First record of Robinia hispida L. (Fabaceae) in South Africa

Abstract

The shrub, Robinia hispida L., commonly known as the bristly locust, is a native to southeastern United States. It has, however, expanded its range within North America, and established invasive native-alien populations in several American states and Canada. Outside of North America, R. hispida has been introduced to Europe and Asia, where it has naturalised and is considered invasive. Notably, the presence of this shrub has never been reported outside of cultivation in Africa. Despite receiving little scientific attention compared to its congeneric species such as the global invader Robinia pseudoacacia L., R. hispida shares morphological and growth characteristics including rapid growth and a suckering habit. It occupies similar environmental niches in both native and introduced ranges, thriving in thin upland woodlands, woodland edges, thickets, fence rows, roadside embankments, banks of drainage canals, vacant lots, and overgrown waste areas. In South Africa, R. hispida was first recorded in a garden in Polokwane in 1986, while the first record outside of cultivation was near the town of Bethlehem in the Free State Province in 2023, and further surveys were conducted locating additional populations near the towns of Zastron and Clarens in 2024. The potential distribution of R. hispida in South Africa was modelled in MaxEnt using areas climatically representative of the species, based on the Koppen-Geiger climate classifications. The potential distribution includes areas of central South Africa, the east and south coast and the Mediterranean climates of the southern Cape. Management strategies suggested for R. hispida in South Africa, considering the small size of the populations, should include eradication efforts using mechanical and chemical means, followed by continuous monitoring to prevent re-emergence.