Thursday, June 18, 2020

[Botany • 2020] Heterostemma carnosum (Apocynaceae, Asclepiadoideae) • A New Species from Papua New Guinea

 Heterostemma carnosum Rodda

in Rodda, 2020. 

The new species, Heterostemma carnosum is described, illustrated and compared with the similar species Heterostemma dalzellii. The two species differ in peduncle, pedicel and corolla size as well as in leaf shape.

Keywords: Ceropegieae, Crater Mountain, Papuasia

Fig. 1. Heterostemma carnosum Rodda.
 A. flowering branch; B. flower, view from above; C. flower, side view; D. pollinarium; E. follicle; F. seed.
(Based on the holotype, drawing by Loh Xiang Yun).

Heterostemma carnosum Rodda, sp. nov.

 Similar to H. dalzellii Hook., as both species have flowers with a rotate corolla, papillose inside, and a compressed-globose sessile corona. They are separated by the length of the peduncle (10–25 mm in H. carnosum, vs < 5 mm in H. dalzellii), pedicel (12–15 mm in H. carnosum vs < 7 mm in H. dalzellii and flower (corolla 2.5–3 cm diameter in H. carnosum vs < 1.5 cm in H. dalzellii).

Etymology. The specific epithet refers to the fleshy leaves and corolla (Latin carnosus = fleshy) that is an unusual feature in a genus that usually has species with thin leaves and corollas. 

Distribution and ecology. Heterostemma carnosum is only known from one specimen collected East of Haia Village, within Crater Mountain Wildlife Management Area, Papua New Guinea. Based on the label information, Heterostemma carnosum was collected in hill forest with some anthropogenic disturbance at the margins of an old garden. 

Michele Rodda. 2020. Heterostemma carnosum (Apocynaceae, Asclepiadoideae), A New Species from Papua New Guinea. Taiwania. 65(3); 326-328.