A reassessment of Marquesan Ochrosia and Rauvolfia (Apocynaceae) with two new combinations

Abstract A reassessment of collections of Marquesan Apocynaceae assigned to the genera Neisosperma Raf., Ochrosia Juss., and Rauvolfia L. revealed that two nomenclatural changes are necessary: 1) transfer of Neisosperma brownii Fosberg & Sachet to the genus Ochrosia, as Ochrosia brownii (Fosberg & Sachet) Lorence & Butaud, comb. nov., and 2) transfer of Ochrosia nukuhivensis Fosberg & Sachet to Rauvolfia as Rauvolfia nukuhivensis (Fosberg & Sachet) Lorence & Butaud, comb. nov. As a result, two species each of Ochrosia and Rauvolfia are recognized from the Marquesas Islands, all endemic. Recent field work has yielded important new data on their distribution, habitat, and conservation status. It is recommended that all four species should be added the IUCN Red List at the Critically Endangered (CR) category.


A reassessment of Marquesan Ochrosia and Rauvolfia (Apocynaceae) with two new combinations Introduction
In his Flora of Southeastern Polynesia, Forrest Brown (1935) incorrectly interpreted three Apocynaceae collections he made at 800 to 900 meters on Nuku Hiva and Fatu Hiva in the Marquesas Islands as belonging to the widespread coastal Indo-Pacific species, Ochrosia parviflora (G. Forst.) Henslow. The latter is now considered a synonym of Ochrosia oppositifolia (Lam.) K. Schum., or alternatively of Neisosperma oppositifoli-um (Lam.) Fosberg & Sachet (Nicolson and Fosberg 2004;Smith 1988), a species not known from the Marquesas but occurring in the Austral archipelago. Based on these three rather poor, incompletely flowering and fruiting collections, Fosberg and Sachet (1972) described two species in Ochrosia Juss., one each from Nuku Hiva and Fatu Hiva, and one in Neisosperma Raf. from Nuku Hiva. Fosberg (1981) later described a species of Rauvolfia L. based on a Sachet collection from Hiva Oa. During the preparation of an account of Apocynaceae for the Vascular Flora of the Marquesas Islands and Flore de la Polynésie française, additional field work by J-FB and study of additional herbarium specimens have greatly increased our knowledge of the Marquesan taxa and their correct identity. For example, collections from field work associated with the project resulted in the discovery of a new species of Lepinia, a genus previously not even known from the Marquesas (Lorence and Wagner 1997). Critical study of the type collections of the four previously described species of Marquesan Apocynaceae, all apparently endemic, coupled with new collections and field observations has resulted in a reassessment of their generic status.

Ochrosia or Neisosperma ?
Traditionally Neisosperma [incorrectly spelled Neiosperma by Fosberg & Sachet (1972)] was separated from Ochrosia based on two morphological features: the gynoecium possesses a nectary comprised of two thin lobes or scales present in the former but lacking in the latter; secondly, the fruit endocarp is fibrous and muricate with no air cavity in the former and fibrous but relatively smooth-surfaced with two air cavities in the latter (Smith 1988: 44). Disintegration of the surrounding pericarp and mesocarp by weathering, however, reveals the endocarp of Ochrosia to be fibrous as well (Lorence and Butaud, pers. obs. 2010). In both cases the fruit consists of usually two mericarps.
Based on morphological and molecular evidence, recent classifications of Apocynaceae tend to recognize only a single genus Ochrosia Simões et al. 2007;Mabberley 2008). Molecular studies of 19 species of Ochrosia using cpDNA (the rps 16 intron) and ITS sequences revealed that Ochrosia species formed a strongly supported clade sister to and nested within a paraphyletic Neisosperma clade (Hendrian and Kondo 2007a, b). However, additional data from combined rps16 intron plus ITS sequences showed a more robust clade of Ochrosia sensu lato, supported by 100% bootstrap value, supporting the inclusion of Neisosperma into Ochrosia and recognition of only one genus (Hendrian and Kondo 2007c), a conclusion we adopt here. Nevertheless, it is possible that additional studies may show that the genus Neisosperma could be resurrected in a narrower concept potentially including two species from Marquesas and one species from the Austral Islands.
Distribution. Nuku Hiva, Marquesas Islands, originally known only from the type collected in the vicinity of the Toovii plateau at about 900 m (Brown 1935). The species was rediscovered by Jean-François Butaud in 2003 on Nuku Hiva where a single tree and some juveniles were located on the Vaioa plateau (at Matahamo, also called Vaipupui) SE of Toovii.
Conservation status. When evaluated using the IUCN criteria for endangerment (IUCN 2001) Ochrosia brownii falls into the Critically Endangered (CR) category, which designates species facing the highest risk of extinction in the wild. IUCN Red List Category: Critically Endangered (CR) B1a, b; B2a, B2b (i-iii): B1, extent of occurrence estimated to be less than 100 km 2 , and B1a, known to exist at only a single location; B1b (i-iii), continuing projected decline in (i) extent of occurrence, (ii) area of occupancy, and (iii) area, extent and quality of habitat; B2, area of occupancy estimated to be less than 10 km 2 , and B2a, a single population known. B2b (i-iii), habitat continuing decline inferred. The suitable habitat for Ochrosia brownii on Nuku Hiva (c. 340 km 2 ) is indicated as an endangered environment, threatened by human activity (deforestation and fire), feral animals, and invasive plants, reducing the extent of the forest. Discusison. Since 2006, a conservation plan proposed by the Environment Direction of French Polynesia has been implemented, with conservation ex situ (seed collection and conservatory plantings) and in situ (fencing enclosure of the population and enrichment planting of seedlings inside). Description. Tree 10−14 m tall, trunk 15−20 cm in diam., branchlets glabrous, leafy twigs 2.5−7 mm in diam., bark wrinkled when dry, latex white. Leaves opposite on smaller branchlets, apparently ternate on larger branchlets; blades elliptic, 5.8−20.2 × 2.4−10.1 cm, base narrowly cuneate, apex shortly acuminate, glabrous, discolorous, when fresh dark green above, pale green below, drying brown, margins slightly revolute; secondary veins 9−20 on each side, prominulous on both surfaces, intersecondaries and tertiaries prominulous on both surfaces; petioles 14−36 mm long. Inflorescence terminal, tri-or quadrichotomous, branching twice, cymose-corymbiform, 52−88 mm long, axes and flowers glabrous, sessile, with 3 primary branches (6−)20−64 × c. 2 mm, subquadrangular, bracts ovate-triangular, 1−1.2 × 1−1.2 mm, ultimate axes with flowers crowded in cymules; flowers with pedicels 2−5 mm long, each with a single bract, calyx cup 2.5 mm long, calyx lobes 5, triangular-ovate, 2.5 × 3 mm, apex obtuse; corollas in bud to 10 mm long; corolla at anthesis white, fragrant, corolla tube 7−8 × 3 mm, corolla lobes 5, contorted to the right, 9−10 × 2−2.5 mm; ovary and nectary not seen. Infructescence with peduncle c. 11.5 cm long. Conservation status. Ochrosia fatuhivensis is currently known only from a single population. When evaluated using the IUCN criteria for endangerment it falls into the Critically Endangered (CR) category, which designates species facing the highest risk of extinction in the wild. IUCN Red List Category: Critically Endangered (CR) B1a, b; B2a, B2b (i-iii): B1, extent of occurrence estimated to be less than 100 km 2 , and B1a, known to exist at only a single location; B1b (i-iii), continuing projected decline in (i) extent of occurrence, (ii) area of occupancy and (iii), area, extent and quality of habitat; B2, area of occupancy estimated to be less than 10 km 2 , and B2a, a single population known. B2b (i-iii), habitat continuing decline inferred. The suitable habitat for Ochrosia fatuhivensis on Fatu Hiva (c. 85 km 2 ) is indicated as an endangered environment, threatened by human activity (deforestation and fire), feral animals, and invasive plants, reducing the extent of the forest.
Discussion. Fosberg & Sachet (1972) suggested Ochrosia fatuhivensis may be related to O. compta K. Schum. of Hawaii, but no molecular-phylogenetic studies have been carried out involving these two species. The local name is ho'ei in Fatu Hiva, similar to the name holei used for species of Ochrosia in Hawaii (Wagner et al. 1990). On Fatu Hiva the seeds were eaten in time of famine according to Brown (1935) and several present day inhabitants.

the Marquesan species of Rauvolfia
A single species of Rauvolfia, R. sachetiae Fosberg was described from Hiva Oa, Marquesas based on a single collection (Fosberg 1981). Recent collections and field observations of Rauvolfia from Nuku Hiva were thought to represent this species. However, a re-examination of the holotype of Ochrosia nukuhivensis Fosberg & Sachet (Brown 432, BISH) reveals that it possesses distinctive whorled leaves and dark, linear or digitate, resiniferous colleters in the leaf axils and adjacent petiole characteristic of most Pacific Rauvolfia species, although the type lacks fruits. In Ochrosia the colleters are generally shortly conical or scale-like and usually obscured by a copious resinous exudate. Additional morphological differences separating these two genera include in Rauvolfia the corolla lobes are left-contorted (sinistrorse), presence of a well-developed annular nectary disc, and the presence of a conspicuous membranous basal collar on the style-head, whereas in Ochrosia corolla lobes are right-contorted (dextrorse), the nectary is absent or consists of 2 small, poorly developed thin lobes alternating with the carpels, and the style head sometimes has a ring of longer hairs near its base but no collar (M. Endress, pers. comm. 2010).
A recent Nuku Hiva collection, Perlman 10014 distributed under the name Rauvolfia sachetiae, compares very well with Brown 432, the type of Ochrosia nukuhivensis, and clearly represents the same species. Furthermore, Perlman 10014 has subglobose or globose, syncarpous fruits characteristic of many Pacific species of Rauvolfia in which normally each of the two carpels contains two ovules, but frequently one aborts so that at maturity the fruit is usually 2-seeded, but sometimes one carpel does not fully develop, resulting in a 1-seeded syncarpous drupe. In Ochrosia the fruits consist of a pair of well separated, distinct or bally basally connate oblong mericarps (Wagner et al. 1990). This Nuku Hiva species differs in leaf and calyx morphology from R. sachetiae on Hivaoa, and the two species may be separated by the following key.
Distribution. Marquesas Islands, known only from Nuku Hiva between 198 and 627 m elevation. Ecology. Rauvolfia nukuhivensis is very rare and localized with fewer than 50 living trees currently known in valley or plateau dry forest with species of Cerbera, Ficus, Maytenus, Phyllanthus, Sapindus, and Xylosma. Currently known in the Terre-Deserte region in the valleys of Motuee, Hakaavao, Haahopu, Haatuatua, Hakaoa, Tapueahu and Uea, and on the plateaus of Tohuahee, Vaiteheii, Maauu, and Putata. As many dead trees as living trees are known. Formerly known from the north coast of Nuku Hiva, between the Haataivea peninsula and behind Aakapa village.
Conservation status. The suitable habitat for Rauvolfia nukuhivensis on Nuku Hiva (c. 340 km 2 ) is indicated as an endangered environment, threatened by human activity (deforestation, exploitation for leaves and bark), feral animals, and invasive plants, reducing the extent of the forest. Following the criteria and categories of IUCN (2001) IUCN Red List Category: Critically Endangered (CR) B1a, B1b (i-iii), D; B1, extent of occurrence estimated to be less than 100 km 2 , and B1a, severely fragmented (several small subpopulations); B1b (i-iii), continuing projected decline in (i) extent of occurrence, (ii) area of occupancy, and (iii) area, extent, and quality of habitat; D population size estimated to number fewer than 50 mature individuals (fewer than 50 total individuals). Description. Tree 6−10 m tall, trunk 20−25 cm in diam., bark furrowed, branches more or less horizontal, twigs and leaves in whorls of 3−4, entire plant glabrous, latex abundant; branchlets 4−6 mm in diam., proximal internodes to 9 cm long, distal ones 0.5−1 cm long toward end of season's growth, terminal buds with abundant clear, brown resin. Leaves elliptic to broadly elliptic, 5.5−22 × 2.5−6.8 cm apex acute to obtuse, base acute to occasionally obtuse, slightly decurrent on petiole, glabrous, chartaceous, light to bright yellowish green when dried, secondary veins 12−15 on a side, brochidodromous, forming a wide angle with costa, secondary and tertiary veins prominulous on both surfaces; petioles 15−35 × 1−2 mm in diam. with 20−30 brown digitate, glandular colleters 0.5−1.2 mm long in each leaf axil. Inflorescences terminal, pseudoaxillary by displacement, compound cymes 3−6 × 8−12.5 cm including the corollas, peduncles verticellate, 1.5−3 cm long, 3−6 times ramified, branches open, widely divergent, ultimate branches trichotomous with central branch usually represented by a single pedicellate flower, most flowers early caducous from all but the most distal branches, each lateral branch subtended by a scale-like, ovate-triangular bract 1−1.5 × 1−1.5 mm, a bract pair subtending each lateral bud, axils of bracts glandular as those of leaves, pedicel of central flower 2−2.5 mm long, lateral buds of a triad subsessile, globose, tending to develop into a new triad with only the central flower of a triad developing to anthesis; calyx turbinate-campanulate, lobed almost to base, lobes 1.5−2 × 1.5−1.7 mm, imbricate, obtuse, margins thin; corolla yellow in bud, at anthesis cream colored, 12−14 mm long including limb, tube 9.5−14 × 1−1.5 mm in diam. medially, slightly dilated at apex and base, lobes slightly left-contorted, ovate, 2.5−3.5 × 2 mm, obtuse or rounded at apex, anthers narrowly ovate, somewhat bluntly acuminate, sagittate at base, subsessile, 1.5 mm long, inserted 1.5 mm below throat, a very few hairs around and below insertion on inside surface of corolla tube; ovary surrounded by cup-like nectary disk with minutely crenulate margin, carpels oblong, free distally, united in lower half, style glabrous, 7−9 mm long, style head thickened, cylindrical (not seen: floral description from Fosberg 1981). Fruit subglobose to globose, 12−15 mm long, fleshy, turning black at maturity (at least when dry), apex rounded or emarginate, subtended by persistent spreading calyx. Seed 1 by abortion (only one mature fruit examined) 12 × 8 × 5 mm, obliquely oblong-ovoid, with one straight and one curved edge, base sub-truncate, apex diagonal from straight edge upward to a blunt point, sides coarsely and shallowly rugose.
Distribution. Marquesas Islands, Hiva Oa, previously known only from a single tree at the type locality above Taaoa. In 2011 one dead trunk probably representing this species was found in a small gulch above Tanaeka valley, at around 430 m elevation (Butaud, pers. obs.).
Ecology. Dry secondary forest or shrubland with Casuarina. Conservation status. Despite careful searches this species has not been found since the last collection was made at the type locality in 1977. In 2010 the area was observed to be overgrazed by goats and invaded by Syzygium cumini.(L.) Skeels (Butaud, pers. obs.). Rauvolfia sachetiae falls into the Critically Endangered (CR) category, which designates species facing the highest risk of extinction in the wild. IUCN Red List Category: Critically Endangered (CR) B1a, b; B2a, B2b (i-iii): B1, extent of occurrence estimated to be less than 100 km 2 , and B1a, known to exist at only a single location; B1b (i-iii), continuing projected decline in (i) extent of occurrence, (ii) area of occupancy, and (iii) area, extent and quality of habitat; B2, area of occupancy estimated