Role of native herbivores in the increasing abundance of Solanum Marginatum l.f. (Solanaceae) in the northern Bale Mountains, Ethiopia

Abstract

Solanum marginatum L. f. (Solanaceae) is a weedy shrub native to Ethiopian highlands, including the Bale Mountains National Park (bmnp) where it is currently rapidly increasing in abundance. In this study, based on two independent datasets, we examined whether and how herbivory activities (e.g., grazing/browsing, and soil disturbance) by wild ungulates might have facilitated the performance of the shrub in the bmnp. In the first dataset, we set up a wire-fenced enclosure to examine the effects of herbivory activities on the survival of S. marginatum seedlings. We collected another independent data set from a total of 88 sample plots established at sites disturbed by Common Warthogs’ [Phacochoerus aethiopicus, (Gmelin, 1788)] herbivory activities (i.e., ground digging) and at sites not disturbed, to examine the effect of these digging activities on seedling establishment of the shrub. Our results indicated that mean S. marginatum seedling abundance was significantly greater outside than inside the enclosure, and in the Warthog-dug sites than the non-dug sites. In contrast, herbaceous vegetation height and cover were significantly greater inside than outside the enclosure and in the non-dug sites than in the dug sites. Herbaceous vegetation cover and height were significantly (negatively) correlated with S. marginatum seedling abundance, while bareground is positively correlated. In conclusion, our findings indicate that herbivory activities of wildlife facilitates the performance of S. marginatum shrub by reducing herbaceous biomass, thus leading to increased resource available to S. marginatum seedlings to establish. Implications of results of the study and future actions needed to manage the shrub in the study area are discussed.