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Social insects are highly diverse in their social structures, aside from the consistent presence of reproductive castes. Among social insects, the Australian paper wasp Ropalidia plebeiana constructs extremely dense colony aggregations consisting of hundreds of colonies within a few square meters; however, little is known about the aggregation structures. We genetically analyzed the colony and population structure of R. plebeiana, and concomitant variations in colony sex ratios. In spring, the foundress (candidate queen) group started their colonies on a single old comb from the previous season, subsequently dividing these old combs via relatedness-based comb-cutting. Female philopatry, a prerequisite condition of Local Resource Competition (LRC), was confirmed. The colony sex ratio of reproductive individuals (male and female offspring for the next generation) became slightly male-biased in larger colonies, as predicted under LRC. However, the number of foundresses was positively associated with the number of reproductive individuals, suggesting that Local Resource Enhancement (LRE) also operates. Although the population structure appears to meet the prerequisites of LRC, the sex ratio appears to be modulated by factors other than LRC. Rather, through LRE, the availability of female helpers at the founding stage is likely to mitigate the sex ratios predicted under LRC., (© 2022. The Author(s).)

Australia's monsoonal (seasonal) tropics are a global centre of ant diversity, but are largely unrecognised as such because the vast majority of its species are undescribed. Here we document another case of undescribed hyper-diversity within a taxon that is formally recognised as a single, widespread species, Meranoplus ajax Forel. We recognise 50 species among 125 specimens of M. 'ajax' that we CO1-barcoded, integrating CO1 clustering and divergence, morphological differentiation and geographic distribution. A large proportion (44%) of these species are represented by single records, indicating that very many additional species are yet to be collected in this extremely remote and sparsely populated region. Sampling has been concentrated in the Northern Territory, where 27 of the 50 species occur. If diversity in Western Australia and Queensland were similar to that in the Northern Territory, as appears likely, then the M. ajax complex would comprise >100 species. In 2000, when Australia's monsoonal ant fauna was estimated to contain 1500 species, Meranoplus ajax was considered to represent a single species. Our previous analyses of a range of other taxa have shown that their diversity has been similarly under-appreciated in this estimate. Our findings suggest that the total number of ant species in monsoonal Australia is several thousand, which would make the region by far the world's richest known. [ABSTRACT FROM AUTHOR]

This paper examines the role of fire in mediating the relative abundance of two of the world's major ecologically dominant ant genera, Iridomyrmex and Oecophylla, where they coexist across the tropical savanna landscapes of northern Australia. These taxa have contrasting biogeographical histories, which are predicted to lead to contrasting responses to fire. Iridomyrmex is an autochthonous Australian genus that has radiated primarily in the arid zone; as such, its abundance is predicted to be promoted by frequent fire because this maintains an open habitat. In contrast, Oecophylla is a genus of leaf-nesting ants occurring in the canopies of Old World tropical rainforest, and is a recent arrival to Australia in geological time; the abundance of these ants is predicted to decline under frequent fire. We test these predictions using results from a landscape-scale fire experiment, where three experimental fire regimes (including no fire) were applied to replicated subcatchments over a 5-year period. Using sweep nets, ants were sampled in the grass layer (the habitat layer of greatest overlap between Iridomyrmex and Oecophylla) in eucalypt woodland (canopy cover < 30%) and open eucalypt forest (canopy cover about 50%) habitats. A total of 27 species from 11 genera were collected during the study; eight were common enough for statistical analysis, and the abundances of four of these were significantly affected by fire treatment. As predicted, the abundance of Iridomyrmex was promoted by fire, whereas that of Oecophylla declined. These changes occurred only under late-season (relatively high intensity) fires, and for Oecophylla occurred only in open forest (not woodland) habitat. This fire-mediated relationship between Iridomyrmex and Oecophylla mirrors the much broader, ecosystem-wide dynamic between eucalypt-dominated savanna and rainforest in tropical Australia, with savannas dominated by fire-resistant sclerophyll elements of Australian origin, and rainforest dominated by fire-sensitive mesophyll elements of South-East Asian origin. [ABSTRACT FROM AUTHOR]

Melophorus hirsutipes Heterick, Castanelli & Shattuck is a recently described taxon that was presented as occurring throughout most of mainland Australia and showing highly variable morphology. One highly variable character is sculpture, which is smooth and shiny in the type specimen but conspicuously scabrid and even rugulose in other forms. The scabrid and rugulose forms occur primarily in the monsoonal (seasonal) tropics of the northern third of the continent, a region that has recently been shown to be a global centre of ant diversity, but largely unrecognized as such because the great majority of species are undescribed. Here, we provide an integrated morphological, genetic (CO1) and distributional analysis of diversity within the scabrid and rugulose forms of M. 'hirsutipes'. We recognize 16 species among the 56 scabrid/rugulose specimens sequenced, along with four shiny or shagreenate species that are embedded within them. We conclude that Melophorus 'hirsutipes' is a highly diverse group of at least 30 species given the very patchy geographical coverage of sequenced specimens. Our findings provide further evidence that the total number of species in monsoonal Australia is likely in the several thousands, which would make it the world's richest known region for ant species. [ABSTRACT FROM AUTHOR]

The article presents a study on ground dwelling ants in areas of Australian Wet Tropics which have high biodiversity value above a small spatial scale. The three measures of biodiversity used in the study include estimated species richness, complementarity analysis, and evolutionary history. Results show that species richness is consistent at lower elevations but decreases at higher elevations. Moreover, narrow altitudinal range of the ants was seen in the complementarity analysis.

1. If a species is translocated outside its native range, some of its traits (evolved to match conditions in the ancestral range) likely will be maladaptive. Identifying ways in which the invader are poorly suited to its new range might provide novel opportunities for biocontrol. 2. The spread of cane toads ( Bufo marinus, native to central and South America) through tropical Australia has created major ecological problems. Although many native predators cannot deal with the toxins of the invasive toads, ‘meat ants’ ( Iridomyrmex reburrus) kill and consume many metamorph toads. Might this be a mismatch between the invader and its newly invaded range, whereby the morphology, locomotor ability and/or behaviour of cane toads renders them vulnerable to a predator that poses little danger to native anurans? 3. To explore this possibility, we measured habitat use and activity patterns in meat ants, metamorph cane toads and metamorphs of seven native frog species ( Litoria bicolor, L. caerulea, L. dahlii, L. nasuta, L. rothii, Limnodynastes convexiusculus, Opisthodon ornatus) in standardized enclosures in the laboratory. 4. Unlike the frogs, (1) toads selected open microhabitats and were active diurnally, thus increasing encounter rates with meat ants; (2) toads failed to detect and evade approaching ants; (3) toads exhibited poor locomotor ability (short slow hops, reflecting their small size and short limbs); and (4) toads frequently relied on an ineffective defence mechanism (crypsis) when attacked. 5. In combination, these traits rendered cane toad metamorphs far more susceptible to predation by meat ants than were any of the native frogs tested. That vulnerability presumably reflects lack of coevolution between cane toads and Australian ants. 6. The inability of invasive toads to escape predatory native ants might be exploited to reduce cane toad numbers, by manipulating ant densities and/or locations during periods of toad metamorph emergence. [ABSTRACT FROM AUTHOR]

The removal rates of fruits (the diaspore) were assessed in exclusion experiments in three shrubby species of Darwinia, endemic to the Sydney Basin of south-eastern Australia. There was a clear pattern of fruit removal in just a few days by small species of ants from the genera Iridomyrmex, Crematogaster and Pheidole. When only ants had access to fruits an average of 41% of fruits were removed, whereas when only vertebrates had access an average of 13% of fruits were removed. There was some variation in the number of fruits removed both between species and within species across study sites or annual seed crops. When ants had access to seeds this variation in removal amounted to 10–80% over 1–4 days. Uniquely in Darwinia, it is the old petals (which remain attached to the fruit) that are attractive to the ants, rather than a specific lipid body. This likely represents a case of successful ecological fitting by Darwinia to take advantage of the widespread presence of myrmecochory in the Australian flora. [ABSTRACT FROM AUTHOR]

• Estimating distances and rates of seed dispersal, especially long-distance dispersal (LDD), is critical for understanding the dynamics of patchily distributed populations and species’ range shifts in response to environmental change. • Daviesia triflora (Papilionaceae) is an ant-dispersed shrub. The ant Rhytidoponera violacea was recorded dispersing its seeds to a maximum distance of 4.7 m, and in more intensive trials seeds of a related species from the study area, to a maximum of 8.1 m. • Microsatellite DNA markers and population assignment tests identified interpopulation immigrants among 764 plants on 23 adjacent dunes bearing D. triflora, and 13 interpopulation seed dispersal (LDD) events (1.7%) were inferred. The distance between source and sink populations ranged from 410 m to 2350 m (mean 1260 m). These distances exceed ant dispersal distances by two to three orders of magnitude but are comparable with previous measurements of LDD for two co-occurring wing-seeded (wind-dispersed) species from the same system. • The observed distances of seed dispersal in this arillate species demonstrate the significance of nonstandard dispersal mechanisms in LDD and the independence of these from primary dispersal syndromes. The likely role of emus in dispersal of the many ‘ant-dispersed’ species in Australia is discussed. [ABSTRACT FROM AUTHOR]

We document diversity and its distribution within the hyperdiverse Monomorium nigrius Forel group of the Australian monsoonal tropics, an unrecognized global centre of ant diversity. The group includes a single described species, but several distinct morphotypes each with multiple clearly recognizable taxa are known. Our analysis is based on 401 CO1-sequenced specimens collected from throughout the Australian mainland but primarily in the monsoonal north and particularly from four bioregions: the Top End (northern third) of the Northern Territory (NT), the Sturt Plateau region of central NT, the Kimberley region of far northern Western Australia, and far North Queensland. Clade structure in the CO1 tree is highly congruent with the general morphotypes, although most morphotypes occur in multiple clades and are therefore shown as polyphyletic. We recognize 97 species among our sequenced specimens, and this is generally consistent (if not somewhat conservative) with PTP analyses of CO1 clustering. Species turnover is extremely high both within and among bioregions in monsoonal Australia, and the monsoonal fauna is highly distinct from that in southern Australia. We estimate that the M. nigrius group contains well over 200 species in monsoonal Australia, and 300 species overall. Our study provides further evidence that monsoonal Australia should be recognized as a global centre of ant diversity. [ABSTRACT FROM AUTHOR]

The Argentine ant ( Linepithema humile Mayr) is a worldwide invasive pest species that has been associated with losses of native ant and non-ant invertebrates in its introduced range. To date, few studies have investigated the effects of Argentine ants on native invertebrates in Australia. This study assessed the effects of Argentine ants on community composition of invertebrates, with particular focus on resident ant communities and functional groups. In this study, the author compared the composition and abundances of invertebrates between invaded and uninvaded locations at four paired sites in Adelaide, South Australia. The results showed that there were significantly fewer non-Argentine ants at invaded sites than at uninvaded sites. In particular, ants from the two common and widespread genera Iridomyrmex and Camponotus showed decreased abundances at the invaded sites. Multidimensional scaling analyses revealed differences in the composition of ant communities at the invaded and uninvaded sites, with uninvaded sites characterized by a similar native ant species composition, while communities at the invaded sites displayed much greater variability in species composition. These results suggest that the presence of Argentine ants may have a negative effect on particular ant genera and functional groups, with likely disruptions to ecosystem processes. [ABSTRACT FROM AUTHOR]

Behaviourally and ecologically dominant ants are thought to structure ant communities through their monopolization of resources. Effects of a dominant ant, Iridomyrmex purpureus, on resource use by ant communities were tested using an exclusion experiment on sandstone outcrops near Sydney, in south-eastern Australia. The success of functionally different ants at honey and mealworm baits placed in rock and vegetation microhabitats was measured in a series of surveys before and after exclusion. I. purpureus was successfully excluded from the outcrops and patterns of resource use following I. purpureus exclusion were consistent with those of sites without I. purpureus and procedural control sites. At sites with I. purpureus, resources were discovered more rapidly, however, other ants were less successful, particularly on rock substrates. Iridomyrmex spp. were more successful on rock than in vegetation, however, in the presence of I. purpureus, the success of other Iridomyrmex on rock substrates and at honey baits was reduced. Camponotine and myrmicine ants had low success at baits and tended to be less successful in the presence of I. purpureus. In contrast, the opportunist Rhytidoponera metallica was not affected by the presence of I. purpureus and was more successful in the vegetation habitat. These findings indicate that the dominant ant affects the success of other ants at baits, particularly the ecologically similar Iridomyrmex. However, effects of I. purpureus on other taxa differ between habitats differing in complexity and resources differing in composition and defensibility. [ABSTRACT FROM AUTHOR]

Kakadu is a global icon for nature conservation, but like similar sites elsewhere it is constantly under threat from exotic species. This apparent eradication of two highly invasive ant species is a clear example that such projects are achievable, and lessons learnt from such successes will assist the ongoing fight against alien species. [ABSTRACT FROM AUTHOR]

Complex distribution patterns of species-rich insect communities in tropical rainforests have been intensively studied, and yet we know very little about processes that generate these patterns. We provide evidence for the key role of homopteran honeydew and plant nectar in structuring ant communities in an Australian tropical rainforest canopy and understorey. We also test the ant visitation of these resources against predictions derived from the ‘ant-mosaic’ hypothesis. Two ant species were highly dominant in terms of territorial behaviour and abundance: Oecophylla smaragdina and Anonychomyrma gilberti. Both dominant ant species monopolised large aggregations of honeydew-producing homopterans. Attended homopteran species were highly segregated between these two ant species. For the use of extrafloral and floral nectar (involving 43 ant species on 48 plant species), partitioning of ant species among plant species and between canopy and understorey was also significant, but less pronounced. In contrast to trophobioses, simultaneous co-occurrence of different nectar foraging ant species on the same plant individuals was frequent (23% of all surveys). While both dominant ant species were mutually exclusive on honeydew and nectar sources, co-occurrence with non-dominant ant species on nectaries was common. The proportion of visits with co-occurrences was low for dominant ants and high for many sub-ordinate species. These findings support the ant mosaic theory. The differential role of honeydew (as a specialised resource for dominant ants) and nectar (as an opportunistic resource for all ants including the co-occurring non-dominant species) provides a plausible structuring mechanism for the Australian canopy ant community studied. [ABSTRACT FROM AUTHOR]

Ants (Hymenoptera: Formicidae) consume a broad spectrum of liquid food sources including nectar and honeydew, which play a key role in their diet especially in tropical forests. This study compares carbohydrates and amino acids from a representative spectrum of liquid sources used by ants in the canopy and understorey of a tropical rainforest in northern Queensland, Australia. Eighteen floral nectars, 16 extrafloral nectars, two wound sap and four homopteran honeydew sources were analysed using high performance liquid chromatography. Wounds comprised flower abscission scars on Normanbya normanbyi L. H. Bailey and bitemarks on Cardwellia sublimis F. Muell. where ants were actively involved in wounding. Discriminant analysis was performed to model differences between food sources in sugar and amino acid concentration and composition. All characteristics varied significantly among plant species. Honeydew contained a broader spectrum of sugars (including melezitose, raffinose, melibiose, lactose and maltose) than nectar (sucrose, glucose, fructose), but certain extrafloral nectars had similar amino acid profiles and, like honeydew sources, were often monopolized by ants. Most common amino acids across the sources were proline, alanine and threonine among 17 α-amino acids identified. Interspecific variability concealed characteristic differences in sugar and amino acid parameters between nectar, honeydew and wound sap across all plants, but these types differed significantly when found on the same plant. Among all sources studied, only a few flower nectars were naturally not consumed by ants and they were significantly less attended than sugar controls in feeding trials. These nectars did not differ in sugars and amino acids from ant-attended flower nectars, suggesting the activity of repellents. Apart from these exceptions, variability in amino acids and carbohydrates is proposed to play a key role in ant preferences and nutrition. [ABSTRACT FROM AUTHOR]

Abstract Ants are widely used as bioindicators in environmental assessment in Australia, partly because the responses of ant communities to disturbance are relatively well understood. In particular, the use of functional groups has provided a predictive framework for analysing ant community responses to disturbance in the absence of reliable information on the responses of individual species. Here we review 45 studies of the responses of Australian ant communities to disturbance, in order to: (i) identify individual species or species-groups that respond consistently to disturbance; and (ii) examine the usefulness of the functional group scheme as a framework for predicting ant community responses under different disturbance regimes in different biogeographical regions. The most common forms of disturbance in our studies were fire (17 studies), mining (12; mostly studies of minesite restoration) and grazing (7), with other disturbances including clearing, logging, flooding, recreation, urbanization and farming. Responses of individual species were inevitably variable because of differences in vegetation type, severity of disturbance and time since disturbance. However, we identified a range of widespread species that showed predictable responses, including species of the metallica group of Rhytidoponera in temperate Australia (‘increasers’ in relation to disturbance), species of the terebrans and denticulatus groups of Camponotus (increasers), the aeneovirens group of Melophorus (increasers) from the arid zone, and Iridomyrmex pallidus (increaser) from the monsoonal region. The functional group scheme assessed here was not designed specifically in the context of disturbance, but nevertheless in some situations provides a useful framework for analysing ant community responses. Three distinct syndromes of functional group responses can be recognized. First, Dominant Dolichoderinae and Hot Climate Specialists are groups that prefer open environments,... [ABSTRACT FROM AUTHOR]

Summary 1.Rates of seed predation are influenced by conditions that alter seed supply and the activity of seed predators. In southern Australia the potential seed supply for the dominant floodplain tree species, the river red gum Eucalyptus camaldulensis , has been reduced through forest clearing to support grazing by introduced livestock. River regulation and water extraction have reduced the frequency of flooding and thus the conditions that promote seed germination on floodplains. To determine if poor recruitment of river red gums could be caused by low seed supply, as a result of post-dispersal seed predation, we used field experiments and observations to investigate how post-dispersal predation on seeds of E. camaldulensis was affected by flooding, livestock management and their interaction. 2.Seed predation was measured before and after different flood treatments (0·5 m depth; short flood of 24 h, long flood of 30 days). Flooding of this kind (return frequency of once per year) did not have any significant effect on rates of seed removal by seed predators. 3.Rates of seed predation in floodplain habitats under widespread livestock management regimes changed seasonally. In all seasons seed predation was lowest at sites grazed by sheep. In winter seed predation was highest at ungrazed sites. In spring and summer seed predation was highest at sites grazed by cattle. Ant communities differed between forested and cleared habitats and seed-eating ant species were most abundant in cleared sites grazed by cattle. 4.Rates of seed predation in forested floodplain sites with different flood histories differed among sites with different livestock management histories. The impact of cattle exclusion on seed predation rates increased as the period since flooding increased. 5.Cattle grazing is widespread on the floodplains of rivers across the southern Murray-Darling Basin, and tree densities and hence seed supplies are low. In this situation small floods may not... [ABSTRACT FROM AUTHOR]

AbstractFrequent low-intensity fires are used in management of Australian forests to reduce fuel loads and protect natural resources and human property. Low-intensity fires are typically patchy and unburned litter microhabitats are often associated with large objects such as logs, which may act as refuges both for vertebrate and for invertebrate fauna. The aim of this study was to determine whether ants were using unburned leaf litter microhabitats associated with logs as a refuge after fire. The study was carried out in Bulls Ground State Forest, New South Wales, Australia, where experimentally burned and unburned sites had previously been established. Species richness and abundance of ants in leaf litter did not differ between habitats adjacent to logs and away from logs, in burned and unburned sites. Fifteen of the 42 ant species were found in all four habitats, and contributed 94% of total ant abundance. Every habitat had a group of unique species, which together made up 30% of the total species richness. There was also a distinct group of species that was not found in the leaf litter associated with the burned/open habitat. However, as 45% of all species were found in low abundance (less than 10 individuals), care must be taken in inferring patterns for these groups. When functional groups were used to assess community structure, ‘cryptic’ species were found to be common in all habitats, whereas ‘subordinate Camponotini’ were found in burned habitats only. This study indicates that in an area where frequent burning is applied on a broad scale, preserving a range of microhabitats, including those associated with retained logs, may make a substantial contribution to conserving ant biodiversity. [ABSTRACT FROM AUTHOR]

In the Mediterranean ecosystems of South Africa and Australia, the role of ants in the dispersal of seeds is well known and antagonistic interactions as well as myrmecochory occur. The high prevalence of seed dispersal by ants, environments. Ant dispersal has been considered unimportant in the Mediterranean region and , until now, no systematic study of ant-seed interaction has been undertaken. In the Mediterranean shrubland of Southern Italy the seed content of functioning nests of the ant Messor minor (André) has been quantitatively analyzed. The existence in the nest of seeds from shrub species, as well as those of the Fabacease and Poaceae, suggest that ant dispersal may be much more widespread in the Mediterranean environments than has been realized. A large proportion of the seeds came from fleshy-fruited shrub species previously reported to be bird dispersed, e.g. Rhamnus alaternus L., Myrtus communis L., Smilax aspera L., Pistacia lentiscus L. and Phillyrea latifolia L. Analysis of nest mounds showed that, although many seeds had been partially predated by the ants, a very large number had been collected, transported to the nest and subsequently removed to the mound without damage. Examination of the structure of the fruits and seeds of R. alaternus and M. communis, and summer fruiting phenology of R. alaternus, provided further evidence of specific adaptation to ant dispersal. The presence of an elaiosome on the seed is reported for the first time in both species. Feeding trials showed that ants selectively remove specific diasporas, preferentially collecting the seeds with the elaiosome. [ABSTRACT FROM AUTHOR]

Anonychomyrma is a dolichoderine ant genus of cool-temperate Gondwanan origin with a current distribution that extends from the north of southern Australia into the Australasian tropics. Despite its abundance and ecological dominance, little is known of its species diversity and distribution throughout its range. Here, we describe the diversity and distribution of Anonychomyrma in the Australian Wet Tropics bioregion, where only two of the many putative species are described. We hypothesise that the genus in tropical Australia retains a preference for cool wet rainforests reminiscent of the Gondwanan forests that once dominated Australia, but now only exist in upland habitats of the Wet Tropics. Our study was based on extensive recent surveys across five subregions and along elevation and vertical (arboreal) gradients. We integrated genetic (CO1) data with morphology to recognise 22 species among our samples, 20 of which appeared to be undescribed. As predicted, diversity and endemism were concentrated in uplands above 900 m a.s.l. Distribution modelling of the nine commonest species identified maximum temperature of the warmest month, rainfall seasonality, and rainfall of the wettest month as correlates of distributional patterns across subregions. Our study supported the notion that Anonychomyrma radiated from a southern temperate origin into the tropical zone, with a preference for areas of montane rainforest that were stably cool and wet over the late quaternary. [ABSTRACT FROM AUTHOR]