Taxonomy and Evolution of the Buckthorn Family (Rhamnaceae) in Southeast Asia

Southeast Asia is one of the world’s most floristically diverse regions, with 50,000 flowering plant species recognised and an estimated 10,000 more that have yet to be scientifically documented. My research contributes to filling this knowledge gap by documenting plants in the Rhamnaceae family from Southeast Asia. Except for Flora of Thailand, which followed the conclusions of our publications, none of the region’s major Flora initiatives have completed accounts for Rhamnaceae. Much of their diversity is still unknown, and species boundaries are unclear. A phylogeny-based tribal classification published in 2000 is the foundation of our current understanding of evolutionary relationships within the Rhamnaceae. The phylogenetic position of some genera is still uncertain. The family is thought to have originated in the Cretaceous and mostly diversified into its current tribes in Gondwana, based on fossil evidence. Recent discovery of older fossils suggest that it may have originated in the Jurassic. We have published taxonomic revisions and new species descriptions in four genera: Ventilago, Smythea, Gouania and Ziziphus. We revised the genus Smythea throughout its range, including six new species descriptions, described three new Ventilago species, plus two additional species in New Caledonia and Vanuatu, revised the genus Gouania in western Malesia, and contributed the first revision of Ziziphus in Borneo, including three new species and two new variety descriptions. This work, carried out between 2016 and 2021, lays the groundwork for a future revision of the entire family across the region. This research will help to understand the evolutionary history of the Rhamnaceae family. Almost all the plants I documented are woody climbers that either twine around the host plant (Smythea and Ventilago), use tendrils (Gouania) or spines along their stems to climb (Ziziphus). Some have wind-dispersed winged fruits (Ventilago, Smythea, and Gouania), while others have fleshy fruits dispersed by animals (Ziziphus). These different means of climbing and fruit dissemination may have affected the evolution and spread of the woody climbing species in different ways.

Grantor dc:publisher

Oxford Brookes University

Year dc:date

2022

Author dc:creator

• Cahen, Daniel

Contributors dc:contributor

• Lack, Andrew

Statement dc:rights

• All rights reserved

Language dc:language

en

DOI dc:identifier

https://doi.org/10.24384/TVVB-ZK97

OAI identifier oai:identifier

tle:7df625d6-240d-484d-9846-6792c8fce84a:d6bd9758-527a-46cd-bfe2-c433766e8fca:1