Temperature Variation, Resource Concentration, and Foraging Behaviour Influencing the Effect of Monomorium Sydneyense (Hymenoptera: Formicidae) on the Ant Community of Tauranga, New Zealand.

Introductions of ants into new areas can dramatically influence resident ant populations. A recent ant introduction to New Zealand is the Australian myrmicine, Monomorium sydneyense Forel. The effects of this ant on the resident ant fauna of Tauranga were assessed, as well as the role of temperature and food concentration on competitive dynamics. Aspects of foraging characteristic and intraspecific behaviour were studied in order to aid management decisions, should population control by toxic baiting be required. There was a significant difference in community structure in M. sydneyense invaded communities compared to uninvaded ones, although the abundance of no individual species was significantly affected or was displaced by M. sydneyense. Temperature was found to play a strong role in the competitive dominance of M. sydneyense. Monomorium sydneyense dominated a larger proportion of baits at warm temperatures, however it secured significantly less foods at cooler temperatures. Temperature preference trials in the laboratory supported field observations as M. sydneyense displayed a preference for warmer temperatures, compared to Pheidole rugosula Forel which showed no preference for any of the temperatures tested. Monomorium sydneyense showed a distinct preference for the protein based food resources that were offered, including the ant bait X-Stinguish®. Foraging distance trials showed that M. sydneyense workers were never observed foraging more than 2.8 m from their nest. The probability of only 50% of baits being occupied by M. sydneyense at a distance of 1 m from a nest suggests that intensive baiting would be required to manage populations of this ant, highlighting that the population management of M. sydneyense would be difficult. Aggressive behaviour was displayed between workers from different nests, suggesting that there is a reduced likelihood of this ant attaining high population densities in New Zealand.