Meryta pastoralis F. Tronchet & Lowry, 2011

Tronchet, Frederic & Lowry II, Porter P., 2011, A new species of Meryta (Araliaceae) from the Marquesas Archipelago, French Polynesia, PhytoKeys 4, pp. 149-156 : 150-153

Meryta pastoralis F. Tronchet & Lowry sp. nov. Figs 1 -2

Latin.

Haec species quoad inflorescentiae structuram ac ovaria omnino libera Merytae choristanthae Harms (ex Insulis Australibus) simillima, sed ab ea foliis anguste obovatis usque spathulatis (vs. late ellipticis usque subobovatis), carpellis 5 ad 11 (vs. 5 vel 6 tantum) atque fructu maturitate 7-9 × 7-10 (vs. 8-12 × 10-15) mm distinguitur; etiam quoad foliorum aspectum M. raiateensi J.W. Moore et aliquantum M. lanceolatae J.R. Forst. & G. Forst. similis, sed ab eis (atque adeo ab omnibus congeneris Societatis Insularum ac Tuamotu) ovariis omnino liberis distinguitur.

Type.

French Polynesia. Marquesas Islands, Hiva-Oa, Hanamenu valley off Hanamenu trail, in Metrosideros-Weinmannia-Dicranopteris linearis wet forest, 09°47'50"S, 139°05'35"W, 908 m, 2 August 2005 (fr), S. Perlman 19767 (holotype: P [P00398408]!; isotypes, PAP!, PTBG!, US!).

Description.

Monocaulous to sparsely branched tree, dioecious, Chamberlain architecture (tending toward Leeuwenberg architecture ( Hallé, 2004) when very old, fide P.A. Schäfer, 1975), 3 –6(– 10) m tall, without milky sap. Leaves simple, alternate, grouped at branch ends; petiole 1.5 –2.5(– 4) cm long, 2-3 mm in diam., base enlarged, slightly clasping, lenticels rarely present abaxially, without dark green transverse striations adaxially when fresh; ligule present adaxially at the base of the petiole, persistent, free portion triangular to widely triangular, 5 –11(– 17) mm long, margins entire, membranous, apex obtuse to acute; blade green, shiny adaxially when fresh, slightly lighter green abaxially, narrowly obovate to spatulate, 20.4-40 × 5.2-9.8 cm (l/w ratio 2.76-5.52), base symmetric to asymmetric, offset 2 –5(– 10) mm, mostly positively centered in adaxial view, attenuate, margin entire, undulate distally, minutely revolute, apex acute to obtuse, the extreme tip obtuse to mucronate, chartaceous to coriaceous, glabrous on both surfaces; venation brochidodromous, light green-yellow when fresh, with prominent arches lacking intramarginal veins; midvein strong and massive, straight, without evident abaxial thickenings; secondary veins (12 –)17– 22 pairs, diverging from the midvein by (53 –)57– 69° (in the widest part of the blade), the distal ones less divergent, weakly recurved near the midvein then strongly recurved toward the margin, joining with the next arch at an obtuse angle without forming a clear intramarginal vein, intersecondary veins present; tertiary veins evident, not reaching the margin, straight to anastomosing at various angles, sometimes forming convex arcs in the intercostals zone; higher order veins visible in dry material, forming a fine, dense reticulum; veinlets forming quadri- to multi-angular areoles 0.5-1.5 mm in size. Juvenile foliage similar to adult, blade with an obtuse apex. Male material unknown (only old inflorescences seen). Female inflorescence terminal, erect, a raceme of spikes, with 1 degree of branching, axes and peduncle light green, bracts brown-red, primary axis 15-20 cm long, 5-8 mm in diam. at the base when fresh, subtended by persistent or sometimes caducous triangular cataphylls 13-24 mm long, without lenticels, margins entire, mostly to almost entirely membranous, apex obtuse, bearing a dorsal, ± foliaceous apicule; secondary axes 8 –13(– 17), 6-12 cm long (shorter distally), straight or sometimes slightly curved upward in the distal portion, diverging 35-60° from the primary axis, each subtended by a caducous, triangular to narrowly triangular bract 7-20 mm long, without lenticels, margin denticulate, mostly membranous, apex acute to acuminate, sometimes apiculate; spikelets with 7 –15(– 27) flowers, the proximal one inserted 3-15 mm from the base of the secondary axis. Female flowers white when fresh, sessile; bractlets caducous or sometimes persistent, broadly triangular, 3-5 mm long, margin weakly dentate, membranous, brown-red, partially covered by the flower and later the fruit, apex acute to obtuse; petals 5-11, caducous in fruit, ovate, 1-2.5 mm long, weakly cucullate, recurved when flowers receptive, with a pronounced adaxial groove, apex acute; androeciuum present, isostemonous, filaments and anthers developed but pollen sacs empty, stamens with filaments 0.5-1 mm long, anthers 0.5 mm long; ovary inferior, (5-)7 or 8(-11)-carpellate, nectar disc epigynous, 2 mm diam., styles weakly differentiated, to 1 mm long, stigmas 1.5-3 mm long at receptivity, often strongly recurved to twisted. Fruit yellow-green when young, light purple at maturity, remains of petals and stamens brown, ovaries entirely free and distinct from one another; drupes globose to sub-globose, 7-9 × 7-10 mm, smooth and fleshy when fresh, ribbed when dry, the ribs corresponding to the 5-11 pyrenes.

Distribution.

Known only from the type locality in the Mt. Temetiu/Feani area at ca. 900 m elevation along the Hanamenu trail on the island of Hiva Oa ( Fig. 3), the largest and highest in the Marquesas archipelago.

Ecology.

Meryta pastoralis occurs on slopes and along streams in low stature, humid montane Metrosideros-Weinmannia forest at and above 900 m elevation.

Etymology.

This species is named in honor of P.A. Schäfer, who was the first to collect it in 1975 while conducting botanical inventory work in the Marquesas, and who has contributed much to our knowledge of the flora of the archipelago. The name Schäfer means shepherd in Alsatian, which when translated into Latin provides the basis for our choice of the epithet pastoralis.

Conservation status.

Meryta pastorali s is known from a single population along a wind-swept ridge below the highest point on Hiva Oa. With an Area of Occupancy of <10 km2 and an Extent of Occurrence that is probably no larger, it meets the area requirements for Critically Endangered status under criteria B1 and B2 of the IUCN Red List Criteria ( IUCN 2001). While the vegetation in the immediate area is still largely intact, increasing impacts from feral pigs, human disturbance and fire during the dry season (D. Lorence, pers. comm.) represent growing threats to Meryta pastoralis , prompting us to assign it a provisional threat status of Critically Endangered (CR B1ab(i,ii,iii,v) + 2ab(i,ii,iii,v)).

Other specimens examined.

French Polynesia. Marquesas Islands, Hiva Oa, trail toward Hanamenu; in gulch off trail, low forest, 3 August 1988 (fr). S. Perlman 10206 (AD!, BISH! [2 sheets], F!, K!, MO!, NY!, P [P00372510]!, PAP!, PTBG!, US!); Teakatu, valley on north side of Hanamenu trail heading down to Hanamenu past summit crest, between Teakatau and Tepuna, along stream bottom in Metrosideros-Weinmannia-Crossostylis montane wet forest, [09°47'29"S, 139°05'41"W], 933 m, 26 August 1995 (st), S. Perlman & J.-Y. Meyer 14894 (BISH!, MO!, PAP!, PTBG!, US!); Feani area, Tepuna, in gulch to north of Hanamenu trail, down west side of summit crest to 1075 meters elev. and drop into gulch, in Metrosideros-Weinmannia forest, 09°47'49"S, 139°05'12"W, 900 m, 29 January 2003 (old ♂fl), S. Perlman 18335 (BISH, P [P00398011]!, PAP, PTBG, US); Feani area, Tepuna, off Hanamenu trail on west side of summit crest, at 1075 meters elev. into gulch north side of trail, scattered plants in Metrosideros-Weinmannia forest, 09°47'49"S, 139°05'12"W, 29 January 2003 (♀fl), S. Perlman 18336 (PAP, PTBG, US); Montagnes NW du Temetiu, entre la haute vallée de Hanamenu et la crête du Temetiu Feani, haute vallée, forêt humide, [09°48'00"S, 139°05'30"W], 925 m, 23 October 1975 (♀fl), P.A. Schäfer 5922 (BISH!, K!, MO! [2 sheets], NTBG!, P [P00372508 & P00372509]!, US!).

Discussion.

Material of our new species most closely resembles specimens of Meryta choristantha Harms from the Austral Islands, with which it shares a similarly structured inflorescence and totally free ovaries, but differs in leaf shape (narrowly obovate to spatulate in Meryta pastoralis vs. widely elliptic to slightly obovate in Meryta choristantha ), number of carpels (5-11 vs. 5 or 6), and fruit size at maturity (7-9 × 7-10 vs. 8-12 × 10-15 mm). The leaves of Meryta pastoralis are similar in appearance to those of Meryta raiateensis J.W. Moore, and to a lesser degree Meryta lanceolata J.R. Forst. & G. Forst., both from the Society Islands, but our new taxon differs from these entities, and indeed all other species in the Society Islands and on Tuamotu, by its totally free ovaries.

Results from ongoing molecular phylogenetic work ( Tronchet et al. 2005a, 2005b, unpubl. data) suggest that Meryta pastoralis is part of a small clade now understood to comprise four species, also including Meryta sinclairii from New Zealand, Meryta tenuifolia A.C. Sm. from Fiji, and Meryta choristantha , which together correspond to Meryta sect. Choristomeryta Harms ( Harms 1938). Material here assigned to Meryta pastoralis was referred to informally as 'M. schaeferi’ in Tronchet et al. (2005b).