Fire influences ant diversity by modifying vegetation structure in an Australian tropical savanna.

Fire is a dominant ecological force shaping many faunal communities globally. Fire affects fauna either directly, such as by killing individuals, or indirectly, such as by modifying vegetation structure. Vegetation structure itself also modulates fire frequency and intensity. As such, faunal responses to fire need to be seen through the lens of variable fire activity and vegetation structure. Here, we incorporate information on fire activity and vegetation structure to enhance an understanding of the response of ants to long-term (17-year) experimental fire treatments in an extremely fire-prone tropical savanna in northern Australia. Previous analysis revealed limited divergence in ant communities after 5 years of experimental fire treatment. Hence, we first investigated the extent to which ant communities diverged over a subsequent 12 years of treatment. We then assessed the relative contribution of fire treatment, cumulative fire intensity (fire activity), and woody cover to responses of ant species frequency of occurrence, richness, and composition. We found that, even after 17 years, fire treatments explained little variation in any ant response variable. In contrast, woody cover was a strong predictor for all of them, while fire activity was a moderate predictor for abundance and richness. Ant species occurrence and richness increased in open habitats receiving higher levels of fire activity, compared with plots with higher vegetation cover experiencing low (or no) fire activity. Moreover, species composition differed between plots with high and low vegetation cover. Our findings provide experimental support to the principle that the effects of fire on fauna are primarily indirect, via its effect on vegetation structure. Furthermore, our results show that a "uniform" fire regime does not have uniform impacts on the ant fauna, because of variability imposed by interactions between vegetation structure and fire activity. This helps to explain why there is often a weak relationship between pyrodiversity and biodiversity, and it lessens the need for active management of pyrodiversity to maintain biodiversity.

Towards precision ecology: Relationships of multiple sampling methods quantifying abundance for comparisons among studies.

Because different sampling techniques will provide different abundance values, it is currently difficult to compare results among many studies to form holistic understandings of how abundance influences ant ecology. Using three sampling methods in the same location we found pitfall traps best confirmed yellow crazy ant A. gracilipes presence recording the fewest zero values (9.1%), card counts were the least reliable (67.1%), and tuna lures were intermediate (30.1%). The abundance of A. gracilipes from card counts ranged from 0 to 20, in pitfall traps from 0 to 325, and the full range of tuna lure abundance scores (0-7) were sampled. We then determined the relationships between these three standard ant sampling techniques for Anoplolepis gracilipes abundance. Irrespective of the data transformation method, the strongest relationship was between pitfall traps and tuna lures, and the least strong was between pitfall traps and card counts. We then demonstrate the utility of this knowledge by analysing A. gracilipes abundance reported within published literature to show where the populations in those studies sit on an abundance spectrum. We also comment on insights into the relative utility of the three methods we used to determine A. gracilipes abundance among populations of varying abundance. Pitfall traps was the most reliable method to determine if the species was present at the sample level. Tuna lures were predominantly reliable for quantifying the presence of workers, but were limited by the number of workers that can gather around a spoonful of tuna. Card counts were the quickest method, but were seemingly only useful when A. gracilipes abundance is not low. Finally we discuss how environmental and biological variation needs to be accounted for in future studies to better standardise sampling protocols to help progress ecology as a precision science.

A new species of Epopostruma (Hymenoptera: Formicidae) from monsoonal Australia.

Epopostruma is an uncommon genus of myrmicine ants endemic to relatively mesic regions of southern and eastern Australia. Here we describe a new species recently recorded from the 'Top End of Australias Northern Territory, E. topendi sp. n. from Melville Island and Nitmiluk National Park. The new species is known from one specimen from each of two sites in the Australian monsoonal tropics, the only records of the genus from this region. This addition brings the number of described species of Epopostruma to twenty.