Ilex danxiaensis (Aquifoliaceae), a Distinct New Tree Species Endemic to Danxia Mountain in Guangdong Province, China, Based on Molecular and Morphological Evidence

Many holly species are dominant species in evergreen broad-leaved forests, and they play an important role in the formation and maintenance of forest ecosystems in tropical and subtropical regions. Here, a new holly species (Ilex danxiaensis K. W. Xu & Q. Fan) of Aquifoliaceae was discovered from Guangdong, China, when conducting biodiversity investigations in the Danxia landform. We inferred the phylogenetic position of the new species based on sequences from three nuclear markers, namely internal transcribed spacer (ITS), external transcribed spacer (ETS), and chloroplast glutamine synthetase gene (nepGS). The results demonstrated a close relationship among the new species and members of I. sect. Lioprinos. The inferred phylogenetic position of the new species is also supported by morphological evidence that all of these species are characterized by having axillary cymes inflorescences and abaxially 1-sulcate pyrenes. However, the new species can be distinguished from others by having puberulent branchlets, petioles, peduncles, and pedicel; (1–)2–3-flowered cymes of male inflorescences; 1-flowered cymes of female inflorescences; ciliate sepals, 4-merous flowers, pink or white female flowers; and 4 pyrenes.