BIOLOGY, GENOMICS, AND INTEGRATED PEST MANAGEMENT OF INVASIVE ANTS
Location: Imported Fire Ant and Household Insects
Title: Analysis of chemical signals in red fire ants by gas chromatography and pattern recognition techniques
Submitted to: Talanta
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: September 8, 2010
Publication Date: September 16, 2010
Citation: Levine, B.K., Mirjankar, N., Vander Meer, R.K. 2010. Analysis of chemical signals in red fire ants by gas chromatography and pattern recognition techniques. Talanta. 83:216-224.
Interpretive Summary: Imported fire ants infest more than 320 million acres in 13 southern tier states and Puerto Rico and are spreading northward. This invasive ant is estimated to be responsible for almost $7 billion annually in damage repair, medical care, and control costs. The affected economic sectors are broad ranging and include households, electric service and communications, agriculture (crops and livestock), schools and recreation areas. Interestingly, ants comprise 5% of the world’s 100 worst invasive alien species, and of the 17 land invertebrates listed, 28% are ants, including fire ants! In the last decade S. invicta has changed from an invasive pest ant in the United States to a global problem, with infestations occurring in Australia Taiwan, mainland China, Mexico, and many Caribbean Island countries. Social insects including the fire ant recognized the chemical signature of their own colony members and are able to maintain and defend territory due to recognition of non-nestmates as different. The consequences of this process are that the each colony is able to insulate itself from incursions from other ant species, predators, and parasites. Cuticular hydrocarbons patterns are very complex and contribute to nestmate recognition cues. Pattern analysis is complex, requiring sophisticated-multivariate techniques. Scientists at the Center for Medical, Agricultural and Veterinary Entomology, USDA, ARS, Gainesville, Florida USA, and the Department of Chemistry, Oklahoma State University, Stillwater, OK, investigated clustering, mapping, discriminant development, etc. to determine which method provides the clearest separation of fire ant colonies based on their cuticular hydrocarbons. Clustering according to the biological variables of temporal social caste (broodtender, reserve, and forager workers) and colony of origin were observed. Pooling the extracts enhanced the recognition of patterns in the hydrocarbon profile data characteristic of colony. This knowledge can be important in designing novel integrated management of this important pest ant.
The combination of gas chromatography and pattern recognition (GC/PR) analysis is a powerful tool for investigating complicated biological problems. Clustering, mapping, discriminant development, etc. are necessary to analyze realistically large chromatographic data sets and to seek meaningful relations between chemical constitution and biological variables. A specific study will be described that highlights the advantages of using GC/PR to decipher the complex chemosensory code of social insects. Gas chromatographic (GC) profiles of cuticular hydrocarbon extracts obtained from individual and pooled ant samples were analyzed. Clustering according to the biological variables of social caste and colony were observed. Pooling the extracts enhanced the recognition of patterns in the GC profile data characteristic of colony. Evidently, the contribution of the ant's individual pattern to the overall hydrocarbon profile pattern can obscure information about colony in the GC traces of cuticular hydrocarbon extracts obtained from red fire ants.