Origins, Patterns, and Ecological Consequences of Biological Invasions in Nigerian Protected Area Networks

Biological invasions represent a globally significant but systematically understudied driver of biodiversity loss in Nigerian protected area networks, where monitoring resources are limited and systematic invasion science has not historically been a management priority. This study investigates the origins, establishment patterns, and ecological consequences of biological invasions by plants, vertebrates, and insects across a stratified sample of eight protected areas spanning Nigeria's ecological zones. A standardised invasion survey protocol was applied across 320 sample plots per protected area, documenting alien and cryptogenic species occurrence, abundance, and impact indicators. Origin pathway analysis using historical trade and introduction records traced invasion vectors. Structural equation modelling linked disturbance history, propagule pressure, and biotic resistance to invasion success. Impact assessments compared native species richness, functional diversity, and ecosystem process rates between invaded and uninvaded matched plots. A total of 187 alien species were documented across the eight protected areas, of which 41 were classified as invasive based on abundance and impact indicators. Invasion intensity was highest in protected areas with adjacent urban centres and active road development, confirming propagule pressure and disturbance as joint drivers. Chromolaena odorata, Tithonia diversifolia, and Prosopis juliflora caused the greatest native plant diversity losses, while the Nile tilapia and common myna had significant impacts on native aquatic and avian communities respectively. The study proposes a national alien species risk assessment protocol and early warning monitoring network applicable to all Nigerian protected areas. Keywords: biological invasions, protected areas, alien species, invasion ecology, Nigeria