Balaka diffusa Hodel, Palms (1999+) 54(4). 2010

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Distribution

Map uses TDWG level 3 distributions (http://www.nhm.ac.uk/hosted_sites/tdwg/geogrphy.html)
Fijipresent (World Checklist of Arecaceae)A

Habitat

  • Balaka diffusa is known from only one, small population straddling the boundary of Serua and Namosi Provinces along the southeastern coast of Viti Levu, Fiji, where it is mostly an understory palm in wet forest at about 200 m altitude on steep slopes near creeks and streams. In a few instances along streams where there is a canopy break, it is an emergent plant with arching leaves. Little is known about its natural history. In 2008 I observed all age sizes but none in a great number, and regeneration was only fair. Pinnae were typically heavily damaged or skeletonized by an unknown insect pest while infructescences appeared heavily foraged. Fuller (1997), in his excellent and comprehensive account of Fijian palms, reported (as B. macrocarpa) that spatial arrangement was clumped, with mature trees closely arranged, regeneration was fair, and infructescences foraged. Flowering and fruiting probably occur nearly year around, but mature fruits are rarely encountered. Watling (2005) reported (as B. macrocarpa) that the masked shining parrot, Prosopeia personata, is the likely forager and gathers large fruits before they are fully ripe. Not a seed disperser but a predator, it opens the seed with its powerful bill and extracts the endosperm. (Hodel, D.R., A synopsis of the genus Balaka in Palms (1999+) 54(4). 2010)B

Discussion

  • The elongate pinnae, relatively large inflorescence, expanded, 2-branched panicle with long, spreading, diffuse rachillae, flower triads along the entire length of the rachillae and large fruit distinguish Balaka diffusa. Moore (1979), Fuller (1997) and Watling (2005) included the Nabukavesi Creek population (B. diffusa) as B. macrocarpa. However, the latter species is restricted to Vanua Levu and differs in its much smaller inflorescence, more compact, mostly simply branched panicle, shorter rachillae and flower triads restricted to the proximal one-half to two-thirds of the rachilla, resulting in the fruit appearing tightly clustered together. The endocarp Watling (2005, p. 69) illustrated as B. macrocarpa is actually B. diffusa. Conservation Status: Balaka diffusa currently has no risk assessment designation (IUCN 2010). However, it should be considered Critically Endangered according to IUCN criteria because of its small population size of only about 200 mature plants in a somewhat disturbed site with encroaching mahogany plantations. Its narrow, restricted range increases susceptibility to a single, disruptive event, like a hurricane, and to potential damage from invasive weeds, animals, pests and disease. Low seedling recruitment and small population size suppress regeneration. Because it is readily and easily accessible on Fiji's main island, fruits and/or small plants have occasionally been gathered, and B. diffusa is now cultivated in Fiji, Hawaii and perhaps elsewhere although it is usually misidentified as B. macrocarpa. Nearly all cultivated specimens identified as B. macrocarpa are actually B. diffusa.
    (Hodel, D.R., A synopsis of the genus Balaka in Palms (1999+) 54(4). 2010)B

Description

  • Solitary, small, slender, unarmed, pleonanthic, monoecious, understory palm to 5(-10) m tall. Trunk 5 cm diam., internodes 2-2.5 cm, nodes 1 cm wide. Leaves 4 or 5, erectspreading, arching, to 2.1 m long; sheath 28-33 cm long, obliquely open distally, covered with reddish brown tomentum; petiole ca. 45 cm long; rachis to 1.25 m long; pinnae 10-12 per side, elongate, to 46x13 cm, margins gradually diverging from base to about ¾ distally then ± parallel or slightly converging in distal ¼, apex 13.5 cm wide, obliquely truncate, praemorse, thick-papery, adaxially only midrib raised and this prominent and knife-like, 1 ± prominent but not raised primary nerve on either side of midrib, other primary nerves obscure, several unequally spaced secondary nerves, numerous unequally spaced tertiary nerves, abaxially nerves with reddish brown, scale-like hairs, apical pair wider and transversely truncate and toothed, to 33x20 cm. Inflorescences 1 or 2 (or 3), infrafoliar, to 75 cm long, 2-branched; peduncle 12-30 cm long cm long, 4-5 cm wide at base, tapering to 3 cm wide at prophyll, flattened, 1 cm thick; prophyll attached 1 cm distally of peduncle base, 29 cm long, bicarinate, covered with reddish brown tomentum, 1st peduncular bract attached 2 cm distally of prophyll, to 32 cm long, just exceeding prophyll, rudimentary 2nd peduncular bract attached 3 cm distally of 2nd peduncular bract, long-triangular, 2x1 cm; rachis 18-25 cm long, 3 proximal branches branched or forked, subpeduncle to 8 cm long, subrachis to 3 cm long, rachillae 12-15, 30-40 cm long, 5 mm diam., 3-sided or -angled and slightly flexuous from floral pits, spreading, diffuse. Flower triads for entire length of rachillae, 1 cm distant and in 2 spiraling rows proximally to 5 mm distant and in 2 distichous rows distally, triads in clefts 8 mm long, 5 mm wide, 1 or 2 mm deep, 1 bracteole to 2 mm long subtending proximal side of triad and forming a multi-lobed lip, pistillate flower completely enclosed by 2 imbricate bracteoles, these to 1.75 mm long, 4-5 mm wide, nerved adaxially, with 3 or 4 broadly rounded lobes, each staminate flower with 1 bracteole on outer side, this 1-1.5 mm long; staminate flowers in bud just prior to anthesis 11x5 mm, bullet-shaped, opening to 15 mm wide; calyx cupular, 2.5-3x5 mm, sepals 3x5 mm, cupular, imbricate nearly to truncate apex; petals 9x4.5 mm, valvate, acute, petals and sepals densely covered with silvery tan to reddish brown tomentum; stamens ca. 50, 6-7 mm long, adnate to base of pistil and slightly above it, filaments 4 mm long, anthers 3 mm long, dorsifixed just below middle; pistillode to 6 mm long, style slender; pistillate flowers 10x8 mm, densely covered with silvery tan to reddish brown tomentum; calyx 5x8 mm, triangular-cupular, sepals cupular, broadly rounded and imbricate nearly to apex, faintly nerved adaxially, the 3 sepals of unequal sizes and successively and progressively more cupular, smallest 5x5 mm and semi-cupular, middle 6x6 mm, largest 6x7 mm and strongly cupular; petals 9x5 mm, boat-like with short, acute, mucronate apex, densely nerved; pistil 9x4 mm, spindleshaped to club-like, perched on 3 mm tall dark stalk, apex trifid, blunt; staminodes lacking or few and tooth-like, 1 mm long, or connate in a ring nearly encircling pistil. Fruit 4.0-4.2x1.6-1.7 cm, ellipsoid-ovoid, orange-red; fruiting perianth 1.0-1.2 cm long; endocarp 3.8-4.0x1.5 cm, with 4 prominent, sharp, longitudinal ridges and a rostrum 1 cm long. (Hodel, D.R., A synopsis of the genus Balaka in Palms (1999+) 54(4). 2010)B

Materials Examined

  • Fiji. Viti Levu. Namosi Prov.: 9 km northwest of Queen?s Highway inland toward Waisoi [along Namosi Road], Nabukavesi Creek drainage, alt. 200 m, 1 February 1996, Fuller et al. 315 (holotype CAS!, isotype SUVA!). (Hodel, D.R., A synopsis of the genus Balaka in Palms (1999+) 54(4). 2010)B
  • Fiji. Viti Levu. Namosi Prov.: 9 kms northwest of Queen's Highway inland toward Waisoi [along Namosi Road], Nabukavesi Creek drainage, 200 m, Fuller 314 (CAS), 330 (SUVA). Serua Prov.: Nabukavesi, Damanu D94 (SUVA). (Hodel, D.R., A synopsis of the genus Balaka in Palms (1999+) 54(4). 2010)B

Bibliography

A. World Checklist of Arecaceae
B. Hodel, D.R., A synopsis of the genus Balaka in Palms (1999+) 54(4). 2010