The South African Journal of Science is a multidisciplinary journal published bimonthly by the Academy of Science of South Africa. Our mandate is to publish original research with an interdisciplinary or regional focus, which will interest readers from more than one discipline, and to provide a forum for discussion of news and developments in research and higher education. Authors are requested to write their papers and reports in a manner and style that is intelligible to specialists and non-specialists alike. Research contributions, which are peer reviewed, are of three kinds: Review Articles, Research Articles and Research Letters.