Professional Assessment of the Status and Threats Facing Rare and Endemic Plant Species in Idanre Hills, Ondo State

Idanre Hills in Ondo State, South West Nigeria, is a globally recognised biodiversity hotspot harbouring rare and endemic plant species, yet a comprehensive professional assessment of their conservation status and specific threats has not been conducted within the framework of current IUCN Red List criteria. This study conducted a professional conservation assessment of 22 candidate rare and endemic plant taxa documented from Idanre Hills, applying IUCN Red List categories and criteria (version 3.1) to assign provisional threat categories. Field assessments combined GPS-referenced population surveys, specimen collection for identification, habitat condition scoring, and threat quantification using structured site disturbance indices. Population size, area of occupancy, extent of occurrence, and population trend data were recorded for each taxon. Results showed that 9 of 22 assessed taxa qualified as Critically Endangered or Endangered under IUCN criteria, primarily on the basis of very small area of occupancy (below 20 km2), restricted extent of occurrence, and ongoing habitat loss from agricultural encroachment and quarrying. Afrotrilepis pilosa, Scleria verrucosa, and two undescribed fern taxa were among the highest-priority Critically Endangered candidates. Three taxa previously documented from Idanre Hills could not be relocated, suggesting possible local extinction. The annual rate of forest habitat loss within the assessment area was estimated at 2.3% based on repeat imagery analysis. The study provides the first IUCN-criteria-based assessment of Idanre Hills endemic plant taxa and recommends immediate legal protection escalation under the Ondo State Forestry Law.

Keywords: rare plants, endemic species, IUCN Red List, Idanre Hills, Ondo State