Pteridophyte Richness and Community Structure in the Tropical Lowland Habitats of Andanan Protected Landscape, Northeastern Mindanao, Philippines

Pteridophytes are among the most diverse vascular plants in the Philippines, with significant conservation and economic value. This study documents the richness and community structure of pteridophytes in the tropical lowland habitats of the Andanan Protected Landscape (APL), North-eastern Mindanao, Philippines. A combination of quadrat sampling and transect walks was used for pteridophyte assessments. A total of 69 species were recorded, belonging to 19 families and 34 genera, representing about 6.3 % of the Philippine pteridophytes. Of these, 11.6 % are threatened, and 2.9 % are Philippine endemics. The Polypodiaceae was the most species-rich family, comprising 17 % of the total species. Forty-eight species were terrestrial, 12 were epiphytes, and six were lithophytes. Selaginella engleri Hieron. was the most important species in the area, with the highest importance value (12.77). The APL exhibited high pteridophyte diversity, with Shannon (H’=3.65) and Simpson (D=0.96) indices, and significant variation in species richness among sampling sites (p<0.05). Among the sampling sites, Mt. Ararat demonstrated the highest pteridophyte diversity (H'=3.4) and richness (n=56). Multivariate analysis revealed a high degree of community similarity (ANOSIM R=0.31, p<0.01), with overlapping compositions between Berseba and Calaitan, while Mt. Ararat showed a more distinct assemblage. The high pteridophyte diversity and the presence of conservation-priority species support the designation of APL as a critical forest landscape for preserving biological communities and their habitats. This study provides a preliminary checklist and distribution of pteridophyte flora to inform management and conservation efforts in the APL, North-eastern Mindanao, Philippines.