Aenigmanu chococola Londoño-Ech. & A.M.Trujillo, 2023

Londoño-Echeverri, Yeison & Trujillo-López, Ana María, 2023, Taxonomic studies in Colombian Picramniaceae (Picramniales): new species of Aenigmanu, Nothotalisia and Picramnia from the Pacific and Magdalena Valley regions, Phytotaxa 622 (5), pp. 281-297 : 282-286

Aenigmanu chococola Londoño-Ech. & A.M.Trujillo , sp. nov. ( Figs 1 , 2 )

Type : — COLOMBIA. Chocó : Mun. Nuquí , costa del Pacífico , correg. Termales , quebrada Piedra-Piedra , 1 hr. SO de Nuquí, hotel Pijibá, 0–55 m, 5°37ʹ0ʹʹN, 77°15ʹ0ʹʹW, 8 Sep 1994 (im fr), Callejas et al. 11230 (holotype: HUA!) .

Aenigmanu chococola differs from A. alvareziae by its longer stipules 8.2–11.3 × 0.8–1.2 mm (vs. ca. 6.5 × 1.5 mm), wider leaf blades (7.0–) 8.3–10.6 cm wide (vs. 3.4–5.5 [–7.5] cm) that are basally convex (vs. cuneate to decurrent) and commonly apically emarginate at the very tip (vs. commonly mucronate) and bracts of pistillate inflorescence longer 1.5–2.3 (–3.7) mm (vs. equal or less than 1 mm).

Shrubs 3–4 m tall, indumentum of simple trichomes, buds and young branchlets densely shortly strigose, glabrescent, stipules 8.2–11.3 × 0.8–1.2 mm, linear to narrowly oblanceolate, apically acute and cuneate to shortly acuminate, shortly strigose on both surfaces, more densely abaxially; primary vein raised, and occasionally secondary veins slightly raised abaxially; caducous, leaving transversal scars up to 3 mm long on fully expanded branchlet nodes. Leaves simple (possibly unifoliolate), alternate, petiole 5–7 mm long, flat adaxially, shortly strigose; blades 18.5–23.6 × (7.0–) 8.3–10.6 cm, broadly obovate, basally obtuse and convex, apically acute to obtuse and acuminate, commonly emarginate at the very tip; shortly strigose abaxially, nearly glabrous on the blade, sparsely so toward the primary and secondary veins; puberulous adaxially, nearly glabrous on the blade, densely so toward the primary and secondary veins; primary vein raised abaxially, flat to slightly raised adaxially, secondary veins 10–13 on each side, raised abaxially, slightly impressed adaxially, brochidodromous, loops consistently of 2° gauge and with course monopodial to slightly sympodial, tertiary veins raised abaxially, slightly raised to flat adaxially, percurrent, vein framework visible up to 6° gauge; margin entire. Staminate inflorescences and flowers not seen. Pistillate inflorescences forming cymules, congested as scaly short-shoots, 1–2-forked, leaf opposed, 7.0– 14.5 mm long (including a common penduncle 2.8– 3.9 mm long), bearing 1–2 flowers at a time, axes shortly strigose; bracts 1.5–2.3 (–3.7) × 0.7–1.4 mm, ovate to lanceolate, apically acute and cuneate to narrowly long-acuminate, shortly strigose throughout and apically densely puberulous on both surfaces, persistent; pedicel ca. 1.5 mm, ca. 0.8 mm diam., densely shortly strigose to puberulous, bracteoles not seen. Pistillate flowers pentamerous (the specimen label indicate “flowers white” but colour is not preserved, the description here provided is from flowers beginning to develop fruits), calyx 3.5–4.0 mm long, connate basally, reflexed but becoming inflexed toward the lobes, the basal connate portion ca. 0.7 mm long; lobes 2.8–3.3 × 1.4–1.7 mm, ovate to lanceolate, apically acute and cuneate, densely shortly strigose to puberulous abaxially, mainly glabrous and only apically puberulous adaxially, margin entire; petals not seen, their scars alternating with the sepals; staminodes not seen; disc ca. 0.6 mm tall, ca. 2 mm diam., intrastaminal, like a gynophore (i.e., not annular, but rather subtending the ovary), glabrous; ovary syncarpous, 7-carpellate, 3.0– 3.4 mm tall, 4.0– 4.6 mm in diam., globose, 7- lobed, densely strigose to puberulous, transversally ridged; common style ca. 0.4 mm long, ca. 0.6 mm diam. (obsolete by fruit expansion), densely strigose to puberulous, stigma 7-lobed, each ca. 0.8 × 0.2 mm, patent to erect, sparsely shortly strigose. Mature fruits not seen. Seeds not seen.

Distribution and habitat:— Endemic to western Colombia, where it has been recorded on nearly coastal areas from the Nuquí Municipality in the Chocó Department ( Fig 3 ), Pacific Biogeographical Region, at 0–50 m in equatorial rainforest climate type (Af), a region globally considered one of the wettest and most biodiverse ( Gentry 1986).

Phenology:— Only immature fruits known in September; flowering on the same date (no flowers preserved).

Etymology:— Referring to the Choco Biogeographical Region (= Pacific Biogeographical Region sensu Bernal 2016).

Conservation status:— Known only from a subpopulation found outside protected areas, with AOO = 4 km 2 and less than 15 km from a populated centre. The forests of the Pacific Biogeographical Region in Colombia, although apparently continuous, exhibit high levels of habitat degradation due to selective logging and mining that, according to Moreno & Ledezma-Rentería (2007), are the main economic activities of the region. Rangel-Ch. (2004) also emphasised the high threats and habitat degradation in this region, suggesting a loss of forest cover at 25–36%. Because to its small distribution outside protected areas and the threats to its habitat, A. chococola should be considered as critically endangered, CR according to criteria B2ab(iii).

Notes:— Aenigmanu chococola is known only by a pistillate specimen collected by Ricardo Callejas, Pedro Acevedo and Steven Paul Churchill in 1994, at which time it would has been almost impossible to consider that it belonged to Picramniaceae . Despite extensive searches for other specimens in Colombian and foreign herbaria, no other specimens have been found.

Because of the absence of additional specimens, the diagnosis is mainly based on vegetative features. Otherwise, only the longer bracts of pistillate inflorescences are useful in recognising A. chococola in the phenological stage of the type specimen. Although the floral and fruit morphology is distinctive among Picramniaceae genera, it is often uniform within each genus, especially in apparently related species, resulting in the wide use of vegetative features for recognition at the species level, e.g., taxonomic keys of Thomas (1988, 1990, 2011) and Thomas et al. (2021). Further studies should supplement the morphological description of A. chococola provided here, permitting the use of additional diagnostic floral features. Nevertheless, the diagnosis here proposed was verified using all available specimens of A. alvareziae and distinguishing A. chococola from any Amazonian specimen of the genus.

Two additional features in foliar architecture of Aenigmanu chococola can be useful, although their taxonomic relevance depends on further study with more specimens of both species: loops between secondary veins consistently of 2° gauge and monopodial to slightly sympodial (vs. loops noticeably reduced in gauge towards the superjacent secondary vein with course strongly sympodial in A. alvareziae ), and veins framework abaxially visible up to 6° giving them a more reticulate appearance (vs. veins abaxially visible up to 5° giving them a less reticulate appearance).

Thomas et al. (2021) described the stipules of Aenigmanu alvareziae as “ ca. 6.5 × 7.5 mm ”, which seems to be a typographical error. Based in the available specimens and the original illustrations of A. alvareizae , this should be ca. 6.5 × 1.5 mm, as in the diagnosis of A. chococola .

Figures

FIGURE 1. Holotype of Aenigmanu chococola.

FIGURE 2. Aenigmanu chococola. A. Flowering branchlet of pistillate plant. B. Stipules. C. Detail of leaves blade at very tip, abaxial view. D. Pistillate inflorescence. E. Pistillate flower beginning to develop fruit. (A–E from the holotype; illustration by Ana Cristina Pareja, HUA).

FIGURE 3. Distribution of Aenigmanu chococola, Nothotalisia karsticola and Picramnia vinacea.