Tree species composition and diversity were assessed in Omo Biosphere Reserve, Ogun State, Nigeria. Systematic sampling design was used to lay two straight line transects, each of 1000 m long and separated by 500 m, in the reserve. Four Temporary Sample Plots (TSP) of size 50×50 m were laid along each transect at 250 m interval. Eight plots were enumerated for identification and frequency of occurrence (FO) of all woody plants with diameter at breast height (DBH) ≥10 cm. Identified tree species were categorised into different diameter classes. Data collected on DBH were used to compute Stem Volume (SV), Basal Area (BA) and Number of Trees per hectare (NT). Shannon Weiner and Simpson's indices were used to assess species diversity. Identified flora species in the reserve were from 30 families, 59 genera and 66 species. Family Ebenaceae had highest FO of 3 2 90±16.25/ha in the study area. The DBH of 146±0.72 cm; SV of 0.47±0.86 m /ha; BA, 86.45±0.34 m /ha; and NT, 405±1.95 were recorded. Shannon Weiner and Simpson's indices obtained were 4.01 and 0.09 respectively indicating a moderately diverse area. This study provides a baseline for the management of the forest reserve in southwestern Nigeria.

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Meliaceae is a family of woody species that are very useful for timber and ethnomedicine in Nigeria. However, there is scarce information on their taxonomic description, which is important in realizing their full potentials. Existing floristic studies on members of Meliaceae have revealed overlap in key morphological characters like number of lateral nerves, shape, size and number of leaflets. Aside the floral and fruit characters, the use of leaf epidermal characters has proven to be gene-dependent and as such provides stable and less expensive grouping compared to the molecular methods. This study investigated the leaf epidermal and petiole anatomical significance in four species of Melieceae; Azadiracta indica, Cederella odorata, Khaya sensegalensis and K. grandifoliola for taxa delimitation. The choice of leaf for this study is based on their regular availability unlike the flowers, which are seasonal. Plant materials of the species were collected from University of Ibadan, Forest Research Institute of Nigeria and National Center for Genetic Research and Biotechnology in south western Nigeria based on availability. Leaf samples were examined under the microscope for epidermal and petiole anatomical characteristics. Characters like epidermal cell shape, epidermal cell wall pattern, trichome type and stomata abundance were differentiated in the four species. Petiole anatomical characteristics for delimiting the taxa include cuticle thickness, presence or absence of crystal, crystal type and vascular bundles arrangement. The analyzed characters produced two major clusters-Cluster 1: Khaya senegalensis and Khaya grandifoliola; cluster 2: Azadiracta indica and Cederella odorata. Azadiracta indica and Cederella odorata are more closely related species than Khaya senegalensis and Khaya grandifoliola. The affinity of the studied characters is an evidence of their correlation and supports the relationship existing among the species. These characters support delimitation of the taxa even in fragment condition.

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