Chrysocoma ciliata L. (Asteraceae) in the Lesotho Highlands: an anthropogenically introduced invasive or a niche coloniser?

Abstract

Over recent decades, concern has been raised regarding the management of Chrysocoma ciliata L. (Asteraceae syn. C. tenuifolia) in the eastern Lesotho Highlands. This shrub species is argued to be a Karroid invasive introduced anthropogenically within the last century. Historical botanical records in Lesotho are scarce, so the origins of this species in the region are as yet uncertain. Speculation is based on the contemporary abundance of these shrubs in overgrazed areas throughout the highlands. This study presents fossil pollen records for the eastern Lesotho Highlands which confirm the presence of this species intermittently throughout the past ~6000 cal yr BP. In so doing, this study refutes claims that the species was introduced anthropogenically within the past 100 years, and of its narrow definition as a Karoo species invasive in Lesotho. The intermittent appearance of this species in the pollen record, however, indicates that it is climate sensitive, colonising the wetlands under conditions unsuitable to other plant species. Evidence presented here calls for a re-evaluation of the categorisation of C. ciliata as an invasive in the Lesotho Highlands, and more critically, for a redevelopment of the environmental management policies which involve this species.