Tropicos | Name - Pavetta owariensis var. opaca S.D. Manning

Project Name Data (Last Modified On 1/16/2022)

Acceptance : Accepted

Taxon Profile (Last Modified On 1/16/2022)

Description: Shrubs or small trees to 15 m tall. Floriferous twiglets glabrous, to 37 cm. Leaves sometimes coriaceous, no ovate blades seen; apex occasionally rounded; acumen to 23 x 12 mm; base sometimes obtuse, only slightly if at all asymmetrical; midrib prominent below at least toward base, domatia absent or present as crypts in some branch vein angles of midrib and occasionally on secondary veins, often puberulent; nodules along midrib and on blade, sometimes rare; venation density fine; fourth and higher order venation obscure or invisible above and below; stipules cup-shaped, glabrous externally, awn to 4 mm. Inflorescences corymbshaped to pyramidal or rotund in outline, 2-15 cm across, sometimes subglabrous proximally, sessile or subsessile, flowers to 350 per inflorescence; sheathing bracts sometimes with linear awns to 2 mm or foliar appendages to 3 mm; foliar bracts sometime; present; other bracts concave, irregular or obovate; calyx tube to 1.8 mm long and to 2.5 mm wide halfway up; lobes 1-3 x 1-2 mm, subglabrous to pubescent; corolla tube subcylindrical or cylindrical, (3-)5-9 x 1-3 mm, lobes 6-11 mm; style subglabrous to pubescent, exserted ca. (6-)10- 15 mm. Fruits ca. 8 mm across, subglobose, puberulent to glabrous, whitish, gray-green, or light green with darker green streaks, without persistent calyx. Seeds 2 or 1, slightly concave when immature. Other character states within ranges described above for variety owarnensis. The most obvious distinguishing feature of variety opaca is the obscure leaf venation above and below as a result of its thick, sometimes brittle leaves. Although this also occurs in variety satabiei, the calyx does not persist in fruit in variety opaca as it does in variety satabiei. The tallest representative of subgenus Baconia in Cameroon belongs to variety opaca (Manning, 1996).

Habitus: Tree

Phenology: Flowers have been observed in February, March and April; Fruits in March, November and December.

Habitat: Mature terra firme forest, between 30 and 800 m in elevation.

Distribution: Gabon, Cameroon

Distribution Note: The species is endemic to Central Africa occurring in Cameroon and Gabon and known from 13 collections made between 1903 (Zenker 2554) and 2018 (Bidault 3998). In Gabon, the species is known from two collections made in Ngounié province: one by Wieringa (7406) in 2013, 15 km on the road Moukabou to Mbigou, and one by Bidault (3998) in 2018 North of Malinga. In Cameroon, it is known from 11 collections (9 occurrences), of which three were made in South province: Zenker made one collection (2554) in 1903 in the region of Bipindi, probably in Ngovayang massif, one was made by Leeuwenberg (5555) in 1965, 60 km S of Edea, and one other collection was made by Bates (1210) in 1919 in Bitye. Two collections were made in Litoral province: one by McKey (109) in 1976 near Lake Tissongo, and one by de Wilde (1295) in 1963, 50 km NW. of Eséka. Finally, 6 collections (4 occurrences) were made in Central province, of which three (two occurrences) were made in the region of Songbong (Bamps 1378, Leeuwenberg 5069, and de Wilde 1538). One collection was made by Benoît (202) in 1956, 16 km from Eséka, and two collections (one occurrence) were made by Zenker (278 and 543) in Yaoundé. However, we consider this last occurrence as now extirpated because of the urbanization around the city of Yaoundé that has induced the disappearance of natural habitats.

Phytogeographical type: Guineo-Congolian Region, Lower Guinea domain.

Literature:

Manning, S. D. 1996. Revision of Pavetta subgenus Baconia (Rubiaceae: Ixoroideae) in Cameroon. Ann. Missouri Bot. Gard. 83(1): 87–150.

Case Study: Other

Conservation assessment (Last Modified On 1/16/2022)

Red List Category: Vulnerable

Status of Conservation Assessment: Published on the Red List

Date of assessment: 31 December 2020

Assessment rationale: Pavetta owariensis var. opaca is a tree up to 15 m tall, known from mature terra firme forest, between 30 and 800 m in elevation. The species is endemic to Central Africa occurring in Cameroon and Gabon and known from 13 collections made between 1903 (Zenker 2554) and 2018 (Bidault 3998).

In Gabon, the species is known from two collections made in Ngounié province: one by Wieringa (7406) in 2013, 15 km on the road Moukabou to Mbigou, and one by Bidault (3998) in 2018 North of Malinga. In Cameroon, it is known from 11 collections (9 occurrences), of which three were made in South province: Zenker made one collection (2554) in 1903 in the region of Bipindi, probably in Ngovayang massif, one was made by Leeuwenberg (5555) in 1965, 60 km S of Edea, and one other collection was made by Bates (1210) in 1919 in Bitye. Two collections were made in Litoral province: one by McKey (109) in 1976 near Lake Tissongo, and one by de Wilde (1295) in 1963, 50 km NW. of Eséka. Finally, 6 collections (4 occurrences) were made in Central province, of which three (two occurrences) were made in the region of Songbong (Bamps 1378, Leeuwenberg 5069, and de Wilde 1538). One collection was made by Benoît (202) in 1956, 16 km from Eséka, and two collections (one occurrence) were made by Zenker (278 and 543) in Yaoundé. However, we consider this last occurrence as now extirpated because of the urbanization around the city of Yaoundé that has induced the disappearance of natural habitats. This occurrence is thus not taken into account in the AOO and EOO calculations. The 11 remaining collections represent 10 occurrences and 6 to 9 subpopulations. Considering forest cover, which is still significant in other areas, we do not regard any of these 10 occurrences as extirpated. Based on a 2 x 2 km cell size, the AOO of this species is estimated as 40 km², below the upper threshold for “Endangered” status under Criterion B2. The EOO is calculated as 94,484 km², far exceeding the upper threshold for “Vulnerable” status under Criterion B1.

One occurrence (Zenker 2555) is probably located in Ngovayang massif, an Important Plant Area (IPA) in Cameroon. However, this locality is also threatened by mining activities. None of the other occurrences are located within protected areas, and in Cameroon, the species is threatened by small-scale agriculture. In Gabon, the two occurrences are located near roads and are threatened by small-scale agriculture and logging. All activities inducing a decline in the quality and the extent of the habitat of the species. As a consequence, the 10 occurrences represent 9 locations (sensu IUCN 2019) with regard to the most serious plausible threat (small-scale agriculture). Based on the past disappearance of the occurrences in the region of Yaoundé, we infer past decline in its AOO, its EOO, the number of locations, and the number of mature individuals. Moreover, since human activity increases the loss of its habitat, we infer current and future continuing decline in its AOO, its EOO, the extent and the quality of its habitat, the number of locations, and the number of mature individuals. This species is thus assessed as VU B2ab(i,ii,iii,iv,v).

Red List DOI: https://dx.doi.org/10.2305/IUCN.UK.2021-3.RLTS.T174412401A174513720.en

Disclaimer: This assessment was prepared on 31 December 2020. The map proposed below is only based on the specimens available on Tropicos, therefore, may not correspond to the information provided in the assessment rationale.

Conservation measures: Since this species is threatened by small-scale agriculture, logging, mining activities and urbanization various conservation measures should be considered. First, the species should be sought in protected areas where it might occur. Second, the species should be regarded as an HCV1 (High Conservation Value), and as a consequence, should be included in the management plan of the industrial concessions within which it occurs, and the destruction of its habitat and possible harvesting must therefore be limited. Third, ex situ conservation should be tested, both within the countries where it occurs and internationally. Fourth, a public awareness campaign must be conducted targeting industrial companies and other private actors, NGOs, scientific institutions, and the government of countries where the species occur to ensure that Pavetta owariensis var. opaca is taken into consideration when decisions are made that could impact its conservation. Finally, the species should be sought in other places, such as Equatorial Guinea, to increase the knowledge of its distribution.