THE ORCHID FLORA OF THE MBAM MINKOM HILLS (YAOUNDE, CAMEROON)

摘要

Despite its tremendous biodiversity, which results from a strong elevation gradient and high habitat diversity, the flora of the Mbam Minkom Hills (Cameroon) is poorly documented. Moreover, these hills have recently become an urgent and major challenge for conservationists because their proximity to the city of Yaounde has considerably increased human pressure on this area considered as the last main block of primary submontane forest around this city. As a consequence, the main objectives of this paper are to provide the first orchid account of the Mbam Minkom Hills, to document the ecology and the distribution of these species and to highlight the importance of this family for the conservation of this threatened ecosystem. A total of 75 orchid taxa within 27 genera were found in the Mbam Minkom Hills. Sixty-one (81%) were epiphytic, 11 (15%) were terrestrial and 3 (4%) were lithophytic. Six of them (8%), one Bulhophyllum, one Diaphananthe, one Polystachya, one Rhipidoglossum and two Stolzia are new taxa. Genera with the highest number of taxa were Polystachya (19 taxa) and Bulhophyllum (12 taxa). Polystochya carnosa is newly recorded for Cameroon. Lowland forest (51 taxa) and inselbergs (29 taxa) are the two habitats with the highest species richness. Species flower mainly between March and May and between July and September. Thirty-four (45%) taxa were endemic or near endemic to the Guineo-Congolian regional centre of endemism, of which 14 (19%) were endemic to the Lower Guinean Domain. Moreover, Bulbophyllum teretifolium, Bulbophyllum sp. nov., Cheirostylis divina var. ochyrae, Polystachya sp. nov. and Stolzia repens var. cleistogama are endemic to Cameroon. According to IUCN criteria, 50 taxa (67%) are least concerned (LC), 4(5%) are vulnerable (VU) and 1(1%) is near threatened (NT). Three taxa (4%), Cheirostylis divina var. ochyrae, Diaphananthe bueae and Polystachya letouzeyana are endangered (EN). Seventeen taxa (23%) are not evaluated (NE). The orchid flora of Cameroon is far from being completely known, as shown by the six new taxa and the new national record found during this study.