Identification and Distribution of Ferns and Fern Allies in Okomu National Park, Edo State

Ferns and fern allies (pteridophytes) are important components of tropical forest understoreys, yet their diversity and distribution within Okomu National Park in Edo State, South South Nigeria, remain poorly documented. This study identified and mapped the distribution of pteridophytes within three vegetation zones of Okomu National Park: the forest interior, forest edge, and riparian corridor. Field surveys were conducted during both wet and dry seasons using the quadrat method (10m x 10m plots) at 30 systematically placed sampling stations. Specimens were collected, pressed, and identified using standard pteridophyte identification keys and cross-referenced with the Kew Plants of the World Online database. A total of 43 pteridophyte species from 22 families were recorded. The riparian corridor harboured the highest species richness (34 species), followed by the forest interior (28 species) and forest edge (21 species). Adiantum philippense, Nephrolepis biserrata, and Asplenium africanum were among the most abundant species. Seasonal variation was significant, with the wet season recording 38 species and the dry season 29 species. Four species were recorded for the first time in Edo State, expanding regional species checklists. Light availability, moisture gradient, and soil organic matter were identified as primary determinants of distribution patterns. The study recommends that pteridophyte diversity be incorporated into the biodiversity management plan of Okomu National Park as a conservation monitoring tool.

Keywords: ferns, pteridophytes, Okomu National Park, species distribution, Edo State