Camponotus (Colobopsis)(Mayr 1861) andMacaranga(Thouars 1806): a specific two-partner ant-plant system from Malaysia

Abstract

Within the paleotropical tree genus Macaranga (Thouars 1806) (Euphorbiaceae), the majority of ant-plant species are associated with specialized Crematogaster (Lund 1831) partner ants from the subgenus Decacrema (Myrmicinae). We have now discovered a completely different myrmecophytic system in which an ant species of the Formicinae lives in symbiosis with the peat swamp forest tree Macaranga puncticulata (Gage 1922). M. puncticulata twigs develop spacious cavities (domatia). An undescribed Camponotus (Colobopsis) (Mayr 1861) species of the C. saundersi-group was the dominant ant inhabitant (65% of the investigated plants) at forest sites, but this species, provisionally named C. (Colobopsis) sp. 1, was only rarely found at open stands. Another 29 opportunistic stem-nesting ant species were collected less frequently. None of them were Crematogaster (Decacrema) ants. C. (Colobopsis) sp. 1 has never been found to nest away from M. puncticulata. The mated queens are capable of locating young M. puncticulata plants and of chewing entrance holes into the domatia. In contrast to all the other obligate plant-ants associated with Macaranga, C. (Colobopsis) sp. 1 never cultivates any trophobionts, neither inside nor outside the domatia. Instead of taking up honey dew from coccids, the ants obtain carbohydrates from extrafloral nectaries along the leaf margins of M. puncticulata. This food source is an uncommon trait within Macaranga myrmecophytes. The association of C. (Colobopsis) sp. 1 with M. puncticulata is therefore the first record of a two-partner ant-plant system without endophytic coccids in the genus Macaranga.