Uvariopsis dicaprio Cheek & Gosline, 2022

Gosline, George, Cheek, Martin, Onana, Jean Michel, Ngansop Tchatchouang, Eric, van der Burgt, Xander M., MacKinnon, Lorna & Dagallier, Léo-Paul M. J., 2022, Uvariopsis dicaprio (Annonaceae) a new tree species with notes on its pollination biology, and the Critically Endangered narrowly endemic plant species of the Ebo Forest, Cameroon, PeerJ (e 12614) 9, pp. 1-21 : 8-12

Uvariopsis dicaprio Cheek & Gosline sp. nov.

Type: Cameroon, Littoral Region, Yabassi, Ebo Forest , 4 Ǫ 20′ 44″ N, 10 Ǫ 24′ 33″ E, 849 m alt. Dicam Trail 2000 m from Bekob camp, male fl. 25 March 2008, MacKinnon 51 (holotype K001381842 ; isotypes MO, YA ).

Syn. Uvariopsis ebo nom. nud. ( Gosline et al., 2021: 5).

Diagnosis. Similar to Uvariopsis solheidii (De Wild.) Robyns & Ghesq. , differing in the stem, petioles and abaxial midrib glabrous (versus tomentose); number of secondary nerves on each side of the midrib 5–8 (versus 8–13); petals yellow-green, (14–) 16 × (5.5–) 9 mm (versus wine brown, 7–10 × 2.5–5 mm).

Cauliflorous, probably monoecious understorey tree 3–4 m tall. Trunk terete, lacking flutes or prop roots, 1.8–2.5 cm diameter at 1.5 m above the ground, bark smooth, dark-brown, with sparse, longitudinal lines of white lenticels ( Fig. 1 ), the crown sparsely branched ( Fig. 2 ). Leafy stems with 3–4 leaves per season’ s growth, terete, internodes (1.2–) 1.5–2.8 (–4.3) cm long, 0.15–0.2 cm diam., pale yellow-green, later orangish brown, glabrous.

Axillary buds dome-shaped 0.5–0.75 × 1 mm, bud-scales numerous, linear, spreading, densely hairy, hairs simple, appressed, c. 0.5 mm long, colourless or red brown. Leaves distichous, with punctations (minute translucent glands in the interior of the blade), lacking scent when crushed (collection metadata, MacKinnon 51), blades oblanceolate 17.7–20.2 (–23) × (6.4–) 7–7.9 cm, acumen narrowly triangular (0.5–) 1–1.3 cm long, base broadly acute with convex edges, minutely cordate, blade mounted above petiole, margins undulate-sinuous (live & dried), midrib impressed on adaxial surface, inconspicuous, below a groove; on abaxial surface subcylindrical, 1–1.2 mm diam., conspicuous; secondary veins 5–8 (–9) on each side of the midrib, brochidodromous, arising at c. 50 Ǫ from the midrib, initially straight, then curving in the outer third, uniting with the secondary nerve above to form a looping inframarginal nerve, attaining 3–4 mm from the margin; intersecondary nerves sometimes present, tertiary nerves raised, conspicuous, forming a reticulum with cells 4–5 mm long, quaternary nerves inconspicuous; glabrous (except in bud when densely orange-brown hairy, hairs c. 0.1 mm long). Petiole stout, shallowly canaliculate, c. 4 (–5) mm long, 1.9–2.1 mm diam., narrowing at base and apex, adaxial groove shallow, c. 0.5 mm wide, glabrous. Female inflorescences unknown. Male inflorescences cauliflorous, scattered along the trunk from near ground level to the top of the trunk 2.5–3 m above the ground, each 1–7-flowered ( Figs. 1 & 2 ). Peduncles patent, c. 2 × 2 mm, pale brown, glabrous, bearing sub-umbellate, radiating, 1-flowered partialpeduncles. Partial-peduncles 0.5–2 × 0.9–1.2 mm, terminating in 1–2 bracts subtending a pedicel. Bracts oblong-elliptic, 1.5 × 0.5–0.6 mm, apex acute, outer surface about 50% covered in appressed white hairs c. 0.15–0.2 mm long, inner surface glabrous. Male flowers. Pedicels 1.8–2.5 cm long, 0.1 cm diam., articulated with the partial-peduncle, with (0–) 1 (–2) scattered, bracteoles in the proximal few mm. Bracteoles similar to the bracts, ovateoblong, shortly sheathing, (1–) 1.25 × 1 mm, outer surface with sparse scattered simple appressed translucent hairs 0.05–0.2 mm long, buds narrowly ovoid to pyramidal, c.16 × 11 mm. Sepals 2, opposite, drying pale brown, reflexed, semi-orbicular, 1–1.5 × 2.1–2.5 mm, glabrous. Petals 4, uniseriate, free, thinly leathery, pale, glossy, yellow-green when live ( Fig. 1 ), drying black, lanceolate-oblong, (14–) 16 × (5.5–) 9 mm, not fleshy but c. 0.25–0.3 mm thick, apex rounded, base rounded, outer surface sparsely and inconspicuously hairy, hairs 7–9 per mm 2 (5% of surface covered), simple, translucent, appressed, c. 0.1 mm long, apices rounded. Inner surface of petals smooth, nontuberculate, with a shallow elliptic-oblong excavation c. 8 × 5 mm, the margin of the excavation raised, the apex with a ridge extending along the midline to the petal apex, glabrous apart from a few scattered erect, minute white hairs 0.05 mm long at the excavation apex. Staminal dome 3.5–4 mm long, 3.5–4 mm diam., consisting of stamens and a receptacular torus. Stamens shortly cylindrical-angular, c. 0.5 × 0.1 (–0.2) mm, connective with two lateral extrorse longitudinal anther cells, each exceeding the connective. Apical connective appendage absent. Female flowers, fruit and seed unknown. Figs. 1–3 .

DISTRIBUTION. Cameroon ( Fig. 4 ) endemic to the Ebo Forest of the Littoral Region on present evidence.

HABITAT. Uvariopsis dicaprio is so far only known from lower submontane forest (850 m elev.). below the elevation for the upper montane forest indicator species Podocarpus latifolius (Thunb.) R.Br. ex Mirb. The geology is ancient, highly weathered basement complex, with some ferralitic areas in foothill areas which are inland, c. 100 km from the coast. Altitude varies from c. 200 m to 1,200 m elevation. The wet season (successive months with cumulative rainfall>100 mm) falls between March and November and is colder than the dry season. Average annual rainfall at Bekob measured 2010–2016 is 2,336 mm (E. Abwe, 2018 Ebo Forest Research Programme, Cameroon, personal communication, Abwe & Morgan, 2008; Cheek et al., 2018a).

CONSERVATION STATUS. Uvariopsis dicaprio is currently known from a single specimen with all male flowers at a single location inside the mid-eastern part of the Ebo Forest ( Fig. 4 ). Less than 50 mature individuals have been observed (B. Morgan, 2021, personal communication), despite the species being highly conspicuous in flower ( Fig. 1 ) and situated on a major footpath close to a research camp used by many biologists over the last 15 years.

Since 2006, botanical surveys have been mounted almost annually, at different seasons, over many parts of the formerly proposed National Park of Ebo. About 2,500 botanical herbarium specimens have been collected, but this species has not yet been seen elsewhere in the c. 2,000 km 2 of the Ebo Forest. However , the area outside the two research camps, especially the western edge, has not been fully surveyed for plants. While it is likely that the species will be found at additional sites within the Ebo Forest , there is no doubt that it is genuinely range-restricted as are some other species of Uvariopsis in Cameroon (see “Introduction”). Botanical surveys and other plant studies for conservation management in forest areas north, west and east of Ebo resulting in tens of thousands of specimens being collected and identified have failed to find any additional specimens of this species ( Cheek et al., 1996; Cable & Cheek, 1998; Cheek, Onana & Pollard, 2000; Maisels, Cheek & Wild, 2000, Harvey et al., 2004; Cheek et al., 2004; Cheek, Harvey & Onana, 2010; Harvey, Tchiengue & Cheek, 2010; Cheek, Harvey & Onana, 2011).

The area of occupation of Uvariopsis dicaprio is estimated as 4 km 2 using the IUCN preferred cell-size. The extent of occurrence is the same. In February 2020 it was discovered that moves were in place to convert the forest into two logging concessions (e.g. https://www.globalwildlife.org/blog/ebo-forest-a-stronghold-for-cameroons-wildlife/ and https://blog.resourceshark.com/cameroon-approves-logging-concession-that-willdestroy-ebo-forest-gorilla-habitat/ both accessed 12 April 2021). Such logging would result in timber extraction that would open up the canopy and remove the intact habitat in which Uvariopsis dicaprio is found. Additionally, slash and burn agriculture often follows logging trails and would negatively impact the population of this species. Fortunately the logging concession was suspended in August 2020 due to representations to the President of Cameroon on the global importance of the biodiversity of Ebo (https://www.businesswire. com/news/home/20200817005135/en/Relief-in-the-Forest-Cameroonian-Government-Backtracks-on-the-Ebo-Forest accessed 12 April 2021). However, the forest habitat of this species remains unprotected and threats of logging and conversion of the habitat to plantations remain, and mining is also a threat. Uvariopsis dicaprio is therefore here assessed as Critically Endangered, CR B1+2ab(iii), D.

PHENOLOGY. Flowering has been observed in late March and early April (B. Morgan, 2021, personal communication).

ETYMOLOGY. This threatened and spectacular tree is named for the American actor and conservationist Leonardo DiCaprio, who, through several months in 2020, lobbied extensively on social media (e.g. https://www.instagram.com/p/B_0LSAhFRue/?hl=en; https://twitter.com/leodicaprio/status/1257729388314943490?lang=en both accessed 12 April 2021) to draw attention to threats for the numerous rare Ebo species from the logging concession that had been announced at Ebo earlier that year. The concession was cancelled in August 2020, surely partly due to his efforts.

VERNACULAR NAMES & USES. None are known.

NOTES. The distal half of the petals and the margins of the proximal half are flat, wing-like and held against each other (applanate) in bud. In section therefore, the distal part of the corolla will appear cross-shaped (see Fig. 1 ). This seems to be an extreme form of the petal structure and pyramidal flower bud shape seen in the probably closely related Cameroonian species Uvariopsis korupenis and U. submontana (see results, above).

Uvariopsis dicaprio is further distinct from all other species of the genus in that a distinct peduncle is present that bears several branches (partial-peduncles) each of which bears and is articulated with a single pedicel ( Fig. 3 ). Other cauliflorous species of Uvariopsis have few to many-flowered fasciculate inflorescences, a peduncle not being observed, the pedicels arising directly from a perennial woody burr. In non-cauliflorous species of Uvariopsis the inflorescences consist of a single, axillary flower.

It was first intended to name Uvariopsis dicaprio as U. ebo and this name was used in the bioRxiv pre-print ( Gosline et al., 2021: 5). However, such pre-prints have no standing as publications for nomenclatural purposes according to the Code ( Turland et al., 2018) because they not intended by the authors as the final publication. Therefore Uvariopsis ebo is classed as a nominum nudum.

Figures

Figure 1 Uvariopsis dicaprio. Cauliflorous inflorescences on trunk. Photo Lorna MacKinnon. Full-size DOI: 10.7717/peerj.12614/fig-1

Figure 2 Uvariopsis dicaprio. Trunk apex with cauliflorous flowers and canopy. Photo Lorna MacKinnon. Full-size DOI: 10.7717/peerj.12614/fig-2

Figure 3 Uvariopsis dicaprio. (A) habit, cauliflorous inflorescences on trunk; (B) leafy branch, one season’s growth; (C) inflorescence, showing pedicel articulations, bracts and bracteoles; (D) flower, with one petal removed to show the staminal dome; (E) detail of sparse hairs on abaxial petal surface; (F) stamen, different views; (G) junction of base of leaf with stem, showing dome-like axillary bud. All drawn from MacKinnon 51 (K) by MEG GRIFFITHS. Full-size DOI: 10.7717/peerj.12614/fig-3

Figure 4 Global distribution of Uvariopsis dicaprio, together with U. korupensis and U. submontana. Full-size DOI: 10.7717/peerj.12614/fig-4