Spatial and Temporal Dynamics of Petiveria alliacea L.: Assessment of Composition, Abundance, and Similarities of Understory Species within Selected Secondary Forests of the University of Ibadan, Nigeria

Background and Aim of the Study: The status of naturalised understory herbs serves as a key indicator of habitat change within forest ecosystems on both local and global scales. Petiveria alliacea, a low-growing, naturalised shrub, forms dense community patches, particularly along secondary forest edges and disturbed areas. Its increasing exploitation for multipurpose uses raises significant concerns regarding its conservation, biodiversity, and the health of ecosystems. This study assessed the composition, abundance, and spatial–temporal differences between P. alliacea and other understory plant species within selected secondary forests of the University of Ibadan, Nigeria. Data and Methodology: Floristic surveys were done at the University of Ibadan’s Teaching and Research Farm (TRF), Botanical Garden (BG), and Department of Botany (DB). At each site, systematic sampling was employed during wet and dry seasons over two consecutive years, establishing four transects at 50 m intervals. Each site has eight 25 m² plots with 40 quadrats laid (35 at the Department of Botany). Relative Importance Value (RIV-%) was calculated to determine species dominance, while the Jaccard Similarity Index (SCJ-%) was used to compare species composition across sites and seasons. Results: Species richness was higher in BG (52 species, 28 families) and DB (51 species, 28 families) than in TRF (41 species, 21 families), with greater richness during wet seasons across all sites. Petiveria alliacea exhibited the highest RIV across seasons and years in TRF and BG, and during dry seasons in DB. Peak RIV values occurred in dry seasons, whereas the lowest values were recorded during wet seasons. Species composition similarity was highest between wet seasons within the same sites and lowest between dry and wet seasons across different sites. Conclusion: Petiveria alliacea is a dominant, fast-spreading species with pronounced spatial and temporal variation but poses no serious threat in the short term to the heterogeneity of the landscape, suggesting its ecological compatibility as a pioneer plant within the secondary forest.