INTRODUCTION

The flora of New Caledonia is one of the most diverse and endemic in the world (Kier et al. 2009), with 3 422 species of native vascular plants, 74.7% of which are endemic (Munzinger et al. 2024). Within this flora, the Fabaceae represent the second most diverse liana family, with 26 species in 14 genera (Isnard & Bruy 2023).

In 2009, a lianescent Fabaceae with a red exudate was observed and collected by Jean-Pierre Butin. This characteristic had never before been observed in New Caledonia. The flowering material was identified on a morphological basis by Jean-Noël Labat in November 2009 as most likely belonging to the genus Oxyrhynchus Brandegee (1912). This genus had never been reported from New Caledonia. Following the death of Jean-Noël Labat (Deroin & Lowry II 2011), the plant remained unstudied for some time. More recent research has rediscovered the first population, and found other individuals of this liana.

Oxyrhynchus is a monophyletic genus included in the Phaseolinae (Delgado-Salinas et al. 1993, 1999; Doyle & Doyle 1993; Kajita et al. 2001), which was revised in the 1960s (Rudd 1967), then more recently (Delgado-Salinas & Estrada-Castillón 2011). This latest revision recognizes four species in the genus, three of which are restricted to the American continent, while the fourth,O. ‌papuanus ‌(Pulle) Verdc. is distributed from Indonesia to the Solomon Islands. Delgado-Salinas & Estrada-Castillón (2011) point out that it remains to be validated that this last, poorly known species does indeed belong to the genus Oxyrhynchus. In fact, the basionym had been described in the genus Phaseolus by Pulle (1910), before being combined in a monospecific genus PeekeliaHarms (1920), endemic to Papua. Verdcourt (1978), again on a morphological basis, considers that geography alone distinguishes Peekelia, and finally combines Phaseolus ‌papuanus ‌Pulle in the genus Oxyrhynchus. The species has not been found or studied since.

Through a morphological and molecular approach (ITS sequence), the aim of this work is to validate the correct attribution of this taxon to the genus Oxyrhynchus, and then to verify whether it is a new species, and if so, to describe it.

MATERIAL AND METHODS

Molecular

Leaves of Fleurot 912 were preserved in silica gel in the field, then it was sent for and sequencing at the large regional genotyping platform of the AGAP lab in Montpellier, France.

Total genomic DNA was extracted from dried leaf tissue using standard SDS/CTAB protocols. PCR followed Munzinger et al. (2022) using KAPA3G Plant PCR Kit (Roche). Sanger sequencing was performed by the DNA Sequencing Facility at UMR AGAP, INRAE, Montpelier, France using ABI BigDyeTM Terminator v3.1 chemistry (Thermo Fisher Scientific) on an Applied BiosystemsTM 3500 XL genetic analyzer. Sequence editing was performed using Sequencher v. 5.4.6 (GeneCodes, Ann Arbor, Michigan). Molecular identification of the ITS DNA sequence was performed using the NCBI database BLASTn search algorithm (Zhang et al. 2000; Morgulis et al. 2008). The sequence is deposited in genbank, under PQ763431 accession number.

Morphology

We used field observations and photographs, and examined all deposited specimens at MPU, NOU (Bruy et al. 2021) and P (Le Bras et al. 2017) (abbreviations follow Thiers 2024). We also studied the virtual collections of the Global Plants initiative (https://plants.jstor.org/) and used the RECOLNAT infrastructure (https://www.recolnat.org/fr/). Plant terminology follows Harris & Harris (2001), and Prenner (2013) for inflorescence terminology.

Coordinates not given on original labels of herbarium specimens were added post-facto using the georep website (https://georep.nc/). When citing material, any information not available on the original label is given between brackets. A preliminary conservation status following IUCN (2012) criteria is also given. We provided the consolidated species distribution dataset to the New Caledonian Red List authority (Endemia & RLA Flore NC 2022) who will officially assess the extinction risk of species according to IUCN criteria.

RESULTS

Molecular identification: using BLAST pairwise alignments and Fast Minimum Evolution tree, and among the 107 million sequences in the database, our target sequence was resolved as most similar to Oxyrhynchus ‌trinervius ‌(Donn.Sm.) Rudd (AF115135, Delgado-Salinas et al. 1999), with a percent identity of 96.59% (Table 1). These in turn were resolved as sister to two samples of Oxyrhynchus ‌volubilis ‌Brandegee (JN008329.1 Delgado-Salinas et al. 2011; AF069114.1, Delgado-Salinas et al. 1999), which in turn were sister to Oxyrhynchus ‌populneus (Piper) Norvell ex A.Delgado & E.Estrada (syn. Vigna ‌populneaPiper; AF115136.1, Delgado-Salinas et al. 1999) (Appendix 1).

So our sequence is more than 95% similar to the four sequences (from three species) of Oxyrhynchus present in genbank (Table 1). To date, no DNA sequence of Oxyrhynchus ‌papuanus ‌(Pulle) Verdc., the fourth and last known species of the genus, has been deposited to any public database. The next closest genera have lower values: Mysanthus ‌G.P.Lewis & A.Delgado (c. 87%) and Strophostyles ‌Elliott (c. 86%), so we conclude that the sequence belongs to the genus Oxyrhynchus.

Morphological identification: using the identification key provided by Delgado-Salinas & Estrada-Castillón (2011), our material from New Caledonia does not match with any species. Notably, it seems very different from the geographic closest species, O. ‌papuanus, from which it can be distinguished, for example, by its calyx with rounded lobes, as long as the tube (versus oblong to lanceolate lobes, longer than the tube), or its broadly rounded-truncated, laterally flattened bud (versus fusiform).

DISCUSSION

The molecular data confirm the morphological hypotheses, and this taxon is well placed in the genus Oxyrhynchus. The material deposited at P was identified in July 2018 by Ashley N. Egan as Oxyrhynchus ‌trinervius ‌(Donn.Sm.) Rudd. This determination is therefore consistent with the molecular identification. It is, however, rather surprising from a geographical point of view, but also morphologically, since according to the key of Delgado-Salinas & Estrada-Castillón (2011). O. ‌trinervius has calyx with overlapping lower lip bases (vs non-overlapping), flower pedicels 8-15 mm long (vs 2-6 mm), fruit 7-11 × 3-4 cm (vs 3.75-5.75 × 1.4-2 cm); seeds (2)3-5, prismatic spherical, 13-16 × 11-15 mm, 12-14 mm thick (vs 1-3, 7-8 × 6-7 mm, 4.5-5 mm thick). This set of differences leads us to consider that it is indeed a distinct species, new to science, endemic to the Northern Province of New Caledonia, that is described here.

SYSTEMATICSFamily ‌ Fabaceae ‌Lindl.Genus ‌ Oxyrhynchus ‌Brandegee

Oxyrhynchusmargueriteae ‌Munzinger & Fleurot ‌sp. nov.,

(Figs 1; 2)

Diagnosis

Among species of Oxyrhynchus, the new species most closely resembles O. ‌trinervius ‌(Donn.Sm.) Rudd because of its calyx lateral lobes ovate to broadly ovate, its flowers 10-14 mm long and its (sub)glabrous fruit. However, in Oxyrhynchus ‌margueriteae ‌sp. nov., the bases of the lower lips are not overlapping (vs overlapping), the flower pedicels are shorter (2-6 mm vs 8-15 mm), the fruit is shorter and less wide (3.75-5.75 cm × 1.4-2 cm vs 7-11 × 3-4 cm), and the seeds fewer (1-3 vs [2]3-5) and smaller (7-8 × 6-7 mm, 4.5-5 mm thick versus 13-16 × 11-15 mm, 12-14 mm thick).

Type material

Holotype

New Caledonia•Province Nord, Plateau de Tango; 20°56’30.5”S, 165°6’36”E; 6.VII.2010; fr.; J.-P. Butin leg.; Munzinger 6047; holo-, P[P02857426]!; iso-, NOU[NOU079486]!, P[P02857425]!).

Paratypes

New Caledonia•Poindimié, Hoeênè; 20°56’37.184”S, 165°06’43.541”E; alt. 150 m; 22.VIII.2021; Fleurot 912; j.fr.; para-, MPU[MPU313240], NOU[NOU091995, NOU107965], P[P01139479])•ibid.; 20°56’36.893”S, 165°06’43.367”E; alt. 142 m; 12.VI.2022; fl. buds; Fleurot 938; para-, NOU[NOU092404, NOU108628] (alc.), P[P01139662]•Tango; [20°56’37”S, 165°06’42”E]; 15.VI.2009; fl.; J.-P. Butin leg.; J. Fambart-Tinel 207; para-, NOU[NOU050883].

Phenology

Buds and open flowers observed in June, fruit in July and August.

Habitat

Oxyrhynchus ‌margueriteae ‌sp. nov. grows in low to medium-altitude dense rainforest (sensu Jaffré et al. 2012), on volcano-sedimentary substrate, between 115 and 150 m altitude. It was observed in a canopy around 25-30 m high, among other lianas, notably Tetracera billardierei Martelli (Dilleniaceae), Hugonia jenkinsii F.Muell. (Linaceae) and Piper sp. (Piperaceae). The tallest liana observed is growing on Elaeocarpus ‌angustifolius ‌Blume (Elaeocarpaceae).

Distribution

The plant appears to be endemic to the Northern Province of New Caledonia (Fig. 3). It is known only from a single forest in a small valley at the confluence of the Hoeênè river (Tango region, Bopope tribe).

Conservation status

Oxyrhynchus ‌margueriteae ‌sp. nov. is only known from a small valley of just over 12 hectares, which contains in its talwegs a relic of dense rainforest covering 5.4 hectares, of which 2.4 ha were surveyed (c. 45%) (Fig. 4). In the western part of the valley, less than one hectare is covered by a former plantation of Pinus ‌caribaea ‌Morelet (Caribbean pine), while the other slopes and ridges are essentially covered by niaoulis savannah with many common ferns (genus Lygodium ‌Sw.). These two secondary environments seem unfavorable to the presence of the liana, which has a forest ecology. As of June 12, 2022, the date of the Fleurot 938 collection, six fertile adult lianas and 1 juvenile liana have been observed and mapped. The main threats to this population are the overabundance of pigs and deers, and anthropogenic fires. Thus, as there are fewer than 50 known mature individuals, we assign O. ‌margueriteae ‌sp. nov., a preliminary status of “Critically Endangered” (CR) according to criterion D.

Vernacular name

Unknown.

Etymology

The plant is dedicated to Marguerite Butin, wife of Jean-Pierre Butin, the plant's discoverer. She was very supportive of his hobby, letting him spend most of his free time scouring the territory for rare plants.

Description

Liana measuring up to 12 cm in diameter at the base and reaching heights of over 20 m, with translucent latex when first bled, then oxidizing to red (a few tens of seconds), not very abundant, gray bark streaked with crevices. Leaves trifoliolate, stipulate, leaflets weakly acuminate, terminal leaflet ovate or broadly ovate, symmetrical (52-)57-70(-85) mm long, (40-)42-48(-67) mm wide, terminal petiolule 19-21 mm long, with a few appressed hairs directed towards the apex, apical pulvinus 4 mm long, hirsute, curved at 90°, stipels narrowly triangular, c. 1 mm long, lateral leaflets broadly oval, very asymmetrical (50-)54-67(-77) mm long, (35-)37-45(-55) mm wide, petiole reduced to a pulvinus 2.5-4 mm long, stipels oblong, 1-2 × 0.5-1 mm, primaries and secondaries veins beige, abaxially prominent, narrower and less prominent adaxially, 2-3 pairs of secondaries, inter-secondaries frequent. Petiole 40-80 mm long, triangular stipules 2 mm long, blackish in herbarium, glabrous or sparsely hairy.

Axillary inflorescence about 11 cm long, up to 33 cm, with flattened inflorescence axis, up to 3 mm wide, hairy in terminal part with long white hairs up to 0.5 mm long, appressed towards apex, glabrescent in basal part, inflorescence a compound raceme with condensed partial inflorescences, with 3 to 20 flowers, irregularly spaced from 5 to 19 mm. Bracts lanceolate, 2 mm long, variegated with black.

Flower bud broadly rounded-truncated, laterally flattened, 6-8 mm long. Flower papilionaceous, 10-14 mm long, mauve with bluish tints, base of petals whitish (in vivo), pedicel 2-6 m long, with hirsute white hairs. Calycle with 0-2 oval bracts, rapidly caducous, veined, 1-1.5 mm long, with ciliated membranous margin, beige, adaxial side weakly tomentose, abaxial side glabrous; calyx campanulate with 5 subequal lobes, as long as the tube; lobes not overlapping, green, rounded, 1. 5 × 1.5 mm for the lower three, 1.5 × 2.0 mm for the upper two, inner surface sericeous, margin ciliate, outer surface subglabrous. The standard bilobed, 12.5-17 mm wide, 7-8.5 mm high, wings broadly obovate to suborbicular, 7-12 mm long × 5-8 mm wide, mitered 3.5-5 mm, petals of keel fused, at least apically, rostrate, with suborbicular central part c. 5 mm in diameter, and tips tapering 3-4 mm. Androecium diadelphous, 9 stamens 11-13 mm long, fused by their filaments, free filament over 3-5 mm of their length, 1 free stamen, c. 10 mm long. Anthers 0.7-1.0 mm long × 0.3-0.4 mm wide, basifixed. Gynoecium c. 15 mm, ovary c. 5 × 0.8 mm, with suture line covered by a line of sericeous hairs, ovary long attenuated into a glabrous style or with a few long hairs scattered at the apex, stigma punctiform.

Legume oblong 37.5-57.5 mm long (in vivo), 13.6-20 mm wide, sparsely pubescent towards apex, becoming glabrous, perianth caducous, pedicel 7-11.8 mm long × 1-1.4 mm diameter. Valves twisting at opening, brown on the outside, white and glabrous on the inside. Seeds 1-3 per legume, black (immature), prismatic spherical, 7-8 × 6-7 mm, 4.5-5 mm thick, with beige hilum forming a bead on one-half to one-third of the circumference.

Acknowledgements

This paper is dedicated to our late colleague and friend Jean-Noël Labat. We would like to thank all the people who accompanied DF in the field: Loïc Bonnetain, Jean-Pierre Butin, Sophie Collin, Patrick Dayé, Jérémie Estèbe, Darren Forcin, Keneth Kela, Yurgen Kela, Christian Laudereau, Lydwine Laudereau, Cheyenne Lolopo, Ensone Welet, Françis Welet, Francisca Welet, Yorick Welet. We thank Jean-Pierre Butin & Christian Laudereau for photographs, and the MPU, NOU and P herbaria for loaning or providing access to our collections and facilities. We deeply thank Sylvain Santoni (INRAe) for sequencing, Chrissen Gemmill for help with BLAST analysis. We thank Matthew Lavin and Alfonso Delgado Salinas for discussions. Our gratitude goes to Roger Lala Andriamiarisoa for his beautiful illustration. An anonymous reviewer and Thierry Deroin (MNHN) helped to improve a previous version of the manuscript. The Muséum national d’Histoire naturelle (MNHN) and the Institut de Recherche pour le Développement (IRD) provided access to the collections in the framework of the Récolnat National Research Infrastructure (ANR-11-INBS-0004). We thank the Environmental Service of the North Province of New Caledonia for providing collection permits.

APPENDICE

Appendix 1

Fig. 5. — Distance Tree provided by BLAST pairwise alignments, with FAST Minimum Evolution Tree Method.

Table 1. — The ten sequences most similar to our Blast-submitted ITS sequence of Fleurot 912 provided by BLAST pairwise alignments, using the FAST Minimum Evolution Tree method (Core nucleotide BLAST database).Scientific Name Max Score Total Score Query Cover E value Per. Ident Acc. Len AccessionOxyrhynchus ‌trinervius ‌(Donn.Sm.) Rudd1074107488%0.096.59%646AF115135.11030103088%0.095.22%643JN008329.1Oxyrhynchus ‌volubilis ‌Brandegee1027102788%0.095.05%642AF069114.1Oxyrhynchus ‌volubilis ‌Brandegee1021102188%0.095.05%639AF115136.1Vigna ‌populneaPiper [= Oxyrhynchus ‌populneus (Piper) Norvell ex A.Delgado & E.Estrada]80780788%0.087.56%639AF069125.1Mysanthus ‌uleanus ‌(Harms) G.P.Lewis & A.Delgado80280288%0.086.84%647JN008330.1Mysanthus ‌uleanus var. dolicopsoides ‌(Hoehne) G.P.Lewis & A.Delgado78978988%0.086.73%650AY508773.1Strophostyles ‌leiosperma ‌(Torr. & A.Gray)Piper78778788%0.086.60%651AY508771.1Strophostyles ‌leiosperma ‌(Torr. & A.Gray)Piper78578588%0.086.58%650AY508776.1Strophostyles ‌leiosperma ‌(Torr. & A.Gray)Piper78478488%0.086.58%650AF115137.1

Fig. 1. — Oxyrhynchus ‌margueriteae ‌sp. nov.: A, flowering shoot; B, flower (front view); C, calyx (side view); D, calyx (top view); E, keel; F, wing; G, standard; H, androecium (side view); I, gynoecium (side view); J, fruiting shoot; K, legume; L, seed (dorsal view); M, seed (lateral view); M, seed (ventral view). Scale bars: A, J-N, 1 cm; B, 4 mm; C-I, 1 mm. Illustration by Roger Lala Andriamiarisoa.

Fig. 2. — Field pictures of Oxyrhynchusmargueriteae ‌sp. nov.: A, trunk, partially necrotic (© C. Laudereau); B, slash (© D. Fleurot); C, shoot and Jean-Pierre Butin (© D. Fleurot); D, abaxial side of a leaf (© D. Fleurot); E, flower (© J.-P. Butin); F, petiole insertion with stipule (© C. Laudereau); G, fruits (© D. Fleurot).

Fig. 3. — Distribution of Oxyrhynchus ‌margueriteae ‌sp. nov. in New Caledonia, with vegetation types (after Jaffré et al. 2012): Grey, sclerophyll forest, wetland and coastal vegetation; dark green, low and medium altitude humid dense forests; light green, high altitude maquis and forest; brown, maquis on ultramafic substrates; beige, Savannahs and secondary thickets. Zoom on Bopope area, with ultramafic substrates in beige.

Fig. 4. — Presence map of known living individuals (yellow dots), and the type that has not been relocated, probably dead (black cross) of Oxyrhynchus ‌margueriteae ‌sp. nov. In yellow, the total watershed of the small valley, in green, the surface area of the rainforest, in white, the surveyed area, in dashed orange, an area planted with Pinus ‌caribaea ‌Morelet.