Synechanthus dasystachys

Synechanthus (sihn-eh-KAHN-tuhs) dasystachys (dah-sis-TAH-kiss)
Photo: Michael H. Grayum, Christel Ramos, Irving Vergara-Pérez & Luis Rojas.
Scientific Classification
Genus: Synechanthus (sihn-eh-KAHN-tuhs) Species: dasystachys (dah-sis-TAH-kiss)
Synonyms
None set.
Native Continent
America
Morphology
Habit: Clustering (soboliferous), (rarely) solitary Leaf type: Simple bifid
Culture
Survivability index
Common names
None.

Habitat and Distribution

Westernmost Colón Province, Panama. on the site of a large copper-mining concession currently administered by Minera Panamá S. A. This area, ranging in elevation from sea level to 431 m, has proved to harbor a unique flora that, since 2009, has yielded more than 20 previously undescribed species of vascular plants (De Gracia et al., in press), as well as numerous country records and other range extensions. The palm flora in this region of Tropical Wet Forest (Holdridge et al. 1971) on the Atlantic slope is particularly diverse. An unpublished, largely vouchered list we maintain for the coppermining site enumerates 45 palm species, including two in the genus Synechanthus: S. warscewiczianus H. Wendl., a common species ranging from Nicaragua to Ecuador, and the species described here as new, which seems to be a local endemic. The most recent revision of Synechanthus (Moore 1971) recognized just two species, S. warscewiczianus and the more northerly S. fibrosus (H. Wendl.) H. Wendl. The latter ranges from southern Mexico to westernmost Panama (Prov. Bocas del Toro), where it has been collected just once (Santamaría et al. 7769; CR, MO, PMA). We believe this to be the first reliable report of S. fibrosus from Panama. No new taxa have been described in Synechanthus since the publication of the aforementioned revision, so the genus is relatively easy to comprehend taxonomically. Synechanthus is broadly characterized morphologically among New World palms by its understory habit, leaflets acute to acuminate at the apex, inflorescences with four or five peduncular bracts, unisexual flowers borne in lines (acervuli) on the inflorescence rachillae, with the proximal flower of each acervulus pistillate and all the distal ones staminate (i.e., the plants are monoecious), sepals connate in a trilobed calyx in the flowers of both sexes, red or reddish, smooth ripe fruits, and seeds with ruminate endosperm. (Dr's MICHAEL H. GRAYUM Missouri Botanical Garden & JOSÉ DE GRACIA Minera Panamá S.A. Torre de Las Américas Torre A, Piso 21 Punta Pacífica, Panama City Republic of Panama.)

A single plant of the new species described in this

Photo: Michael H. Grayum, Christel Ramos, Irving Vergara-Pérez & Luis Rojas.

paper was encountered by the first author

in the Donoso region in 2014, and a collection including both flowering and fruiting rachillae was prepared. Although grossly resembling certain species of the dioecious genus Chamaedorea, this individual exhibited both apparent stamens and mature fruits, suggesting monoecy and a closer affinity with Synechanthus. We knew at once that, if this were indeed a Synechanthus, it had to be an undescribed species, but we were unable to confirm our suspicions in the field. However, subsequent critical examination of this and additional material obtained in the same region have removed all doubt. Differs from the other members of the genus by its consistently simple leaves and unbranched (spicate) inflorescences, with the rachis pilosulous and the acervuli densely disposed all around it. The new species is endemic to Panama and known by just six collections, all from the Distrito de Donoso, Provincia de Colón, in lowland tropical rainforest at elevations below 300 m (91– 294 m). We estimate that only about 30 individuals have been located in the wild to date. Plants have been found with both flowers and fruits in March, September, and December. (Dr's MICHAEL H. GRAYUM Missouri Botanical Garden & JOSÉ DE GRACIA Minera Panamá S.A. Torre de Las Américas Torre A, Piso 21 Punta Pacífica, Panama City Republic of Panama.)

Description

Synechanthus dasystachys. Stem cespitose or (rarely) solitary, procumbent to erect, 0.5–1.5 (–2.0?) m tall, 2–3 cm diam., brown, smooth, ringed. Leaves 5–10, simple; sheath 15–30 cm long; petiole green, 35–60 cm long, about 1 cm diam., sulcate adaxially; blade 45–85 × 15–30 cm, narrowly obovate, bifid (divided, about 1/4– 1/2 to the base), the distal lobes acuminate at apex, with 15–20 primary lateral veins per side. Inflorescences 2–5 per plant, infrafoliar, simple, bisexual; prophyll about 2 cm long, tubular, bicarinate; peduncle 24–37 cm long; peduncular bracts 5, 2–10 cm (the proximal 3) or 15–30 cm (the distal 2) long, fibrous; rachis 10–24 cm × 1.5–3.5 mm, acutely angled to narrowly winged longitudinally, pilosulous with uniseriate trichomes to about 0.3(–0.4) mm long, with lines of flowers (acervuli) distributed all around the circumference. Flowers cream-colored; staminate flowers (5) 6 or 7 (–10) in each acervulus, biseriate, about 1.5–2.0 mm tall, turbinate and ± strongly trigonous in bud, maturing basipetally; calyx deeply trilobed, the lobes about 1 × 1 mm, ovate to triangular, acute at the apex, weakly if at all nerved (when dried); petals 3, valvate, apparently connate basally, about 1.5 × 2.0 mm, broadly rhombic, subacute at the apex, strongly nerved (when dried); stamens 3, the filaments 2–3 mm long, inflexed distally in bud, long-exserted at anthesis, the anthers basifixed, about 1 mm long; pistillode absent (or not clearly evident); pistillate flower 1 and proximal in each acervulus, about 1.5– 2.2 mm tall, subhemispherical and weakly trigonous in bud; calyx shallowly to deeply trilobed, the lobes 0.8–1.0 × about 2.0 mm, transversely rectangular or transversely oblong to semicircular or broadly triangular, subtruncate to broadly rounded at the apex, weakly nerved (when dried); petals 3, imbricate, apparently distinct, 1.5–2.0 × 1.5–3.0 mm, suborbicular and ± cucullate, rounded at the apex, strongly nerved (when dried); staminodes evident in all flowers examined, to at least 4, adnate to the petals, sometimes at least partly connate in a low ring basally, minute to about 0.5 mm long, rimlike to dentiform; stigmas 3, short, recurved. Fruits green to yellow or orange to red, 1.8–2.0 × 0.8–1.0 cm, narrowly oblongoid or ellipsoid to obovoid, smooth, glabrous, with basal stigmatic residue. Seed dark brown, about 15 × 6 mm, with ruminate endosperm. Germination and eophylls unknown. (Dr's MICHAEL H. GRAYUM Missouri Botanical Garden & JOSÉ DE GRACIA Minera Panamá S.A. Torre de Las Américas Torre A, Piso 21 Punta Pacífica, Panama City Republic of Panama.) Editing by edric.

Synechanthus dasystachys bears a strong superficial resemblance to various simple-leaved species of Chamaedorea Willd. (see, e.g., Hodel 1992), from which it may be distinguished by its monoecious (rather than dioecious) sexuality, with staminate and pistillate flowers borne together in lines (acervuli) on each inflorescence. In these respects, it accords more closely with Gaussia H. Wendl. (see especially Quero & Read 1986), an oligospecific genus of northern Mesoamerica and the Greater Antilles; however, the new species differs from Gaussia (and finds a home in Synechanthus) by virtue of its understory (vs. arborescent) habit (Dransfield et al. 2008: 370), sepals connate in a trilobed calyx (vs. distinct) in the flowers of both sexes (Henderson 1990: 9), and seeds with ruminate (vs. homogeneous) endosperm (Quero & Read 1986: 150–151). Our own observations confirm the foregoing differences and suggest that Gaussia is also distinct in having pistillate flowers that are smaller than the staminate flowers and with the petals valvate or subvalvate (at least distally), vs. subequal to or slightly larger than the staminate flowers and with the petals imbricate in Synechanthus (including our new species). (Dr's MICHAEL H. GRAYUM Missouri Botanical Garden & JOSÉ DE GRACIA Minera Panamá S.A. Torre de Las Américas Torre A, Piso 21 Punta Pacífica, Panama City Republic of Panama.)

It may seem imprudent of us to be describing a new species in Synechanthus, given the notorious morphological variability of one of the established species, S. warscewiczianus (see, e.g., Moore 1971). Yet, Synechanthus dasystachys differs notably from both of its congeners in having consistently simple, bifid leaves and unbranched (spicate) inflorescences, with the rachis relatively thick and pilosulous and the acervuli disposed comparatively densely (especially proximally) all around it (the flowers of each sex being distinguishable by their slightly different sizes and, especially, shapes and aestivation types). Both of the other species in the genus typically have pinnately compound leaves, but S. warscewiczianus varies remarkably in this regard, and populations with simple leaves have been documented (see, e.g., Grayum 2003: 292); indeed, simple-leaved individuals of S. warscewiczianus apparently occur in the Donoso region, if we may accept the comments of Meerman (2009: 14) associated with his photos labeled "Hyospathe elegans" (but which clearly depict S. warscewiczianus). The two previously recognized species of Synechanthus always have branched inflorescences, so far as we know, typically with 17–75 rachillae. But here again, S. warscewiczianus, as presently circumscribed, is highly variable and populations with reduced numbers of inflorescence rachillae are especially frequent in central Panama, whence specimens with as few as three rachillae have been collected (e.g., Croat 14277, MO; Mori & Kallunki 2730, MO). The rachillae of these aberrant specimens are, however, filiform (ca. 0.8–1.5 mm thick), glabrous, and with distichous acervuli, as typical of S. warscewiczianus but not S. dasystachys; moreover, the specimens in question all have pinnately compound leaves. The new species agrees with S. fibrosus in having relatively few staminate flowers per acervulus, but its individual staminate flowers have just three stamens with the filaments inflexed distally in bud and long-exserted at anthesis, as is characteristic of S. warscewiczianus (see, e.g., Grayum 2003: 290). According to our investigation, the "minutely scaberulous" (Moore 1971: 12, 14) inflorescence rachillae of S. fibrosus often scarcely differ perceptibly from the glabrous or glabrate rachillae of S. warscewiczianus; however, on some specimens of S. fibrosus (e.g., Rivera H. et al. 1234, MO; southern Mexico), this "scaberulous" rachillar indumentum rises nearly to the level of pilosulous or hispidulous (at least on a microscopic level), differing from that of S. dasystachys only by degree (the individual enations or trichomes never attaining even 0.1 mm in S. fibrosus). We carefully considered the possibility that Synechanthus dasystachys might have been described previously in another genus (particularly Chamaedorea) but believe we have falsified that hypothesis to our satisfaction. Once the significance of our discovery was realized, we conducted thorough herbarium searches at MO and PMA for additional material of our new species, not only in the Synechanthus folders but also those for related or superficially similar genera including Chamaedorea, Gaussia, Geonoma Willd., and Hyospathe Mart., as well as palm specimens undetermined to genus. This search (which included South American material) yielded but a single additional specimen of S. dasystachys: McPherson & van der Werff 20004 (MO, PMA), also from the Donoso region, collected during the early stages of the mine-site inventory. Rather embarrassingly, this collection (with immature fruits) had been examined previously by the first author of this paper, who determined it (in 2008) as Chamaedorea deckeriana (Klotzsch) Hemsl.! The last-mentioned species is indeed strikingly similar (especially in fruit) to Synechanthus dasystachys in its gross morphology, and as the latter was not yet known to exist, no genus other than Chamaedorea was considered in identifying this specimen, hence acervuli were not sought (though the scars of the fallen staminate flowers are clearly visible under the dissecting scope, in linear formation). There is also evidence that S. dasystachys was encountered at some point between June 2007 and February 2009 by by J.C. Meerman, an ecologist based in Belize who inventoried palms and cycads at the Donoso mine site during that period. Meerman, with a good general knowledge of Central American palms, produced an illustrated guide for the mine site (Meerman 2009) but prepared no herbarium vouchers (indeed, it was a need for proper palm vouchers that instigated our work). Meerman's photos (2009: 11) labeled "Geonoma cf cuneata" almost certainly depict Synechanthus dasystachys (no Geonoma species known to us has yellow fruits), but in the absence of a voucher, it is impossible to be certain. Likewise unverifiable are Meerman's comments about his "Geonoma cf cuneata," which state that the leaves can "rarely" be pinnate. While such leaf dimorphy has been documented for many palm species (including the real Geonoma cuneata H. Wendl. ex Spruce), none of the specimens of S. dasystachys in our possession has pinnate leaves, and Meerman may have been conflating two or more species in his account. (Dr's MICHAEL H. GRAYUM Missouri Botanical Garden & JOSÉ DE GRACIA Minera Panamá S.A. Torre de Las Américas Torre A, Piso 21 Punta Pacífica, Panama City Republic of Panama.)

Culture

Cold Hardiness Zone: 10a

Comments and Curiosities

Cespitose palms on slope above creek in primary forest, the stems ca. 1 m tall. Leaves 7-8 in crown. Inflorescences infrafoliar, cream-colored (inflorescence apparently in male phase borne on same stem with infructescence). Ripe fruits bright orange.

The epithet of the new species name, a noun used in apposition, reprises the long-abandoned genus name Dasystachys Oerst., established originally (Örsted 1859: 25–26) to accommodate the palm species now known as Chamaedorea deckeriana, to which our new species bears a close superficial resemblance. The literal meaning of the name, from the Greek dasys (= hairy or dense) and stachys (= spike), is also especially apt (in both senses of its first element) for the new species. (Dr's MICHAEL H. GRAYUM Missouri Botanical Garden & JOSÉ DE GRACIA Minera Panamá S.A. Torre de Las Américas Torre A, Piso 21 Punta Pacífica, Panama City Republic of Panama.)