Polydomy and intraspecific aggression in the Asian needle ant, Pachyconcyla chinensis (Emery)

Single ant colonies inhabiting spatially separated nests are a well-documented phenomenon known as polydomy. In addition to multiple nests, polydomy is further characterized by increased nest density, and decreased intraspecific aggression. The invasive Asian needle ant, Pachycondyla chinensis (Emery), is recognized as a public-health concern and ecologically-dominant species. As an invasive ponerine ant species, P. chinensis presents an opportunity to document potential range expansion and subsequent ecological impacts of a group of ants relatively unknown as pests. Literature accounts report that P. chinensis colonies are polydomous; however this behavior has not been thoroughly examined. To determine if P. chinensis colonies exhibit polydomy, the nest density of ant colonies at four locations were compared. In addition intracolony and intercolony nestmate recognition assays were conducted in laboratory and field trials. Nestmate recognition assays were organized into three treatment categories; within nest, within location, and between location trials. Recognition assays were scored on a 0-4 (low to high) aggression scale.  Mean aggression scores for each of the three possible pairings were compared using an ANOVA (P  = 0.05).  Results from nestmate recognition assays suggest that P. chinensis colonies are polydomous as intercolony aggression did not increase with nest distance.  These data also indicate a potential for large, unicolonial populations when contiguous habitat is available.