Submitted to: Journal of Entomological Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/22/2010
Publication Date: 10/1/2010
Citation: Defauw, S.L., Rojas, M.G., Morales Ramos, J.A., Boykin, D.L. Extracted Venom and Cuticular Compounds of Imported Fire Ants, Solenopsis spp., and Chemotaxonomic Applications Across a Persistent Hybrid Zone. J. Entomol. Sci. 45(4): 335-352. 2010.
Interpretive Summary: Imported fire ants have successfully invaded over 320 million acres in the United States spanning 13 states and Puerto Rico. Red (Solenopsis invicta Buren), black (S. richteri Forel), and hybrid imported fire ants are distinguished from each other based on biomolecules extracted from their surfaces. We developed a new gas chromatography and mass spectrometry (GC-MS) method to identify these ants. Application of these techniques would be especially useful in refining regionally-based biological control strategies such as the release of phorid flies (Pseudacteon spp.) or other species that use airborne biochemicals to detect appropriate hosts.
Technical Abstract: Characterization of cuticular biomolecular assemblages for imported fire ants permit basic distinctions among colonies of S. invicta, S. richteri, and their hybrids; thus, providing opportunities to investigate details of landscape ecology for this species complex as well as to assess levels of invasiveness and the efficacy of best management practices to suppress ant dispersion based on regional factors. We introduce a new method for the biochemical analysis of imported fire ants that is complementary to a widely used method based on calculating cuticular hydrocarbon and venom alkaloid indices. Results from this new GC-MS method were analyzed using various hierarchical and normal mixtures clustering methods to test the stability of group membership. Principal component and discriminant analyses were used to produce three-dimensional views of group separation. The relative proportions of 12 peaks served to differentiate imported fire ant hybrids into four assemblages – hybrids closely allied with S. invicta, hybrids close to S. richteri, a ‘core’ hybrid grouping, and an ‘outlier’ hybrid group. The most influential peaks of the twelve-peak assemblage (based on F-values) included three peaks with the piperidine structural motif and an alkane. Use of three peaks identified by stepwise linear discriminant analysis resulted in misclassification of 5% of the ant colonies, whereas use of four peaks resulted in the misclassification of 2.5%. Thus, this new cost-effective GC-MS method and multivariate assessment of biochemical data may facilitate the finer-scale distinction of hybrid colonies in terms of their surficial semiochemical complexity and ‘alliance’ with parental species. Application of these techniques would be especially useful in refining regionally-based biological control strategies such as the release of phorid flies (Pseudacteon spp.) or other species that use semiochemicals to detect appropriate hosts.