Geonoma maxima (Poiteau) Kunth (1841: 229)

Henderson, Andrew, 2011, A revision of Geonoma (Arecaceae), Phytotaxa 17, pp. 1-271 : 96-97

37. Geonoma maxima (Poiteau) Kunth (1841: 229) . Gynestum maximum Poiteau (1822: 388) . Type: FRENCH GUIANA. Without locality, no date, A. Poiteau s.n. (holotype P!).

Plants 3.2(1.0–9.0) m tall; stems 2.9(1.0–7.0) m tall, 1.2(0.5–2.3) cm in diameter, solitary or clustered, canelike; internodes 2.4(0.5–8.7) cm long, yellowish and smooth. Leaves 9(4–19) per stem, undivided or irregularly pinnate, if regularly pinnate the pinnae with 1 main vein only (rarely with several lateral veins), not plicate or plicate, bases of blades running diagonally into the rachis; sheaths 12.6(4.0–30.0) cm long; petioles 34.6(1.0–100.0) cm long, drying green or yellowish; rachis 44.0(7.3–120.0) cm long, 3.6(1.4–7.1) mm in diameter; veins raised and rectangular in cross-section adaxially; pinnae 8(1–31) per side of rachis; basal pinna 43.2(8.2–132.0) cm long, 3.9(0.1–34.0) cm wide, forming an angle of 47(7–87)° with the rachis; apical pinna 32.8(8.5–86.0) cm long, 9.6(0.2–42.5) cm wide, forming an angle of 23(7–42)° with the rachis. Inflorescences branched 1–3 orders; prophylls and peduncular bracts not ribbed with elongate, unbranched fibers, flattened, deciduous or persistent; prophylls 10.6(3.7–21.8) cm long, not short and asymmetrically apiculate, the surfaces not ridged, without unequally wide ridges; peduncular bracts 8.7(4.7–13.0) cm long, well-developed, inserted 0.6(0.2–3.0) cm above the prophyll; peduncles 8.2(3.2–19.5) cm long, 4.9(1.5–10.0) mm in diameter; rachillae 19(4–50), 11.4(4.8–24.3) cm long, 2.7(0.7–6.0) mm in diameter, the surfaces without spiky, fibrous projections or ridges, drying brown or yellow-brown, without short, transverse ridges, not filiform and not narrowed between the flower pits; flower pits spirally arranged, glabrous internally; proximal lips with a central notch before anthesis, often the two sides of the notch overlapping, not recurved after anthesis, not hood-shaped; proximal and distal lips drying the same color as the rachillae, not joined to form a raised cupule, the proximal lip margins overlapping the distal lip margins; distal lips well-developed; staminate and pistillate petals not emergent, not valvate throughout; staminate flowers deciduous after anthesis; stamens 6; thecae diverging at anthesis, inserted directly onto the apiculate filament apices; anthers not short and curled at anthesis, usually elongate, spiraled and twisted or sometimes remaining straight; nonfertilized pistillate flowers deciduous after anthesis; staminodial tubes lobed at the apex, the lobes spreading at anthesis, acuminate, those of non-fertilized pistillate flowers not projecting and persistent after anthesis; fruits 11.8(6.9–18.2) mm long, 9.0(5.5–13.0) mm in diameter, apices not conical, the surfaces not splitting at maturity, without fibers emerging, not bumpy, not apiculate; locular epidermis without operculum, smooth, without pores.

Taxonomic notes:— Geonoma maxima is a member of the G. macrostachys clade, differing from all other species in its locular epidermis without an operculum. It also has more branched inflorescences (4–50 rachillae) compared to the rest of the clade (1–9 rachillae). It is another variable species which has been treated differently by Wessels Boer (1968) and Henderson et al. (1995). Unlike other species complexes, for example G. macrostachys , G. maxima exhibits rather well–defined geographic disjunction and morphological variation, allowing for recognition of various subspecies, as explained below.

Subspecific variation:— Four traits vary within this species (stem branching, leaf division, leaf plication, pistillate flower persistence). There are very few data for stem branching, and this and leaf division are excluded from the following analyses. Leaf plication and pistillate flower persistence divide the specimens into three groups. However, leaf plication is difficult to score in this species and specimens with persistent pistillate flowers may be of hybrid origin (see below). Furthermore, there is no geographic separation between these groups. Geonoma maxima is widespread across the Amazon region, and there are isolated populations in the Magdalena valley and Pacific coast of Colombia and eastern Andean slopes in Venezuela.

Apart from traits, one attribute (leaf division) divides the specimens into two groups. Leaves of one group are regularly pinnate and the pinnae (at least those from the middle part of the leaf) have several main veins, usually three to five. In the second group, all specimens have either undivided leaves, irregularly pinnate leaves (sometimes with 1-veined pinnae present), or leaves with 1-veined pinnae (at least those from the middle part of the leaf).

The first group — with regularly pinnate leaves with 3–5-veined pinnae — can be divided into four separate subgroups based partly on geography and partly on variables. ANOVA shows that for pair wise comparison probabilities, 18 variables (plant height, stem diameter, internode length, petiole length, rachis length, rachis width, basal pinna length, basal pinna width, apical pinna length, apical pinna angle, prophyll length, interbract distance, peduncle length, peduncle width, rachilla length, rachilla width, number of rachillae, fruit diameter) differ significantly (P <0.05) between at least one pair of subgroups, although no variable differs amongst all four subgroups. Based on these results and geography, these four subgroups are recognized as subspecies (subspp. hexasticha , maxima , multiramosa, sigmoidea).

The second group — with leaves undivided, irregularly pinnate (sometimes with 1-veined pinnae present), or regularly pinnate with 1-veined pinnae — can be divided into six separate subgroups based partly on geography, partly on variables, and on one trait (leaf plication). ANOVA shows that for pair wise comparison probabilities, 22 variables (plant height, stem diameter, leaf number, petiole length, rachis length, rachis width, number of pinnae, basal pinna length, basal pinna width, basal pinna angle, apical pinna length, apical pinna width, apical pinna angle, prophyll length, interbract distance, peduncle length, peduncle width, rachilla length, rachilla width, number of rachillae, fruit length, fruit diameter) differ significantly (P <0.05) between at least one pair of subgroups, although no variable differs amongst all six subgroups. Based on these results and geography, these six subgroups are recognized as subspecies (subspp. ambigua , chelidonura , camptoneura , compta, dispersa, spixiana ).

Key to the subspecies of G. maxima

1 Prophylls 5.6(3.7–7.0) cm long; north of the Amazon region on the Pacific coast and Magdalena valley in Colombia, and eastern Andean slopes in Venezuela................................................................................................ subsp. dispersa

- Prophylls 10.9(4.0–21.8) cm long; Amazon region...................................................................................................... 2

2 Leaves regularly pinnate with 3–5-veined pinnae (except for basal and apical ones); rachis 68.4(25.5–120.0) cm long; pinnae 19(4–31) per side of rachis ..................................................................................................................... 3

- Leaves undivided, irregularly pinnate (sometimes with 1-veined pinnae present), or regularly pinnate with 1-veined pinnae; rachis 36.6(7.3–98.0) cm long; pinnae 5(1–29) per side of rachis................................................................... 6

3 Rachillae 36(21–47); Amazonian Ecuador and adjacent Colombia (Caquetá, Putumayo) and Peru (Loreto) .............. ........................................................................................................................................................ subsp. multiramosa

- Rachillae 21(6–50); Amazonian Colombia, Venezuela, Peru, Brazil, Bolivia, and the Guianas ................................. 4

4 Rachillae 28(16–42), 1.0(0.7–1.2) mm in diameter; Amazonian Colombia (Amazonas, Caquetá).. subsp. sigmoidea

- Rachillae 21(6–50), 2.5(1.5–3.6) mm in diameter; Amazonian Colombia (Guainia), Venezuela, Brazil, Bolivia, and the Guianas................................................................................................................................................................... 5

5 Rachillae 13(6–25); southern Venezuela and adjacent Colombia (Guainia) and Brazil (Amazonas) ............................ ............................................................................................................................................................ subsp. hexasticha

- Rachillae 31(9–50); central and eastern Amazon region of Brazil and the Guianas .............................. subsp. m axima

6 Leaves regularly pinnate with 1-veined pinnae; rachis 44.5(11.0–87.0) cm long; basal pinna 0.3(0.1–0.5) cm wide; mostly south or west of the Amazon in Colombia, Brazil, Peru, and Bolivia........................................ subsp. compta

- Leaves undivided or irregularly pinnate (sometimes with 1-veined pinnae present); rachis 35.6(7.3–98.0) cm long; basal pinna 6.1(0.2–34.0) cm wide; widespread .......................................................................................................... 7

7 Leaves plicate; basal pinna forming an angle of 13(4–20)° with the rachis; central–western Amazon region of Brazil and adjacent Colombia.......................................................................................................................... subsp. spixiana

- Leaves not plicate; basal pinna forming an angle of 41(10–87)° with the rachis ........................................................ 8

8 Rachis 51.9(38.0–70.0) cm long; western Amazonian Brazil (Acre), Peru, and Bolivia.............. subsp. camptoneura

- Rachis 28.4(7.3–63.0) cm long; central-western Amazon region of Brazil and adjacent Colombia, Peru, and Bolivia, and the Guianas ............................................................................................................................................................ 9

9 Rachis 40.0(13.0–59.0) cm long; Guyana and adjacent Venezuela and Brazil..................................... subsp. ambigua

- Rachis 25.0(7.3–63.0) cm long; central-western Amazon region of Venezuela, Colombia, Brazil, Peru, and Bolivia. .......................................................................................................................................................... subsp. chelidonura