Inter- and Intraspecific Aggression in the Invasive Longlegged Ant (Hymenoptera: Formicidae)

The longlegged ant, Anoplolepis gracilipes</it> (Fr. Smith) (Hymenoptera: Formicidae), is a highly invasive species that can aggressively displace other ant species. We conducted laboratory assays to examine interspecies aggression of A. gracilipes versus 15 sympatric ant species found in the urban environment and disturbed habitat in Malaysia: Monomorium pharaonis</it> (L.), Monomorium floricola</it> (Jerdon), Monomorium orientale</it> Mayr, Monomorium destructor</it> (Jerdon), Pheidole parva</it> Mayr, Crematogaster</it> sp., Solenopsis geminata</it> (F.), Tapinoma indicum</it> (Forel), Tapinoma melanocephalum</it> (F.), Technomyrmex butteli</it> Forel, Dolichoderus thoracicus</it> (Smith), Paratrechina longicornis</it> (Latrielle), Oecophylla smaragdina</it> (F), Camponotus</it> sp., and Tetraponera rufonigra</it> (Jerdon). A. gracilipes showed aggressive behavior toward all opponent species, except the smallest M. orientale. Opponent species size (body size, head width, and mandible width) was significantly correlated with A. gracilipes</it> aggression level and mortality rate. We also found a significant positive relationship between A. gracilipes</it> aggression level and the mortality of the opponent species. The results suggest that invasive populations of A. gracilipes</it> would have the greatest impact on larger ant species. In addition, we examined the intraspecific aggression of A. gracilipes</it>. We found that A. gracilipes</it> from different localities in Malaysia showed intraspecific aggression toward one another. This finding differs from the results of studies conducted in Christmas Island earlier. Differences in the genetic variability among populations may explain these differing results.