Trade-off between chemical and biotic antiherbivore defense in the south east Asian plant genus Macaranga

The plant genus Macaranga is known for its manifold mutualistic association s with ants. The plants provide food for the ants and in turn get protectio n from herbivores. Depending on the strength of the plant-ant interaction, the plant's investment in ants and the biotic defense derived front them is more or less effective. We conducted a comparative study on tannin content in 12 Macaranga species that were selected based on their associations wit h ants (three nonmyrmecophytes and nine myrmecophytes, three of which start their ontogeny as nonmyrmecophytes). Different developmental stages were i nvestigated in three Macaranga species. Extracts of every individual plant analyzed for tannins were also tested for their effects on larval growth em ploying larvae of the common cutworm (Spodoptera littoralis). The studied M acaranga species differed significantly in their tannin contents as well as in the effects of their leaf extracts on the growth of S. littoralis larva e. A correlation analysis shows a connection between tannin contents and la rval growth. High tannin contents and, thus more effective chemical defense , were observed in nonmyrmecophytic Macaranga species associated only facul tatively with ants as compared to obligate myrmecophytes. Our study support s the hypothesis or a trade-off between chemical and biotic defense in the genus Macaranga.