Assessing the extinction risk of Malagasy orchids to develop effective conservation approaches – a case study of the Itremo Massif Protected Area.

– Madagascar harbours high numbers of threatened orchid species, making it critical for orchid conservation. The Itremo Massif Protected Area (Itremo Massif PA), a Key Biodiversity Area in the Central Highlands, comprises diverse habitats essential for orchid survival. Previously, only 30% of the 83 orchid species recorded in the Itremo Massif PA had been assessed for the IUCN Red List. This research documents and analyses their habitats and threats to propose conservation approaches. – We compiled a dataset of orchid species native to the Itremo Massif PA, including information on endemicity, conservation status, habitats, and threats from IUCN Red List assessments and field observations. A species-by-habitat matrix was constructed, and species composition across habitats was analysed using a β-diversity framework. Overall β-diversity (β ) was partitioned into species turnover and nestedness components. We also evaluated the proportion of threatened orchid species (Critically Endangered – CR, Endangered – EN and Vulnerable – VU) associated with the primary habitats and threats in the PA. – Of the 83 orchid species native to the Itremo Massif PA, 64% (53 spp.) are endemic to Madagascar and 41% (34 spp.) are threatened (1 CR, 16 EN, 17 VU). Species composition varies markedly between habitats (β = 0.83), primarily driven by species turnover (0.66). Bare soil and rock host the most orchid species (60%, 50 spp.). Bare soil and rock and grassland share the most species (14%, 12 spp.), while humid forest contains the most species restricted to a single habitat (16%, 13 spp.). Orchids are primarily threatened by mining and quarrying, increased fire intensity/frequency, logging and wood harvesting, and shifting agriculture. – Conservation should prioritise humid forest for its unique orchid species, and bare soil and rock for their richness in endemic and threatened species. Grassland also represents essential habitat for terrestrial orchids. Further research on population dynamics, pollination, and fungal interactions is needed to better assess extinction risk and manage conservation.