Geonoma brongniartii subsp. brongniartii

Henderson, Andrew, 2011, A revision of Geonoma (Arecaceae), Phytotaxa 17, pp. 1-271 : 43-44

6a. Geonoma brongniartii subsp. brongniartii

Geonoma metensis Karsten (1856: 409) . Type: COLOMBIA. Meta: Villavicencio, no date, H. Karsten s.n. (holotype LE n.v.).

Geonoma cuneifolia Burret (1931a: 199) . Type: PERU. Loreto: Río Ucayali, 215 m, 17 November 1923, G. Tessmann 3317 (holotype B, destroyed, isotype NY!).

Leaves veins raised and rectangular in cross-section adaxially or not raised or slightly raised and triangular in cross-section adaxially. Inflorescences unbranched; fruits 6.9(5.3–8.3) mm long, 5.8(4.9–6.5) mm in diameter.

Distribution and habitat:— From 7°14’N– 17°50’S and 63°39’– 77°20’W in the western Amazon and sub-Andean regions of Ecuador, Peru, Bolivia, and Brazil, with an outlier in Venezuela, at 373(75–1720) m elevation, often in low-lying, flooded areas, in lowland or, less often, montane rainforest ( Fig. 10 ).

In southern Colombia and Ecuador, specimens are relatively uniform and have pinnate leaves, raised adaxial veins, more pinnae than usual, and slender rachillae. There is an absence of specimens from southeastern Ecuador and adjacent Peru. In this area, Geonoma macrostachys is abundant.

In northeastern Peru (Loreto) and adjacent Colombia and Brazil, specimens are similar to those from southern Colombia and Ecuador, except pinnae are fewer and some leaves undivided, and rachillae larger. Some specimens are considerably larger than others (e.g., Vásquez 9744). Geonoma brongniartii is again absent from southwest of Iquitos, where G. macrostachys is abundant.

In these northern populations, in Colombia, Ecuador, northeastern Peru and adjacent Brazil, there is geographical variation. Regression shows there are significant associations between longitude and eight leaf variables. Squared multiple R for the regression of petiole length on longitude is 0.58, number of pinnae 0.24, basal pinna length 0.50, basal pinna width 0.29, basal pinna angle 0.34, apical pinna length 0.20, apical pinna width 0.17, and apical pinna angle 0.50. There is a change in leaf shape, from specimens in the east having shorter petioles and fewer, wider and longer pinnae with narrower angles to those in the west having longer petioles, more, narrower and shorter pinnae with wider angles.

In Brazil (Acre) and adjacent Peru most specimens are relatively uniform. There are some specimens (e.g., Daly 10582, 10947) with thicker rachillae and the flower pits arranged in closer spirals, as in central Peru (see below).

There is extreme variation in central Peru on eastern Andean slopes and adjacent areas. In Ayacucho, Huánuco, Pasco, San Martín, and Ucayali some specimens have larger leaves and longer, thicker rachillae along which the flower pits are wider and are arranged in closer spirals (large-sized morphotype). These larger-sized specimens sometimes occur together with the more usual-sized specimens. Some resemble G. poeppigiana and two (Schunke 16280, 9912) have bracts more like those of G. poeppigiana ), and may be hybrids with that species.

Two other specimens (Foster 7846, Roncal 182) from Pasco have longer stems. One (Foster 7846) has a stem that is reported to be 2–3 m tall, and the other (Roncal 182) has cane-like stems with the internodes longer than wide. Both have short inflorescences, and in Roncal 182 they appear to be pendulous. One other specimen (Smith 3849) appears similar. These occur near to an isolated population of Geonoma deversa subsp. deversa , killipii morphotype, and it is possible they represent hybrids with that morphotype. These and other possible hybrids are excluded from the above description.

In San Martín, one specimen (Schunke 8080) has the shortest prophyll (5.7) cm and interbract distance (0.5 cm) of all specimens, and the adaxial veins are not raised. It occurs sympatrically with another isolated population of G. deversa subsp deversa , and may also be a hybrid.

One specimen from Huánuco (Moore 8355), with branched inflorescences, has unusually short rachillae and comes from an unusually high elevation (1575 m). It may be a hybrid.

Most specimens from southern Peru (Cusco, Madre de Dios, Puno) and Bolivia have non-raised adaxial veins, and thin, elongate rachillae along which the pits may be tricussately arranged, especially in the central part of the rachilla. A few specimens from northern Bolivia ( Moreno 124, Fuentes 3911, Macia 3986, Beck 18258, Croat 51638, Beck 16466, Williams 941, Williams 939) and southern Peru (Foster 9721, 9576) have thicker rachillae and the flower pits arranged in closer spirals, as found in the large central Peruvian specimens. A few specimens ( Moreno 227, Gerlach 214, Foster 13393, Hodge 6079, Plowman 5062) from southern Peru and Bolivia have exceptionally long interbract distances (10.3–18.5 cm).

There is variation in connectives in this species. Specimens are scored as having the thecae inserted almost directly onto the filament apices, the connectives bifid but scarcely developed. However, in some specimens the connectives appear not to be bifid, and are similar to those of G. macrostachys .

Figures

FIGURE 10. Distribution maps of Geonoma braunii, G. brenesii, G. brongniartii subsp. brongniartii, and G. brongniartii subsp. pascoensis.