keywords: Botanical garden, conservation, extinction, indigenous plants, invasive species, biodiversity
Exotic plant species can replace native species by becoming invasive and causing change in habitat structure, affect ecosystem processes and threaten biodiversity if not detected and managed early. In some cases it might even lead to local extinction of native species. Botanical garden of Ahmadu Bello University Zaria (ABU) is an insitu conservation site where the composition and rate of invasion by exotic species is yet unknown. As such for proper management and control, this survey was designed to document the number of indigenous and exotic plants species in the garden. The garden was divided into 19 plots based on existing concrete walk-ways and map. Plants were collected from each plot using modified "Whittaker technique" and identified at the Herbarium Department of Botany ABU, Zaria. The plants were further grouped into indigenous and exotic species using the savanna keys as well as other literature sources. A total of two hundred and twenty two (122) species belonging to forty eight (48) families, including eighty three (83) exotics and thirty nine (39) indigenous were recorded. Members of the family Fabaceae were dominant with fifteen (15) species of which eleven (11) were exotic plants. Evaluation of the data revealed that exotic plant species were significantly (p <0.01) overrepresented over the indigenous plant in the garden. Albizialebbeck, Bauhinia monandra and Gmelinaarborea which are exotics were the most dominant plant species.It was concluded that, the exotic plant species have higher representatives in almost all the plots and needs to be managed to prevent local extinction of natives in the garden.