Interaction between epiphytic chemical allelopathy and ant-pruning determining the composition of Amazonian ant-garden epiphytes

Abstract

In Ant-gardens, ants build nests with organic materials and take specific seeds of some species of epiphytes which germinate. In this mutualistic interaction, a variety of other epiphytes could colonize the nests and develop, but it doesn't happen. We assume that there is chemical allelopathy with epiphytes inhibiting the germination and growth of other species of epiphytes, and with ants cutting off non-mutualistic epiphyte species. To investigate this, we performed chemical and prune tests which determine the composition of the epiphyte species of Ant-Gardens of parabiotic ants, Camponotus femoratus (Fabricius, 1804) and Crematogaster levior Longino, 2003. For the chemical allelopathic test, we administered the extract of the stem and leaves of Peperomia macrostachya (Vahl) A. Dietr. and Codonanthe calcarata (Miq.) Hanst. (the most common species in parabiotic AGs) in different concentrations. For the prune test, we used seedlings of the mutualistic plant Peperomia macrostachya and non-mutualistic plant Cucumis sativus as a control, then we inspected the nests to evaluate the ants pruning the seedlings. In the chemical allelopathy tests, the species Codonanthe calcarata decreased the germination speed indexes in relation to the control (distilled water). On the contrary, the length and weight of the seedlings were positively influenced by epiphyte extract. In the prune test, most of the plants pruned were non-mutualistic. The results of the chemical allelopathy and prune experiments showed that both mutualistic epiphytes and ants play a decisive role in the composition of epiphytes in Ant-Gardens.