Colony foundation and acquisition of coccoid trophobionts by Aphomomyrmex afer (Formicinae): co-dispersal of queens and phoretic mealybugs in an ant-plant-homopteran mutualism?
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In coastal forests of Cameroon, colonies of the ant Aphomomyrmex afer are found in hollowed twigs of two species of trees, most commonly the myrmecophyte Leonardoxa africana T3. Established colonies of this ant are always associated with coccoid homopterans (the pseudococcid Paraputo anomala or the coccid Houardia abdita, or both) within hollow twigs, and ants appear to be dependent on these sap-sucking trophobionts. We dissected domatia of juvenile host-plants that had not yet acquired an established colony to determine (1) how colonies are founded, and (2) when and how trophobionts are acquired. Colony foundation is claustral. A single queen chews an entrance hole into an unoccupied domatium that serves as the founding chamber. The entrance hole is partially closed by debris and later by callus growth. Nineteen foundresses were located while still in the claustral phase, with no workers or a few nanitic workers. Of the 19 foundresses, 12 had at least a single Paraputo anomala individual in the same domatium. One of the queens had two female P. anomala nymphs attached to her body. The remaining 7 foundresses were not associated with coccoids.¶These results indicate that mealybug and ant may co-disperse by phoresis of juvenile female mealybugs on founding queens. Association with mealybugs should provide foundresses with a food source during claustral foundation. The coccid Houardia does not seem to co-disperse with ants, and foundresses originating from adult colonies that tend only coccids must acquire trophobionts later.
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