Pichonia munzingeri Gâteblé & Swenson, 2019

Gâteblé, Gildas & Swenson, Ulf, 2019, Pichonia munzingeri (Sapotaceae), a new and rare micro-endemic species from New Caledonia, Candollea 74 (1), pp. 1-7 : 2-4

Pichonia munzingeri Gâteblé & Swenson , spec. nova

( Fig. 1B , 2–3 ).

Pichonia munzingeri Gâteblé & Swenson is similar to but differs from P. daenikeri (Aubrév.) Swenson et al. in being a much smaller shrub having small, up to 5 cm long, oblong, almost glabrous leaves; petioles being canaliculate and less than 10 mm long.

Holotypus: NEW CALEDONIA. Prov. Sud: Mont-Dore, La Coulée, Captage de la Oumbéa , 21°11'19"S 166°34’ 22"E, 150 m, 14.III.2018, fl., Gâteblé & Rochard 1011 ( P [ P001156237 ]! ; iso-: G [ G00341841 ]!, MO!, MPU!, NOU [ NOU089084 ]!, S [ S18-39759 ]!) .

Shrub up to 3–4 m tall, usually erect but sometimes decumbent and even with erect and decumbent branches on the same plant. Branches tomentulose when young, ferruginous, soon glabrous. Leaves simple, alternate (a few sometimes subopposite), usually oblong but sometimes broadly elliptic to obovate, blade 3.0–5.0 (–7.0) × 1.5–2.5 (–3.0) cm, coriaceous, somewhat conduplicate in its entire length, slightly revolute; young leaves tomentulose, quickly glabrescent on both surfaces, with some scattered, usually short, appressed trichomes remaining below, especially along the midvein, but all eventually vanish; leaf base round; leaf apex obtuse or sometimes retuse; leaf venation brochidodromous with weak submarginal loops, midvein impressed above, prominent below; secondary venation of 8–12 pairs, weak; tertiary venation laxly reticulate, faint; higher venation areolate (high magnification); petiole 5–7(–10) mm long, ferruginously tomentulose, usually glabrescent and canaliculate. Flower 5-merous, bisexual, usually axillary and solitary, rarely in fascicle of two, sessile or subsessile, subtended by a minute bract. Sepals ovate, 2–3 mm long, base c. 1.5 mm wide, the outers tomentulose on the entire outer surface, the inners with tomentum in the central part, flanked with glabrous surfaces and fimbriate margins, all being glabrous inside. Corolla campanulate, yellowish or greenish with paler lobe margins, 4–5 mm long, glabrous; corolla lobes suborbicular or quadrangular in shape, of about the same length as the corolla tube. Stamens inserted in the tube orifice, shorter than the corolla lobes; anthers c. 1 mm long. Staminodes inserted in the corolla sinus, oblong to lanceolate, entire. Gynoecium flask-shaped, c. 5 mm long in total; ovary c. 2 mm long, pubescent; style 2.5–3.0 mm long, glabrous, slightly exserted, simple, without visible stigmatic areas. Fruit 1-seeded, ellipsoid, 28 × 14 mm, crowned with 3-mm-long remnant style; seed ellipsoid with a scar 25% of circumference and 100% of the seed length (observed from a single immature seed); cotyledons planoconvex without endosperm and radicle.

Etymology. – This new species is named in honor of our colleague and friend Jérôme Munzinger who has revised, along with numerous authors, many taxa in New Caledonia. Jérôme used the Centre IRD in Nouméa for seven years as his base for numerous fieldworks in the archipelago. His eye for undescribed species has generated too many novelties for a single researcher to handle and that is why he built an extensive collaborator network across the world. In 2011 Jérôme returned to Montpellier ( France) where he continues his excellent botanical studies. At the time of writing, he has described 69 endemic species for New Caledonia of which 46 are Sapotaceae .

Distribution and Ecology. – Pichonia munzingeri is so far only known from the Oumbéa Creek, one of the tributaries of La Coulée River within the Mont-Dore municipality ( Fig. 4 ). It grows in degraded maquis and rainforest remnants, on the lower and wettest parts of the slopes, though it is not a riparian species. It occurs on ultramafic substrate with peridotites rocks. It seems to flower and fruit mainly between March and June. So far, during seven visits between 2016 and 2018, only one fruit has been observed. One possible explanation is habitat destruction and a decline of natural pollinators following the fire in 2005 (see conservation status below). We suspect that the species is protandrous with pollen release before the style becomes exserted and receptive to pollen in order to prevent self-pollination.

Conservation status. – Even if only preliminary results are available, Pichonia munzingeri has a unique phylogenetic position, being the sister species to all congeners in New Caledonia and, hence, the oldest lineage of its kind in the territory. It has been found in only one location with two very small subpopulations on both sides of Oumbéa Creek separated by less than 600 m. The upper subpopulation has some 30 individuals whereas only three have been located in the lower one. In the upper subpopulation, P. munzingeri grows along a track to a water catchment area built in 1997 that was expanded in 2001. It is possible that some individuals were removed when the catchment area was established. Oumbéa Creek, Coulée River, and the Montagne des Sources protected area were severely damaged by a deliberately set fire at the end of the 2005 dry season that burned around 43 km ² ( Fig. 1A ). Both subpopulations of P. munzingeri must have been badly impacted by this anthropogenic fire because most plants are regrowth from burnt stumps and not juveniles. The lower subpopulation is adjacent to a popular water hole where people enjoy swimming during the hot season and where the vegetation (including the new Pichonia ) is regularly cut down for setting up camp fires. After the 2005 Montagne des Sources severe fire, the ground has become infested by Pteridium esculentum (G. Forst.) Cockayne , a species that is highly flammable in the dry season and well known to facilitate the spread of new fires ( JAFFRÉ et al., 1998). Hence, the main threat to Pichonia munzingeri is the frequent anthropogenic fires which are likely to further reduce the populations size. The calculated Area of occupancy (AOO) value is only 4 km ² (grid of 2 × 2 km) a value also applicable for Extent of Occurrence (EOO). All in all, effective in situ conservation appears very important to maintain high genetic diversity and we therefore suggest that P. munzingeri is assigned a preliminary status of “Critically Endangered” [CR B1ab(i,ii,iii,iv,v)+2ab(i,ii,iii,iv,v); C2a(i); D] based on the IUCN Red List Categories and Criteria ( IUCN, 2012).

Notes. – Pichonia munzingeri is particularly similar to Pycnandra francii in habit, from which it is distinguished by an areolate venation and the presence of staminodes (see above). The areolate venation is a feature present in all species of Pichonia and Pleioluma (Baill.) Baehni , but Pichonia have stamens inserted in the tube orifice (not in the lower half of the corolla tube) and seeds with plano-convex cotyledons without endosperm (not foliaceous cotyledons with endosperm). Among the congeners, P. daenikeri is the most similar but P. balansae (Baehni) Swenson & Munzinger is also to some extent similar. The foliage of P. munzingeri is much smaller (usually less than 5 cm long) and somewhat conduplicate with canaliculate, shorter petioles (usually no more than 7 mm long) than those of P. daenikeri and P. balansae . The foliage together with sessile (or subsessile) flowers make P. munzingeri a species easy to identify in the field.

Paratypi. – NEW CALEDONIA. Prov. Sud: Mont-Dore, La Coulée, Captage de la Oumbéa, 21°11'19"S 166°34'22"E, 150 m, 8.V.2017, fl., Gâteblé 936 ( MPU, NOU, P, S) ; ibid. loco, 8.V.2017, fl., Gâteblé 937 ( NOU, P, S) ; ibid. loco, 14.III.2018, fl., Gâteblé & Rochard 1012 (P) ; ibid. loco, 14.III.2018, fl., Gâteblé & Rochard 1013 ( NOU) ; ibid. loco, 14.III.2018, fl., Gâteblé & Rochard 1014 (S) ; ibid. loc., 21.V.2018, fr., Gâteblé 1026 ( NOU, P) .

Figures

Fig. 1. – Pichonia munzingeri Gâteblé & Swenson. A. Overview of the Montagne des Sources fire on 29 December 2005, the arrow points to the fire in the Oumbéa creek; B. Upper population in degraded maquis vegetation showing Pteridium esculentum (G. Forst.) Cockayne flammable dead whitish fronds along the pipe to the water catchment, arrows point to ten individuals of Pichonia munzingeri. [Photos: G. Gâteblé]

Fig. 2. – Pichonia munzingeri Gâteblé & Swenson. A. Overview of a single shrub; B. Decumbent shrub with leaves from above, resembling those of Pycnandra francii (Guillaumin & Dubard) Swenson & Munzinger; C–E. Sessile flower; F. Immature fruit. [Photos: A–D, F: G. Gâteblé; E: G. Rochard]

Fig. 3. – Pichonia munzingeri Gâteblé & Swenson. A. Flowering branch; B. Leaf with brochidodromous leaf venation; C. Lower surface of leaf showing an areolate higher leaf venation; D. Canaliculate petiole; E. Axillary solitary flowers; F. Flowers; G. Sepals, outer surface of an outer sepal (left), inner surface of an outer sepal (middle), and outer surface of an inner sepal (right); H. Open corolla with stamens and staminodes; I. Flower with sepals and corolla removed; J. Transection of fruit.

Fig. 4. – Geographic distribution of Pichonia munzingeri Gâteblé & Swenson.