A new report by Buczkowski & Krushelnyky of Tapinoma sessile spreading in Hawaii (pdf) raises a rather chilling prospect:
Because the odorous house ant ranges as far north as southern Canada and occurs at elevations over 4000 m in North America, there is serious cause for concern that, unlike most invasive ant species in Hawaii, it will be capable of invading high elevation habitats.
Hawaii has no native ants, and the tropical ants introduced to the archipelago are causing serious ecological problems at lower elevations. Now higher elevations may be vulnerable to ants as well. This is not good news.
Tapinoma sessile has always been a home-grown pest in North America, and although the species shows a suite of behaviors common to globally important invaders it had never established elsewhere. Until Hawaii.
What I find particularly interesting about Tapinoma sessile is how its pestiness has apparently increased over time. It is as though proximity to human landscapes has selected for larger colonies of more disturbance-tolerant ants and converted a previously minor nuisance into a more serious concern. This possibility, that some native ants may evolve into global pests simply through extended interactions with our own species, is troubling. New pests might be able to emerge from a much larger and less predictable pool of species that I had imagined.
source: Buczkowski, G., Krushelnycky, P. 2011. The odorous house ant, Tapinoma sessile (Hymenoptera: Formicidae), as a new temperate-origin invader. Myrmecol. News 16: 61-66; published Online Earlier 30 September 2011.