Interactions between weaver ants Oecophylla smaragdina, homopterans, trees and lianas in an Australian rain forest canopy

1. Tritrophic interactions between the weaver ant Oecophylla smaragdina (Fabricius) (Hymenoptera: Formicidae), plants and honeydew-producing trophobionts (Hemiptera: Sternorrhyncha and Auchenorrhyncha, Lepidoptera: Lycaenidae) were studied in a rain forest canopy in Northern Queensland, Australia. 2. Most commonly attended trophobionts by O. smaragdina at this study site were Coccidae (Coccus sp., Milviscutulus sp.) and Membracidae (Sextius sp.), followed by Toxoptera aurantii (Aphidae), Planococcus citri (Pseudococcidae), Icerya sp. (Margarodidae), an unidentified species of Eriococcidae, Austrotartessus sp. (Cicadellidae), and lycaenid butterfly larvae (Anthene seltuttus, Arhopala centaurus group). 3. Most trophobionts were highly polyphagous, and trees and lianas from many plant species and families acted as homopteran hosts. However, lianas were found to play a key role. First, the majority (68%) of aggregation sites was found on lianas, especially on the legumes Entada phaseoloides and Caesalpinia traceyi, and secondly, per capita ant visitation rate (VR) at coccoids was significantly higher on lianas compared to trees. In total, VR to homopterans was 64% higher on lianas. 4. Sites of ant-homopteran aggregations were regularly replaced by new locations on fresh plant growth. The mean longevity of nests of this polydomous ant species was 131 days, of individual aggregation sites with membracids 54 days and with coccoids 130 days. 5. Our results suggest that plant-specific differences in suitability for honeydew production (especially the availability of lianas) and the availability of preferred trophobionts have a strong influence on the vigour of Oecophylla colonies.