seeds received from Coimbra originating from Angola and others from seeds received from Kirstenbosch originating from Namibia. Published illustrations of male cones provided only limited further evidence on cone characters. Examination of herbarium specimens of known origin showed that male cone characters fully agreeing with those of group 1 occur in material from Angola, whereas cone characters of plants of group 2 are typical for specimens from Namibia, particularly from the Swakop area. The differences suggest the existence of two subspecies. The controversial nomenclature of W. bainesii and the reasons for avoiding this epithet for the subspecies are briefly discussed. Instead the new combination W. mirabilis subsp. namibiana is validated. A lectotype is designated for the binomial W. mirabilis. As a further result, a total of three male cones with bracts arranged in verticils of three, instead of the regular two, were found among more than 3000 cones screened. One was found on a plant of group 1 grown at Berlin-Dahlem, one in a sample originally received from J. D. Hooker probably of Angolan origin, and one in a herbarium specimen from Namibia.