Biogeography of Zehneria (Cucurbitaceae) and a New Species from India

Abstract

Abstract— Zehneria is one of the most diverse genera in Cucurbitaceae with 75 accepted species mainly in Southeast Asia and tropical Africa. Here, we describe Zehneria neorensis, a new species from Neora Valley in the mountains of West Bengal, India, which has 7‐10 cm long twisted fruiting pedicels, the longest pedicels reported in the genus so far. Based on morphological data, we also suggest the transfer of Melothria morobensis to the genus Zehneria. With a molecular phylogenetic and global biogeographic analysis based on 3856 nucleotides of plastid and nuclear ribosomal DNA, we demonstrate that the genus Zehneria most likely originated on the African continent 24 (30‐19) million years ago and spread from there at least five times to Madagascar and three times to Asia. Zehneria neorensis represents an independent colonization event from Africa to India about 11 (15‐7) million years ago. Three lineages reached New Guinea/Australia and finally moved into Polynesia. We infer a rate of at least 20 long-distance dispersal (LDD) events per 10 million years in the genus. This high LDD frequency is most likely a result of the small berry fruits and small flattened seeds of Zehneria, which seem perfectly adapted to long-distance bird dispersal. Field observations are needed to investigate a potential effect of the newly discovered extended and coiling pedicels in Zehneria neorensis on seed dispersal efficiency. The new species adds to a growing list of rather old Cucurbitaceae lineages in the Himalayan foothills, supporting the hypothesis of long climatic stability in the region.