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Invasive ants in Australia: Documented and potential ecological consequences

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Abstract

A growing number of species are being transported and introduced by humans to new locations and are establishing self-sustaining populations outside their native ranges. Since ants play many ecological roles, introduction of an invasive ant species, and subsequent disruption of Australia's rich and abundant native ant fauna, has the potential for numerous adverse consequences. Over 6700 ants representing 105 species from 73 genera have been intercepted at Australian ports of entry in the last 20 years and all six of the world's most destructive invasive ants have become established in the country. Here we review the current and potential consequences of these ants on Australia's natural and agricultural environments. To date, several studies, most involving the big-headed ant, Pheidole megacephala, and the Argentine ant, Linepithema humile, have documented a decline in native ant species richness. The displacement of native ants by these invaders could have multiple consequences for the native flora and fauna. Since few of these have been investigated in Australia, we combine knowledge from invasions elsewhere, the ecology of the interactions, and data on current and predicted geographic ranges of introduced ants to hypothesise about likely indirect effects of invasive ants in Australia. Further investigations that are aimed at testing these predictions will also aid in justifying and prioritising national prevention and control efforts, and will contribute to some of the long-standing questions about ant invasions globally.

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... In Australia, the strongest native competitors of L. humile are typically other members of the dolichoderine group including Iridomyrmex species such as I. purpureus since they share similar ecological niches and resource requirements (6,37,42,43). While L. humile is often more common in closer proximity to human habitations and I. purpureus is more common in rural and less disturbed areas, their distributions frequently overlap across Australia and direct conflict between our two target species is therefore common in nature (37,(42)(43)(44)(45)(46). L. humile is not confined to completely urbanized or degraded areas and can be found across a continuum of human-altered habitats in Australia and elsewhere across its non-native range (37,(42)(43)(44)(45)(46). ...
... While L. humile is often more common in closer proximity to human habitations and I. purpureus is more common in rural and less disturbed areas, their distributions frequently overlap across Australia and direct conflict between our two target species is therefore common in nature (37,(42)(43)(44)(45)(46). L. humile is not confined to completely urbanized or degraded areas and can be found across a continuum of human-altered habitats in Australia and elsewhere across its non-native range (37,(42)(43)(44)(45)(46). In our study, for example, both species were sourced from the same field location (SI Appendix, Supplementary Methods). ...
... Alternatively, the prediction that smaller non-native ants may be more dominant in simplified or disturbed habitats could inform priority areas for management interventions. Advances in the management of non-native invasive ants are of global biosecurity significance since they constitute some of the most important pest animals in the world, with environmental, agricultural, economic, and health impacts equivalent to billions of dollars per year (44,(50)(51)(52)(53)(54)(55). ...
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In social animals, success can depend on the outcome of group battles. Theoretical models of warfare predict that group fighting ability is proportional to two key factors: the strength of each soldier in the group and group size. The relative importance of these factors is predicted to vary across environments [F. W. Lanchester, Aircraft in Warfare, the Dawn of the Fourth Arm (1916)]. Here, we provide an empirical validation of the theoretical prediction that open environments should favor superior numbers, whereas complex environments should favor stronger soldiers [R. N. Franks, L. W. Partridge, Anim. Behav. 45, 197-199 (1993)]. We first demonstrate this pattern using simulated battles between relatively strong and weak soldiers in a computer-driven algorithm. We then validate this result in real animals using an ant model system: In battles in which the number of strong native meat ant Iridomyrmex purpureus workers is constant while the number of weak non-native invasive Argentine ant Linepithema humile workers increases across treatments, fatalities of I. purpureus are lower in complex than in simple arenas. Our results provide controlled experimental evidence that investing in stronger soldiers is more effective in complex environments. This is a significant advance in the empirical study of nonhuman warfare and is important for understanding the competitive balance among native and non-native invasive ant species.
... In addition, the ant's capacity to form facultative symbiotic associations with homopterans such as mealybugs and scale (Jahn and Beardsley 1993;Reimer et al. 1993;Lach 2003) is thought to be a threat to the conservation of susceptible native vegetation communities. In contrast to the above mentioned island environments, Australia's xeric ecosystems are believed to be comparatively resistant to invasive ants, owing to the harsh, dry environmental conditions (Hoffmann 1998;Heterick et al. 2000), and the highly aggressive and abundant native ant fauna, characterized by the genus Iridomyrmex (Hoffmann et al. 1999; Thomas and Holway 2005;Walters and Mackay 2005;Lach and Thomas 2008). Nevertheless, most studies on the impacts of P. megacephala in Australia have shown that incursions are associated with significant reductions in the richness and abundance of most native ant species (Heterick 1997;Vanderwoude et al. 2000). ...
... The disappearance of the native ant fauna from invaded ecosystems is thought to have major direct and indirect impacts on biodiversity (Hoffmann 1998;Vanderwoude et al. 2000) and ecosystem functioning (Lach and Thomas 2008). Ant assemblages are recognized as particularly important components of Australian terrestrial ecosystems owing to their ubiquity (Andersen 1997), their high biodiversity (Folgarait 1998), their participation in complex symbioses with other invertebrates (including members of the Hemiptera, Lepidoptera and Coleoptera) (Lach and Thomas 2008), and the many vital ecosystem services that they perform (Holldöbler and Wilson 1990). ...
... The disappearance of the native ant fauna from invaded ecosystems is thought to have major direct and indirect impacts on biodiversity (Hoffmann 1998;Vanderwoude et al. 2000) and ecosystem functioning (Lach and Thomas 2008). Ant assemblages are recognized as particularly important components of Australian terrestrial ecosystems owing to their ubiquity (Andersen 1997), their high biodiversity (Folgarait 1998), their participation in complex symbioses with other invertebrates (including members of the Hemiptera, Lepidoptera and Coleoptera) (Lach and Thomas 2008), and the many vital ecosystem services that they perform (Holldöbler and Wilson 1990). Ants are recognized as major predators, scavengers (Petal 1980), and seed dispersers (Berg 1975), as well as "ecosystem engineers" (Folgarait 1998) because of their pedogenetic roles. ...
Article
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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.
... Both species can commonly be found on flowers throughout invaded areas of Australia (Lach & Thomas, 2008) and P. megacephala is a common predator on honeybees in Africa (Yang et al, 2009). ...
... Ants are common visitors to flowers and while their presence on an inflorescence may provide some defence against herbivores (Heil & McKey, 2003) they are poor pollinators and reduce pollen viability with the antibiotic secretions used in nest hygiene (reviewed in Chapter 1). As predators and nectar thieves, they also make flowers less attractive to other visitors by influencing the behaviour of potential pollinators (Altshuler, 1999;Ness, 2006;Lach, 2008). While a wide range of plant species possess physical traits that block ant access to flowers or chemical deterrents usually originating from pollen (Raine et al, 2002;Nicklen & Wagner, 2006;Junker et al, 2007;Willmer et al, 2009; this thesis Chapter 2), many do not and some even benefit from the increased pollination movement between flowers caused by ants (Maloof & Inouye, 2000;Irwin et al, 2001). ...
... Pheidole megacephala (Myrmecinae) and visits by native pollinators were reduced (Lach, 2008). ...
... Ants are easily transported by human movements and by trade (45,61,70). While most introduced ant species remain confined to human-modified habitats, several are successful invaders of more natural environments and six are recognised as among the most destructive of all invasive arthropod species (47,61). ...
... Ants are easily transported by human movements and by trade (45,61,70). While most introduced ant species remain confined to human-modified habitats, several are successful invaders of more natural environments and six are recognised as among the most destructive of all invasive arthropod species (47,61). Invasive ant species share characteristics that allow successful establishment of a colony in new areas: the species are typically unicolonial, forming 'super colonies' of genetically similar, non-aggressive, interconnected nests. ...
... Invasive ants often expand their range at the expense of native ant species, and the number of invasive ants can exceed that of all the native ant species within a comparable area (47). The loss of native ant species has important implications for the ecological processes that these insects provide, such as seed dispersal and predation, but the invasive ants may not (61,98). Serious negative effects have been recorded not only on other ant species but also through the disruption of invertebrate and vertebrate ecosystems (44,57,78,98,125). ...
Article
Many arthropod species have been transported around the globe and successfully invaded new regions. Invasive arthropods can have severe impacts on animal and human health, agriculture and forestry, and the biodiversity of natural habitats as well as those modified by humans. The economic and environmental effects of invasion can be both direct, through feeding and competition, and indirect, such as the transmission of pathogens. In this paper, the authors consider ten examples that illustrate the main mechanisms of introduction, the characteristics that enable species to rapidly expand their ranges and some of the consequences of their arrival.
... Ants are among the most economically [1,2,3] and ecologically significant groups of biological invaders [4,5,6,7,8,9]. However, despite the introduction of hundreds of ant species outside of their native ranges and considerable research only a handful of introduced ant species have been shown to have clear negative effects on native ant species. ...
... Mean total ant abundance per site was higher in invaded sites ( X X invaded = 32.1615.2) than for non-invaded plots ( X X non-invaded = 14.3615.1) (F1234567891011121314151617181920 = 11.95; p = 0.0025). ...
... However, mean native ant abundance per site was two times lower within invaded plots ( X X invaded = 7.163) than in non-invaded plots ( X X non-invaded = 13.863) (F1234567891011121314151617181920 = 19.56; p = 0.0003). ...
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Biological invasions represent a serious threat for the conservation of biodiversity in many ecosystems. While many social insect species and in particular ant species have been introduced outside their native ranges, few species have been successful at invading temperate forests. In this study, we document for the first time the relationship between the abundance of the introduced ant, Pachycondyla chinensis, in mature forests of North Carolina and the composition, abundance and diversity of native ant species using both a matched pair approach and generalized linear models. Where present, P. chinensis was more abundant than all native species combined. The diversity and abundance of native ants in general and many individual species were negatively associated with the presence and abundance of P. chinensis. These patterns held regardless of our statistical approach and across spatial scales. Interestingly, while the majority of ant species was strongly and negatively correlated with the abundance and presence of P. chinensis, a small subset of ant species larger than P. chinensis was either as abundant or even more abundant in invaded than in uninvaded sites. The large geographic range of this ant species combined with its apparent impact on native species make it likely to have cascading consequences on eastern forests in years to come, effects mediated by the specifics of its life history which is very different from those of other invasive ants. The apparent ecological impacts of P. chinensis are in addition to public health concerns associated with this species due to its sometimes, deadly sting.
... Only ~25% of previously recorded visitors were documented in our study, but most species (and those recorded by Yates et al. 2005) were capable of pollinating Jarrah flowers to some extent. Members of the Formicidae (ants) however are likely an exception as they potentially impact pollen quality and viability through the excretion of antifungal compounds (Peakall et al. 1990;Lach & Thomas 2008;Takeda et al. 2021). Although ant species (both invasive and native) have been identified as nectar thieves and pollinator deterrents (Galen & Butchart 2003), ant-mediated pollination does occur, though uncommon (Das & Das 2023) it can be highly mutualistic (Delnevo et al. 2020b). ...
... Although ant species (both invasive and native) have been identified as nectar thieves and pollinator deterrents (Galen & Butchart 2003), ant-mediated pollination does occur, though uncommon (Das & Das 2023) it can be highly mutualistic (Delnevo et al. 2020b). While it is unlikely that ants facilitate Jarrah pollination, the impact of ant visitation on the pollination of eucalypts has not been thoroughly investigated (Lach & Thomas 2008). In contrast to 26 years ago, ants were the most prolific visitor to Jarrah flowers in our study at all times of the day. ...
Article
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The recent decline of terrestrial insects in many parts of the world is of growing concern due to the fundamental ecosystem services they perform. Pollination is a vital ecosystem service predominantly performed by insects, with inestimable environmental and economic benefits. Accurate assessment and management of insect pollinator declines, and of other ecosystem impacts are hindered by a lack of long-term monitoring data and notably an absence of Southern Hemisphere studies. This preliminary study aims to address some of these gaps by determining if the diversity of insect floral visitors and potential pollinators of the canopy tree species Jarrah (Eucalyptus marginata) within Kings Park may have changed over 26 years by replicating the methods employed by previous research (undertaken by Yates et al. in 2005). Additionally, this study aims to determine if the relative abundance of the introduced European honeybee (Apis mellifera) compared to native bees visiting Jarrah flowers may have also changed. We observed insect visitors to flowers at three trees across the morning, midday, and evening over three consecutive days in mid-December 2023 (peak flowering). A total of 3023 individual observations were made, recording insects of 7 orders, 25 families, 39 genera, and 45 species. We found that abundances were comparable to 26 years ago but found a substantial shift in the composition of insect visitors with 46% less species documented and only 25% of species reoccurring. Ten additional families were observed that were not documented 26 years ago, with most visitors capable of performing pollination to varying efficacies. Ants had replaced the European honeybee as the most common visitor to Jarrah flowers, and while the relative abundance of honeybees was still significantly greater than native bees, the proportion of honeybee visitors had declined, at least at the time of our study. The documented shift in the composition of Jarrah insect pollinators should be confirmed by more replicated studies in Kings Park, and highlights the importance of long-term monitoring, and the need for further avenues of urban pollination research to accurately assess and address any widespread decline of insects. This is important for protecting the pollination services that insect pollinators provide at local and global scales.
... Despite many studies examining the ecological impacts of introduced ant species (e.g., PORTER & SAVIGNANO 1990, MAY & HETERICK 2000, HOLWAY & al. 2002a, O'DOWD 2003, ALLEN & al. 2004, WALTERS 2006, LACH & THOMAS 2008, substantial gaps still exist in our understanding of the factors contributing to the success of non-native ants (KRUSHELNYCKY & al. 2009). ...
... Pheidole megacephala invasions have strongly altered the abundance and diversity of native ants (HETERICK 1997, HOFFMANN & al. 1999, VANDERWOUDE & al. 2000, and have also affected nonant invertebrates (HETERICK 1997, HOFFMANN & al. 1999, HOFFMANN & PARR 2008. Pheidole megacephala also has the potential to influence native plants by disrupting antplant interactions, seed dispersal, and seed harvesting (LACH & THOMAS 2008). ...
Article
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The African big-headed ant, Pheidole megacephala, is a widespread invasive species that threatens native ecosystems and has been implicated in the decline of native ants. Although the consequences of P. megacephala invasion have been relatively well studied, the mechanisms responsible for success remain unclear. We examined the survival of P. megacephala under differing thermal conditions in the laboratory, as well as daily and seasonal variation in foraging activity in disturbed urban bushland. In two comparable sets of laboratory experiments, high temperatures had a strong negative effect on worker survival of P. megacephala, particularly under low moisture conditions. In contrast, common native species of Iridomyrmex had significantly greater survival at high temperatures. Foraging activity of P. megacephala at baits was directly related to variation in soil surface temperatures. In addition, proportional bait occupancy by P. megacephala was higher during warm seasons (early autumn) than during cool seasons (early spring), and in autumn, bait occupancy was higher in the cool morning than in the warmer afternoon (all these effects were moderated by significant variation among sites). In contrast, native ants dominated baits under warmer afternoon conditions, with almost no cooccurrence of native ants with P. megacephala. This study suggests that daily and seasonal variation in abiotic conditions can modify the dynamics of P. megacephala foraging interactions with native ants, thereby affecting local community dynamics.
... Research into the impacts of invasive ants in Australia and New Zealand is relatively new (Lach & Thomas 2008;Ward 2009;Ward et al. 2010). However, ecological impacts have been well documented for Australia (Lach & Thomas 2008), including that of competitive displacement with native ant species with potentially severe flow-on effects because of the diversity of ants in Australia and their roles in pollination and seed dispersal. ...
... Research into the impacts of invasive ants in Australia and New Zealand is relatively new (Lach & Thomas 2008;Ward 2009;Ward et al. 2010). However, ecological impacts have been well documented for Australia (Lach & Thomas 2008), including that of competitive displacement with native ant species with potentially severe flow-on effects because of the diversity of ants in Australia and their roles in pollination and seed dispersal. In New Zealand, the focus has been on Argentine ants and, because of the very low diversity of native ants, research has been directed at impacts on non-ant invertebrates, decomposition and impacts on plants. ...
Chapter
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Exotic invertebrates make up a sizeable, and growing, proportion of invertebrates in both Australia and New Zealand. However, there is a general lack of awareness of the impacts (realised or potential) of invasive invertebrates, and very few species have a high public profile. Border interception records show the sheer number and diversity of invertebrates being transported around the globe by human trade. In-depth studies on empty sea containers, ants and forestry insects, confirm that trade pathways are regularly contaminated with timber, agricultural and nuisance arthropod pests. A principal feature of the biosecurity systems in Australia and New Zealand is their holistic nature of managing invasive species through assessing threats pre-border, having high levels of surveillance at the border, and their rapid response to any incursions of new species. However, despite these systems many new species establish each year. Several issues are discussed that will be important over the next few decades: (i) the need for evidence of ecological impacts; (ii) climate change and trade liberalisation (which will affect which species will become invasive in the future); and (iii) improved technology and capability (needed to show there is the ability to manage invasive invertebrates). Introduction Intensification of human transportation and commerce around the world has led to the widespread movement of many species outside of their native range (Mack et al. 2000). As a result, biological invasions are now a global phenomenon, and are widely recognised as a significant component of global change, affecting agro-forestry industries, natural ecosystems and social activities (Mack et al. 2000; Pimentel 2002).
... (Wetterer 2009a) Most ants are translocated without purpose as stowaways in containers and other boxes together with soil, wood, ornamental plants, fruits, etc. with ships or airplanes (e.g. Lester 2005; Suarez et al. 2005; Ward et al. 2006; Lach and Thomas 2008). Interestingly, and in accordance with alien insect data in general (Kenis et al. 2007), intercepted ant species are not necessarily the most invasive ones, although repeated introductions increase propagule pressure and can foster their establishment (Suarez et al. 2005). ...
... Ants are regularly detected in border controls, at least in North America, Hawaii, Australia and New Zealand (e.g. Suarez et al. 2005; Ward et al. 2006; Lach and Thomas 2008), whereas in Europe only few species are intercepted (Kenis et al. 2007). As stressed by Hoffmann et al. (2009), a more proactive policy is needed for invasive ant management. ...
Article
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Alien ants are among the most deleterious predatory invertebrates causing havoc to native biodiversity including negative effects on other ant species, other invertebrates and vertebrates, particularly birds and lizards, ecosystem function, economy, animal and human health. The patterns of alien ant invasions and reasons for their success are among the most intensively studied facets of invasion ecology, with feedback to a general understanding of ant ecology. Alien ant management can intervene at any step during the invasion process, with action for preventive measures being the most efficient. Beside standard chemical treatments, new methods and technologies for mitigation and control of ant invasions are mostly in a trial stage. A brief outlook on the most promising offensive lines is given with particular attention paid to Wolbachia-symbiosis. Ultimately, an integrative alien species management strategy is imperative to cope with accelerating biodiversity losses due to biological invasions. KeywordsAlien ants–Biological control–Formicidae–Hymenoptera–Integrative alien species management–Invasive
... The Argentine ants form large supercolonies owing to their extraordinary social organization (Giraud et al. 2002). The long established major supercolonies of Argentine ants include Australian (Walters 2006;Rowles and O'Dowd 2007;Lach and Thomas 2008;Suhr et al. 2011), Californian (Van Wilgenburg et al. 2010; Gordon and Heller 2014; Menke and Holway 2020), European (Giraud et al. 2002), South African (Luruli 2007; Wossler 2014, 2016), and New Zealand colonies (Corin et al. 2007;Ward 2009). The colonies of Argentine ants in the southern USA are distributed in small patches within the urban areas (Buczkowski et al. 2004). ...
Article
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The Argentine ant is one among the 100 worst invasive animal species of the world. It has invaded six continents, and poses significant threats to the native invertebrate fauna. Prior knowledge on the suitable ecological niches of Argentine ants may help to devise better management plans. This study delineates the niches of Argentine ants using the ecological niche modeling approach by maintaining the temporal match between the distributional information and environmental data. We used an exhaustive methodological framework to understand the niche characteristics of Argentine ants in their native and invaded ranges. The model developed using combined native and invaded range distributional information provided better habitat suitability predictions in the invaded ranges. Efforts were also made to identify the suitable niches of this invasive species globally. The current global model was projected onto two future periods (2041–2070 and 2071–2100) under two different emission scenarios (SSP126 and SSP585). Our study highlights four important features related to the ecological niches of Argentine ants: (1) large habitat preference towards permanent streams in the native ranges, (2) native ecological niche is only partly conserved across invaded ranges, (3) invaded range niches are largely differentiated, and (4) global warming induces an increase in habitat suitability in the northern hemisphere. The results of this study may provide potential insights for the effective implementation of management strategies.
... Many ant species have demonstrated success in establishing persistent alien populations and causing ecological degradation worldwide (McGlynn 1999). This ability is evident in P. megacephala, which has a wide global distribution and causes significant damage to agricultural production and ecological structure in invaded areas (Lach and Thomas 2008). Research has shown that P. megacephala invasions severely impact the abundance and diversity of native ant species (Heterick 1997, Vanderwoude et al. 2000. ...
Article
The big-headed ant, Pheidole megacephala (Fabricius), has a widespread distribution across numerous regions globally. The International Union for Conservation of Nature (IUCN) has identified it as one of the 100 worst invasive alien species worldwide, given the severe ecological and economic harm it causes in invaded areas. In this study, we predicted the present and future global distribution of P. megacephala, taking into account known distribution points and bioclimatic factors. Our results indicated that temperature is the primary factor affecting the distribution of P. megacephala, with potential suitable areas currently found mainly in South America, Southern North America, Western Europe, Coastal areas of the Mediterranean and Red Seas, Southern Africa, Southern Asia, Islands in Southeast Asia, and coastal regions of Australia. The total suitable area spans 3,352.48 × 104 km2. In China, the potential suitable area for P. megacephala is 109.02 × 104 km2, representing 11.36% of China’s land area. In the future, based on different climatic conditions, the suitable area of P. megacephala generally showed a declining trend, but some newly added suitable areas showed that it had a tendency to expand to higher latitudes. Relevant agencies should implement effective measures to control P. megacephala populations to mitigate damage in invaded areas and slow down or prevent the spread of big-headed ants into noninvaded regions.
... It seems that by niche constructionor perhaps in this case niche deconstructionpines are able to invade and establish in new environments. (18,20,21) are known to have caused dramatic change in the ecosystem landscape, including disruption of co-evolved inter-species relations such as seed dispersal and cross-feeding (22)(23)(24). These, in turn, alter biotic, a-biotic, and even structural aspects of the ecosystem. We suggest that in such cases disturbance of the environment should be seen not only as a coincidental result of invasion, but as a part of a set of traits that facilitates the invasion's success. ...
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Many invasive species establish uniquely, or with particular success, in disturbed ecosystems. We propose that for an invasive species, ecosystem disruption may thus constitute an adaptive strategy of niche construction. Accordingly, a species’ propensity to induce large-scale ecosystem change is likely to increase not only its expected damage as an invasive species but also its success as one. We suggest that this perspective, focusing on positive feedback mechanisms driven by invasive species, may be instrumental in understanding and predicting invasive species’ dynamics. It complements the common view, which focuses on invasion dynamics’ effects on native species but not on their effect on the invasive species itself.
... Pheidole megacephala is currently one of six invasive ant species present in Australia and is listed in the worst 100 pests in the world (Lach & Thomas 2008;Lowe et al. 2000). This species is one of the most significant pest invertebrates in Australia, with serious ecological, agricultural and social impacts, and a long history of management (Hoffmann et al. 2017). ...
Article
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The trade and keeping of exotic pets has serious implications for both biosecurity and biodiversity conservation. In Australia, the online trade of live invertebrates is an understudied and unregulated issue, with almost non‐existent monitoring. It is uncertain what species are being traded, whether they are being identified correctly, and how they are being sourced (i.e., captive bred or wild harvested, native, or alien). Consequently, potential invasion risks and conservation concerns remain unknown. Here, we explored the online trade of terrestrial invertebrates in Australia across a range of publicly available e‐commerce platforms. We detected 264 species of invertebrate traded, from 71 families and 168 genera over 12 months. The native Extatosoma tiaratum (giant prickly stick insect) was the most traded species, while the most popular families were Phasmatidae (stick insects), Formicidae (ants) and Theraphosidae (tarantulas). Three species are known to be invasive in Australia, while 87% of species traded were native. The conservation status of almost of the species (92%) listed in the invertebrate trade has not been evaluated. Exploring socio‐demographic relationships, we found that human population density was positively correlated with the location of invertebrate sellers. Further, we found the classifieds website had lower prices in contrast to traditional online pet‐stores (median of c. A$7 less). Finally, we did not observe a saturation in the number of species traded in our one‐year study, exemplifying the need for large scale monitoring and risk assessments for Australia's online terrestrial invertebrate trade. We recommend continued surveillance of live invertebrate trade on e‐commerce sites. Substantial changes to legislation and monitoring methods are required at a national level to control the vast number of invertebrates traded across the country, and to minimise the future risks of the invertebrate trade.
... [14][15][16][17][18] Ants, and in particular invasive ants, are some of the most economically important insect pests in both urban and agricultural settings. 19,20 Invasive ant species can substantially alter ecosystems by outcompeting native species or by facilitating the growth of other pest or invasive populations. [21][22][23] Consequently, a substantial amount of effort and resources is spent annually on the management and monitoring of pest ants. ...
Article
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BACKGROUND A frequent goal of pest management strategies targeting social insects is total colony elimination. Insecticidal baits are highly effective at controlling social insect pests, although their ability to provide total colony elimination has only been well studied in a few species. Genetically testing colony elimination in many urban pest ants can be challenging due to indistinct colony boundaries observed in unicolonial, invasive species; however, some pest ants, such as the dark rover ant (Brachymyrmex patagonicus), maintain strict colony borders through aggression towards non‐nestmates. Each of these distinct colonies can be identified using molecular markers, allowing for the tracking of individual colonies pre‐ and post‐treatment to measure colony density. While counting the number of foraging workers to assess treatment efficacy may suffice in some cases, it offers little insight into the colony‐level impacts of a treatment. RESULTS Using microsatellite markers, distinct rover ant colonies were identified and tracked around residential structures before and after the application of an imidacloprid bait. The number of foraging ants at the treated structures was reduced by an average of 83.0% over a 28‐day observation period. Baiting also significantly reduced the total number of colonies present. At the treatment structures, only ~25% of the original colonies remained at the end of the study. Colonies with foraging trails <1.5 m from a bait station had a higher chance of being eliminated. CONCLUSION Using insecticidal baits against B. patagonicus can be highly effective at colony elimination; however, with such small foraging ranges and high colony densities, proper placement is required to ensure enough bait is properly positioned to treat all colonies affecting a structure. © 2022 Society of Chemical Industry.
... In our opinion, this contributes to its faster spread, since newly founded colonies are able to unite with the supercolony where their protected territories meet each other (Stukalyuk & Netsvetov 2018) that makes C. subdentata even become highly invasive than some other invasive species. Many invasive species, for example, L. humile, hurt the species richness of local ant communities, crowding out even the dominant species (Cammell et al. 1996;Lach & Thomas 2008), or surrounding their foraging areas by the territories of their own supercolonies, as do L. neglectus (Paris & Espadaler 2012). In the case of C. subdentata in Crimea, we observed the crowding out of the local dominant (M. ...
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The native (primary) range of Crematogaster subdentata Mayr lies in Central Asia. Within the secondary range in Ukraine and Russia, it is invasive. The 1 st objective of this work was to study the evolution of the biological and ecological features (habitats, queen number, colony structure, behavior, worker's activity on foraging trails) of C. subdentata in the urban environments (Tashkent) and secondary ranges (Crimea, Rostov-On-Don region). Whilst, the 2nd objective was to compared these parameters in the natural habitats in the native (Uzbekistan) range. Result showed that in the territory of the primary range in Kyzylkum, colonies of C. subdentata are strictly monogynous; in Zarafshan's oasis (riparian forests) they were polygynous (5.0±1.2 queens), but in cities of Uzbekistan C. subdentata forms supercolonies with hundreds of nests, and in total with hundreds of queens (on average 17.7±4.4 queens per one nest in supercolony). In the secondary range, C. subdentata forms even larger supercolonies with thousands of nests, containing 53.0±8.7 queens per nest. C. subdentata avoids contacts with another invasive ant species, Lasius neglectus, in the foraging territories both in the primary and secondary ranges, but other ant species avoid C. subdentata. Workers of C. subdentata are aggressive toward conspecific ones from other nests in the natural habitats, but are tolerance to those in both the secondary range and in the cities in the primary range. In conclusion, our results show that some ants may acquire invasive species traits in the urban habitats in the primary range. Serangga 2021, 26(4): 1-29. Stukalyuk et al. ISSN 1394-5130 2 ABSTRAK Taburan natif (primer) Crematogaster subdentata Mayr terletak di Asia Tengah. Di antara kawasan sekunder, Ukraine dan Rusia adalah invasif. Tujuan utama kajian ini adalah untuk melihat evolusi, ciri biologi dan ekologi (habitat, bilangan ratu, struktur koloni, kelakuan, aktiviti pekerja di sepanjang laluan mencari makan) spesies C. subdentata di kawasan urban (Tashkent) dan kawasan sekunder (Crimea, Rostov-On-Don). Objektif kedua kajian ini adalah untuk membandingkan parameter tersebut di habitat semulajadi di kawasan natif (Uzbekistan). Di teritori kawasan primer di Kyzylkum, koloni C. subdentata adalah monogynous, manakala di oasis Zarafshan (hutan riparian) adalah polygynous (5.0±1.2 ratu), tetapi di bandar Uzbekistan C. subdentata membentuk superkoloni dengan ratusan sarang dengan jumlah (purata 17.7±4.4 individu per sarang dalam superkoloni). Di kawasan sekunder, C. subdentata membentuk superkoloni lebih besar dengan ribuan sarang yang mengandungi 53.0±8.7 ratu per sarang. Crematogaster subdentata mengelak dari berhubung dengan spesies semut invasif, Lasius neglectus di teritori mencari makanan di kawasan primer dan sekunder, tetapi spesies semut lain juga mengelak dari berhubung dengan C. subdentata. Pekerja C. subdentata adalah sangat agresif dan konspesifik untuk sarang yang lain di habitat semulajadi, tetapi bertoleransi di kawasan sekunder dan primer. Hasil kajian ini menunjukkan spesies semut memerlukan ciri spesies invasif di habitat urban di kawasan primer.
... Baker 2008). This is even more surprising when considering the biodiversity threats posed by invasive ants in this country (Lach and Thomas 2008;Wylie and Janssen-May 2016), and the monetary expenditures associated with their management (Hoffmann and Broadhurst 2016). Another striking example is the complete absence of the lesser mealworm Alphitobius diaperinus from our database, despite the massive efforts that are being deployed worldwide for combating the pullulations of this poultry house pest (Wolf et al. 2015). ...
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Invasive species are a major driver of global biodiversity loss, hampering conservation efforts and disrupting ecosystem functions and services. While accumulating evidence has documented ecological impacts of invasive species across major geographic regions, habitat types and taxonomic groups, appraisals for economic costs have remained relatively sparse. This has hindered effective cost-benefit analyses that inform expenditure on management interventions to prevent, control, and eradicate invasive species. Terrestrial invertebrates are a particularly pervasive and damaging group of invaders, with many species compromising primary economic sectors such as agriculture and health. The present study provides synthesised quantifications of economic costs caused by invasive terrestrial invertebrates on the global scale and across a range of descriptors, using the InvaCost database. Invasive terrestrial invertebrates reportedly cost the global economy US1.26trillionovertheinvestigatedperiod(19602020),mostlyduetoinvasiveinsects(>90 1.26 trillion over the investigated period (1960–2020), mostly due to invasive insects (> 90%). Overall, costs were not equally distributed geographically, with North America (76%) reporting the greatest costs, with far lower costs reported in Europe (4%) Asia (4%), Africa (3%), South America (2%), and Oceania (1%). These costs mostly resulted from direct resource damages and losses (76%), particularly to agriculture and forestry; relatively little (4%) was invested in management. A minority of monetary costs was directly observed (43%), but costs were mostly sourced from highly reliable estimates (58%). Economic costs displayed an increasing trend with time, with an average annual cost of US 20.67 billion since 1960, but reporting lags reduced costs in recent years. The massive global economic costs of terrestrial invertebrates require urgent consideration and investment by policymakers and managers, in order to prevent and remediate the economic and ecological impacts of these and other invasive species groups.
... We also found that invasion by P. megacephala reduced levels of biotic defense in A. drepanolobium, consistent with other studies showing that invasion-driven declines in native ant assemblages can disrupt mutualistic services including seed dispersal (reviewed in Ness andBronstein 2004, Lach andThomas 2008), plant protection (Lach 2003, Lach and Hoffmann 2011, Ludka et al. 2015 and the pruning of encroaching vegetation (Mikissa et al. 2013). The partial reassembly of the symbiosis between A. drepanolobium and T. penzigi within invaded habitats appears to offer some protective benefit to host plants relative to unoccupied and P. megacephala-occupied trees, but these benefits were strongly reduced compared to the those offered by T. penzigi in uninvaded habitats. ...
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Biological invasions can lead to the reassembly of communities and understanding and predicting the impacts of exotic species on community structure and functioning are a key challenge in ecology. We investigated the impact of a predatory species of invasive ant, Pheidole megacephala, on the structure and function of a foundational mutualism between Acacia drepanolobium and its associated acacia‐ant community in an East African savanna. Invasion by P. megacephala was associated with the extirpation of three extrafloral nectar‐dependent Crematogaster acacia ant species and strong increases in the abundance of a competitively subordinate and locally rare acacia ant species, Tetraponera penzigi, which does not depend on host plant nectar. Using a combination of long‐term monitoring of invasion dynamics, observations and experiments, we demonstrate that P. megacephala directly and indirectly facilitates T. penzigi by reducing the abundance of T. penzigi’s competitors (Crematogaster spp.), imposing recruitment limitation on these competitors, and generating a landscape of low‐reward host plants that favor colonization and establishment by the strongly dispersing T. penzigi. Seasonal variation in use of host plants by P. megacephala may further increase the persistence of T. penzigi colonies in invaded habitat. The persistence of the T. penzigi–A. drepanolobium symbiosis in invaded areas afforded host plants some protection against herbivory by elephants (Loxodonta africana), a key browser that reduces tree cover. However, elephant damage on T. penzigi‐occupied trees was higher in invaded than in uninvaded areas, likely owing to reduced T. penzigi colony size in invaded habitats. Our results reveal the mechanisms underlying the disruption of this mutualism and suggest that P. megacephala invasion may drive long‐term declines in tree cover, despite the partial persistence of the ant–acacia symbiosis in invaded areas.
... Invasive ants are among the worst IAS (37). They have enormous ecological impacts on other ant species as well as on other taxa (38,39), ranging from decreases in the abundance and richness of native species (37) to the disruption of species interactions (40,41), invasion meltdown (41,42), local species extinctions (42), and whole ecosystem functioning alteration (39). Invasive ants also have tremendous negative impacts on human activities, notably agriculture (43), human health (44), and infrastructure (39). ...
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Significance Biological invasions are the second most severe threat affecting biodiversity worldwide with major economic and societal impacts. Yet, the multitude of species with the potential to be invasive makes it extremely difficult to anticipate invasions to develop efficient management plans. Predicting which species are likely to become invaders and where they are likely to invade even before their introduction outside their native range has always been a prime objective of invasion biology. Based on the example of ants, we provide a profiling method to predict future invaders and future invasions, and in this manner, we identify 18 ant species likely to become new invaders and regions at risk for these invasions.
... De même, les chats domestiques Felis s. catus, largement dispersés sur les îles mondiales depuis leur domestication par l'homme, ont constitué des populations férales sous toutes les latitudes, responsables de la disparition définitive de plusieurs dizaines d'espèces de vertébrés insulaires et directement impliquées dans les menaces qui affectent plus d'une centaine d'autres espèces actuellement considérées comme sévèrement menacées d'extinction globale (Medina et al., 2011). Enfin, différentes espèces de fourmis invasives dont certaines présentent un caractère quasi cosmopolite sont connues pour avoir des effets particulièrement délétères sur la biodiversité insulaire , Lebreton et al. 2003, Hill et al. 2003, Lach et Thomas 2008, Hoffman & Saul 2010, y compris sur les espèces vertébrées (reptiles, oiseaux), bien que cette dernière situation ait fait l'objet de trop peu d'études à ce jour , 2005, Hansen & Müller 2009). ...
... IAS include species from all major taxonomic groups, but we currently have a substantially better understanding of the status and implications of vertebrate and plant IAS in the Asia-Pacific region in comparison with invertebrates and microbes. Species that can directly affect human health, such as coronaviruses (Al-Tawfiq et al., 2014), some aggressive ant species (Foucaud et al., 2010;Lach & Thomas, 2008;D. F. Ward, 2007), and species causing substantial economic losses such as major agricultural and forest pest species (e.g. ...
... However, the success of an introduction is dependent on numerous favourable biotic and abiotic factors including the absence of natural enemies, propagule pressure, the organism's dispersal ability (Duncan 2016;Liebhold and Tobin 2008) and its capacity to exploit its new environment including food resources (Cassey et al. 2004;Snyder and Evans 2006). Although not all incursions overcome these factors and become established, many do, and have gone on to become urban and agricultural pests or cause serious issues to human and ecosystem health (Lach and Thomas 2008). ...
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The European earwig, Forficula auricularia, is a cosmopolitan insect endemic to Europe, West Asia and North Africa, which has invaded many temperate regions of the world including Australia and New Zealand. F. auricularia has been shown to be a complex of morphologically identical, reproductively isolated lineages that possess two distinct clades of mitochondrial DNA. Entomological collection data, historical literature and further field collections were used to develop a greater understanding of Australian F. auricularia’s invasion biology and its current distribution. Genetic analysis of F. auricularia collected from Australia and New Zealand using two mitochondrial genes (COI and a fragment overlapping parts of the COI -COII genes) was also undertaken. To identify the possible source populations of the Australasian invasion these sequences were compared to those from 16 locations within Britain and continental Europe. All Australasian populations were shown to be of the clade B lineage. Tasmanian and New Zealand populations consist of a single subclade comprised of only 4 and 1 haplotypes respectively. The Australian mainland populations also contained a second subclade consisting of up to 11 haplotypes indicating that multiple introductions possibly occurred on the Australian mainland. Comparison of mitochondrial genomes from Australasian and European populations showed the Australian mainland subclade to be most closely related to Portuguese haplotypes, and the Tasmanian and New Zealand clade closely related to those in Brittany, France. No European haplotypes perfectly matched the Australasian sequences. Therefore, the original source populations are still to be identified with harbours on the Iberian Peninsula’s western coast and those on the English Channel likely candidate areas.
... First detected at Ashmore Reef in 1992 , recent work has demonstrated that, as a generalist scavenger and predator, tropical fire ants have caused seabird and turtle nest failures . Elsewhere tropical fire ants have impacted native invertebrate communities, soil seed banks and ecosystem functions (Holway et al. 2002;Lach and Thomas 2008;Plentovich et al. 2009). Due to the impacts, a pilot control program has been completed to assess tropical fire ant control and detection at Ashmore Reef. ...
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Invasive species threaten endangered species worldwide and substantial effort is focused on their control. Eradication projects require critical resource allocation decisions, as they affect both the likelihood of success and the overall cost. However, these complex decisions must often be made within data-poor environments. Here we develop a mathematical framework to assist in resource allocation for invasive species control projects and we apply it to the proposed eradication of the tropical fire ant (Solenopsis geminata) from the islands of Ashmore Reef in the Timor Sea. Our framework contains two models: a population model and a detection model. Our stochastic population model is used to predict ant abundance through time and allows us to estimate the probability of eradication. Using abundance predictions from the population model, we use the detection model to predict the probability of ant detection through time. These models inform key decisions throughout the project, which include deciding how many baiting events should take place, deciding whether to invest in detector dogs and setting surveillance effort to confirm eradication following control. We find that using a combination of insect growth regulator and toxins are required to achieve a high probability of eradication over 2 years, and we find that using two detector dogs may be more cost-effective than the use of lure deployment, provided that they are used across the life of the project. Our analysis lays a foundation for making decisions about control and detection throughout the project and provides specific advice about resource allocation.
... Tropical fire ant (Solenopsis geminata F.) is an invasive species originating from central and south America and is now widespread in the tropics (Plowes et al. 2007, Wetterer 2010). It may have been present in northern Australia for at least 100 years (Wetterer 2010), although the first confirmed record is from 1939 (Lach and Thomas 2008). Outside of its home range, it is a significant and aggressive pest of urban, agricultural and natural environments and due to its potent sting, of human health concern (Risch and Carroll 1982, Plowes et al. 2007, Chin 2008, Plentovich et al. 2009, 2010, Wetterer 2010). ...
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Tropical fire ant is present in northern Australia, occurring in urban, agricultural and natural environments. Synergy® Ant Bait was evaluated for direct nest treatment of tropical fire ant (Solenopsis geminata F.) and some native nuisance species on a golf range in Darwin (Australia). Synergy® was applied directly to nests of tropical fire ant, meat ant (Iridomyrmex sanguineus Forel), pale tyrant ant (Iridomyrmex pallidus Forel) and Monomorium sp. (rothsteini gp) at rates of 1 to 16g per nest and colony viability evaluated over a period of several months. Almost all nests were eliminated within 37 days and all but two large meat ant nests were inactive by 68 days after application. These two remaining meat ant colonies were considered moribund as there were very few worker ants active and excavation of the main nest resulted in little or no defensive response from the colony. Synergy® used as a direct nest treatment provided very effective control of nests of tropical fire ant and several species of nuisance ants in managed turf on a golf range in northern Australia.
... With the numerical advantage gained by this high reproductive ability, invasive ants overwhelm native ants and almost completely displace them in the infested area . The direct displacement of arthropod fauna including native ants causes indirect negative impacts on many other taxa related to them Lach 2003;Ness and Bronstein 2004;Krushelnycky et al. 2005;Lach and Thomas 2008]. Sometimes the impact can be so huge that the landscape is altered. ...
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Social insects have obtained their prosperity by cooperation among individuals. This can be applied particularly to the success of invasive ants, which form unusual social structure called supercolonies, within which individuals can move freely among physically separated nests, and thereby gain high population densities to dominate indigenous ants. Native to South America, the Argentine ant Linepithema humile has been unintentionally introduced into many parts of the world during the last 150 years. Although it is well known that the introduced Argentine ant populations form much larger and fewer supercolonies than the native populations, the relationship among beyond-ocean populations has been poorly understood. Recent studies, however, are uncovering the behavioral, chemical and genetic relationships among introduced Argentine ant populations worldwide. Individuals from the dominant supercolonies around the world have very similar cuticular hydrocarbon profiles (nestmate recognition cue), and do not show aggressive behavior toward each other, when artificially put into contact. The supercolonies constitute the largest cooperative unit ever known. Their genetic closeness suggests a common introduction pathway. Considering historical records, descendants of the most ancient introduced population have spread to many parts of the world, without losing memory of their roots. In this chapter, we introduce the nestmate recognition system and mechanism of supercolony expansion in invasive ants, with the global empire of Argentine ants as an example.
... New research approaches to understanding the effects of invasive species in the Ambatovy area and across the island should be initiated and should be based on knowledge and ecological monitoring of individual species (Simberloff, 1997). In Madagascar, as in Australia (Lach & Thomas, 2008), introduced ants may negatively influence ecological aspects of the native ant species. ...
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Rakotonirina, J C. 2010. Survey of leaf litter ant species and assessment of invasive ants in the mining sites at Ambatovy, Madagascar. In Biodiversity, exploration, and conservation of the natural habitats associated with the Ambatovy project, eds. S. M. Goodman & V. Mass. Malagasy Nature, 3: 77-91. Abstract To validate the Biodiversity Action Plan (BAP) for the
... tended to be more frequently the only species on a given branch than were the other species and, when together with another species, it was important food resource for ants, shaping the ecology of ant communities (e.g., Schroeder et al., 2010) and of entire canopy arthropod communities (Blüthgen et al., 2000). Invasive ant species visiting EFN-bearing plants can affect the ecology of native ant communities (e.g., Savage et al., 2009), with still poorly known consequences for natural and agricultural environments (Oliver et al., 2008;Lach & Thomas, 2008). Such consequences have been found to be rather detrimental for the native species (e.g., Savage et al., 2009;Eichhorn et al., 2011), although in few cases, both invasive and native ants may benefit from the EFNs (e.g., Lach et al., 2009). ...
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Many plants bear extrafloral nectaries (EFNs) that produce a sweet secretion attracting ants (and other arthro-pods), which in return often protect plants from herbivory. These interactions are common in the tropics and subtropics but rarer or absent in temperate regions. Yet, several plants with EFNs are cultivated in temperate regions, but it is un-known if their EFNs are functional, and if ants visit them. Therefore, we surveyed EFNs and visitors in 16 non-native plant species cultivated at the botanical garden of the Brissago Islands in the Southern Alps. EFNs appeared non-functional in Bauhinia yunnanensis and Bignonia capreolata, whereas nectar was visible in nine species (Erythrina crista-galli, Gossypium hirsutum, Kennedia rubicunda, Passiflora caerulea, P. racemosa, Senna hebecarpa, S. mexicana, Tecoma stans, Thunbergia grandiflora) and cryptic in the remainder (Ba. corniculata, Clerodendrum bungei, Cylindropuntia imbricata, Opuntia engelmannii, Vanda coerulea). Five ants (Formica fusca, Lasius emarginatus – the most common, Myrmica rubra, Tetramorium sp., Temnothorax unifasciatus) and two wasps (Sceliphron destillatorium, Vespula vulgaris) visited EFNs. Tetramorium appeared as the most abundant and resource dominant of the three ant species found on S. mexicana. EFNs of non-native plants cultivated outdoors in temperate regions could represent an important additional food resource for ants and other arthropods, thus, shaping their community nutritional ecology. Riassunto: Interazioni tra formiche indigene e piante esotiche attraverso nettari extraflorali: novità dalle Isole di Brissago (Cantone Ticino, Svizzera) Molte piante posseggono i nettari extraflorali (NEFs) che producono una secrezione dolce che attrae le formiche (e altri artropodi) i quali spesso ricambiano la pianta proteggendola da insetti erbivori. Queste interazioni sono frequenti nei tropici e nei subtropici ma più rare o assenti nelle regioni temperate. Nonostante ciò, diverse piante con NEFs sono coltivate in zone temperate, ma non si sa se i loro NEFs sono funzionali e visitati dalle formiche. In questo lavoro, abbiamo quindi studiato i NEFs e gli invertebrati che le visitano in 16 specie esotiche coltivate nel Parco Botanico delle Isole di Brissago al Sud delle Alpi della Svizzera. Il nettare extraflorale è stato osservato in nove specie (Erythrina crista-galli, Gossypium hirsutum, Kennedia rubicunda, Passiflora caerulea, P. racemosa, Senna hebecarpa, S. mexicana, Tecoma stans, Thunbergia grandiflora), era criptico in cinque (Bauhinia corniculata, Clerodendrum bungei, Cylindropuntia imbricata, Opuntia engelmannii, Vanda coerulea), mentre in due specie (Ba. yunnanensis and Bignonia capreolata) i NEFs sono risultati non funzionali. Cinque specie di formiche (Formica fusca, Lasius emarginatus – la più comune, Myrmica rubra, Tetramorium sp., Temnothorax unifasciatus) e due vespe (Sceliphron destillatorium, Vespula vulgaris) hanno visitato i NEFs. Delle tre specie di formiche trovate su S. mexicana, Tetramorium sp. sembra essere la più abbondante e quella che domina maggiormente le risorse alimentari. I NEFs di piante esotiche coltivate all'aperto in regioni temperate potrebbero rappresentare una risorsa alimentare importante per formiche e per altri artropodi, ciò che potrebbe influenzare l'ecologia nutrizionale delle loro comunità. Parole chiave: Mutualistmo formiche-piante, piante invasive, difesa delle piante, San Pancrazio INTRODUCTION
... Hoffmann and Andersen (2003) recognize R. metallica group and some Iridomyrmex species as "increasers" in response to disturbance. Dolichoderines, particularly in the genus Iridomyrmex, are well known for their aggressive behavior and almost always dominate native ant communities in open habitats (Lach and Thomas 2008), and this group has been hypothesized to limit the range expansion of many invasive ants (Andersen 1997). In our study, Iridomyrmex recorded a rapid increase in abundance after S. invicta was reduced to zero, which matches observations made throughout the program of I. rufoniger frequently sharing mounds with S. invicta and occupying old and abandoned S. invicta mounds posttreatment. ...
Article
In 2001, the red imported fire ant (Solenopsis invicta Buren) was identified in Brisbane, Australia. An eradication program involving broadcast bait treatment with two insect growth regulators and a metabolic inhibitor began in September of that year and is currently ongoing. To gauge the impacts of these treatments on local ant populations, we examined long-term monitoring data and quantified abundance patterns of S. invicta and common local ant genera using a linear mixed-effects model. For S. invicta, presence in pitfalls reduced over time to zero on every site. Significantly higher numbers of S. invicta workers were collected on high-density polygyne sites, which took longer to disinfest compared with monogyne and low-density polygyne sites. For local ants, nine genus groups of the 10 most common genera analyzed either increased in abundance or showed no significant trend. Five of these genus groups were significantly less abundant at the start of monitoring on high-density polygyne sites compared with monogyne and low-density polygyne sites. The genus Pheidole significantly reduced in abundance over time, suggesting that it was affected by treatment efforts. These results demonstrate that the treatment regime used at the time successfully removed S. invicta from these sites in Brisbane, and that most local ant genera were not seriously impacted by the treatment. These results have important implications for current and future prophylactic treatment efforts, and suggest that native ants remain in treated areas to provide some biological resistance to S. invicta.
... P. megacephala is dominant in the many areas it has invaded [31]. In Australia, it has been shown that threatens native biodiversity and natural ecosystems, infests houses, and negatively impacts horticultural and agricultural production [33]. The species' ecological success can be linked to its unicolonial social structure. ...
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Background: Biological invasions are recognized as a major cause of biodiversity decline and have considerable impact on the economy and human health. The African big-headed ant Pheidole megacephala is considered one of the world's most harmful invasive species.
... The presence of the invasive L. humile may be of concern given its notorious ability to promote hemipteran pest densities (Addison & Samways 2000; Daane et al. 2007) and homogenise ant assemblages (Walters 2006;Rowles & O'Dowd 2007). L. humile has been recorded in all States except the Northern Territory (Lach & Thomas 2008), and commonly establishes in disturbed environments such as urban parks (e.g. Walters 2006). ...
Article
Ant diversity in Australia is exceptionally high compared to other regions of the world, with semiarid regions being the most species-rich. Ants perform numerous ecological functions and have been used in various biomonitoring programs. The role of ants in vineyards is unclear although other studies have focussed on controlling the invasive Argentine ant, Linepithema humile (Mayr), which significantly promotes mealybug and scale insect densities. While ants have been surveyed in a range of habitats throughout the continent, little is known about the diversity of ants in Australian vineyards. In this study, 147 native ant species were identified with pitfall trapping from 50 vineyards distributed in five regions in Victoria and South Australia. Species richness, compositional similarities and assemblage structure varied within and across regions although the ant fauna in semiarid vineyards was the most diverse. Linepithema humile was only detected in seven vineyards in one region. High ant diversity in vineyards could potentially contribute to ecosystem services, including biological control, and provide insurance to ecosystem functioning. Vineyards and other perennial agroecosystems could be important in maintaining invertebrate biodiversity particularly in a structurally diverse agricultural landscape.
... Similarly, information on A. gracilipes and W. auropunctata was largely relegated to the grey literature and regional taxonomic journals until the 1970s (Fabres & Brown 1978 ;Fluker & Beardsley 1970 ). Pheidole megacephala has continued to receive considerable research attention, especially in Australia (Hoffmann & Parr 2008 ;Lach & Thomas 2008 ) and islands in the South Pacifi c (Savage et al. 2009 ). ...
Chapter
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IntroductionThe InvadersNew Food Chains for OldThe Balance Between PopulationsEcological Resistance and the Role of DisturbanceStanding on Elton's ShouldersAcknowledgementsReferences
... P. megacephala is dominant in the many areas it has invaded [31]. In Australia, it has been shown that threatens native biodiversity and natural ecosystems, infests houses, and negatively impacts horticultural and agricultural production [33]. The species' ecological success can be linked to its unicolonial social structure. ...
Article
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Biological invasions are recognized as a major cause of biodiversity decline and have considerable impact on the economy and human health. The African big-headed ant Pheidole megacephala is considered one of the world's most harmful invasive species. To better understand its ecological and demographic features, we combined behavioural (aggression tests), chemical (quantitative and qualitative analyses of cuticular lipids) and genetic (mitochondrial divergence and polymorphism of DNA microsatellite markers) data obtained for eight populations in Cameroon. Molecular data revealed two cryptic species of P. megacephala, one inhabiting urban areas and the other rainforests. Urban populations belong to the same phylogenetic group than those introduced in Australia and in other parts of the world. Behavioural analyses show that the eight populations sampled make up four mutually aggressive supercolonies. The maximum distance between nests from the same supercolony was 49 km and the closest distance between two nests belonging to two different supercolonies was 46 m. The genetic data and chemical analyses confirmed the behavioural tests as all of the nests were correctly assigned to their supercolony. Genetic diversity appears significantly greater in Africa than in introduced populations in Australia; by contrast, urban and Australian populations are characterized by a higher chemical diversity than rainforest ones. Overall, our study shows that populations of P. megacephala in Cameroon adopt a unicolonial social structure, like invasive populations in Australia. However, the size of the supercolonies appears several orders of magnitude smaller in Africa. This implies competition between African supercolonies and explains why they persist over evolutionary time scales.
Chapter
Ants are probably the most dominant insect family on earth, and flowering plants have been the dominant plant group on land for more than 100 million years. In recent decades, human activities have degraded natural environments with unparalleled speed and scale, making it increasingly apparent that interspecific interactions vary not only under different ecological conditions and across habitats, but also according to anthropogenic global change. This is the first volume entirely devoted to the anthropogenic effects on the interactions between these two major components of terrestrial ecosystems. A first-rate team of contributors report their research from a variety of temperate and tropical ecosystems worldwide, including South, Central and North America, Africa, Japan, Polynesia, Indonesia and Australia. It provides an in-depth summary of the current understanding for researchers already acquainted with insect-plant interactions, yet is written at a level to offer a window into the ecology of ant-plant interactions for the mostly uninitiated international scientific community.
Chapter
The vast numbers of alien arthropods across the world collectively impose major conservation concerns. Many insect invaders are presumed to be pests but, even for acknowledged pest species, debates can become divisive both in (1) assessing severity of impacts beyond an immediate pest context and (2) the remedial actions needed. The Australian Light brown apple moth (Epiphyas postvittana, Tortricidae) in California, where it was recorded first in 2007, is highly polyphagous with its larvae reported to feed on more than 200 plant species, including many crops. This discovery led to a massive eradication campaign. However, as discussed by Chen (2010), some entomologists doubt that it is really a recent invader but may have been in California for several decades over which it did not come to notice through any significant damage to crops. In that case, a highly expensive eradication campaign would not be needed, and is highly unlikely to succeed. E. postvittana, as a well-known and economically significant insect, simply indicates the problems that arise in seeking sound information on impacts and any remedial steps in a new, or previously undetected, environment where, essentially, the history and reality of invasion is unknown. Pest management, to a large extent founded on invasive insects of economic, social or ecological importance, continues to provide examples of the diverse impacts of invasive taxa, and parallels with conservation management – albeit often from different ‘directions’ of suppression or encouragement.
Article
The most commonly documented consequence of alien ant invasions is the displacement and local extinction of native ant species. However, several processes may lead to low native ant diversity in the presence of non-native species. Invasive ants may, indeed, competitively exclude native ants. Conversely, invasive ants may not be able to spread into diverse, competitively dominant native ant communities. Finally, complementary distribution of invasive and native ants may be non-interactive and instead driven by divergent responses to heterogeneous environmental factors. Here, I review studies of non-native ants that have associated negative impacts on native ant communities, discuss how native ant communities are reorganized in invaded habitats, summarize reports of vulnerable and resistant ant species, and ex-amine evidence for mechanisms of reduced native ant diversity. Invasive ants are often, but not always, associated with lower native ant abundance, reduced species diversity, and randomly structured, homogenized native ant communities. Native ants are unlikely to co-occur with invasive ants 1) in habitats with environmental conditions suitable to and / or modified for the invader, 2) during the height of an invasion when an invading species is at its peak density, 3) when native ants are ecologically similar to the invading species and lack potent chemical defenses. Little evidence supports the biotic resistance hypothesis for native ants. Instead, suitable environmental conditions are primary determinants of the establishment and success of invasive ants. While invasive ants generally thrive in disturbed areas, many studies docu-ment the spread of invasive ants into undisturbed habitats and support the notion that invasive ants can drive declines in native ant diversity. More experimental studies are needed to explicitly test the importance of interactive and non-interactive processes in determining the spread of invasive ants and their impacts on native ant diversity.
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Introduction of alien organisms is a major risk that follows international trade. Ants are among the most harmful groups of invasive organisms, with five species, including the Argentine ant Linepithema humile, listed among the world's 100 worst invasive species by the IUCN. We review the damage, ecology, and dispersal of invasive ants, with the Argentine ant as a representative. Invasive ants attain high population densities in the introduced range, and cause damage to ecosystems, agriculture, and human well-being by the sheer number. The high density may stem partly from formation of expansive "supercolonies (a supercolony is a large network of cooperative nests). In the Argentine ant, the high consistency of their supercolony identities makes them important units in inferring the dispersal history of this species. We highlight two topics in the dispersal history of the species: 1) formation of an unprecedented intercontinental supercolony by the 150th year of international trade; 2) recent successive introductions to Pan-Pacific region seemingly in accordance with globalization.
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We present the first review of Hymenoptera alien to Europe. Our study revealed that nearly 300 species of Hymenoptera belonging to 30 families have been introduced to Europe. In terms of alien species diversity within invertebrate orders, this result ranks Hymenoptera third following Coleoptera and Hemiptera. Two third of alien Hymenoptera are parasitoids or hyperparasitoids that were mostly introduced for biological control purposes. Only 35 phytophagous species, 47 predator species and 3 species of pollinators have been introduced. Six families of wasps (Aphelinidae, Encyrtidae, Eulophidae, Braconidae, Torymidae, Pteromalidae) represent together with ants (Formicidae) about 80% of the alien Hymenoptera introduced to Europe. The three most diverse families are Aphelinidae (60 species representing 32% of the Aphelinid European fauna), Encyrtidae (55) and Formicidae (42) while the Chalcidoidea together represents 2/3 of the total Hymenoptera species introduced to Europe. The first two families are associated with mealybugs, a group that also included numerous aliens to Europe. In addition, they are numerous cases of Hymenoptera introduced from one part of Europe to another, especially from continental Europe to British Islands. These introductions mostly concerned phytophagous or gall-maker species (76 %), less frequently parasitoids. The number of new records of alien Hymenoptera per year has shown an exponential increase during the last 200 years. The number of alien species introduced by year reached a maximum of 5 species per year between 1975 and 2000. North America provided the greatest part of the hymenopteran species alien to Europe (96 species, 35.3%), followed by Asia (84 species, 30.9%) and Africa (49 species, 18%). Three Mediterranean countries (only continental parts) hosted the largest number of alien Hymenoptera: Italy (144 spp.), France (111 spp.) and Spain (90 spp.) but no correlation was found with the area of countries. Intentional introduction, mostly for biological control, has been the main pathway of introduction for Hymenoptera. Consequently, the most invaded habitats are agricultural and horticultural as well as greenhouses. To the contrary, Hymenoptera alien in Europe are mostly associated with woodland and forest habitats. Ecological and economic impacts of alien Hymenoptera have been poorly studied. Ants have probably displaced native species and this is also true for introduced parasitoids that are suspected to displace native parasitoids by competition, but reliable examples are still scarce. The cost of these impacts has never been estimated.
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Exotic species often form beneficial, facultative associations with indigenous species. However, we still have a limited understanding of the influences that these positive associations may have on the dynamics and impacts of species invasions. Highly invasive species may respond differently than less invasive species to resources that are exchanged in mutualisms, leading to trait-mediated indirect interactions between native species via invaders that may reshape native communities. In this study, we tested the hypothesis that the highly invasive ant species, Anoplolepis gracilipes, exhibits stronger trait changes in response to increasing levels of nectar than co-occurring, less invasive ant species. Across two islands in the Samoan Archipelago, we located multiple sites dominated by A. gracilipes and multiple sites dominated by other, less invasive species. At each site, we manipulated nectar levels on a common extrafloral nectary-bearing shrub and assessed short-term changes in ant worker recruitment and aggression. We found that the recruitment response of the highly invasive ant species A. gracilipes was not unique: other dominant ant species also increased recruitment in response to increasing nectar levels. However, A. gracilipes did show unique changes in aggressive behaviors: as nectar levels increased, the proportion of prey discovered, attacked and removed by A. gracilipes workers and the speed at which they performed these aggressive behaviors all increased strongly. Other ant species showed no such responses. In addition, fewer subordinate ants persisted on plants at sites invaded by A. gracilipes. Finally, plot-level, simultaneous manipulations of ant access to the plants and nectar availability demonstrated that Morinda citrifolia-ant mutualisms influenced the b-diversity of local arthropod communities differently when A. gracilipes dominated local ant assemblages. These results suggest that mutualisms between invasive ants and native plants can modify interactions between invaders and co-occurring arthropods, possibly leading to more negative consequences for native communities. They also underscore the importance of incorporating both positive species interactions and indirect pathways into our studies of both community ecology and invasion biology.
Book
From scorching, barren deserts to humid tropical forests, from deep in the soil, to high in the tree canopies, ants are everywhere! Comprising a substantial part of living biomass on earth, ants are integral to the functioning of terrestrial ecosystems. More than 12,000 species have been described to date, and it is estimated that perhaps as many still await classification. Their social structure provides a rich ground for exploring how division of labour affects the acquisition of resources, foraging and defensive behaviours, and coevolution with the flora and fauna with which they interact. The study of ants has led to significant advances in our understanding of insect evolution, global diversity patterns, competitive interactions, mutualisms, ecosystem's responses to change, and biological invasions. Ant Ecology explores these and other key ecological issues and new developments in myrmecology across a range of scales. The book begins with a global perspective on species diversity in time and space and explores interactions at the community level before describing the population ecology of these social insects. The final section covers the recent ecological phenomenon of invasive ants: how they move across the globe, invade, affect ecosystems, and are managed by humans. Each chapter links ant ecology to broader ecological principles, provides a succinct summary, and discusses future research directions. The Synthesis and Perspectives highlights contributions of ant ecology to ecology more broadly, and outlines promising areas for future research.
Article
The impact of the imported fire ant (IFA) is complex, in large part, because several very different species of "Fire Ants" have invaded and one of these has two forms, all of which are hard to separate by the public, as well as, some investigators not focused on the ant. Each of these different "IFA" species and forms differ in their impact. Further, these ants impact a number of "things" ranging from the environment and wildlife (plants and animals) as well as people, their environment and infrastructure. In addition, they can not only lead to death of living things (including people), but they can destroy many aspects of our environment and infrastructure at the cost of millions of dollars. But there are some beneficial aspects and some people can make many thousands of dollars due to their presence. This is an attempt to look at these issues.
Article
The spread of non-native invasive species is affected by human activity, vegetation cover, weather, and interaction with native species. We analyzed data from a 17-year study of the distribution of the non-native Argentine ant (Linepithema humile) and the native winter ant (Prenolepis imparis) in a preserve in northern California (U.S.A.). We conducted logistic regressions and used model selection to determine whether the following variables were associated with changes in the distribution of each species: presence of conspecifics at neighboring sites, distance to development (e.g., roads, buildings, and landscaped areas), proportion of vegetation cover taller than 0.75 m, elevation, distance to water, presence of both species at a site, temperature, and rainfall. Argentine ants colonized unoccupied sites from neighboring sites, but the probability of appearance and persistence decreased as distance to development, vegetation cover, and elevation increased. Winter ants appeared and persisted in sites with relatively high vegetation cover (i.e., highly shaded sites). Presence of the 2 species was negatively associated in sites with high vegetation cover (more winter ants) and sites near development (more Argentine ants). Probability of colonization of Argentine ants decreased where winter ants were most persistent. At sites near development within the preserve, abundant Argentine ant populations may be excluding winter ants. The high abundance of Argentine ants at these sites may be due to immigration from suburban areas outside the preserve, which are high-quality habitat for Argentine ants. In the interior of the preserve, distance from development, low-quality habitat, and interaction with winter ants may in combination exclude Argentine ants. Interactions among the variables we examined were associated with low probabilities of Argentine ant colonization in the preserve.
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Vetches (Vicia spp.) were studied in the San Francisco Bay Area of California in the spring of 1978. The stipular nectaries of the vetches are visited by the Argentine ant, Iridomyrmex humilis Mayr. The nectaries were removed to exclude ants in controlled experiments to determine if these ants protect the vetches from herbivores or seed predators. Plants with excised nectaries suffered substantially greater damage to their foliage than control plants, indicating that ants protect the foliage. There was no indication that ants protect the vetches from seed predators, but fruit set was substantially lower in plants with excised nectaries. Analysis of sugar and amino acid composition of extrafloral nectar served as a basis for feeding tests with Argentine ants by using artificial nectar solutions. Ants preferred sucrose and glucose solutions over fructose. They showed no preference for any one sugar mixture over another, nor did they exhibit differential recruitment to artificial nectar solutions containing only sugars or sugars and amino acids.
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Red imported fire ants (Solenopsis invicta) (Hymenoptera: Formicidae) are a relatively new arrival to Australia. Currently a concerted eradication program is in place that aims to eradicate them by 2006. If red imported fire ants are not eradicated, they are likely to spread to many parts of the Australian continent. There can be no doubt that S. invicta will pose a substantial risk to Australia's fauna if it spreads beyond its current Australian range and is not eradicated. If the worst-case scenario occurs and their range increases to cover most of the continent as predicted, wide-ranging species declines in a variety habitats are to be expected. Although endangered species are of particular concern, many common Australian animal species have experienced range declines, and the additional pressure caused by S. invicta may be sufficient to result in a new wave of species losses. It is crucial that we determine which groups have already been negatively affected by fire ants in Australia and that we establish which fauna is most at risk to ensure any future research and conservation funding is applied appropriately.
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The Big-headed Ant Pheidole megacephala is a major threat to native invertebrate assemblages and to agricultural production world-wide. This paper reviews its known biology including its foraging ecology, colony founding and dispersal behaviour. A case study is presented to illustrate its potential conservation significance for northern Australia. At Howard Springs Nature Park in the Darwin region of the Northern Territory, an infestation of P. megacephala was found to cover 25 ha and is continuing to spread, with its distribution centred on a rainforest patch. The abundance of P. megacephala within the rainforest was 37?110 times that of total native ant abundance at uninfested sites. Only two individuals of a single native ant species were found in the highest abundance of P. megacephala and abundance of other invertebrates was only 15% of natural levels. Pheidole megacephala is a serious potential threat to native biodiversity in monsoonal Australia. Successful eradication on a large scale is a realistic option and control methods are discussed, including chemicals and fire.
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Smicrocotis obscura Kirkaldy feeds at night and is tended by ants of the genus Camponotus. Details of the ant-hemipteran association and the taxonomy of Smicrocotis Kirkaldy are discussed and compared with other known ant associations within related groups. Smicrocotis sidnica Kirkaldy is newly synonymised with S. obscura.
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This paper reports on the apparent displacement of native and exotic ants from gardens in the Perth Metropolitan region by the coastal brown ant (Pheidole megacephala (Fabricius)). Twelve gardens were sampled, four with P. megacephala present, and eight (the controls) where the ant was judged to be absent. Eight out of the 26 ant species recorded (including the coastal brown ant) were introduced. Ninety-two per cent of pitfall trap contents comprised the four most abundant species: P. megacephala, lridomyrmex chasei (Forel), Tetramorium simillimum (F. Smith) and Paratrechina ?obscura (Mayr). Three of the four P. megacephala-dominated gardens were depauperate of almost all other ant species. The fourth P. megacephala-infested garden had a relatively small number of coastal brown ants (104), and the highest number of ant species was found in that garden. The removal of this outlier garden left an average range of one to three species for the other three P. megacephala-infested gardens. Control gardens had between five and 12 ant species. Total ant abundance ranged from an average of 1 027 per P. megacephala-infested garden (increasing to 1 171 if the outlier garden is removed) to 146 at control gardens. There was a significant difference both in ant richness and ant abundance between the controls and P. megacephala-infested gardens (P < 0.05). This remained the case when figures for coastal brown ants were excluded from calculations.
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A framework for the analysis of ant-plant interactions has been provided by Hocking (1975) and Gilbert (1979), who grouped insect-plant interactions into 7 main categories according to the relative roles of the species involved. I shall consider ant-plant interactions under the 10 main categories listed below.
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The White-throated Climacteris leucophaea, Red-browed C. erythrops and Brown C. picumnus Treecreepers are sympatric in south-eastern Australia. All three appear to feed largely on ants. I compared the ecology and behaviour of these birds in the non-breeding season of 1976 at Wollomombi Falls, forty kilometres east of Armidale, NSW. Here the three species occur in the same habitat and may be seen foraging on the same trees at the same time. The Brown spent almost half its time on the ground or on lwgs but the Red-browet and Whitethroated foraged almost entirely on trees. The last two species occurred at similar helghts and on branches of similar sizes but an different types of trees and had different foraging techniques. The White-throated mostly foraged by pecking and excavating pieces of bark from rough-barked trees such as stringybarks. The Red-browed typically peered and probed into ribbons of bark hanging from smoothbarked trees such as Yellow Box Eucalyptus melliodora. These two species also differed in social organization; the White-throated was territorial and usually solitary but the Red-browed occurred in groups of three or four individuals. In aggressive encounters the larger Brown Treecreeper dominated the other two. The Red-browed always dominated the White-throated although these two species are similar in size.
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The effect of native vegetation on the distribution of the green ant, Oecophylla smaragdina, and the main insect pests in cashew, Anacardium occidentale, plantations in tropical northern Australia was studied by field surveys and by observations. O. smaragdina was an efficient predator and the most abundant ant species in cashew plantations. Infestations of the main insect pests in the trees lacking ant nests were significantly higher than in those with ant nests. Although O. smaragdina were abundant on a wider range of native tree species, they preferred Acacia aulacocarpa and Planchonia careya, and they also thrived on cashew trees after dispersing into cashew plantations. In cashew plantations, O. smaragdina preferentially colonized trees with thick canopies irrespective of tree height. Fierce fights between O. smaragdina colonies were a major factor responsible for changes in population sizes, colonization and distribution of O. smaragdina in cashew plantations. The availability of preferred native trees and the distance between the native vegetation and the cashew plantation appear to play important roles in both the rate and the pattern of initial colonization of cashew plantations by O. smaragdina . These factors also indirectly influence the distribution and abundance of the insect pests of cashews. We suggest that, in the management of modern cashew crops, managers cannot rely on the natural dispersal of O. smaragdina to control insect pests. We recommend the use of native trees to enhance O. smaragdina populations in controlling cashew insect pests.
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The area occupied by the Western Australian wheatbelt has experienced extensive land clearing for agriculture between 1900 and 1970. In many areas >90% of the original vegetation has been cleared, and exotic predators (fox and cat) are common. Of the 56 mammal species recorded for the region since agricultural settlement, 25% have become extinct and a further 21% have declined in range. Yet not all species have been equally affected. The echidna Tachyglossus aculeatus acanthion, a termite- and ant-eating specialist, remains ubiquitous and its populations are stable. It is successful because (a) it is not restricted by habitat; (b) it specializes on an abundant and reliable food source for which there is no apparent competition: (c) it is metabolically capable of tolerating low energy conditions, such as drought- or fire-induced food shortages; (d) its shelter requirements are independent of vegetation; (e) predation on adult animals is minimal; and (f) it can survive outside nature reserves, and is capable of dispersing to distant remnants.Morphological and physiological adaptations to myrmecophagy (termite- and ant-eating) now enable Tachyglossus to cope with exotic predators and the loss and fragmentation of habitat. These adaptations are likely to benefit other mammalian myrmecophages living in similar environments. The native numbat Myrmecobius fasciatus is an exception. It has declined to <10% of its former range because it lacks an effective defence against exotic predators, and is today restricted to habitats where log shelters provide a measure of protection from fox and feral cat.
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Experiments are described which test the hypothesis that more host-specific species of caterpillars should be less aceptable to a generalist predator than polyphagous species. Caterpillars of all species were tested in paired choice tests with the Argentine ant, Iridomyrmex humilis. Experiments were replicated ten times, videotaped and later analyzed. Brightly colored specialist species (normally considered to be aposematic) were clearly the least palatable, while more cryptic specialists were also significantly less acceptable than generalists overall. Leaf-tying species were considered separately; all were highly palatable independent of host range. The results indicate that among caterpillars that do not construct leaf shelters, those with a wide post range are more acceptable than those with a narrow host range. This is consistent with the notion that generalist predators provide selection pressure favoring narrow host range in their herbivorous prey.
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Weaver ants, Oecophylla smaragdina (Fabricius), have been successfully used to control the main insect pests of cashew plantations in northern Australia and Papua New Guinea. The red-banded thrips, Selenothrips rubrocinctus (Giard), is an economically important insect pest of mango, Mangifera indica L., orchards in the Northern Territory. This work was undertaken to evaluate whether weaver ants, which are abundant in mango orchards, have the potential to control the red-banded thrips. Field surveys, field experiments and laboratory trials were carried out in four mango orchards in the Darwin area over four years. In field surveys, the number of shoots damaged by the thrips was significantly lower on trees with abundant weaver ants (2.8%) than with fewer ants (21.1%), or without the ants (30.3%). Trees with abundant weaver ants also produced the highest numbers of flower panicles. Leaf examinations revealed that newly mature leaves on trees with abundant weaver ants had significantly fewer thrips than on trees with fewer or no ants. Field experiments showed that weaver ants were as effective as chemical insecticides in limiting fruit damage by thrips. In laboratory trials, seedlings without weaver ants were heavily damaged, and lost all their leaves within six weeks, while seedlings with weaver ants grew well and lost no leaves. This work suggests that the weaver ant is an effective biological control agent of the red-banded thrips, and the use of weaver ants in mango orchards is discussed.
Article
Seed harvesting by ants refers to the removal and subsequent consumption of seeds (i.e. seed predation), as distinct from the dispersal of seeds possessing an ant-attracting appendage (i.e. myrmecochory). Outside Australia, seed harvesting is primarily a phenomenon of arid regions. The seeds of ephemeral plants represent a valuable food source in desert environments, which typically support large populations of granivores, mostly rodents, birds, and ants (Mares and Rosenzweig 1978; Brown et al. 1979; Abramsky 1983). The ants are primarily species of the myrmicine genera Pogonomyrmex, Messor, Veromessor, Monomorium and Pheidole, and, although strictly they are not specialist granivores (Bohart and Knowlton 1953; Brown et al. 1979), seeds nevertheless constitute a major portion of their diets. Foraging by these ants can have a marked impact on seed densities and distributions (Reichman 1979) and consequently on the community structure of desert plants (Inouye et al. 1980). Most of these ant species are confined to deserts, and harvester ants are often absent altogether from other habitats (e.g. Brown et al. 1975). Harvester ants can be prominent in seasonally arid habitats, such as in mediterranean California (Hobbs 1985), tropical Mexico (Carrol and Risch 1984), and African savannahs (Levieux 1983), but there are no records of them being important in temperate habitats anywhere in America, Europe, or Africa.
Book
Ants are one of the most influential elements in Australian ecosystems, having a major impact on plant growth and reproduction, and soil structure. They act as predators and competitors of other arthropods, and are an important food source for other animals. The book provides details on separating genera from those which are superficially similar and those which are commonly confused. The distribution, habitat preferences and general biologies of each genus are discussed, and there is an introduction to the more important research papers investigating each group.
Article
The yellow buttercup occurs abundantly in association with several different vegetational types in the SW of Western Australia. In remnant urban bushland at Perth, Western Australia, seeds are collected by two Melophorus species, Rhytidoponera violacea and Iridomyrmex discors. In banksia low woodland at Cooljarloo, a species of the Iridomyrmex rufoniger group and R. violacea collect seeds of H. hypericoides. One of the Melophorus species discriminates between potentially viable seeds, which are enclosed by a pulpy aril and non-viable seeds which show only a thin, short aril. Large numbers of potentially viable seeds are collected; the aril is consumed and the seeds discarded in the refuse heaps of the colony. -from Authors
Article
Ant pollination systems are remarkably rare. We show that pollen exposed to ants for brief periods exhibits reduced viability, reduced percent germination, and shorter pollen tubes relative to control pollen. Pollination with ant-borne pollen also results in lower seed-set than pollination with untreated pollen. This disruption of pollination processes must have exerted a powerful selection pressure against the evolution ofant-pollination systems. It is suggested that the nestbuilding and brood-rearing habits of ants require that they secrete large amounts of antibiotics to combat pathogenic microorganisms. It is these secretions that disrupt pollen function. Bees and wasps exhibit very different nesting behavior, consequently there are no chemical barriers to their coevolving with flowers as pollinators.
Article
Sampling of invertebrate fauna was carried out on Mt Coot-tha, between 25 February and 11 March 1992, to determine whether the presence of the coastal brown ant, Pheidole megacephala (Fabricius), affected the abundance and diversity of other invertebrates. Four plots were sampled; in two the coastal brown ant was present and in two it was absent. The overall abundance of invertebrates did not differ significantly between plots. The abundance of Collembola did vary significantly, but intraplot variability was large. Mite numbers did not differ significantly between plots, except for the family Laelapidae. Abundance of other ant species did not differ significantly between plots, but there was a difference in species composition; Dolichoderinae and Ponerinae were absent or poorly represented in plots where the coastal brown ant was present.
Article
Top-down control by predaceous insects has rarely been demonstrated in terrestrial communities, but invasive species may be particularly suited to exert such control. The red imported fire ant, Solenopsis invicta, has strong interactions with spiders, other ants and phytophageous insects, and we predicted that it would exert top-down control, cascading to plants in early successional plant communities. In forest gaps in South Carolina, we measured levels of folivory, growth and fecundity for five common herbaceous plant species in plots where ants were present vs. excluded (ant exclusion study) and in plots with varying abundance of fire ants and sympatric ants (ant substitution study). For all plant species in the ant exclusion study, folivory was greater when fire ant abundance was low (P < 0.01). Light levels, spider abundance and herbivore abundance were also related to folivory for some plant species in both studies (P < 0.01). Mean folivory over the growing season was low for all plant species (mean amount of leaf tissue removed for the most-chewed species was 11%). Variation in plant growth and fecundity were not well explained or consistent for any plant species in either study (partial R2 ≤ 0.10 for eight significant variables related to aboveground vegetative biomass and three significant variables related to reproductive biomass). Our results indicated that fire ants are important in determining the level of folivory on early successional plants; however, their top-down influence was not enough to cascade and impact plant growth or fecundity.
Article
The Argentine ant (Linepithema humile) is a highly invasive 'tramp' species from South America that has spread to many countries of the world. Human-assisted transportation of ant colonies is the main mechanism of dispersal to new areas. L. humile was first found in Auckland in 1990. It is now widespread within Auckland, but still patchily distributed, and has established at a number of other sites around New Zealand from Northland to Canterbury. Although mainly established in urban areas, the first population reported from conservation land administered by the Department of Conservation has established on Tiritiri Matangi Island. The potential distribution of L. humile is predicted using temperature and land cover data. Much of Northland and coastal areas of the North Island are considered to be at risk of establishment. Except for urban areas, most of central and southern New Zealand is considered too cold. Indigenous scrub/low stature vegetation is the native habitat considered most at risk, while indigenous forest is unlikely to be invaded. Many offshore islands contain suitable habitat for the establishment of L. humile should it be transported there. Spread to areas outside urban development will be slow, as unassisted dispersal is only about 150 m/yr. At sites of establishment, most other ant species will be replaced by L. humile, and the structure of the non-ant invertebrate community will be altered. Currently, baiting is considered the most effective method for control, and several bait products are commercially available. For areas of high conservation significance, such as offshore islands, eradication of populations is desirable rather than management requiring ongoing chemical application. An eradication strategy is being tested on Tiritiri Matangi Island and two urban populations using the insecticide fipronil in an experimental protein bait developed in Australia. The first treatment has resulted in a huge reduction in the density of L. humile, but follow-up treatment is required to achieve eradication. If successful, the strategy will provide a method to eliminate L. humile from important conservation areas. Eradication is labour intensive so is best undertaken while infestations are small, requiring targeted monitoring of key conservation sites.
Article
Two adjacent parallel dune systems on the west coast of Wilsons Promontory differ in their CaCO3 content and therefore their soil pH. The calcareous dunes are more species rich than the siliceous dunes and although the major species on both dune systems are similar, at least one species. (Swainsona lessertiifolia), appears to be calcicolous. The scrub on the stable dunes mostly consists of even-aged stands as a result of numerous past fires. In most stands on Norman Bay Leptospermum laevigatum is dominant and Leucopogon parviflorus sub-dominant. The proportion of these species in the vegetation is likely to depend on the age of the stand and the frequency and severity of fires and droughts. In old stands, L. laevigatum is senescent with little or no regeneration due to seed harvesting by ants and persistent browsing by mammals. By contrast, L. parviflorus is rarely browsed, is more shade bearing and fire tolerant and although it remains vigorous in old stands it is damaged by sustained drought. It is likely to become the stand dominant in the presence of herbivores and in the continued absence of fire and severe drought, or any other disturbance. In severe SW storms fine calcareous beach sand at Norman Bay, is winnowed out over the dune scrub for up to 200 m inland, may delay normal processes of podzolization.
Chapter
Symbioses between ants and plants are widespread in the tropics. Trees are usually defended by their ants, while epiphytic plants probably obtain mineral nutrients via the ants. In northern Australia three Malesian genera of ant-epiphytes are found: Myrmecodia and Hydnophytum (Rubiaceae) and Dischidia (Asclepiadaceae). Myrmecodia and Hydnophytum form large tubers with cavities, some of which have specialized warts, probably for absorption. In Dischidia the leaves form sacs which are entered by adventitious roots. Ants, usually Iridomyrmex cordatus, occupy these cavities and sacs. They deposit organic remains in the cavities with warts. Radio-isotopes fed to the ants are later absorbed by the plants. The behaviour of the ants and other occupants of the ant-plant are discussed in relation to the symbiosis. The three species of Myrmecodia and two of Hydnophytum in Australia require moist tropical conditions, but are absent from the rain forest. In coastal and savanna vegetation, where other epiphytes are rare, they are abundant, probably due to improved mineral nutrition from the symbiosis. In Dischidia transpirational water loss may be reduced by the symbiosis, enabling the plants to use drier habitats. Illustration and a key to Australian species are given together with nomenclatural notes. Species of ants which have been found in ant-plants are tabulated.
Article
Black ironbark trees secrete nectar during the night. Argentine ants collected 42% of the nectar before honeybees started foraging in the morning.Swartysterbasbome skei nektar snags af. Argentynse miere het 42% van die nektar versamel voordat heuningbye in die oggend begin wei het.
Article
Acacia cyclops is found along the coast of SW Australia and of mediterranean-climate South Australia, associated with naturally- and artificially-disturbed habitats. Reproduction occurred only by seed. Birds have distributed the seed in regurgitated pellets or in faeces. Pellets were usually associated with feeding sites while faeces were common under perches and near watering points. Seed moved in these ways was found <200 m from the nearest mature bush. Secondary dispersal of seeds by 6 ants species was observed. Ants left seeds on the surface or took them into their nests: dispersal distances were <2 m. Seed-feeding bugs were common in the litter beneath bushes but absent from bare ground. Higher temperatures experienced by seeds on bare ground are likely to enhance germination. Dispersal away from canopies onto bare ground may allow successful establishment because of reduced predation and enhanced changes of germination and establishment.-from Author
Article
Invasive ant species represent a serious threat to the integrity of many ecological communities, often causing decreases in the abundance and species richness of both native ants and other arthropods. One of the most in-depth and well-known studies of this type documented a severe impact of the imported red fire ant, Solenopsis invicta, on the native ant and arthropod fauna of a biological field reserve in central Texas (USA) during the initial invasion in the late 1980s. I sampled the community again in 1999, 12 years later, utilizing the same methodology, to compare the short- and long-term impacts of this invasion. Pitfall traps and baits were used to obtain quantitative measures of the ant and arthropod community, and hand collecting was additionally employed to determine the overall ant species composition. Although the abundance and species richness of native ants and several other arthropod groups decreased precipitously immediately after the S. invicta invasion, all measures of native ant and arthropod species diversity had returned to preinvasion levels after 12 years. Solenopsis invicta was still the most abundant ant species, but not nearly as abundant as it was during the initial phase of the invasion. The results of this study indicate that the impact of such invasive ants may be greatest during and shortly after the initial phase of an invasion.
Article
Flightless worker ants of the species complex Iridomyrmex gracilis (Lowne) are effective pollinators of Microtis parviflora R.Br. in the Castlereagh Forest near Sydney. Field and laboratory observations and experiments showed that this orchid is self-compatible but not autogamous and ant pollination results in very high levels of seed set. This is the first study to show that wingless ants can be exclusive pollinators. Ants forage persistently, visiting individual flowers and inflorescences repeatedly for nectar. Foraging patterns most likely result in high levels of selfing, but leptokurtic distributions of pollinator travel distances suggest that some pollen transfers result in cross pollination. Microtis pollen carried by I. gracilis workers is unaffected by antibiotic secretions from the metapleural glands which, in other ant species, may reduce pollen viability drastically. Pollinia are separated from the ant integument by a short stalk and are always carried on the frons, remote from the metapleural glands. This study shows that worker ants, although wingless, can be efficient pollinators and suggests that the presence of metapleural glands is not necessarily inimical to the evolution of ant pollination, particularly if mechanisms, such as stalked pollinia, prevent direct contact between ants and pollen.
Article
Ants are by far the most important post-dispersal seed predators at a woodland site in SE Australia, and they rapidly remove many seeds from the ground. This paper uses experimental manipulations of seed densities and ant populations to examine the likely impact of seed predation by ants on seedling recruitment in Eucalyptus baxteri and Casuarina pusilla. When seedfall was light, as usually occurs in the absence of fire, the elimination of ants resulted in a 15-fold increase in seedling densities for E. baxteri, whose seeds are removed at particularly high rates. Seeds of C. pusilla are removed less rapidly by ants, and increases in seedling densities following ant elimination were less marked for this species. Experimental dumpings of seeds at high densities, simulating the massive release of seeds from woody fruits which occurs following fire, resulted in predator satiation and in comparison to controls produced high numbers of seedlings. These results suggest that seed predation by ants limits seedling recruitment in the absence of fire, and that predator satiation plays an important role in successful recruitment following fire.
Article
The behavioral organization of territoriality in the green tree ant (Oecophylla smaragdina) was studied in the field of North Queensland, Australia. The establishment and maintenance of territories in O. smaragdina is based on a complex behavioral communication repertory which appears to be almost identical to that of its only living congeneric species, the African weaver ant O. longinoda. In our study areas, individual territories sometimes covered an area of up to 1500 m2 comprising 21 major trees. The polydomous nest organization makes it possible for an Oecophylla colony to patrol and crop much of the volume of the territory in a very cost efficient way. The guard and defense force which consists primarily of old workers with reduced fatbodies and ovaries, is housed in special barrack nests, located at the territorial boundary. A selective "enemy identification" seems to be the major behavioral mechanism for interspecific territoriality and for the mosaic distribution of ecologically dominant ant species.
Article
As invasive ants spread, their interactions with plants are inevitable and have potentially great implications for agriculture and conservation. When considered in the context of pre-existing models of ant-plant interactions, the higher abundance, aggressive nature, and attraction to high-carbohydrate resources typically associated with invasive ants lead to hypotheses about how invasive ants may differ from native ants in protecting plants from herbivores, tending of Homoptera, and interactions affecting plant reproduction. Examples demonstrate that all three of these traits common to invasive ants can influence the outcome of interactions between invasive ants and plants, but ant biology and attributes of other organisms also determine the consequences for the plant. Drawing from these examples and considering traits of the invasive ants, plants, and other organisms that interact with the plant, I offer predictions for the contexts in which plants will be at high and low risk of adverse outcomes or may benefit from interacting with an invasive ant. The potential for effects of invasive ants on plants to counteract, and the complexity and context-dependency that are hallmarks of ant-plant interactions generally, preclude drawing simple conclusions about the net impacts of invasive ants on plants. Further research on interactions between invasive ants and plants will contribute directly to conservation and agriculture, and provide insights to invasion ecology and our understanding of ant-plant interactions.
Article
Influences of ant behavior on fate of elaiosome-bearing seeds were investigated in fire-prone sclerophyll vegetation near Sydney, New South Wales. Most seeds were taken directly to ant nests. Mean dispersal distance was 1.1m (range 0.06-11m). Pheidole sp.1 appeared to eat most seeds soon after collection but also stored some seeds in small caches within the nest. Both Rhytidoponera "metallica' and Aphaenogaster longiceps removed most seeds from the nest intact (the elaiosome having been consumed) and discarded them on the surface, but left some within nests at depths <12cm. Seeds discarded on the soil surface may undergo secondary dispersal by other ants. Transition matrix analysis indicated that a significant proportion of seeds initially removed by A. longiceps and R."metallica' will eventually be eaten by Pheidole. Some seeds will be discarded in the nests of species other than the original seed remover. Seeds initially taken by A. longiceps and R. "metallica' would be more likely to survive than those taken by Pheidole. As many Australian ant-dispersed seeds are stimulated to germinate by fire, long-term seed fate was investigated by monitoring seedling emergence after fire from ant nests that had been fed a known quantity of seeds. Overall emergence was c1% of seeds fed into nests. Greatest emergence was from nests of A. longiceps. However, the low overall emergence rate meant the power of this experiment to detect statistical differences between ant species was limited. Seedlings from the nests of Pheidole were considerably more clumped than those from nests of the other three species. -from Authors
Article
A temperate species, Passiflora incarnata, of the predominately tropical family Passifloraceae, possesses two sets of extrafloral nectaries which are visited by five species of ants. In an old field, plants with the extrafloral nectaries removed attracted fewer ants, experienced greater herbivory and produced fewer fruits than plants with extrafloral nectaries intact. The number of ants per plant was positively correlated with the number of extrafloral nectaries and negatively correlated with the percent herbivory.
Article
Summary1. We used the composition of nest middens to describe the extent of dietary partitioning in an exceptionally diverse assemblage of harvester ants in the Kakadu region of northern Australia. Eight of the >15 harvester species known from adjacent 30 × 30-m plots, comprising four species of Meranoplus and two species each of Monomorium and Pheidole, maintained conspicuous nest middens.2. All these eight harvester species are monomorphic (or functionally so in the context of seed collection), with total body length ranging from 2·0 to 5·0 mm. The two species of Monomorium are column foragers, whereas the others apparently forage solitarily. Nests averaged 0·1 m2, but were highly patchy both within and between plots.3. Seed fragments from a total of 33 plant species were identified from 50 middens sampled during the end of the wet season, with up to 19 seed species recorded from a single midden. Seed species diversity was greatest in middens of Meranoplus minimus, Monomorium sp. 1 (rothsteini group) and Pheidole sp. 1 (mjobergi group), and least in middens of the diversus group of Meranoplus.4. Despite a high overall diversity of seed species, each harvester species collected primarily two or three seed species (with one exception, all grasses), and there was virtually no overlap in these species between harvesters. The pronounced dietary separation of harvester species was demonstrated by multivariate analysis of midden composition.5. The extent to which differential seed selection is determined by intrinsic preferences, vs. interactions between, harvester species is unknown, nor is it clear why the diversity of harvester ants is so high. However, it is likely that differential seed selection plays a significant role in species coexistence.
Article
The Argentine ant, Linepithema humile (Mayr), is a widespread invasive ant species that commonly displaces native ants and other ground-dwelling invertebrates in its introduced range. Previous studies have documented a relationship between the spread of Argentine ants and abiotic conditions (particularly water availability) in invaded areas, suggesting that the invasion success of Argentine ants may be related to specific abiotic factors. This study describes the relative humidity preferences and survival of Argentine ants and a dominant native ant, Iridomyrmex ‘rufoniger’ sp. group, in the laboratory. In a preference experiment, Argentine ant workers showed a significantly greater propensity than Iridomyrmex to locate themselves in containers with the highest relative humidity. A series of survival trials revealed that the survival of both species was related to the relative humidities within experimental containers. The survival of Argentine ant colonies was reduced in comparison with those of Iridomyrmex sp. after 4 h, however by 24 h both species displayed similar levels of survival in all relative humidity conditions. These findings confirm a relationship between the level of available moisture and the distribution and survival of Argentine ants, and may help to account for the current distribution and invasion success of Argentine ants in Australia.
Article
Invasion by the red imported fire ant, Solenopsis invicta, has had negative impacts on individual animal and plant species, but little is known about how S. invicta affects complex mutualistic relationships. In some eastern forests of North America, 30% of herbaceous species have ant-dispersed seeds. We conducted experiments to determine if fire ants are attracted to seeds of these plant species and assessed the amount of scarification or damage that results from handling by fire ants. Fire ants removed nearly 100% of seeds of the ant-dispersed plants Trillium undulatum, T. discolor, T. catesbaei, Viola rotundifolia, and Sanguinaria canadensis. In recovered seeds fed to ant colonies, fire ants scarified 80% of S. canadensis seeds and destroyed 86% of V. rotundifolia seeds. Our study is the first to document that red imported fire ants are attracted to and remove seeds of species adapted for ant dispersal. Moreover, fire ants might damage these seeds and discard them in sites unfavorable for germination and seedling establishment.
Article
The relatively fire-sensitive tree, alpine ash was studied in the Brindabella Range, Australian Capital Territory. An experimental high-intensity fire was used at Bushrangers Creek to determine whether massive, synchronized seedfall and subsequent seedling recruitment are linked to 1) satiation of postdispersal seed predators and/or 2) reduction of the physical and biotic resistance to seedling growth and survivorship. Overall results were consistent with the predator-satiation hypothesis. -from Authors
Article
The composition of the Christmas Island (Indian Ocean) ant fauna is reviewed, leading to the recognition of 52 species in 24 genera and 7 subfamilies. This account amalgamates previously published records and recent extensive surveys of Christmas Island's ant fauna. Eight species represent new records for Christmas Island: Technomyrmex vitiensis, Camponotus sp. (novaehollandiae group), Cardiocondyla kagutsuchi, Monomorium orientale, M. cf. subcoecum, Tetramorium cf. simillimum, T. smithi and T. walshi. Although some of these new species records represent recent taxonomic advances rather than new introductions, we consider four species to be true new records to Christmas Island. These include Camponotus sp. (novaehollandiae group), M. orientale, T. smithi and T. walshi. None of the 52 species reported here are considered endemic. In general, the Christmas Island ant fauna is composed of species that are regarded as worldwide tramps, or that are widespread in the Indo-Australian region. However, Christmas Island may fall within the native range of some of these species. We provide a key to the ant species of Christmas Island (based on the worker caste), supplemented by comprehensive distribution maps of these ants on Christmas Island and a short synopsis of each species in relation to their ecology and world-wide distribution. Because of the large number of world-wide tramp ants on Christmas Island, this key may also prove applicable for introduced species resident on other oceanic islands.
Article
We compare the dispersal spectra of diaspores from varied plant communities in Australia, New Zealand, and North America, assigning dispersal mode to each diaspore type on the basis of apparent morphological adaptations. Species with ballistic and external dispersal modes were uncommon in most communities we surveyed. Ant dispersal was also rather uncommon, except in some Australian sclerophyll vegetation types. The frequency of vertebrate dispersal ranged up to 60% of the flora, the highest frequencies occurring in New Zealand forests. Wind dispersal ranged as high as 70% of the flora, with the highest values in Alaska, but usually comprised 10–30% of the flora. Many species in most communities had diaspores with no special morphological device for dispersal. Physiognomically similar vegetation types indifferentbiogeographic regions usually had somewhat dissimilar dispersal spectra. The frequency of dispersal by vertebrates often increased and the frequency of species with no special dispersal device decreased along gradients of increasing vertical diversity of vegetation structure. Elevation and moisture gradients also exhibited shifts in dispersal spectra. Within Australia, vertebrate‐ and wind‐dispersal increased in frequency along a soil‐fertility gradient, and dispersal by ants and by no special device decreased. Habitat breadths (across plant communities) and microhabitat breadths (within communities) for species of each major dispersal type did not show consistent differences, in general. Ant‐dispersed species often had lower cover‐values than other species in several Australian vegetation types. We discuss the ecological bases of these differences in dispersal spectra in terms of the availability of dispersal agents, seed size, and other ecological constraints. Seed size is suggested to be one ecological factor that is probably of general relevance to the evolution of dispersal syndromes.