Styrax zhejiangensis has been treated as a synonym of S. macrocarpus. Examination of herbarium specimens and observation of wild living plants demonstrates that S. zhejiangensis is a distinct species and is clearly distinguishable from S. macrocarpus through its flowering phenology in which leaves and flowers open simultaneously, its smaller corolla lobes and filaments, and its white-stellate-pubescent seeds. On this basis, we reinstate S. zhejiangensis as an accepted species. Photographic images and a distribution map of the two species are provided. A lectotype of S. zhejiangensis is also designated.

Flowering phenology, Styracaceae, Styrax zhejiangensis, S. macrocarpus, synonym

Styrax zhejiangensis S.M. Hwang & L.L. Yu (Hwang 1983) (Styracaceae) was described on the basis of four specimens of one collection, X. Y. He 29344 (IBSC, HHBG, NAS; Fig. 1A), from Jiande, Zhejiang Province, China. In the protologue, the authors stated that this species was similar to S. macrocarpus Cheng (Cheng 1938) (Fig. 1B), but differed by its bush-like habit, broadly elliptic to ovate-oblong leaves, smaller fruits, and sparsely white-stellate seeds. It was recognized by later authors, including Hwang (1987), Li and Ding (1989), Fang (1992), and Hwang and Grimes (1996), but was synonymized with S. macrocarpus by Huang et al. (2003). Huang et al. (2003) purported that there were no essential morphological differences between the two species emphasized by Hwang (1983) other than the presence of stellate trichomes on the seeds in S. zhejiangensis versus their absence in S. macrocarpus, a difference which they regarded as taxonomically trivial. According to Huang et al. (2003), S. macrocarpus sensu lato is a species with a disjunct distribution between southeastern Hunan and western Guangdong (Fig. 2).

After critical examinations of the relevant Styrax specimens in major Chinese herbaria, combined with our field observations in the type localities of each entity, we find that S. zhejiangensis is a species distinct from S. macrocarpus, differing from it in a combination of taxonomically significant morphological characters. Here we provide updated detailed morphological descriptions of these two species, a table of their morphological character differences, a distribution map, photographic images, and conservation assessments.

Figure 1. 

Lectotype sheet of Styrax zhejiangensis, China, Zhejiang, Jiande, X. Y. He 29344 (IBSC) (A) and holotype sheet of S. macrocarpus, China, Hunan, Yizhang, Mang mountain, W. C. Cheng s.n. (PE) (B).

Figure 2. 

Distribution map of Styrax zhejiangensis ([INSERT FIGURE 003]) and S. macrocarpus.

Morphological comparisons were made through herbarium studies and field observations. Herbarium studies were conducted in AU, BNU, CSFI, HHBG, IBK, IBSC, JXAU, KUN, NAS and PE. Field observations were made in the type localities of Styrax zhejiangensis in Jiande, Zhejiang Province, and S. macrocarpus on Mang Mountain, Hunan Province. Moreover, we use IUCN Red List categories (IUCN 2012) to evaluate the conservation status of the two species.

Styrax zhejiangensis differs from S. macrocarpus in a combination of morphological characters (Table 1, Figs 3–5). S. zhejiangensis produces flowers and leaves simultaneously (vs. flowers before the leaves in S. macrocarpus), has smaller flowers (4.0–5.5 cm vs. 6.0–7.5 cm in diameter) with shorter corolla lobes (1.8–2.7 cm vs. 2.8–3.8 cm) and stamens (10–12 cm vs.14–16 cm), and has a seed surface with sparse to dense white-stellate trichomes (vs. glabrous). Furthermore, S. zhejiangensis is shrub-like, 1.5–3 m (only one individual reaches 7 m in our observation), with multiple branches from the base, whereas S. macrocarpus is tree-like, often over 7 m and with single stem. The pubescence on the corolla also helps to distinguish the two species, with S. zhejiangensis having inconspicuous pubescence or being glabrous, and S. macrocarpus having conspicuous pubescence.

Figure 3. 

Styrax zhejiangensis (Jiande, Zhejiang, China) A habitat and habit B inflorescence C leaf blades D flower (top view) E flower (back view) F flower (side view) G opened flower H corolla lobes I sepals (two sepals pulled apart at the lobe margins of one calyx) J stamens. Photographed by Yu-Qing Ruan and Ming Tang.

Figure 4. 

Styrax macrocarpus (Yizhang, Hunan, China) A habitat and habit; red arrow indicates S. macrocarpus B inflorescence C leaf blades in adaxial (left) and abaxial (right) view D flower (top view) E flower (back view) F flower (side view) G corolla lobes H sepals (two sepals pulled apart at the lobe margins of one calyx) I stamens. Photographed by Yu-Qing Ruan and Ming Tang.

Figure 5. 

Morphological comparison between Styrax zhejiangensis (A1, B1, C1, D1) and S. macrocarpus (A2, B2, C2, D2). A1, A2 Flower B1, B2 corolla lobes C1, C2 stamens D1, D2 seed (Note the enlarged stellate trichomes in the red circle in figure D1). Photographed by Yu-Qing Ruan and Ming Tang.

Li and Ding (1989) and Hwang and Grimes (1996) described the flowering phenology for Styrax zhejiangensis and S. macrocarpus and they have been confirmed in our field observation, and undoubtedly serve as a diagnostic character. Li and Ding (1989) also pointed out that the species can also be distinguished by the size of the corolla lobes and numbers of stamens. We observed a substantial difference in the size of their corolla lobes, but no distinct difference in the numbers of their stamens, with 13 to 16 stamens for S. zhejiangensis and 11 to 15 for S. macrocarpus. Huang et al. (2003) pointed out that the number of stellate trichomes distributed on the seed surface of S. zhejiangensis varies from several to dozens, which is consistent with our observation, and they considered that this character by itself cannot be used to distinguish S. zhejiangensis from S. macrocarpus. However, it should be noted that the seed surface of S. macrocarpus is glabrous by our observation, never with stellate trichomes. Thus, combined with the other differences observed, warrant the treatment of S. zhejiangensis as an accepted species distinct from S. macrocarpus.

We are grateful to Dr. Chen Ren, Dr. Peter W. Fritsch and Dr. Yasen Mutafchiev for their valuable comments on the manuscript. We also thank the curators of AU, BNU, CSFI, HHBG, IBK, IBSC, JXAU, KUN, NAS and PE for access to their specimens and allowing us to use their scanned images of specimens. This work was supported by the National Natural Science Foundation of China (grant no 31960043, 31500166) and the Science and Technology Research Project of Jiangxi Education Department (grant no. GJJ170255).