Acrocomia Mart., Hist. Nat. Palm. 2: 66 (1824)

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Distribution

Map uses TDWG level 3 distributions (http://www.nhm.ac.uk/hosted_sites/tdwg/geogrphy.html)

About 34 species have been described, but there are probably far fewer, distributed throughout the West Indies and from Mexico southwards to Argentina. Henderson et al. (1995) accept just two species, Acrocomia aculeata and A. hassleri and Gastrococos crispa (now Acrocomia crispa) however, this may be too sweeping a synonymy. (J. Dransfield & N. Uhl & C. Asmussen & W.J. Baker & M. Harley & C. Lewis, Genera Palmarum. The evolution and classification of palms. 2008)A

Discussion

Diagnosis

Biology And Ecology

Common Name

Etymology

Uses

Description

  • Dwarf to large, solitary, spiny, pleonanthic, monoecious palms. Stem very short, subterranean and geotropic, or erect, columnar or sometimes swollen and spindle-shaped, covered in persistent leaf bases and eventually becoming bare, or armed heavily with spines at first, soon becoming bare, eventually smooth, ringed with leaf scars. Leaves few to numerous, pinnate, marcescent or abscising neatly; sheath disintegrating into a mass of fibres, usually both spiny and finely bristly; petiole short or ± absent, adaxially channelled, abaxially rounded, usually spiny and finely bristly, often with tomentum; rachis usually curved, armed with robust spines, especially along the margins, adaxially channelled near the base, angled distally, abaxially angled or rounded; leaflets numerous, single-fold, linear, acute or shallowly bifid, sometimes plicate, subregularly arranged (rarely) or grouped, usually held in different planes giving the leaf a plumose appearance, usually coriaceous, acute or briefly bifid, adaxially usually glabrous, abaxially glabrous, glaucous or pubescent, transverse veinlets obscure. Inflorescences axillary, interfoliar, shorter than the leaves, arching or becoming pendulous, apparently protandrous, branching to 1 order; peduncle ± oval in cross-section, often elongate, spiny and/or tomentose, rarely unarmed; prophyll tubular, 2-keeled, closely sheathing, usually remaining ± hidden within the leaf sheaths, soon tattering and splitting irregularly, glabrous or densely shaggy hairy, sometimes also spiny; peduncular bract inserted near the prophyll, much larger than the prophyll, persistent, tubular, enclosing the rachillae in bud, strongly beaked, woody, splitting along the abaxial face, then expanded or ± cowl-like, abaxial surface densely shaggy tomentose, and often sparsely to densely spiny, spines sometimes restricted to near the beak, adaxial surface glabrous, often conspicuously pale yellow; rachis longer or shorter than the peduncle, variously spiny, tomentose, or glabrous, bearing few to numerous, spirally arranged rachillae, each subtended by a short triangular bract; rachillae short to elongate, straight or somewhat flexuous, often with a pulvinus (?nectariferous) at the base, usually cream-coloured or yellowish, with a very short to long basal, bare portion, then bearing 1–several, rather distant spirally arranged triads, distal to these a few pairs of staminate flowers, in the distal portion bearing dense spirals of solitary staminate flowers, each flower group subtended by a short-triangular bract, those subtending the staminate flowers forming shallow pits; floral bracteoles small, mostly obscured within the pits. Staminate flowers creamy yellow, usually rather strongly earthy smelling, symmetrical or somewhat asymmetrical, those of the triads briefly stalked, those of distal portion of rachillae sessile; sepals 3, distinct or connate, small, narrow to broadly triangular, sometimes irregularly ciliate; petals 3, distinct except at the very base, much longer than the sepals, ± boat-shaped, ± fleshy, valvate; stamens 6, filaments distinct or briefly adnate to the base of the petals, elongate, inflexed at the tip, anthers ± rectangular, dorsifixed or medifixed, latrorse; pistillode small, trifid. Pollen oblate triangular, occasionally oblate square, usually symmetric; aperture a distal trichotomosulcus or occasionally a tetrachotomosulcus; ectexine semi-tectate or tectate, coarsely perforate, perforations widely separated and indented, or finely reticulate, aperture margin may be slightly finer; infratectum columellate; longest axis 37–62 µm [3/3]. Pistillate flowers larger than the staminate, conic-ovoid; sepals 3, distinct, ± imbricate, broadly triangular or connate in a 3-lobed cupule; petals much longer than the sepals, 3, ± distinct except sometimes near the base, or connate, always with broad, imbricate, distinct margins, except for valvate tips; staminodes 6, united to form a staminodal ring, free, or briefly adnate to the petals, 6-toothed, usually bearing well-developed but empty rounded anthers; gynoecium irregularly ovoid, trilocular, triovulate, variously scaly or tomentose, stigmas 3, fleshy, conspicuous, sometimes violet in colour, reflexed beyond the petals at maturity, ovule laterally attached, orthotropous. Fruit usually 1-seeded, globose, or rarely somewhat pyriform, olive-green to yellow-brown, the stigmatic remains apical; epicarp smooth, or tomentose-bristly, mesocarp fleshy, with abundant short fibres adnate to the endocarp; endocarp very thick, stony, sometimes pitted, dark brown, with 3 pores ± at the equator. Seed basally attached, endosperm homogeneous, sometimes with a central hollow; embryo lateral opposite one of the pores. Germination adjacent-ligular; eophyll not recorded. Cytology: 2n = 30. (J. Dransfield & N. Uhl & C. Asmussen & W.J. Baker & M. Harley & C. Lewis, Genera Palmarum. The evolution and classification of palms. 2008)A

Fossil record

  • A fruit (Palmocarpon acrocomioides) recorded from the Middle Oligocene of Puerto Rico is compared with Acrocomia crispa (Hollick 1928). Two monosulcate palm pollen types are recovered from the Pliocene, Gatun Lake Formation, Panama (Graham 1991). The first of these types, asymmetrical and scabrate tectate, is a very common arecoid pollen type and difficult to place. It has been compared with pollen of Aiphanes, Manicaria, Reinhardtia or, possibly, a “monocolpate form” of Acrocomia. However, pollen of Acrocomia is always trichotomosulcate; Reinhardtia is the most probable comparison. (J. Dransfield & N. Uhl & C. Asmussen & W.J. Baker & M. Harley & C. Lewis, Genera Palmarum. The evolution and classification of palms. 2008)A

Relationships

  • Acrocomia is resolved as monophyletic, mostly with high support (Hahn 2002b, Gunn 2004, Asmussen et al. 2006, Baker et al. in review). Although several studies have explored the relationships between the five genera of Bactridinae (Hahn 2002b, Gunn 2004, Asmussen et al. 2006, Couvreur et al. 2007, Baker et al. in review), much conflict and ambiguity remains. Only one relationship, placing Acrocomia as sister to the remaining Bactridinae, is highly supported (Hahn 2002b, Baker et al. in review). Two studies provide moderate support for a sister relationship between Astrocaryum and Bactris (Gunn 2004, Baker et al. in review), but this is contradicted by Hahn (2002b) who resolves Bactris as sister to Desmoncus. Hahn (2002b) also places Aiphanes as sister to the Bactris–Desmoncus clade with moderate support. A number of other relationships among genera of Bactridinae have been recovered, but these are not supported by bootstrap analysis. (J. Dransfield & N. Uhl & C. Asmussen & W.J. Baker & M. Harley & C. Lewis, Genera Palmarum. The evolution and classification of palms. 2008)A

Taxonomic accounts