New Records of Subaerial Epilithic Algae from Elevated Rock Surfaces in Mt. Makiling Forest Reserve Laguna, Philippines

Background: Subaerial microalgal communities, particularly those inhabiting elevated rock surfaces, remain understudied in the Philippines. This study presents the first floristic survey of microalgae from such unique habitats within the Mt. Makiling Forest Reserve. Methods: Rock surface samples were collected from various elevations in the reserve and subjected to morphological examination using light microscopy. Species were identified using standard morphological techniques and taxonomic references. Results: A total of 18 species of microalgae were described taxonomically, of which seven species belonged to Cyanophyceae, five species to Bacillariophyceae, three species to Chlorophyceae, two species to Trebouxiophyceae, and one species to Mediophyceae. Notably, Synechococcus elongatus (Nägeli) Nägeli, a rare cyanobacterium, and Stephanocyclus meneghinianus (Kützing) Kulikovskiy, Genkal & Kociolek, a diatom, are reported for the first time in the Philippines. All documented taxa represent new distributional records for this habitat type. This survey significantly expands the known diversity of subaerial microalgae in the country and underscores the ecological importance of rock surface habitats as reservoirs of algal biodiversity. Conclusion: These findings provide critical taxonomic and biogeographic data that can support further ecological and conservation studies.