﻿An unexpected new tree species from Gansu, China: Illiciumgansuense (Schisandraceae)

﻿Abstract We describe the newly-discovered species Illiciumgansuense (Schisandraceae), discovered in the Yuhe area of Giant Panda National Park, Gansu, China. Morphologically, I.gansuense resembles I.ternstroemioides and I.arborescens. However, the new species can be distinguished by its smaller leaf size, the larger number of tepals, tepal margin ciliate, and distinct flowering and fruiting seasons.


Introduction
The genus Illicium L., which belongs to the family Schisandraceae (APG IV 2016), consists of 35 species distributed across the southeastern United States, Mexico, the West Indies (five species), and eastern Asia (approximately 30 species) (Keng 1993).Linnaeus (1759) published the 10 th edition of Systema Naturae, which included the first named species of Illicium (I.anisatum L.) based on Kaempfer's monograph.In 1947, Smith published the first comprehensive study of the genus Illicium, "The Families Illiciaceae and Schisandraceae", which divided the genus into two subgenera based on perianth morphology: 1) I. subgen.Illicium with thin, membranaceous and narrowly oblong or ligulate inner perianth segments; and 2) I. subgen.Cymbostemon with carnose to papyraceous and usually ovate to suborbicular inner perianth segments (Spach 1839;Smith 1947;Lin 1997).Both Hao's and Morris' results suggested that the previous division based on perianth morphology wasn't monophyletic (Hao et al. 2000).Morris et al. (2007) utilized a distinguishable seed character to reflect their evolution history: I. sect.Cymostemon contains seven species with a hilar rim around seed hilum; and I. sect.Illicium consists of all the other species which do not have a hilar rim.
China, especially the southwest and southeast parts of the country, is home to many species of Illicium species.In particular, the species I. henryi Diels. is known to occur only in southern Gansu Province.
Illicium has considerable economic value, with I. verum Hook.f.being particularly valuable domestically in China and exported worldwide.The fruits of I. verum are used as a spice, and the leaves and fruits are steam distilled to create an aromatic oil (star anise oil) for use as a flavoring, as well as a therapeutic agent in traditional Chinese medicine (TCM).Other species of Illicium are used ornamentally or as a source of fine wood for furniture.
While surveying plants in the Yuhe area of the Giant Panda National Park, Gansu, in October 2020, we discovered an unknown species of Illicium.Based on field surveys, morphological and phenological studies, and taxonomic literature reviews, we concluded that this species should be included in I. sect.Cymbostemon (Spach) A.C.Smith (Smith 1947).However, because the specimen differed from other members in the section, we named and established the specimen as a new species (I.gansuense), as described herein.

Figure 2 .
Figure 2. Illicium gansuense Z.F.Bai & Xue L.Chen A flowering branch B adaxial and abaxial leaf surface C flower D tepals E removal of tepals showing gynoecium and stamens F, G stamens, dorsal and ventral views H carpel I fruiting branch J, K fruits L seed.(Drawn by Jianlu Bai based on type specimen).

Figure 4 .
Figure 4. Illicium gansuense Z.F.Bai & Xue L. Chen A flower at front view B flower at side view C the largest tepals D all parts of flower E stamen F follicle G fruit at front view H fruit at side view I seed.Photographed by Zengfu Bai.