Land-Use Is More Important Predictor of Native Abundance and Diversity Than Invasive Tithonia Diversifolia - Evidence From a Tropical Savanna

Abstract

Invasive alien species (IAS) and land-use represent major threats to native plant communities around the globe. However, studies on IAS and potential ecological impacts in the context of land-use are limited in sub-Saharan Africa. Using a set of 45 plots in Jos metropolis in central Nigeria, we assessed the abundance of invasive Tithonia diversifolia (Hemls.) A. Gray, and its relationship with abundance and diversity of native plant species among land-use types. Abundance of T. diversifolia was the highest in farmland when compared to riparian and roadside land-use types. Also, the abundance and diversity of native species were lowest in farmland when compared to the roadside and riparian plant communities with increased T. diversifolia abundance. We showed that while T. diversifolia has low impact on native species, land-use type is an important predictor of native abundance and diversity. Although T. diversifolia has benefitted from the disturbances across land-use types, we found a very weak negative estimate of T. diversifolia effects on native species. These results consolidate existing evidence that land-use transformation in sub-Saharan Africa provides opportunities for alien plant invasion and native species decline. More important is the preservation of land-use types, which will result in a synergy of conservation effort - both reducing T. diversifolia abundance and preserving native plant abundance and diversity in central Nigeria.