Abstract
SummaryThe genus Ziziphus (Rhamnaceae) is revised for Borneo. 13 species are recognised using morphological evidence, including three new endemic species: Ziziphus cuspidata, Z. domatiata and Z. puberula. Borneo is therefore the island with the greatest known diversity of Ziziphus species. The area surrounding Mount Kinabalu is particularly diverse, with nine species occurring in Ranau. Two new varieties of Z. borneensis are also described here, Z. borneensis var. ranggam and Z. borneensis var. velutina, five new synonyms are established, including the placement of Z. elmeri as a synonym of Colubrina beccariana. A taxonomic treatment, including a preliminary IUCN conservation status assessment, is presented for each species and variety.
Highlights
Ziziphus Mill. is a genus in the Rhamnaceae of about 80 species of deciduous and evergreen shrubs, climbers and trees occurring throughout the Old World (OW) tropics, subtropics and warmer temperate regions (Hauenschild et al 2016; Medan & Schirarend 2004; POWO 2019)
Morphological differences between Old World (OW) and New World (NW) species had been reported by several authors and an analysis of ITS, 26S rDNA and trnL-F data by Islam & Simmons revealed that the genus was not monophyletic, with OW and NW species belonging to separate lineages
An additional analysis of trnL-F and ITS sequence data by Hauenschild et al (2016) further supports that the genus Ziziphus as previously defined is not monophyletic and NW species have subsequently been reattributed to the genera Sarcomphalus P.Browne in Paliureae and Pseudoziziphus Hauenschild in Rhamneae Hook.f. emend
Summary
Ziziphus Mill. is a genus in the Rhamnaceae of about 80 species of deciduous and evergreen shrubs, climbers and trees occurring throughout the Old World (OW) tropics, subtropics and warmer temperate regions (Hauenschild et al 2016; Medan & Schirarend 2004; POWO 2019). In Borneo, no complete taxonomic treatment of Ziziphus has been published, checklists for the island (Merrill 1929; Masamune 1942) and the Mount Kinabalu area (Beaman & Anderson 2004) are available, with Merrill listing five species, of which one is excluded in this revision The most complete overview of Ziziphus species occurring in Borneo was restricted to Sabah and Sarawak (Schirarend 1995). It includes a detailed account of Z. angustifolia and recorded seven climbing species in the key only. Many of the species occurring in Borneo have a small distribution range: five are endemic to the island Four new synonyms are established within the genus and Z. elmeri a tree species with pinnate venation, is placed here as a synonym of Colubrina beccariana
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