Taxonomic Evaluation of Homosporous Leptosporangiate Ferns (Pteridophytes) in Southwestern Nigeria
Taxonomical studies of leptosporangiate ferns collected from Southwestern Nigeria were carried out for taxonomic re-evaluation, additional diagnostic features and for establishing the missing gaps in the taxonomy of fern species in this region. The habitats from where these ferns were collected include humid areas, waterlogged, road sides and rock crevices. Features investigated were rhizomes, croziers, fronds, ramenta, stipe's colour; leaf type: shape, hairiness, margins, length and breadth; apex shape and type; leaflet shape and margins, indusia, spores, sporangia and sori arrangements. These features were used to construct artificial taxonomic key for the thirteen families of ferns collected. The quantitative data obtained were coded for statistical analysis using Principal Component Analysis. Different growth forms and growth duration were also recorded. The results of the scatter diagram shows how closely or distantly related these fern species are to one another. The dendogram showed two main clusters, two sub-clusters and four minor sub-clusters. An artificial taxonomic key produced was found valuable for the identification of the thirteen families of ferns studied. Most of these ferns are perennials accumulating biomass while few are annals. The ferns had different growth forms such as spreading, tangle and climbing. The agreement of the results of dendogram and scatter diagram showed that ferns form natural groupings with their close or distant relationships. The possession of tubers, rhizomes, gemmae and numerous spores by a fern species is an adaptation for effective distribution and dispersal.