Distribution and Abundance of Wild Sunflower (Verbesina encelioides) and its Impacts on Plant Biodiversity in The Central Rift Valley of Ethiopia

Abstract

Wild sunflower (Verbesina encelioides) is a newly identified emerging invasive weed with adverse consequences that require management efforts. Surveys were conducted in the Central Rift Valley of Ethiopia during the main rainy season of the year 2020. The research aimed to determine the geographic distribution of wild sunflower, generate data on the quantitative measures, the threats posed by the weed to native plant biodiversity, and assess the influence of some environmental factors on wild sunflower. A total of 220 sampling points were assessed across 22 different sites. Ecological indices were used to assess the distribution and diversity of the weed species. The significance of nine key variables: rainfall, temperature, altitude, species abundance, richness, diversity, and the density, frequency, and dominance of wild sunflower, were assessed using principal component analysis. A total of 42 taxa that belong to 18 plant families were recorded. Wild sunflower was found in 68.64% of the total sampling points. The infestation was more prevalent at low altitudes, such as Fentale, Boset, and Adama. On the roadside, wild sunflower was the dominant weed species. It has also been observed in different crop fields, like common beans, onions, and tef. Principal component analysis showed that the first two of the nine principal components (largely wild sunflower density and frequency) accounted for 77% of the variation in the data set. Rainfall, altitude, and temperature were among the environmental factors that influenced wild sunflower distribution. The highest density of wild sunflower (54.19 plants m-2) was observed to significantly reduce the diversity of other plant communities (H′ = 2.47). Thus, practical and effective measures are required to prevent and control the spread of this exotic invasive weed to other parts of the country where it has not yet been introduced.