Coping with Enemy-Filled Space: Herbivores on Endospermum in Papua New Guinea

It is hypothesize that colony initiation was less successful in the pubescent morphs in part because of a parasitic fly that attacks foundress ants.

Abstract

Insect herbivores that specialize on ant-plants must contend with a resident colony of predators that can use the insect as food or at least deter it from feeding on the plant. In Papua New Guinea, the euphorb Endospermum labios Schodde is commonly inhabited by Camponotus quadriceps F. Smith ants that are easily alarmed, recruit effectively, and bite intruders on the host plant. Plants that lack Camponotus often have other resident ant species. We compared the size, herbivore load, herbivory level, frequency of plants supporting vines, and degree of ant defense on E. labios with different ant inhabitants growing intermixed in disturbed forest. A glabrous morph of this tree had distinctly larger colonies of Camponotus, was dramatically larger on average, and suffered very little herbivore damage compared to pubescent morphs even though the morphs appeared to be equally preferred by foundress ants for colony initiation and as food by uraniid caterpillars. Herbivores on E. labios escaped ant defenses by exploiting plants that lacked Camponotus colonies. We hypothesize that colony initiation was less successful in the pubescent morphs in part because of a parasitic fly that attacks foundress ants.