Abstract
Rhamnella brachycarpa Z. Qiang Lu & Y. Shuai Sun, a new evergreen woody species from Hainan Island, is described and illustrated. The specimens of this new species have previously been identified and placed under R. rubrinervis (H. Lév.) Rehder, with which it shares evergreen leaves, erect and climbing habits and axillary flowering branches with bracteole leaves. However, the specimens from three distinct Hainan populations significantly differ from those of R. rubrinervis from other regions with smaller length to width ratios of leaves, fruit and seeds, smaller sizes of fruit and seeds and mucronate seed apices. Principal Component Analysis of the closely related taxa, based on multiple morphological characters, further recognised two separated groups. One of them comprises R. tonkinensis and R. rubrinervis, the other merely includes all individuals from these distinct Hainan populations. Therefore, R. brachycarpa, based on these distinct Hainan populations, is here erected as a new species, distinctly different from its published relatives.
Highlights
The buckthorn family (Rhamnaceae) comprises 11 tribes and approximately 61 genera (Hauenschild et al 2016)
After examining all specimens of R. rubrinervis preserved in the Chinese Virtual Herbarium and Global Biodiversity Information Facility in 2017, we found that one distinct specimen from Hainan Island placed under R. rubrinervis might represent a new species because it was clearly different from a representative specimen of this species from Guangxi with the characters of shorter fruit and smaller leaf length to width ratio (Figure 1)
Our specific field survey on the special record on Hainan Island showed that no extant tree similar to R. rubrinervis existed in Tayang Township, Qionghai City (Figure 1A) and that the habitat was badly destroyed by human activity
Summary
The buckthorn family (Rhamnaceae) comprises 11 tribes and approximately 61 genera (Hauenschild et al 2016). Lév.) Rehder is the only evergreen species with both erect and climbing habits within this genus in China and is distributed in S and SE Yunnan, SW and S Guizhou, Guangxi and Hainan Island (Chen and Carsten 2007). After examining all specimens of R. rubrinervis preserved in the Chinese Virtual Herbarium Cn) and Global Biodiversity Information Facility (https://www.gbif.org/) in 2017, we found that one distinct specimen from Hainan Island placed under R. rubrinervis might represent a new species because it was clearly different from a representative specimen of this species from Guangxi with the characters of shorter fruit and smaller leaf length to width ratio (Figure 1). We conducted a field survey across the total distribution range of R. rubrinervis, including this Hainan population, to collect enough specimens for the examination of their morphological variations at the population level
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