Capparis buwaldae Jacobs (Capparaceae). A new Myrmecophyte from Borneo

Capparis buwaldae, a climber of primary forests endemic to Borneo, is a myrmecophyte with stem domatia. The stems become hollow by pith degeneration and develop oval openings allowing ants to enter. These openings are localized at a strictly defined area above the insertion of the leaves and a pair of nodal thorny stipules. They gradually split open from the outside. The openings may develop into elevated chimney-like structures or close again by growth if not kept open by ants. The plant may be inhabited by various opportunistically nesting arboreal ants including Crematogaster, Monomorium, and Camponotus species. Specialized myrmecophytic ants could not be found. Neither nectaries, nor food bodies, nor trophobiotic endophytic homopterans could be observed. In the Rijksherbarium, Leiden 65 other Capparis species and subspecies from the Indo-Australian region were examined for ant-plant characters. None of these species showed any myrmecophytic character.