XVI International Botanical Congess
Several south-east Asian pioneer tree species of the palaeotropical genus Macaranga exhibit strong mutualistic interaction with ants, mostly of the genus Crematogaster. Nuclear rDNA ITS sequences revealed a close relationship of the obligate mutualistic species of Macaranga sect. Pachystemon s.str., as well as of the transitional mutualists of the M. pruinosa group. The phylogenetic analysis clearly shows that todays less specialized ÔtransitionalÕ species are not the ancestors of obligate myrmecophytists. Macaranga winkleri, a morphologically different species, is sister-group of two non-myrmecophytic species, which allows to postulate an additional, independent origin of myrmecophytism in Macaranga. Plant - ant mutualistic interaction thus seems to be an advantageous trait in disturbed environments.