Ecological factors influencing the diversity and distribution of Orchidaceae members in the Intercontinental Biosphere Reserve of the Mediterranean of Northern Morocco

The complex interplay of ecological gradients, habitat heterogeneity, and species-specific traits usually shape orchid diversity and distribution in Mediterranean ecosystems. In this study, we surveyed terrestrial orchids across 65 diversified sites in northern Morocco’s Intercontinental Biosphere Reserve of the Mediterranean (IBRM). Overall, 26 orchid taxa were recorded across different substrates and environments with calcareous substrates supporting 1,775 individuals compared to 128 on siliceous ones. The Outlying Mean Index analysis revealed clear patterns of ecological specialization across environmental gradients. Five orchid species ( Epipactis tremolsii, Limodorum trabutianum, Orchis anthropophora, Ophrys battandieri , and Orchis mascula subsp. laxifloriformis ) exhibited strong marginality indicating high specialization associated with narrow niches and specific environmental preferences (particularly in cooler, mid- to high-elevation habitats with distinct substrates), while others were moderately specialized or generalists displaying broader tolerance (more common at higher elevations and warmer sites). The main drivers influencing orchid distribution were temperature, elevation, precipitation, latitude, slope, moisture, forest and substrate type. Hierarchical clustering further distinguished four ecological groups linked to specific habitat types and environmental conditions. Serapias spp. mainly occurred in high-moisture habitats, whereas most Ophrys and Orchis taxa preferred forested calcareous sites. Our findings underscore the importance of habitat heterogeneity and substrate type in maintaining orchid diversity, thus providing a valuable framework for conservation strategies in Mediterranean North Africa and beyond.