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Research Article
Causonis sessilifolia (Vitaceae), a new species from Thailand
expand article infoAnna Trias-Blasi, Manop Poopath§, Li-Min Lu|, Gaurav Parmar
‡ Royal Botanic Gardens, Kew, Richmond, United Kingdom
§ Department of National Parks, Wildlife and Plant Conservation, Bangkok, Thailand
| Institute of Botany, Chinese Academy of Sciences, Beijing, China
¶ National Botanical Garden, Lalitpur, Nepal
Open Access

Abstract

A new species, Causonis sessilifolia, from Thailand is described, based on morphological and phylogenetical methods. A full description, conservation assessment, a key, images and phylogenetic tree are provided. Diagnostic characters for this species are sessile leaves that are sometimes opposite and inflorescence insertion interfoliar.

Keywords

Causonis, Thailand, new taxon, taxonomy

Introduction

The genus Cayratia Juss. in the broad sense (s.l.) has consistently been found to be paraphyletic (Wen et al. 2007; Trias-Blasi et al. 2012; Lu et al. 2013; Parmar et al. 2021). To maintain the monophyly within Vitaceae, the species in Cayratia sect. Discypharia Suess. (Suessenguth, 1953; Latiff, 1981) which was later treated as Cayratia subg. Discypharia (Suess.) C.L.Li (Li 1996, 1998; Chen et al. 2007), were placed in the newly-re-instated genus Causonis Raf. (Wen et al. 2013; Parmar et al. 2021). This genus can be separated from the Cayratia s.l. as it lacks a distinct membrane enclosing the ventral infolds in seeds (Wen et al. 2013; Parmar et al. 2021). Causonis can be distinguished from other Vitaceae genera by plants being hermaphroditic, flowers 4-merous, inflorescences mostly axillary, but sometimes pseudo-axillary.

Causonis comprises about 16 species and four varieties and is found in tropical, subtropical and temperate Asia to Australia including the Pacific Islands (Parmar et al. 2021). Trias-Blasi and Parnell (2020) reported two Causonis species in Thailand, but the specimen from Nakhon Sawan in the northern floristic region of Thailand, was found to be morphologically distinct from other species reported from the region.

In autumn 2019, an expedition was conducted in a 5-hectare area adjacent to Kriangkrai River in the Nakhon Sawan Province (Fig. 1), because of concerns relating to high levels of deforestation in the lowland floodplain forests in Thailand. Additionally, very few specimens had been collected from this habitat. Generally, these areas are flooded every year during September-November when the water increases by 1–3 metres. This species was found in an open area along the riverbank.

Methods

This study is based on the material collected in October 2019 in Nakhon Sawan. Morphological characters were studied using a hand lens (30–60× magnification) and stereomicroscope and documented by photography. Collected specimens were thoroughly compared with protologues and types of all Causonis species occurring in Thailand and neighbouring regions. Additionally, herbarium material of Causonis, deposited in K, was studied (herbarium codes according to Thiers 2021). Herbarium vouchers for this study are deposited in BKF. The description follows the style and level of details outlined in Trias-Blasi and Parnell (2020), while the general terminology is based on Beentje (2016). The conservation assessment is based on the most recent version of the guidelines of IUCN Standards and Petitions Subcommittee (IUCN 2012).

Figure 1. 

Map of the specimen collected (black circle).

Genomic DNA for the new taxon was extracted from silica-gel-dried leaf material using DNeasy Plant Mini Kit Qiagen (Qiagen, Hilden, Germany) following manufacturers’ protocols. All other sequences for different taxa were downloaded from GenBank. The DNAs were amplified for four chloroplast loci (atpB-rbcL, trnC-petN, trnH-psbA and trnL-F) following the protocols in Lu et al. (2018). The PCR products were purified and examined on a 1% agarose gel before being sent to Majorbio Company in Beijing, China, for sequencing on a Roche 454 sequencer with the same PCR amplification primers using a standard GS FLX Titanium sequencing kit XL+ (454 Life Sciences, Branford, CT, USA). The voucher specimens and the sequences’ GenBank accession numbers are provided in Table 1.

Geneious 8.1.9 was used to assemble forward and reverse sequences (Kearse et al. 2012). Geneious was also used to edit contiguous sequences and check chromatograms for base validation. Following that, sequences were aligned using MAFFT 1.3.1 (Katoh et al. 2002) and then manually adjusted in Geneious. On the CIPRES Science Gateway (Miller et al. 2010), phylogenetic analyses were first performed for individual DNA loci using the Maximum Likelihood (ML) approach in RAxML-HPC2 on XSEDE (8.2.12) using the GTR + G model with 1000 bootstrap replicates (Stamatakis 2014). Single tree analyses did not detect well-supported topological conflicts amongst individual DNA loci (i.e. ML BS < 70%; Hillis and Bull 1993). As a result, for further phylogenetic analyses, the four chloroplast DNA loci were concatenated. For the four chloroplast (4cp) dataset, partitioned ML and Bayesian Inference (BI) analyses were performed and the best fitting models for individual data partitions were selected using PhyML 3.0 (Guindon et al. 2010) with the Akaike Information Criterion (AIC). The nucleotide substitution model GTR + G was found to be the most suitable for trnC-petN and trnL-F and HKY85 + G for atpB-rbcL and trnH-psbA. MrBayes 3.2.6 was used to conduct Bayesian analysis on the CIPRES Science Gateway (Ronquist et al. 2012). For a total of 10,000,000 generations, four Markov Chain Monte Carlo analyses were conducted, with one tree sampled every 1,000 generations. The standard deviation between the split frequencies was found to be less than 0.01, indicating that enough generations had been completed. Following the burn-in of the first 25% of trees, the remaining trees were used to determine a 50% majority-rule consensus tree and posterior probabilities (PP). The trees obtained from ML and BI were analysed for topological conflicts through FigTree v.1.4.4 (Rambaut 2018).

Taxonomic treatment

Causonis sessilifolia Trias-Blasi & G.Parmar, sp. nov.

Diagnosis

Morphologically, Causonis sessilifolia and Causonis japonica (Thunb. ex Murray) Raf. share similarity in possessing 5-foliolate leaves, but the former taxon has sessile leaves and 2–5-furcate tendrils (vs. petiolate leaves and 2–3-furcate tendrils in C. japonica).

Table 1.

Voucher information and GenBank accession numbers for the sequences used in this study.

Taxon Voucher No. Locality atpB-rbcL trnC-petN trnH-psbA trnL-F
Causonis australasica L.M.Lu & Jackes AU015 (PE) Australia, Queensland MW408585 MW408375 MW408696 MW408491
Causonis clematidea (F.Muell.) Jackes Wen 12184 (US) Australia, New South Wales, Sydney (cult.) KC166297 KC166475 KC166552 KC166625
Causonis corniculata (Benth.) J.Wen & L.M.Lu YSL4758 (PE) China, Taiwan MW408551 MW408342 MW408665 MW408460
Causonis daliensis (C.L.Li) G.Parmar & L.M.Lu VN2014116 (PE) Vietnam, Lam Dong MW408540 MW408333 MW408654 MW408450
Causonis fugongensis (C.L.Li) G.Parmar & L.M.Lu CPG36648 (PE) Myanmar, Kachin MW408564 MW408355 MW408676 MW408473
Causonis japonica (Thunb.) Raf. var. japonica Wen 8537 (US) Japan, Chiba KC166313 KC166488 KC166564 KC166637
Causonis japonica var. pseudotrifolia (W.T.Wang) G.Parmar & J.Wen Wen 8085 (US) China, Chongqing AB234920 KC166498 KC166573 AB235006
Causonis maritima (Jackes) Jackes AU020 (PE) Australia, Queensland MW408567 MW408358 MW408679 MW408476
Wen 9403 (US) China, Taiwan KC166314 JF437193 JF437079 JF437299
Causonis mollis (Wall. ex M.A.Lawson) G.Parmar & J.Wen CPG23617 (PE) Vietnam, Vinh Phuc MW408535 MW408328 MW408650 MW408445
Causonis sessilifolia Trias-Blasi & G.Parmar Poopath & Duangjai 2511 Thailand, Nakhon Sawan OK338627 OK338628 OK338629 OK338630
Causonis timoriensis var. mekongensis (C.Y.Wu ex W.T.Wang) G.Parmar & L.M.Lu CPG18926 (PE) China, Yunnan MW408580 MW408370 MW408692 MW408486
Causonis trifolia (L.) Mabb. & J.Wen CPG27533 (PE) China, Yunnan MW408575 MW408365 MW408687
CPG38701 (PE) India, Kerala MW408576 MW408366 MW408688
LA17 (PE) Laos, Luang Namtha MW408577 MW408367 MW408689 MW408484
Wen 7488 (US) Thailand, Chiang Mai KC166323 KC166500 KC166574 AB235007
CPG19178 (PE) Indonesia, Bali KC428757 KC428783 KC428800 KC428819
Pseudocayratia pengiana Hsu & J.Wen YSL4764 (PE) China, Taiwan MW408587 MW408377 MW408698 MW408493
Pseudocayratia speciosa J.Wen & L.M.Lu Wen 12026 (US) China, Fujian KC166377 KC166616 KC166682

Type material

Thailand. Northern floristic region: Nakhon Sawan, Muang, Kriangkrai subdistrict, abandoned area at the bridge of Kriangkrai Canal, 15°44'40"N, 100°11'9"E, 23 October 2019, M. Poopath & S. Duangjai 2511 (holotype, BKF! (SN229663 (Fig. 5)), isotype BKF! (SN229662)).

Description

Slender herbaceous climber. Stem cylindrical, 2–5 mm diameter, branched, glabrous, young stems purplish-green, hairy with some bent hairs to glabrous; tendril 2–5-furcate, slender, wiry, leaf-opposed, cylindrical, with a straight section, then bifurcating and coiling, 5–10 cm long, glabrous. Leaves compound, pedately 5-foliolate, alternate or opposite; petiole absent, central petiolule 0.5–1.5(–3) cm long, middle petiolules sessile, lateral petiolules 0.5–2 mm long, mostly glabrous, sometimes with bent hairs; central leaflet blade lanceolate to slightly rhombic, 2–5 by 1–2.5 cm, base cuneate; middle leaflet blade lanceolate, 1–3 by 0.5–1.5 cm; lateral leaflet blade lanceolate often with a single asymmetric acute lobe, 0.5–1.75 by 0.2–1.25 cm, base cuneate; margin broadly denticulate, apex acuminate to mucronate; adaxial and abaxial sides glabrous, mid-rib raised on upper surface, each leaflet with 2–5 pairs of lateral veins, if leaflet lobed then lower lateral vein may be more distinct. Inflorescence ramified, interfoliar or pseudo-terminal, mostly dividing dichotomously, with numerous ramifications, 0.7–2 by 1–2.5 cm, lax, erect; peduncle 2–8 cm long, glabrous, pedicel 0.75–2 mm long, glabrous. Buds ovoid, 1–2 by 1–2 mm. Calyx cupuliform, entire, margin sinuate, 0.5–1 by 1–1.25 mm, glabrous, dark red. Corolla petals 4, ovate, 1.5–2 by 1.25–2 mm, apex cucullate, glabrous, dark red. Stamens 4; filaments flattened, broadening at the base, 1 mm long, cream; anthers elliptic, medifixed, 0.5–1 mm long, cream. Ovary adnate to the disc; disc with 4 distinct lobes, cupular, 0.5 by 1.5 mm, glabrous, dark red outside and whitish inside. Style conical, 0.5 mm long; stigma inconspicuous, dark red. Fruit berry, globose, 4–7 mm in diameter, glabrous, smooth, green. Seeds 2, 4–5 by 3 mm, adaxial side with two faces, abaxial side convex and ovate with a linear chalazal knot (Fig. 2).

Figure 2. 

Causonis sessilifolia A habit B pedately 5-foliolate leaves C flowers and opposite leaves D fruits. Images: Sutee Duangjai and Manop Poopath.

Phenology

Flowering and fruiting in October.

Figure 3. 

Causonis sessilifolia. Habitat. Images: Manop Poopath.

Etymology

The specific epithet “sessilifolia” refers to the sessile leaves of the taxon.

Figure 4. 

Phylogeny of selected species of Causonis including C. sessilifolia, based on the combined chloroplast dataset (atpB-rbcL, trnC-petN, trnH-psbA and trnL-F). Maximum Likelihood bootstrap values and Bayesian posterior probability values are indicated above branches respectively.

Distribution and habitat

Thailand (Northern floristic region, Nakhon Sawan). Lowland floodplain forest, along the bank of canal in open areas; 30 m alt. (Figs 1, 3).

Figure 5. 

Holotype of Causonis sessilifolia.

Conservation status

This species is only known from the type locality and, therefore, has an Area of Occupancy (AOO) and Extent of Occupancy (EOO) of 4 km2. This suggests that it might be Critically Endangered as the AOO is less than 10 km2 and is only found in one location. The species has been found to grow outside any protected areas and in an abandoned area next to a canal. This could mean the species is more vulnerable than others as it is unprotected. Additionally, all the surrounding areas are used for agriculture and, therefore, it is likely this forested area might also be transformed for this use. Due to this threat, the restricted AOO and number of locations, we think that this taxon could be driven to being Critically Endangered or Extinct in a very short time; therefore, we assess the taxon as VUD2 (IUCN 2012).

Taxonomic remarks

Phylogenetically, this pedately 5-foliolate leaved species lies in a clade previously known with species of exclusively trifoliolate leaves such as Causonis trifolia (L.) Mabb. & J.Wen and Causonis maritima (Jackes) Jackes (Parmar et al. 2021), but C. sessilifolia lacks the petiolate leaves found in C. trifolia and C. maritima. In particular, this species is phylogenetically most closely related to C. maritima (ML BS = 74%; Bayesian PP = 0.99; Fig. 4), but morphologically differs from it in having pedately 5-foliolate leaves (vs. trifoliolate), leaves sometimes opposite (vs. leaves always alternate), leaves sessile (vs. leaves petiolate), inflorescence insertion interfoliar (vs. axillary), calyx and corolla glabrous (vs. hairy).

Key to Causonis in Thailand (including Causonis maritima)

1 Leaves 3-foliolate 2
Leaves 5-foliolate 3
2 Tendrils 2–3-furcate, tips without adhesive disc; hooked hairs confined to mid-vein on adaxial surface 1. C. maritima
Tendrils 3–5-furcate, tips with adhesive disc; hairs all over abaxial and adaxial surfaces 2. C. trifolia
3 Petiole present; inflorescence leaf-opposed, pseudoaxillary or axillary 3. C. japonica
Petiole absent; inflorescence interfoliar 4. C. sessilifolia

Acknowledgements

We thank Steven Bachman for helpful discussions about the Conservation Assessment of this species. We are grateful to Jinren Yu for supporting molecular work. We are grateful to Sutee Duangjai for providing images of this species.

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