Ottelia fengshanensis, a new species (Hydrocharitaceae) from southwest China is here described and illustrated. Comparing its morphological features to putative close relatives O. guanyangensis, it has 3–4 flowers (vs. 2–5) each spathe, hexagonal-cylindric fruit, white styles (vs. yellow), green leaves (vs. dark green) and fruit tiny winged (vs. winged obviously). Molecular phylogenetic investigation of four DNA sequences (ITS, rbcL, trnK5’ intron and trnS-trnG) and the Poisson Tree Processes model for species delimitation (PTP) analysis, further resolves O. fengshanensis as a new species that is close to O. guanyangensis with distinct support.

karst, bisexual flowers, molecular phylogeny

Ottelia Persoon (1805:1) has about 22 species and is widely distributed in the tropical, subtropical and temperate regions. In comparison with other genera within the family Hydrocharitaceae, Ottelia is morphologically complex and variable, e.g. the leaf type of the genus is exceptionally erratic even within an individual depending on the developmental stage, as well as within the varieties or populations (Li et al. 2018). The flower sexuality varies within species and flowers can be either bisexual or unisexual. Southwestern China possesses complex terrain and various ecosystems and is a center of diversity for Ottelia species (Chen et al. 2017, Zhai et al. 2018). To date, six species and three varieties of O. acuminata Dandy (1934: 132) have been recorded from the area with narrowly endemic distribution in karst rivers or lakes. Among these, just three species, O. alismoides Persoon (1805: 273), O. balansae Dandy (1934: 137) and O. guanyangensis Z.Z. Li, Q.F. Wang & S. Wu (2018: 294) are bisexual and can only be found in specific karst regions, except for the widespread species O. alismoides (Cook et al. 1984, Cook and Urmi-Konig 1984, Li 1981).

In 2017–2018, we found and reported a new bisexual species O. guanyangensis in Guilin City, China (Li et al. 2018). We deemed that there are some previously undetected potentially new Ottelia species in Guangxi province’s karst steams (Fig. 1). We made further aquatic plant investigations in Guangxi province, China, in 2018. From the Fengshan County, we found once again a species with bisexual flowers which generally appeared to be like O. balansae. Based on investigations of herbarium specimens in GXMG, HIB, IBSC, KUN and PE, and literature review, only three bisexual species of Ottelia are known from China. These are O. guanyangensis, a species described in 2018 (Li et al. 2018), O. balansae, and O. alismoides, the latter two recorded from “Flora of China”. Compared to the recorded three bisexual species, it was interesting that the population from Fengshan county had some unique flowers (e.g. white styles and over three flowers each spathe) and leaf traits (e.g. triplinerved with obvious cross-veins). We transplanted several individuals to the greenhouse at Wuhan Botanical Garden, Chinese Academy of Sciences, to observe the growth. Here we formally describe and discuss this taxon as a new species based on careful morphological observations and molecular phylogeny.

Figure 1. 

Distribution record of Ottelia fengshanensis Z.Z.Li, S.Wu & Q.F.Wang (red triangle) from Fengshan county, Guangxi province, China.

The comparison among three bisexual species, O. fengshanensis, O. guanyangensis and O. balansae, is presented in Table 2. The new species had unique features, including the number of flowers, white styles, trinerved venation with distinct cross veins and longer leaf shape.

Morphological characters distinguish O. fengshanensis from the three bisexual species. For O. alismoides, there is only one flower in each spathe and it is easy to distinguish from the new species. However, O. guanyangensis and O. balansae, which are distributed in Guangxi province and Guizhou province respectively, are closest to the new species. The critical diagnostic characters of O. fengshanensis include having white styles, longer leaf shape and number of flowers in each spathe. Moreover, these three species are also isolated geographically, O. fengshanensis was only found in Fengshan county, but O. guanyangensis was found in Guilin city. O. balansae was only recorded in Guizhou province based on a recent survey. Karst terrain will play an important role in species divergence in this lineage.

Four sequence regions (ITS, trnS-trnG, rbcL and trnK5’ intron) were aligned and concatenated into a 3623 bp sequence. 605 variable nucleotides were detected. Two clades were displayed with high support (BS= 70, PP= 0.7). PTP analysis further recognized four species with O. fengshanensis having the highest support (0.678). Based on phylogenetic analyses, O. fengshanensis was resolved as sister to O. guanyangensis with high support (BS= 100, PP= 1.0) and only distantly related to O. balansae, which clusters together with O. acuminata (Fig. 4), and based on PTP analysis, O. balansae was not supported as a species, but was more likely to be treated as a bisexual variety of O. acuminata. In combination, the morphological and molecular phylogenetic analyses support that O. fengshanensis is a distinct species closely related to O. guanyangensis, a species also distributed in Guangxi province.

Ottelia possesses complex floral traits and may have bisexual and unisexual flowers. Based on the previous studies (He 1991, Chen et al. 2012) bisexual flowers have evolved multiple times in Ottelia. Here we report a new bisexual species O. fengshanensis and verify that bisexual flower indeed has multiple origins in Ottelia. Ottelia fengshanensis probably has a common ancestor with the unisexual O. acuminata var. songmingensis. Besides, we also suggest that O. balansae should be treated as a variety of O. acuminata. This point has also been put forward by Yu Ito et al. (2019). It will also help us have a better understanding of the diversity and evolution of sex evolution in Ottelia.

Description of the new species

Ottelia fengshanensis Z.Z.Li, S.Wu & Q.F.Wang, sp. nov.

urn:lsid:ipni.org:names:77202741-1

Fig. 3

Description

The new species is similar to Ottelia guanyangensis in having bisexual flowers, three stamens, but differs through having (3)-4 flowers in each spathe (vs. 2–5), white styles (vs. yellow), green leaves (vs. dark green) and by fruits which are tiny winged (vs. obviously winged).

Type

CHINA. Guangxi, Hechi City, Fengshan County, elev. 507 m, 24°34'20"N, 107°10'17"E 11 September 2018, Z. Z. Li & S. Wu-Otte51 (holotype HIB-lzz51!).

Annual or perennial herb. Rhizome, short. Leaves entirely submerged, dark green and opaque, linear or oblong, 30–70 × 8–14 cm, base rounded, apex acute or obtuse; longitudinal veins 9; midrib conspicuous, stretched to the apex, becoming trinerved with obvious cross-veins at a distance of 5–7 cm from the base; petiole smooth, green, 8.0–10.0 cm long, the base expanded into a sheath. Spathe oblate, ca 3. 0 × ca. 3.5 cm, warty along edges or smooth, longitudinally ribbed and winged on the lateral margins, containing 3–4 (3) flowers; flowers bisexual; sepals reddish green, 1.0–1.5 × ca. 0.5 cm, with longitudinal ribs; petals white with yellow base, obovate, ca. 2.0 × ca. 2.0–2.5 cm, with longitudinal pleats; stamens 3, opposite to sepals, anthers elliptic, connective obscure, filaments 3.0–5.0 mm long; glands 3, 0.5–1.0 × 0.5–1.5 mm, opposite to petals, pale yellow. Ovary hexagonal-cylindric to the cylinder, 5–10 cm long, with 3 carpels; styles 3, white, slender and hairy, 1.2–1.5 cm long, stigma bifid, divided to base; stigmas 6, liner and hairy, ca. 8 mm long. Fruit a hexagonal-cylindric capsule, with 6 inconspicuous wings, dark green, with persistent calyx, 4.0–9.0 cm × ca. 6.5 mm, always longer than spathe. Seeds numerous, fusiform, ca. 1.0 mm long, both ends hairy. Pollen, subglobose, ca. 40μm in diam, with spiny granules.

Figure 3. 

Illustration of Ottelia fengshanensis Z.Z.Li, S.Wu & Q.F.Wang. Drawn by Shuai-Jie Li.

Figure 4. 

Phylogenetic tree and PTP analysis of O. fengshanensis sp. nov. and Blyxa japonica as an outgroup. Posterior probabilities (PP > 0.70) and bootstrap values (BS > 70) based on Bayesian Inference and maximum likelihood (ML) analysis are shown above the branches.

Distribution and habitat

Ottelia fengshanensis is known from a single population in Fengshan County, Guangxi Province, China. The species inhabits a karst river less than 1.5 m in depth. Due to the complex underground river system in the karst region, it is probable that the species occurs in nearby areas as well.

Conservation status

Only one population of new species was found at Fengshan County, Guangxi Province, China. Although it might be distributed in adjacent karst rivers. Until now, approximately 50–100 individuals were found in a single population. However, there is not enough information on population size and dynamics. According to the IUCN Red List Categories and Criteria (IUCN 2017), we suggested that the species be evaluated as Data Deficient (DD).

Phenology

The new species was found in flower from April to November.

Etymology

The epithet is derived from the name of Fengshan County, which is the only known locality of occurrence.

Other specimens examined (paratypes)

CHINA. Guangxi, Hechi City, Fengshan County, elev. 507 m, 11 September 2018, Z. Z. Li & S. Wu Otte 056 (HIB!)

This study was supported by grants from the Strategic Priority Research Program of the Chinese Academy of Sciences (No. XDB31000000), Wuhan Botanical Garden (CAS) (No. Y655261W03), and the Special Funds for the Young Scholars of Taxonomy of the Chinese Academy of Sciences (ZSBR-013).