Chemistry of the postpharyngeal gland secretion and its implication for the phylogeny of Iberian Cataglyphis species (Hymenoptera: Formicidae)

A comparative morphological and chemical study of six endemic species of Cataglyphis from the Iberian Peninsula: C. ibericus, C. rosenhaueri, C. hispanicus, C. humeya, C. velox and C. floricola and the Moroccan species C. bombycinus is described. The morphological study relied primarily on genitalia characteristics, whereas the chemical study concentrated on the postpharyngeal gland constituents. Cladograms based on the morphological and chemical data were performed using Ward's method. The dendrogram based on morphological features revealed that the Iberian Cataglyphis can be classified into three species groups albicans, altisquamis and emmae. The same pattern occurred when the dimethylalkanes constituents of the postpharyngeal gland were utilised as character states, with a slight displacement of species within the altisquamis group. However, when the complete hydrocarbon blend was utilised major discrepancies in the dendrograms occurred. Cataglyphis velox proved to be very similar to C. bombycinus, whereas C. floricola clustered with the other two species of the altisquamis group. Based on the geographical distribution and paleontological data (Tinaut 1993) it is assumed that C. floricola recently invaded the Iberian Peninsula. Based on the chemical findings we postulate that chemical character displacement occurred in C. floricola as a result of its sympatry with C. velox after the former colonized the Iberian Peninsula. We further discuss the possible reason for the different dendrograms obtained when only the dimethylalkanes are considered and its implication for the communicative role of the postpharyngeal gland secretion in these ants.