Ant communities in the grasslands of the Australian Capital Territory and the role of ants in the ecology of the pink-tailed legless lizard, Aprasia parapulchella

Abstract

This study examined the ant communities of several grasslands of the Australian Capital Territory (ACT) and their relevance to the pink-tailed legless lizard, Aprasia parapulchella (Pygopodidae). A. parapulchella is a fossorial species that shares burrows with, and eats the brood of, several grassland ant species.
Foraging ants were collected from sites by pitfall trapping throughout one calendar year and comparisons of ant communities made between seasons and sites of differing vegetation structure. Competition between ant species for artificial nest sites and the effects of temperature on selection of nest site selection were also studied. The role that ants play in the distribution of A. parapulchella was investigated by (i) comparing ant faunas from several sites throughout the geographic range of the lizard, including sites in New South Wales and Victoria, (ii) performing feeding preference experiments with A. parapulchella, and (iii) investigating the seasonal nature of brood production and nest establishment by ants in ACT grasslands. Major findings were used to make recommendations to assist in the management, including rehabilitation, of A. parapulchella grassland sites.
Low insolation appears to significantly affect the ant species composition of grassland sites in the ACT relative to other Australian vegetation types. In the ACT grassland sites, large species of the Dominant Dolichoderinae functional group were absent, or present only in very low numbers. The communities were species-poor relative to other Australian studies with only 60 species being recorded across all sites studied, with no more than 21 species recorded at any site on any sampling occasion. Whilst ant species community structure was highly variable between seasons and sites, more than 95% of ants were from the three functional groups, Dominant Dolichoderinae, Generalized Myrmicinae and Opportunists. The communities were numerically dominated throughout the year by the ubiquitous species groups Iridomyrmex rufoniger' and Rhylidoponera metallica '. Almost all taxa increased in foraging abundance during summer months and Pheidole spp., Monomorium spp., Crematogaster sp., Paralrechina sp. and Notoncus ectalomoides were occasionally locally abundant. There were no significant relationships between ant and vegetation community structures, but Solenopsis sp. showed an alliance with sites that had a high abundance of Themeda australis (kangaroo grass), whilst Crematogaster sp. and Paratrechina sp. are potential bioindicators of disturbance from grazing or pasture improvement.
Iridomyrmex 'rufoniger ’ were the numerically dominant foraging ants, making up 50% of all captures, but they held only 80% of their nest sites when faced with competition from other species. R. ’metallica' and Pheidole spp. on the other hand, gained 80% more nests than they lost to other taxa. I. ’rufoniger ’ and R. ’metallica' both preferred nest sites with warmer temperature regimes when given the choice, and this assisted them to tend brood throughout the year. All ant species in ACT grasslands had summer peaks in brood production. Most nests were inactive throughout the cooler months and nest founding was predominantly between September and November. The common species, Iridomyrmex spp., Paratrechina sp. and R. 'metallica' held winged reproductives in their nests from April and all ant taxa had released all alates by mid- November.
Although there were differences in ant community structure throughout the range of A. parapulchella, the ubiquitous R. ’metallica ’ and I. 'rufoniger ’ were always abundant, whilst again, Dominant Dolichoderinae and associated subordinate taxa were absent or present only in relatively low numbers. The lizards consumed brood from all the common ant species in ACT grasslands and showed preference for consuming brood of, and living with, small Iridomyrmex spp. The range of the small Iridomyrmex spp. preferred by A. parapulchella extends far beyond that of the lizard. Its distribution is apparently not restricted by the range of its ant prey species.
For rehabilitation of A. parapulchella sites in the ACT, it is recommended that a significant ground cover of native grasses is established to ensure the low abundance of large and territorial ants from the Dominant Dolichoderinae functional group. Along with a high abundance of shallow surface rocks, this will ensure the establishment of ant communities that are numerically dominated by small Iridomyrmex spp., which are preferred by A. parapulchella for homesite sharing and as a food source.

Date of Award	1996
Original language	English
Supervisor	David Williams (Supervisor), Will OSBORNE (Supervisor) & Arthur GEORGES (Supervisor)