Chamaedorea vanninii Cascante & Muller, 2020

Cascante-Marín, Alfredo & Muller, Fred, 2020, A new species of understory palm of the genus Chamaedorea (Arecaceae: Arecoideae) from Costa Rica, Phytotaxa 436 (1), pp. 79-84 : 80-83

Chamaedorea vanninii Cascante & Muller sp. nov. ( Figs. 1 , 2 )

Diagnosis: — Chamaedorea vanninii is morphologically very similar to C. robertii Hodel & Uhl (1990: 120) from subgenus Chamaedoropsis Oersted (1858: 15) in its simple and bifid leaves and spicate inflorescences in both genders. The new species differs from C. robertii in having conspicuously echinulate-medusoid and orange ripe fruits versus smooth and black purple fruits in the latter species. Also, peduncle bracts in developing pistillate inflorescences of C. vanninii are green as opposed to burgundy in C. robertii . The androecium of staminate flowers of C. vanninii is composed of a single whorl of three stamens.

Type:— COSTA RICA. San José: Copey, Dota. Estribaciones de la Cordillera de Talamanca, región del Pacífico Central , 10 May 2018 (fr.), Cascante-Marín et al. 2761. (holotype: USJ!; isotypes: CR!, MO!) .

Solitary understory palm, stem decumbent, apically erect to 90 cm high (at leaf height). Stem 6–9 mm in diameter, green, ringed, internodes 1.0– 2.5 cm long, developing adventitious roots. Leaves 6–9, blade simple and bifid; sheath 7.5–10.5 cm long, splitting opposite petiole and tubular in proximal 2/3; petiole 12.0–17.5 long, channeled adaxially, rounded abaxially; blade 22.5–32.5 × 15.5–26 cm, incised apically 2/3–1/2 its length, each lobe 14.5–19.5 cm long, tips 16.0– 23.5 cm apart; (10) 12–14 raised and prominent primary nerves on each side of the rachis, margins conspicuously toothed in the distal half. Inflorescences 3–4 per plant, solitary, spicate, becoming infrafoliar with age. Staminate with peduncle to 6.5 cm long; erect-ascending, 3–4 peduncular bracts, green; rachis or flowering portion to 16.5 cm long, pendulous, flowers develop basipetally. Pistillate inflorescence with peduncle to 11.5 cm long; erect-ascending, green but turning orange in fruit, 3–4 peduncular bracts green, deciduous; rachis or flowering portion to 5.5 cm long. Staminate flowers arranged in 5 spirals, closely placed but not contiguous, greenish-yellow; sepals to 1.5 mm long, connate, 3-lobed apically, lobes with a lateral thickening; petals 3–3.5 mm long, not nerved, connate in basal 2/3, 3- lobed apically, thickened and persistent in fruit; filaments 3, basally connate, similar in length with the petals; anthers to 0.7 mm long, slightly protruding between the corolla lobes; pistillode present, shortly 3-lobed. Pistillate flowers in 5 spirals, densely arranged, contiguous, yellow, sunken in circular depressions 2.5 mm across; calyx ring-like, ca. 0.5 mm high, sepals connate; petals connate; stigma 3-lobed, protruding from the corolla; staminodes absent. Fruits globose, 8–9 mm in diameter, not angled or compressed by mutual pressure, epicarp echinulate-medusoid, green when immature changing to yellow and orange-red when mature. Seeds not examined.

Additional specimens examined (paratypes): — COSTA RICA. Same location as the holotype. 12 December 2018 (staminate, fl.), Cascante-Marín et al. 2827 ( USJ) ; 12 December 2018 (pistillate, fl.), Cascante-Marín et al. 2828 ( USJ) .

Distribution: —Endemic to the foothills of the Talamanca Mountain Range in the Central Pacific region of Costa Rica at 820 m asl.

Habitat and Ecology: —The only known population grows in the understory of a humid riverine forest on a steep terrain. The vegetation is classified as Very Humid Premontane Forest according to Holdridge’s Life Zones System ( Bolaños & Watson 1993). Other congeners growing in the site were the dwarf and simple-leaved C. pumila H. Wendl. ex Dammer (1904: 246) and the short-stemmed, acaulescent long-pinnate leaved C. brachyclada Wendland (1880: 101) .

Phenology: —Flowering from November to December; fruiting from December through May.

Etymology: —The epithet honors Mr. Jay Vannini, an enthusiastic naturalist with a great knowledge of Chamadorea and a mentor to the junior author.

Preliminary conservation assessment: —At present, this new species is known from the type locality which is outside protected national parks and represents a small Area of Occupancy (AOO) of nearly 1 km 2. Thus, C. vanninii should be preliminary given the conservation status of Critically Endangered (CR) following the IUCN Red List criteria ( IUCN, 2012). A potential threat for C. vanninii is the negative effect of unscrupulous collecting by plant hobbyists ( Hodel 1992) and for that reason, we have concealed the specific locality from the species information.

Discussion:— Chamaedorea vanninii falls into Hodel’s (1992) subgenus Chamaedoropsis , characterized by its distinct petals that persist in fruit and solitary staminate flowers with upright and spreading petals not connate at their tips. This new species shares a similar growth habit and morphology with C. robertii from the mountains of southern Central America ( Costa Rica and Panama) and also with C. castillo-montii Hodel (1990: 397) ( Fig. 3 ), an endemic species from the mountains of northern Central America in Guatemala. This group of closely-related species develop very similar-looking simple and bifid leaves and also share inflorescence morphology in both genders. Inflorescences are interfoliar, sometimes infrafoliar when in fruit, spicate, and the pistillate erect-spreading and staminate abruptly pendulous. The remarkable echinulate-medusoid fruit surface of C. vanninii separates it from the other two species. The quite similar C. robertii also differs from the new species by its mature black fruits (vs. orange-red) and the burgundy peduncle bracts in newly emerged pistillate inflorescence (vs. green). C. vanninii also differs from C. castillo-montii in its orange-red, globose, fruits 8–9 mm in diameter while those of the latter species are black, oblong and narrowed at both ends, and 13 × 7 mm ( Fig. 3 ).

The diagnostic fruit epicarp in C. vanninii is an uncommon feature among Chamaedorea species, which mostly possess smooth fruits and is only shared with C. coralliformis Hodel (1996: 212) . Grayum (2003) included the latter species within the concept of C. crucensis Hodel (1990: 166) from subgenus Stephanostachys Klotzsch (1852: 363) . Hodel´s (1996) original description of fruits mentions: “epicarp in apical region densely and sharply wrinkled, giving surface a nearly spiny appearance and texture”, “obovoid but corn-kernel-shaped and angled by mutual compression at maturity”. In C. vanninii fruits do not agglomerate at maturity, are globose-shaped and the epicarp is completely covered by the echinulate-medusoid ornamentation.Also, individuals of C. crucensis are robust plants with erect stems to 2.5 m in height and develop pinnately-compound leaves versus smaller and decumbent plants with simple leaves in this new species.

The presence of a single whorl of three antesepalous stamens in male flowers is an additional peculiar feature of C. vanninii ( Fig. 1E & 1F ). Chamaedorea species are reported as having staminate flowers with an androecium composed of six stamens distributed in two whorls, which are more or less inserted at the same level ( Hodel 1992, Askgaard et al. 2008). Reduction in the number of stamens has been reported from other palm genera (Moore & Uhl 1982) but, as far as we know, it has not been previously observed in Chamaedorea . The examined material (15 flowers from two male inflorescences) consistently showed three stamens, but they came from a single collected specimen (Cascante-Marín et al. 2827, USJ). Additional collections of staminate individuals would corroborate the constancy of this atypical floral trait in this new species.

Figures

FIGURE 1. Chamaedora vanninii.A. Staminate plant habit. B. Male inflorescence, C. Male flowers arrangement. D. Male flowers closeup. E. Male flower drawing. F. Dissected male flower drawing. Photos and drawings by A. Cascante-Marín.

FIGURE 2. Chamaedora vanninii.A. Pistillate plant habit. B. Female inflorescence. C. Female flowers arrangement. D. Female flowers close-up. E. Developing fruits with persistent and thickened petals. F. Immature fruits. Photos by A. Cascante-Marín.

FIGURE 3. Plant habit and fruits (inserted picture) of A. Chamaedorea vanninii Cascante & Muller, B. Chamaedorea robertii Hodel & Uhl, C. Chamaedorea castillo-montii Hodel. Photos by A. Cascante-Marín (A) and F. Muller (B, C).