Leichhardtia weari Gâteblé, Meve & Liede, 2023

Gâteblé, Gildas, Meve, Ulrich & Liede-Schumann, Sigrid, 2023, A new threatened New Caledonian Leichhardtia (Apocynaceae, Asclepiadoideae, Marsdenieae) species discovered from a TV programme and social media, Phytotaxa 591 (2), pp. 91-100 : 95-97

Leichhardtia weari Gâteblé, Meve & Liede , sp. nov. ( Figs. 1 , 3 , 4 )), (LSID: 77315163-1).

Type: — NEW CALEDONIA. Province Nord. Poum, Yandé Island, Mariri , 17 m, 20°02’46.265’’S, 163°47’48.628’’E, 21 August 2021, Fleurot & Dayé 902 (holotype, P!; isotype, NOU [ NOU091991 !]) .

Diagnosis: — Leichhardtia weari is most similar to L. neomicrostoma and L. mackeeorum ( Meve et al. 2017: 60) Liede et al. in LiedeSchumann et al. (2020: 122) but differs from the former by leaves 1.5–5 mm long, peduncle nearly absent (to 0.3 mm), corolla 2–3 mm long, pollinia broadly ellipsoid and around 0.2 mm long (vs. leaves 6 to 8 cm long, peduncle 5–7 mm long, corolla 4–6 mm long, pollinia oblong and around 0.33 mm long in L. neomicrostoma ). Leichhardtia weari differs from L. mackeeorum by sciadoidal inflorescences, corolla tube rounded in outline and longer than wide, corolla lobes widely pubescent to pilose (vs. bostrychoid inflorescences, corolla tube rounded pentagonal in outline and broader than long, corolla adaxially bearded below sinus of otherwise glabrous corolla lobes in L. mackeeorum ).

Plants suffrutescent, ascending, twining 0.5 to 1 m high, up to 1 cm in diameter at the base, sparsely branched. Shoots semi - perennial, herbaceous, sericeous with 0.15–0.25 mm long trichomes; internodes 0.5–2 cm long, 1–2 mm diam. Latex white, abundant. Leaves opposite; petiole 1–3.7 × 0.4–0.7 mm, canaliculate, sericeous especially on adaxial surface with 0.2–0.3 mm long trichomes, green to reddish on fresh material; blade without colleters at base (1.5–) 2.5– 4.1 (–5.1) × (0.2–)0.3–0.4 (–0.5) cm, flat, linear (to very narrowly spatulate), apex with mucro 0.3–0.5 mm long; base cuneate, margin entire, slightly revolute, coriaceous, both surfaces mostly glabrous with rare scattered short trichomes, discolorous, adaxially green, abaxially usually purplish; midrib protruding abaxially, impressed adaxially, secondaries indistinct. Inflorescences extra-axillary, condensed, sciadioidal racemes, 5–15 flowered, 1–5 flowers open at a time. Peduncles 0.2–0.3 × 0.5–0.7 mm, sericeous with ca. 0.2 mm long trichomes. Flowers with floral bracts ca. 0.2 × 0.1 mm, triangular, with trichomes, caducous. Pedicels 1–3 × 0.3–0.5 mm, green to purplish, mostly glabrous with rare short trichomes. Floral buds 2–2.5 × 1.5–1.9 mm, ovoid. Calyx with 1–2 calycine colleters in sepal sinuses, sepals quincuncial, 1.3 × 1 mm, broadly ovate with round apex, brownish-red, ciliate, abaxially densely pubescent, especially in the central part and flanked with more or less glabrous sides. Corolla tubular to narrowly urceolate, slightly fleshy, glabrous, whitish; tube ca. 2.5–3 × 1.5–2 mm, adaxial corolla surface with two broad rings of trichomes, an upper one consisting of long antrorse, white trichomes on the basal halves of the corolla lobes and mouth of the tube, forming a cone of trichomes closing the corolla throat and hiding the gynostegium, a lower one consisting of scattered, horizontally spreading white trichomes surrounding the gynostegium; corolla lobes valvate in bud, lobes up to ca. 1 × 1 mm, triangular to broadly ovate, bent upward at anthesis, apically often pinksish, margins thin, even. Corolline corona absent; gynostegial corona of free staminal lobes, ca. 0.5 mm long, 0.5 mm wide basally, shorter than the gynostegium; lobes ligulate, whitish, laminar, with recurved margins. Gynostegium subsessile, conical, ca. 1.2 × 1.3 mm, filament tube basally with wing-like extensions; anther wings (guide-rails) ca. 300 µm long, consisting of distal and proximal ridge, oblique to 20–25°; connective appendages ca. 450 × 300 µm, lanceolate, narrower than the stamen, conniventerect and appressed to style-head. Pollinarium: corpusculum 180–205 × 60–70 µm, oblong; caudicles ca. 150 × 30 µm, basally inserted at the corpusculum, bent upwards, linear, slightly broadened at both ends; pollinia basally attached to the caudicles, erect, ca. 200 × 100 µm, broadly ellipsoid, narrowly elliptic in cross-section. Style-head ca. 0.9 × 0.8 mm diam., upper part ca. 0.5 mm long, conical. Ovaries ovoid, glabrous. Follicles unknown.

Additional specimens examined:

NEW CALEDONIA: Poum , Yandé , Mariri , 15 m, 20°02’48.207’’S, 163°47’48.207’’E, 11 June 2021, Fleurot , Yandé people & Caledonia TV Wéari team 838 ( NOU [ NOU091854 ]); ibid. loc., 24 m, 20°02’38.975’’S, 163°47’50.202’’E, 21 August 2021, Fleurot & Dayé 905 ( NOU [ NOU0091993 , NOU107969 alc.], UBT alc.) .

Phenology: —Flowering in June and August.

Distribution and habitat:— New Caledonia, narrow endemic to the island of Yandé in the extreme north of Grande Terre. The species is known from degraded maquis vegetation ( Fig. 1B ) on serpentine soils (a kind of soils derived from ultramafic and more specifically from serpentinite rocks) at low elevation (14–17 m). It is so far only recorded from the Mariri creek area at the base of the Bwaadé massif ( Fig. 4 ).

Etymology:—The name refers to the Wéari programme from the Caledonia television channel and made available on YouTube. The Caledonia channel journalist Cédric Tyea named his programme Wéari because it is a word meaning protect, preserve or conserve in Paicî native language from the Paicî-Cèmuhi customary area. Paicî is the most spoken native language on mainland New Caledonia and its area of influence is between Monéo to Amoa on the east coast and Poya to Koné on the west coast (https://www.alk.nc/langues/paici). Yandé (or Yaadé) Island belongs to the Hoot ma Whaap customary area, to the Nénéma district and the native language spoken there is the Nêlêmwa ( Bril 2002). The customary authorities of Yandé, Dominique Fleurot and Cédric Tyea welcome the proposed specific epithet. The epithet is here treated as a word in apposition and indeclinable ( Turland et al. 2018, Art. 23.1, 23.2) as advocated for example for names derived from native languages in New Zealand ( Webb et al. 1999, Heenan et al. 2021).

Conservation status:—The narrow endemic Leichhardtia weari is restricted to the island of Yandé. Chromium and cobalt used to be mined at the end of 19 th century and the beginning of 20 th century and presumably participated (along with probably deliberately set fires for mining access) to the lunar-like or tragic erosion situation known nowadays. Three mining rights have expired and one remains active (in the northern and highest part of the island) but without being operated (https://georep.nc/explorateur-cartographique). Thanks to its isolation and to the small concession, there should be no mining threat in the near future. The main current threat to the biodiversity of the island is anthropogenic fire that is regularly set up. Even though the Vulcain portal (http://geoportail.oeil.nc/alerteincendies/) does not reflect this status, the fire threat is high and at least a large wildfire impacted the island in December 2016. The island is not well known from a botanical perspective, and so far the new species is only known from a few individuals in the northwestern part of the island. Considering the small size of Yandé island and the population of L. weari thereof, as well as potential impact of a fire event, the proposed provisional IUCN Status is “Critically Endangered” using Red List criteria (IUCN 2017) under the criteria CR B B1ab(iii,v) + 2ab(iii,v); D.

Notes: —Regarding habit, leaf and flower morphology, Leichhardtia weari is very similar to L. neomicrostoma , so that quantitative characters (length of leaves, peduncle, corolla, pollinia) are most suitable for immediate recognition (s. diagnosis and key). Floral details are nevertheless also different like the almost sessile gynostegium in L. weari (shortly stipitate in L. neomicrostoma ), the foliar corona lobes that are twice as long as the guide-rails (corona lobes inconspicuous, mostly a rounded thickened fringe, occasionally pointed, in L. neomicrostoma ), guide-rails oblique up to 25° (oblique to 35° in L. neomicrostoma ) and the pollinia that are broadly ellipsoid (oblong in L. neomicrostoma ) (cf. Liede-Schumann et al. 2020). However, the two species do not seem as closely related as morphology suggests because in the molecular analysis ( Fig. 2 ) the new species is member of New Caledonian Clade I, the older of the two subclades (stem age 20.6 Ma, Liede-Schumann et al., 2022), where it is sister to the other two north-western species on ultramafic soils, L. neocaledonica and L. kaalaensis . Notwithstanding, Leichhardtia weari is easily distinguished from L. neocaledonica and L. kaalaensis because both have campanulate flowers (versus tubular to narrowly urceolate for L. weari ). We were unable to highlight any clear synapomorphy among the three species because morphological characters in Asclepiadoideae, and particularly in Marsdenieae , are usually at best indicative of relationships ( Liede-Schumann et al. 2022). Leichhardtia neomicrostoma , also a north-western species, is sister to the widespread L. koniamboensis , both also on ultramafic soils, and member of New Caledonian Clade II (stem age 15.1 Ma, Liede-Schumann et al., 2022). Leichhardtia neomicrostoma and L. weari are yet another example of the high degree of morphological convergence found in unrelated Asclepiadoideae under similar ecological conditions.

Figures

FIGURE 1. Leichhardtia weari. A. Screenshot of the Weari programme “Yandé l’île mystérieuse” from Caledonia channel available on YouTube (https://www.youtube.com/watch?v=4E9Xt8eIEH8) displaying for the first time the new species (originally identified as Leichhardtia neomicrostoma). B. Degraded maquis vegetation in the Mariri creek area; C. A fertile branch with inflorescences; D. Detail of an inflorescence with flowers in lateral view; E. Flower in frontal view displaying the gynostegium. A, C showing Fleurot 838, B Fleurot & Dayé 902, and D–E Fleurot & Dayé 905. Photos by D. Fleurot.

FIGURE 2. Maximum Likelihood tree of Marsdenieae.The outgroup, and all Marsdenieae clades except for Leichhardtia are summarized as triangles. Numbers at important nodes indicate bootstrap percentages. New Caledonian clades I and II with yellow background, Australasian clades with grey background. Yandé species L. weari and L. neomicrostoma marked red, other New Caledonian accessions not shown in Liede et al. (2022) marked blue.

FIGURE 3. Leichhardtia weari. A. Adaxial view on parts of longitudinally cut corolla; B. Gynostegium in lateral view (lanceolate connective appendages hide the style-head); C. Single corona lobe, adaxial view; D. Single anther, adaxial view; E. Pollinarium; F. Isolated gynoecium with style-head atop. All from D. Fleurot & P. Dayé 905 (UBT, in alc.). Drawn by U. Meve.

FIGURE 4. Distribution map of Leichhardtia weari (stars) in New Caledonia in an insert showing the Yandé island and the Mariri creek in blue. Ultramafic substrates are shown in grey. Map by D. Fleurot.