FORAGING BEHAVIOR IN TROPICAL HERBACEOUS CLIMBERS (ARACEAE)

1. Climbing aroids grow through the forest, and demonstrate changes in their shoot developmental patterns associated with the changes in microhabitat resulting from displacement of the apex. Through allometric development or metamorphosis, shoots are able to shift growth forms: by altering their mobility, meristems of climbing species may disperse from their site of germination on the ground to their site of maturation on tree trunks, and then become sessile. Some species have the ability to become mobile again should environmental conditions change. 2. Shoot developmental patterns in Araceae lie along a continuum from sessile to mobile, within which four broad classes of growth form can be recognized, based on the shape of the internodes: acaulescent, in which internodes are ten or more times as wide as long; caulescent, in which internodes are about as wide as long; climbing or creeping, in which internodes are about ten times as long as wide, and flagellar, in which internodes are thirty or more times as long as wide. 3. The relationship between shoot development and foraging behaviour is two-fold. The set of shoot developmental pathways allowed by the genetic system of a species determines its overall foraging pattern. Environmentally mediated switching between pathways or alterations of rates or directions of progress within pathways allow adjustments to the foraging pattern. 4. Foraging behaviour is illustrated for five species of climbing Araceae: Anthurium subsignatum, Monstera skutchii, Philodendron fragrantissimum, Philodendron scandens and Syngonium triphyllum. For comparison, data are presented on one terrestrial species, Dieffenbachia seguine. Data are based on measures of lengths and diameters of successive internodes along shoots. Shoot development is represented graphically by plotting the trajectories traced by successive shoot segments through an internode size-shape space.