Experimental analysis of nestmate recognition in the imported fire ant Solenopsis invicta Buren (Hymenoptera:Formicidae).

摘要

This study examines the mechanism and adaptive significance of nestmate recognition in monogyne colonies of the imported fire ant, Solenopsis invicta. Discrimination of nonnestmates was quantified in a bioassay that measured agonism in the context of nest defense directed at "intruder" ants placed near (but not in) the nest. The following results were obtained: (1) Environmentally correlated cues dominated the recognition cue hierarchy of laboratory and field colonies, and diet alone significantly altered recognition "labels" and "templates" of laboratory-reared workers. (2) Heritable recognition cues ("discriminators") of workers constituted some portion of the recognition-cue hierarchy of this species. (3) Gas-liquid chromatographic and multivariate analyzes indicated that cuticular hydrocarbon pattern was a poor predictor of recognition response when colonies were reared under different environmental regimes (laboratory vs field). (4) Queen-derived cues ("queen discriminators") did not significantly alter labels or templates of workers in nests requeened with an alien field queen for 1 month, or reared from the larval stage for 5 months in the absence of a queen. (5) However, workers that tended mother queens in small cups were attacked more often by kin than non-tending workers. Aggression directed at these workers was not significantly associated with ovarian development of the tended queen. (6) Template-label matching of dietary odors was based on overall "similarity" rather than on a "discrete odor" mechanism. (7) The recognition bioassay was extended to within and between species tests among laboratory-reared (1 year) colonies of S. invicta, S. richteri and their Mississippi hybrid. Within-group recognition scores were highest for hybrids and lowest for S. invicta, suggesting greater genetic variability for heritable recognition cues in hybrid populations, and least variability in S. invicta populations. Results are applied to the dynamics of the Mississippi fire ant hybrid zone and contrasted with electrophoretic studies of "neutral," Mendelian markers in fire ant populations.