Length, branch production, orientation, spinescence and biomass were measured for current shoots of Acacia tortilis shrubs in a range of habitats in Botswana. All shoot characteristics varied between individuals and between habitats with longer, less spinescent shoots produced in the habitat recently protected from wildlife. Biomass allocated to woody material increased with shoot length at the expense of leaf mass, whilst investment in straight prickles was as much as 6% of shoot dry mass. Shoot length had significant effects on total current shoot mass per shrub which was greatest in the recently protected area but the mean number of shoots per shrub also varied between habitats. Age and history of disturbance, including herbivory, appear to be important determinants of morphology and growth pattern of individual shrubs. Fitness of A. tortilis individuals and the consequence of flexibility in growth responses for vegetation structure and community organization are discussed.
