Passerina quadrifaria (Thymelaeaceae): a new species from the southern Cape and Little Karoo in South Africa

Abstract

Passerina L. is an endemic southern African genus, with the exception of two species that have outliers in eastern Africa. The genus comprises about 20 species and four subspecies. P. quadrifaria Bredenkamp and Van Wyk is a new species occurring in the Karoo Mountain, Langeberg and Southeastern phytogeographic centres of the Cape Floristic Region. It is most closely related to P. comosa C.H.Wright as the leaves and bracts of both species are abaxially hairy. The most obvious diagnostic feature of the new species is the distinct four-ranked appearance of the leaves, which are decussate, imbricate, sessile and spreading at an angle of ± 45°. The species have complementary nonoverlapping ranges, P. comosa occurring from the Kamiesberg of the Northern Cape Province to the Roggeveld, Witteberg and Klein Swartberg mountain ranges of the Western Cape Province, whereas P. quadrifaria is restricted to mountain ranges of the southern Cape and western parts of the Eastern Cape Province. There are two morphological forms of P. quadrifaria, the first form corresponding to the general species description and a second form with slightly longer internodes, smaller leaves and the apices of the bracts more rounded. As the leaves of these two forms are anatomically identical, they are not given formal taxonomic status.