Five new species of Barringtonia ( Lecythidaceae ) from Papua New Guinea

Five new species of Barringtonia from Papua New Guinea are described and discussed: B. lumina, B. monticola, B. pinnifolia, B. serenae and B. tagala. All five species belong to section Barringtonia with closed flower buds. Notes are also provided for the seven monocaulous pachycaul species of Barringtonia in New Guinea.


INTRODUCTION
During the course of a long residence in Papua New Guinea one of us (MJ) studied the genus Barringtonia extensively in the field and found a number of putative new species.These were partially written up over fifteen years ago, but due to other commitments were never published.GTP is in the process of preparing a monograph of the genus and so the new species upon which we both agree are published here prior to the monograph (Prance in prep.).
New Guinea is one of the three main centres of diversity of Barringtonia, the others being Peninsula Malaysia (see Prance 2010) and Borneo.The addition of these five species brings the total for PNG to 24.One of the most interesting features of the Barringtonias of PNG is the number of monocaulous species exhibiting Corner's model of tree architecture.These include three of the new species described here (B. lumina, B. monti cola and B. pinnifolia).All five of the new species belong to the section Barringtonia which has a preanthic calyx completely enclosing the flower buds.The pachycaulous species of Barringtonia, with the exception of B. corneri Kiew & K.M.Wong from the Malay Peninsula, are apparently New Guinea endemics occurring mainly in northern PNG and the adjacent Bismark Archipelago.Barringtonia ca lyptrocalyx is undoubtedly the most widespread species, being found throughout the north coast forests up to 1500 m, as well as in Central and Western Provinces on the south coast (see Map 1).It is characterised by its slender lanceolate leaves, and fusiform fruits.Two similar species occur within its range.Barringtonia pinnifolia found in Morobe and Northern Provinces has a more obovate leaf, as well as being an altogether more slender and petite species.Barringtonia papuana of the north and south coast of Central Province is found through to Irian Jaya and has the most slender leaves in the genus, characteristically widest at the centre and not towards the apex as with the foregoing.We believe that B. josephstaalensis should be placed in synonomy under B. papuana.

The New
These three species are in many ways very similar, and appear to occupy a similar ecological niche, being small understorey trees rarely exceeding 6 m in height.Barringtonia calyptrocalyx in particular shows great variation in leaf size, and in some populations gives the impression that two taxa are present, one with large leaves, a thick stem, larger inflorescence and bigger fruits, and the other smaller in all dimensions.Fruit shape and size varies considerably, some collections having clearly fouror eight-angled or ridged fruits.
From Central and Sepik Provinces there are a few collections of B. calyptrocalyx with ant-inhabited stems.The phenomenon of hollow stems with ant-occupants is an intriguing feature of many New Guinea understorey trees.It has been recorded for over 32 species from 11 families, amongst them Annonaceae, Leguminosae, Meliaceae and Monimiaceae (MJ pers.obs.).In other features many of these trees show no other specialisations towards ant-occupancy, and the relationship appears more commensural than mutualistic.Many such relationships are clearly facultative, with certain forest areas containing numerous ant-inhabited trees, often adjacent to one another, while in other areas no ants may be present, even when the same species are involved.
Two other species, not to be confused with the foregoing by their massive construction, also occur; in New Britain Barringtonia papeh, and on the mainland B. lumina.These two species have thick, often unbranched stems to 15 m tall with a solitary whorl of 1.5-2 m long leaves at its apex.As with the foregoing species the plants are capable of branching, although usually as a result of injury to the primary stem rather than as a normal character state.
Barringtonia papeh is recorded as having a terminal inflorescence, although this apparently a variable feature, the species probably conforming to Chamberlain's Model of tree architecture.In B. lumina the inflorescences are borne on the trunk, well below the whorl of leaves.The two species differ markedly in their calyx and fruit characters, the former having a 4-lobed calyx divided in the bud, and a square-sectioned fruit, while the latter has a closed calyx that splits circumscissily, even though there are four apparent sulci in the bud, and a round-sectioned fruit.The two are probably closely related.
Most species of Barringtonia are low-altitude plants.Payens (1967) only records eight species as reaching to 1000 m.Bar ringtonia monticola is therefore unique in that it has not been collected below 1200 m, and occurs up to 1950 m.It is found in Morobe and East Highlands Provinces.The recently described B. jebbiana Takeuchi (2010) from the limestone Muller Range is also an high-altitude species at 1450 m.Unfortunately these altitude limits coincide with the maximum density of human populations in Papua New Guinea, making forest at these altitudes scarce and fragmented in the central highlands.Furthermore, monocaulous Barringtonia species suffer from direct selection pressure, their straight stems are often preferentially felled for house construction.It may be that the species is more common and widespread than anticipated, certainly it is abundant in the Okapa and Aseki areas.Barringtonia monticola (Fig. 2) is a large leaved species similar to a broad-leaved B. calyptrocalyx.Lastly B. clemensii, which was placed in synonomy within B. sa moensis A.Gray by Payens (1967), is not easy to characterise architecturally.It can certainly flower as a monopodial treelet, although it appears to develop into a branching tree later through reiteration.Barringtonia clemensii is certainly distinct from B. sa moensis and will be recognised in a forthcoming monograph of the genus.
Distribution & Habitat -Jayapura, Sepik, Morobe, Milne Bay and Bougainville, forest.Altitude: 0-300 m.Note -This species is similar to B. procera but differs in the much larger leaves, the quadrangular buds and the distinctive velvety pubescence of the hypanthium and calyx.At some times of the year it is reported as being deciduous, with only the large terminal bud remaining (A.Hay pers.comm.).It can commence flowering when 2 m tall.The prominent and pinkcoloured terminal bud is reminiscent of a candle flame atop the unbranched stem particularly if the leaves have fallen (Lat.lumina = candle or light).Monocaulous treelet to 4 m tall; architecture conforming to Corner's Model.Leaves in a single whorl in mature trees; petioles 1-3 cm long, winged almost to base; leaf blades chartaceous and slightly bullate, oblong to oblong-lanceolate, 65 -85 by 13 -19 cm, widest at about 2/3 of its length; apex abruptly acuminate, the acumen 10-15 mm long; base gradually tapering to a short petiole; midrib prominent above and below, rounded, longitudinally ridged; primary veins 25 -35 pairs, arising obliquely from midrib, straight and parallel, confluent to a marginal vein; margin entire.Cataphylls lanceolate, to 5 cm long.Inflorescences cauliflorous, pendulous, 22-35 cm long, the rachis 2 mm diam, accrescent to 4 mm, sparsely puberulous; calyx closed in bud, pulverulent on exterior, circumscissile leaving an irregularly lobed or fringed part.Flowers borne on short bosses, pedicels 1-2 mm, puberulous; hypanthium coneshaped, slightly four lobed, 3 mm tall by 3 mm diam; petals 4, oblong, 10-14 by 4-6 mm; staminal whorls 4-5, the inner one staminodal, staminal tube 3 mm high; ovary 3-locular, 2 ovules per locule; disc annular, 3 mm diam; style equalling filaments in length.Fruit ovoid, 3-5 by 4 cm, slightly tetragonous, dark red when mature, not tapered, exterior rugose after drying, with short pedicel 2 -3 mm long, with concave calyx area at apex.

cm
Distribution & Habitat -Madang Province.Rare?Only known from two collections.Growing on coral rock by river edge at 100 m.

Barringtonia tagala
Distribution & Habitat -Known from the Gogol valley of Madang Province.In lowland forest.In common with many other Barringtonia apparently shows poor seed dispersal.Individual trees are often accompanied by large crops of surrounding seedlings.
Note -Although the leaves of B. tagala are similar to those of B. serenae this new species can be distinguished from the latter by its much longer inflorescence, longer pedicels that are not articulated and the smaller flowers.The raceme length, fruit size, its long cylindric shape and the 2-3-loculed ovary are exceptional.The generic name for Barringtonia in the Madang region is 'Tagal'.