Vincetoxicum glabrum × V. pycnostelma (Apocynaceae): A New Natural Hybrid from Hyogo Prefecture, Japan

Abstract

A new natural hybrid of Vincetoxicum (Apocynaceae) from Hyogo prefecture, Japan, is reported as V. glabrum (Nakai) Kitag. × V. pycnostelma Kitag. It showed morphologically intermediate characteristics between Vincetoxicum species found in the habitat, i.e., V. glabrum and V. pycnostelma. There are six positions in the sequence of the nuclear ribosomal ETS region showing polymorphisms that were additive between the two putative parent species. These results suggest that the new hybrid originated from V. glabrum and V. pycnostelma. In addition, flower-visiting insects that have not been recorded from the parent species were observed in V. glabrum × V. pycnostelma. This implies that the hybridization may have led to the acquisition of new pollinators, and further suggests the potential role of the hybrid formation in the diversification of the genus Vincetoxicum.