Clerodendrum fistulosum (Verbenaceae), an unspecific Myrmecophyte from Borneo with spontaneously opening domatia

Clerodendrum fistulosum Becc. is a true myrmecophyte as it offers nesting space for ants in hollow internodes. In contrast to previous reports our investigations proved that these domatia open by themselves, thus providing cavities for a variety of different ant species. In Sarawak, Malaysia, we did not find an obligate relationship between C. fistulosum and a specific ant-partner. For comparison, studies on herbarium material of other Clerodendrum species were carried out: a further species, C. deflexum from the Malay Peninsula and Sumatra presumably also is myrmecophytic.