Impacts of an incursion of African Big-headed ants, Pheidole megacephala (Fabricius), in urban bushland in Perth, Western Australia

An incursion of the African Big-headed Ant, Pheidole megacephala, has recently been recorded in bushland in Perth, Western Australia. This unexpected discovery prompted an investigation into the effects of the incursion on the native ant assemblages. Extensive pitfall trapping in invaded and non-invaded areas revealed that the incursion had a significant negative impact on ant species richness, diversity and evenness. Approximately 53% of native ant species present in non-invaded bushland were not sampled in areas occupied by P. megacephala, while the remaining species suffered considerable declines in frequency of occurrence. Many of these species perform important ecosystem functions, and their loss was thought to have had serious consequences on the ecosystem. Changes to the prevalence of the various ant Functional Groups indicated major disruptions to the composition of the assemblage as the abundance of P. megacephala increased. Ants that avoided direct competition with P. megacephala, by occupying temperature dependant temporal niches, were more persistent in its presence. Estimates of the ant biomass sampled indicated that the invasive population was larger than that of all other ant species combined by several orders of magnitude. A feeding trial revealed intensified exploitation of food resources in invaded areas, which could have flow-on effects on other invertebrates and plants. Changes to predation, decomposition, and soil amelioration regimes, as well as possible disruptions to ant-plant interactions and invertebrate symbioses resulting from the disappearance of native ant species, were thought to have further eroded the conservation values of the ecosystem

Diversity and richness of ant species in a lowland wet forest reserve in Sri Lanka

Sinharaja Forest Reserve (SFR) represents one of the largest remaining stands of mixed dipterocarp forest in southwestern Sri Lanka. It is characterised by high floral and faunal endemicity and is gazetted as a World Heritage Site. Research was undertaken to study the ground-dwelling ants in the SFR using pitfall traps and leaf litter extraction. The collection was carried out in disturbed and undisturbed primary forest, old selectively-logged forest (30 years old) and periphery forest (agricultural buffer zone) along a small elevation gradient (200 m – 700 m). A total of 173 species and morphospecies in 11 subfamilies and 54 genera were caught. Pheidole and Tetramorium were the most speciose genera, with 19 and 18 species respectively; Cerapachys followed with 12 species. These results demonstrate the high diversity of litter dwelling ant species in the SFR. There were no significant differences in species richness between sites within the forest. Future studies should analyse species assemblages in each forest type in relation to forest structure and environmental parameters to further understand the distribution of ant species across this unique and complex forest

Computer Modelling as an Aid to Forest and Woodland Restoration

Reclamation of terrestrial ecosystems tends to be focussed on two main land uses, mining and degraded agricultural or forested lands. Modelling has great potential to assist in both situations. The aim of many restoration programs is to restore biodiversity and a self-sustaining, fully functional ecosystem, which is intimately linked with the return of the plants, the vertebrates and, particularly, the invertebrate fauna, whose presence plays a pivotal role in most ecosystem functions and processes. A thorough understanding of these plant-fauna associations is essential if restoration is to succeed. It could also equip us with the knowledge to decide how minimalistic our information needs can be when modelling progress with restoration, for instance: by quantifying certain biophysical parameters; these plus certain vegetation indices; or by both plus a range of faunal attributes. As well as streamlining the restoration monitoring process, this could lead to the enhancement of the conservation value of the restoration, and a clear understanding of the ecological links between flora and fauna would also help develop bioindicators as components of completion criteria schedules. Using Western Australian bauxite mining in the Jarrah (Eucalyptus marginata) forest as a case study, this paper reviews rehabilitation prescriptions and trends in development of plant assemblages, invertebrate colonization and litter decomposition, and applies a systems dynamic modelling approach model to test assumptions regarding the evolution of plant-fauna assemblages in time and assess whether it is feasible to predict temporal changes in the rehabilitation of this ecosystem. Secondly, in relation to efforts to purchase and rehabilitate land to reconnect remnant woodland vegetation close to the south coast of Western Australia, network analysis and multi-level simulations are applied in order to decide the best locations to acquire land and to restore it in order to optimise connectivity

Ant litter fauna of forest, forest edges and adjacentgrassland in the Atlantic rain forest region of Bahia, Brazil

The litter ant fauna was sampled by Winkler sacks and pitfall traps along transects running through Atlantic rain forest into an adjacent grassland. Transects ran 65 m into the forest and 45 m into the field. Ninety-seven species of ants were sampled and scored, 85 were found in the forest, 48 were found in the field and 36 were common to both habitats. There was some evidence that species richness was lowest in the field and high at the deepest point within the forest. The composition of the ant community at the different distances into the forest and field was analysed by a number of hierarchical clustering procedures and also by ordinating the data in three-dimensional space. A two-way table of the ant assemblages derived from the clustering procedure versus the groupings of transect distances obtained by the same procedure indicated that certain ant species had preferences for the field or particular distances into the forest. It is concluded that although the ant fauna of Atlantic rain forest is severely affected by clearing, a forest-like ant fauna is able to persist right up to the interior edge of the forest

Powdery bark in Eucalyptus accedens deters arthropods? An evaluation using ants

Powderbark wandoo (Eucalyptus accedens) has a powdery triterpenoid-containing substance on the surface of its smooth bark, which is formed from sloughing peridermal cells. When compared with the similar-appearing wandoo (E. wandoo), which occurs inthe same area and which does not accumulate powder, fewer bark-associated arthropods are found. Exposure to this powder accelerated mortality of the ant, Iridomyrmexchasei, a species that tends scale and other sap-sucking insects on the foliage of eucalypts. Ants of this and two other species were unable to reach baits on the top of vertical wooden dowels that had been coated with powder taken from the bark of E. accedens. The powdermay deter arthropods from living or moving on the bark by chemical or physical means. It is postulated that the function of the powder is to reduce the threat from herbivorous or scale-tending arthropods that may live on, or traverse, the bark of this species

Impact of fire on leaf nutrients, arthropod fauna and herbivory of native and exotic eucalypts in Kings Park, Perth, Western Australia

The vegetation of Kings Park, near the centre of Perth, Western Australia, once had an overstorey of Eucalyptus marginata (jarrah) or Eucalyptus gomphocephala (tuart), and many trees still remain in the bushland parts of the Park. Avenues and roadsides have been planted with eastern Australian species, including Eucalyptus cladocalyx (sugar gum) and Eucalyptus botryoides (southern mahogany), both of which have become invasive. The present study examined the effect of a recent burn on the level of herbivory on these native and exotic eucalypts. Leaf damage, shoot extension and number of new leaves were measured on tagged shoots of saplings of each tree species in unburnt and burnt areas over an 8-month period. Leaf macronutrient levels were quantified and the number of arthropods on saplings was measured at the end of the recording period by chemical knockdown. Leaf macronutrients were mostly higher in all four species in the burnt area, and this was associated with generally higher numbers of canopy arthropods and greater levels of leaf damage. It is suggested that the pulse of soil nutrients after the fire resulted in more nutrient-rich foliage, which in turn was more palatable to arthropods. The resulting high levels of herbivory possibly led to reduced shoot extension of E. gomphocephala, E. botryoides and, to a lesser extent, E. cladocalyx. This acts as a negative feedback mechanism that lessens the tendency for lush, post-fire regrowth to outcompete other species of plants. There was no consistent difference in the levels of the various types of leaf damage or of arthropods on the native and the exotic eucalypts, suggesting that freedom from herbivory is not contributing to the invasiveness of the two exotic species

Trunk invertebrate faunas of Western Australian forests and woodlands: Influence of tree species and season

Trunk-associated invertebrates were sampled on two rough-barked tree species (jarrah, Eucalyptus marginata and marri, E. calophylla) at Karragullen, in the hills near Perth, Western Australia, and on these two species plus two smooth-barked species (wandoo, E. wandoo, and powderbark wandoo, E. accedens) at Dryandra, a drier site situated 150 km to the south-east. Invertebrates were sampled by intercept traps, which collect animals that attempt to land on the trunks, and photo-eclector bark traps, which collect invertebrates that move, or live, on the trunk. The range and abundance of invertebrates sampled was generally greater in the intercept than the bark traps. Invertebrate abundance and activity (but not biomass) on bark was strongly seasonal, with greater numbers being found during the moister periods. The two smooth-barked species supported, and were visited by, more invertebrates than the two rough-barked species. There was some evidence that jarrah supported more invertebrates than marri at both Karragullen and Dryandra, although the results were equivocal. Within the two smooth-barked species, wandoo tended to support more invertebrates than powderbark wandoo. These trends are discussed in terms of the characteristics of the bark of these trees and the environments in which they occur

A comparison of the autecology of two seed-taking ant genera, Rhytidoponera and Melophorus

Members of the genus Rhytidoponera and, to a lesser extent, certain Melophorus spp. are keystone mutualists for the dispersal of seeds in the southwest of Western Australia, with important ramifications for the ecology and speciation of plants in this biodiversity hotspot. For this reason, it is important to understand the autecology of the relevant ant species and the way in which they interact with plant seeds. This paper addresses key aspects of the ecology of three such ant species, Rhytidoponera violacea (Forel), R. inornata Crawley and Melophorus turneri perthensis Wheeler. Data are presented on their geographic distribution, seasonality of foraging, diurnal activity, response to fire, nest site preference, nest structure, colony size, feeding habits, foraging response to seed availability, and seedling emergence from nests. The role of all three species as seed dispersers is confirmed, and all three species have ecologies that are well-suited for dispersal and survival of native plant seeds. Preservation of this interaction is important for the conservation of plants, and it is fortuitous that all three species are able to survive disturbance and return to rehabilitated areas. However, the smaller R. inornata, and to a lesser extent, the larger R. violacea, are vulnerable to invasive ant [Pheidole megacephala (Fabricius)] incursions. M. turneri perthensis is able to coexist with the invasive ant unless this is at high densities, probably as a result of its ability to forage during high temperatures when the invasive species is inactive