Geonoma interrupta (Ruíz & Pavón) Martius (1823: 8)

Henderson, Andrew, 2011, A revision of Geonoma (Arecaceae), Phytotaxa 17, pp. 1-271 : 81-82

29. Geonoma interrupta (Ruíz & Pavón) Martius (1823: 8) . Martinezia interrupta Ruíz & Pavón (1798: 296) . Type: PERU. Huánuco: between Pozuzo and Cuchero, November 1820, J. Pavón s.n. (holotype MA n.v., holotype image!, isotypes K!, M!, MO!).

Plants 3.7(1.0–8.0) m tall; stems 3.2(0.3–8.0) m tall, 3.7(2.6–5.0) cm in diameter, solitary, not cane-like or cane-like; internodes 1.5(0.8–2.8) cm long, yellowish and smooth. Leaves 13(8–24) per stem, irregularly pinnate, not plicate, bases of blades running diagonally into the rachis; sheaths 28.7(15.0–60.5) cm long; petioles 63.4(9.0–110.0) cm long, drying green or yellowish; rachis 129.6(55.0–200.0) cm long, 8.7(3.8–16.0) mm in diameter; veins raised and rectangular in cross-section adaxially; pinnae 18(4–47) per side of rachis; basal pinna 47.4(23.5–75.5) cm long, 5.7(0.2–27.0) cm wide, forming an angle of 43(24–60)° with the rachis; apical pinna 40.3(23.0–65.5) cm long, 20.3(0.4–39.0) cm wide, forming an angle of 29(14–40)° with the rachis. Inflorescences branched 2–4 orders; prophylls and peduncular bracts not ribbed with elongate, unbranched fibers, flattened, deciduous or persistent; prophylls 20.1(11.5–40.0) cm long, not short and asymmetrically apiculate, the surfaces ridged and densely tomentose with widely to closely spaced ridges, the ridges unequally wide, often dividing from and rejoining other ridges, the prophyll margins with irregular, spine-like projections, the prophylls usually splitting irregularly between the ridges; peduncular bracts 17.8(10.5–25.5) cm long, well-developed, inserted 4.1(1.0–8.0) cm above the prophyll; peduncle 22.7(7.0– 34.0) cm long, 13.6(2.5–20.1) mm in diameter; rachillae 71(22–120), 19.1(9.2–29.7) cm long, 2.3(1.3–3.4) mm in diameter, the surfaces without spiky, fibrous projections or ridges, drying brown, with faint to pronounced, short, transverse ridges, not filiform and not narrowed between the flower pits; flower pits spirally arranged, densely hairy internally distally only (rarely some hairs on lateral) margins of the pits; proximal lips without a central notch before anthesis, not recurved after anthesis, hood-shaped at anthesis, sometimes splitting post-anthesis; 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 absent; staminate and pistillate petals not emergent, not valvate throughout; staminate flowers deciduous after anthesis; stamens 6; thecae diverging at anthesis, inserted almost directly onto the filament apices, the connectives bifid but scarcely developed; anthers short and curled over at anthesis; non-fertilized pistillate flowers persistent or deciduous after anthesis; staminodial tubes crenulate or shallowly lobed at the apex; staminodial tubes of nonfertilized pistillate flowers not projecting and persistent after anthesis; fruits 5.8(4.4–7.5) mm long, 4.6(3.6– 6.3) mm in diameter, the bases without a prominent stipe, the apices not conical, the surfaces not splitting at maturity, without fibers emerging, bumpy from the numerous, subepidermal, tangential, short fibers present, these coming to a point at fruit apices; locular epidermis without operculum, sculpted, usually also with a raised, meridional ridge, without pores.

Taxonomic notes:— Geonoma interrupta is a member of a group of species characterized by its lack of a distal lip of the flower pit and flower pits hairy internally. This group, the G. interrupta clade, also includes G. euspatha , G. frontinensis , G. pinnatifrons , and G. simplicifrons . These species have had a checkered taxonomic history. Geonoma interrupta has been treated in a broad (e.g., Henderson et al., 1995) or narrower sense ( Wessels Boer, 1968). Geonoma interrupta differs from G. euspatha , G. frontinensis , and G. simplicifrons in its prophyll surfaces with unequally wide ridges, and from G. pinnatifrons in its flower pits which are densely hairy internally distally only.

Wessels Boer (1968) used rachillae hairs to distinguish G. interrupta from G. pinnatifrons . This was refined somewhat by Hammel et al. (2003) who described G. interrupta as having hairs to ca. 0.15 mm long with at least some branched, and G. pinnatifrons (as G. oxycarpa ) as having unbranched hairs 0.1–0.5 mm long. As stated in the Materials and Methods section, rachillae hairs are not used in the present study because potential states can not be scored unequivocally and hairs are early deciduous. However, G. interrupta and G. pinnatifrons can be distinguished by rachillae hairs if rachillae at an early stage are present.

Subspecific variation:— Two traits vary within this species (stem type, pistillate flower persistence). Excluding stem type, for which there are few data, state distributions of the remaining trait (pistillate flower persistence) divide the specimens into two subgroups. Within each subgroup there is geographic discontinuity.

The first subgroup, with persistent pistillate flowers, occurs in the Andes in Colombia, and plants are reported to be rheophytes. This subgroup is recognized as a subspecies ( subsp. rivalis ).

The second subgroup, with deciduous pistillate flowers, has several gaps in its distribution, and there are several potential geographic subgroups. There is considerable variation in several variables (number of pinnae, prophyll length, peduncular bract length, interbract distance) and combining these with geographic division, three subgroups can be recognized: Central America and Colombia (with longer bracts and more pinnae); Ecuador, Peru, and Bolivia (shorter bracts and fewer pinnae); and Venezuela and just reaching adjacent Colombia (longer bracts and fewer pinnae). ANOVA shows that for pair wise comparison probabilities, seven variables (stem height, sheath length, rachis length, number of pinnae, prophyll length, peduncular bract length, interbract distance) differ significantly (P <0.05) between one pair of groups, although no variable differs amongst all three groups. Based on these results and geographic discontinuity, the three subgroups are recognized as subspecies ( subsp. magnifica from Central America and Colombia, subsp. interrupta from Ecuador, Peru, and Bolivia, and subsp. purdieana from Venezuela and adjacent Colombia).

Key to the subspecies of Geonoma interrupta

1 Non-fertilized pistillate flowers persistent after anthesis; rheophytes; Central Cordillera in Colombia... subsp. rivalis

- Non-fertilized pistillate flowers deciduous after anthesis; non-rheophytes; widespread ............................................ 2

2 Pinnae 25(4–47) per side of rachis; Mexico, Belize, Guatemala, Honduras, Nicaragua, Costa Rica, Panama, and Colombia.............................................................................................................................................. subsp. magnifica

- Pinnae 9(4–14) per side of rachis; Venezuela and adjacent Colombia, Ecuador, Peru, and Bolivia............................ 3

3 Peduncular bracts inserted 3.0(1.2–8.0) cm above the prophyll; Ecuador, Peru, and Bolivia............ subsp. interrupta

- Peduncular bracts inserted 7.1(6.5–7.5) cm above the prophyll; Venezuela and adjacent Colombia subsp. purdieana