Native Ants Research Articles

Identification of the Argentine ant Linepithema humile (Hymenoptera: Formicidae) using an artificially synthesized trail pheromone and its effects on native Japanese ants

Invasion by the Argentine ant Linepithema humile (Mayr) (Hymenoptera: Formicidae) causes the collapse of global ecosystems. Attempts to exterminate this invasive ant have mostly been unsuccessful after colonization. However, some attempts are successful when they are applied in the initial stage of invasion, or the invaded area is limited. This indicates that early identification of invasion is crucial for successful extermination. The current methods of identification require special training and skills, suggesting that a new easy and fast method of identification is urgently required. Here, we report a method of identification using a species-specific trail pheromone. The Argentine ant uses (Z)-9-hexadecenal as a trail pheromone. (Z)-9-Hexadecenal is commercially available, because it is used to control the reproduction of a moth (Chilo suppressalis). We applied (Z)-9-hexadecenal 10 cm away from the trails of Argentine ants and 12 native Japanese ant species. The Argentine ant trails were largely disturbed, while the effect on the native Japanese ants was almost undetectable. These results suggest that this “trail disruption identification method” is an easy and fast method of identifying Argentine ants in Japan and that the effects of this method on native Japanese ants, if any exist, are small.

Invasive ants disperse seeds farther than native ants, affecting the spatial pattern of seedling recruitment and survival

Mutualists can vary in the quantity and quality of service which they provide to their partners. Variation in seed disperser quality depends on seed-processing traits, dispersal distance, and deposition location, all of which ultimately affect plant fitness. Here, we compared these aspects of seed dispersal quality between a native and an invasive ant species, and examined how they affect competition and plant performance. Using experimental mesocosm communities, we examined how these two ant species affect the spatial pattern of recruitment and establishment for four myrmecochorous plant species, including one invasive species. We measured the locations of dispersed seedlings relative to ant nests, adult plants, and other dispersed seedlings, as well as measured the effects of location on plant performance. The invasive ant, Myrmica rubra, secondarily dispersed seeds farther from its nests, creating a less clumped pattern of seedling recruitment compared to the native ant, Aphaenogaster rudis. Plant species responded differently to dispersal. Invasive seedlings recruited farther from adult plants than native seedlings, and had higher survival the farther they were from conspecifics. In contrast, native plants had higher survival and grew taller when dispersed farther from invasive plants. We show that seed-dispersing ant partners differ in mutualist quality creating differences in dispersal distance and deposition location that affects a plant's competitive environment. Our results reveal the potential for long-term consequences on plant community structure with changing ant partner identity. We emphasize the need to examine dispersal quality in addition to quantity to uncover the importance of partner identity in structuring communities.

Reducing Native Ant Abundance Decreases Predation Rates in Midwestern Grasslands.

Diverse and robust predator communities are important for effective prey suppression in natural and managed communities. Ants are ubiquitous components of terrestrial systems but their contributions to natural prey suppression is relatively understudied in temperate regions. Growing evidence suggests that ants can play a significant role in the removal of insect prey within grasslands, but their impact is difficult to separate from that of nonant predators. To test how ants may contribute to prey suppression in grasslands, we used poison baits (with physical exclosures) to selectively reduce the ant population in common garden settings, then tracked ant and nonant ground predator abundance and diversity, and removal of sentinel egg prey for 7 wk. We found that poison baits reduced ant abundance without a significant negative impact on abundance of nonant ground predators, and that a reduction in ant abundance decreased the proportion of sentinel prey eggs removed. Even a modest decrease (~20%) in abundance of several ant species, including the numerically dominant Lasius neoniger Emery (Hymenoptera: Formicidae), significantly reduced sentinel prey removal rates. Our results suggest that ants disproportionately contribute to ground-based predation of arthropod prey in grasslands. Changes in the amount of grasslands on the landscape and its management may have important implications for ant prevalence and natural prey suppression services in agricultural landscapes.

Direct evidence of native ant displacement by the Argentine ant in island ecosystems

Ecological impacts associated with ant introductions have received considerable attention, but most studies that report on these impacts contrast species assemblages between invaded and uninvaded sites. Given the low inferential power of this type of space-for-time comparison, alternative approaches are needed to evaluate claims that ant invasions drive native species loss. Here, we use long-term data sets from two different Argentine ant eradication programs on the California Channel Islands to examine how the richness and composition of native ant assemblages change before and after invasion (but prior to the initiation of treatments). At four different sites on two different islands, pre-invasion native ant assemblages closely resembled those at uninvaded (control) sites in terms of species richness, species composition, and the presence of multiple indicator species. Invader arrival coincided with large (> 75%) and rapid (within 1 year) declines in species richness, shifts in species composition, and the loss of indicator species. These impacts will hopefully be reversed by the recolonization of formerly invaded areas by native ant species following Argentine ant treatment, and long-term studies of native ant recovery at these sites are ongoing. Unchecked spread of the Argentine ant on other islands in this archipelago, however, poses a grave threat to native ants, which include a number of endemic taxa.

Similar compositional turnover but distinct insular environmental and geographical drivers of native and exotic ants in two oceans

AbstractAimThis study aims to quantify the patterns in compositional turnover of native and exotic ants on small islands in two oceans, and to explore whether such patterns are driven by similar environmental, geographical and potentially biotic variables.LocationPacific and Atlantic islands.Time periodPresent.Major taxa studiedAnts.MethodsWe applied Multi‐Site Generalised Dissimilarity Modelling (MS‐GDM), which relates zeta diversity, the number of species shared by a given number of islands, to differences in environmental, geographical and biotic drivers. The use of zeta diversity enabled us to differentiate the contribution of rare species (shared by few islands) from those of widespread ones (shared by multiple islands) to compositional turnover. For completion, we also related species richness of insular ants per island with the same set of explanatory variables using Generalised Additive Models (GAM).ResultsPacific and Atlantic islands have similar patterns of ant species turnover and richness, albeit partly driven by different drivers. Native and exotic species turnover are mostly explained by the same set of variables in the Pacific (annual precipitation and distance to the nearest island), but not in the Atlantic (annual precipitation is a good predictor of native species turnover, but none of the variables considered in our study explained exotic species turnover). No signal of biotic interactions was detected at the insular community level.Main conclusionsSuccessful invasion strategies may depend on a combination of factors specific to the region in question. In the Pacific, milder environments and the absence of natives on certain islands enable exotic ants to select the same types of environment as native ants. In the harsher Atlantic Ocean, however, native ant species are likely to be well adapted to local environmental conditions, making it harder for exotics to become established. Exotic ant species, therefore, potentially rely on other attributes to establish, such as a combination of tolerance to a wide range of environmental conditions and human‐mediated colonization.

The potential protective value of ants in Northern Australian coffee plantations

Native ants are the oldest example of biological control agents used in tropical tree crops. Unfortunately, intensification of agricultural practices has led to a simplification of habitat and subsequent loss of native ant biodiversity. This article describes research that evaluated the native and introduced ants present in the canopies of two Australian sun coffee plantations, their distribution pattern and their potential to limit pests. The presence in coffee plantations of a range of beneficial insects and parasites, plus the effect of ants, most notably Iridomyrmex suchieri Forel, may maintain potential pests at low levels in coffee plantations. These effects may be important for future biological control programs of coffee pests in Australia, although the sun coffee grown here does not harbor a large variety of canopy ant species.

Invasions of four South-American tramp ants: a systematic review

The invasion and spread of four native South American ants (Hymenoptera: Formicidae) Linepithema humile, Solenopsis invicta, Wasmannia auropunctata and Paratrechina (Nylanderia) fulva all over the world, their environmental and economic impact, and intended control tactics are documented. Displacement of these invasive species is triggered by human international movement of goods, and in one case, P. fulva, a deliberately introduction as a candidate for biological control of Atta spp. and snakes. These tramp ants displace native ants, attack native birds and reptiles, protect and transport sap sucking insects, cause damage to human commodities, and are able to cause health problems to men and domestic animals. Chemical control, producing negative environmental side effects, has shown poor success and short residual effect. Current tendencies use biological control agents, the natural enemies, parasites, predators and diseases of their original range. Quarantine and eradication programs have been implemented. The success of the tramp ants involves a small size that permits hiding in all types of packing materials, their organization in societies, varied diets, and in many cases to their late detection and initial control.

Non-native ant invader displaces native ants but facilitates non-predatory invertebrates

Many invasive ants, such as the European fire ant (Myrmica rubra), are particularly successful invaders due to their ability to form multi-nest, multi-queen ‘supercolonies’ that appear to displace native invertebrates in invaded regions. Myrmica rubra has invaded many areas in the Northeastern United States, including Western New York. Myrmica rubra invasion corresponds with decreases in native invertebrates, particularly ants, an effect which may be attributable to direct displacement, or because M. rubra prefers habitat unsuitable for native ants. We surveyed Western New York parklands to investigate native ant and non-ant invertebrate abundance in M. rubra-invaded and uninvaded areas. We then tested these observations with an ant pesticide treatment targeting M. rubra to investigate the direct impacts of M. rubra on the native ant and invertebrate community. A consistent, negative relationship was found between M. rubra and native ants in both the observational and experimental research, and native ant species only appeared in the pesticide-treated plots (with reduced M. rubra abundance). These data strongly suggest that M. rubra actively displaces the native ants with invasion instead of segregating by habitat. Myrmica rubra effects on non-ant invertebrates appeared more nuanced, however, in both the observational and experimental research. The absence or removal of M. rubra corresponded with decreased predatory invertebrate populations and increased non-predatory invertebrates. It appears that M. rubra has altered invertebrate communities in Western New York. Native invertebrate communities may be able to rebound with time, but our data suggest native recovery unlikely without management intervention.

Spread of Camponotus novogranadensis (Hymenoptera: Formicidae), a Non-Native Carpenter Ant in Florida

The New World carpenter ant Camponotus novogranadensis Mayr has a broad, apparently continuous range, extending from subtropical Brazil (29.8°S) to central Mexico (∼23.7°N). In 2012, a non-native population of C. novogranadensis was discovered in southwestern Florida. Here, I examine the ecology and geographic distribution of C. novogranadensis, and report additional records of C. novogranadensis in Florida. I documented C. novogranadensis at five sites in southwestern Florida from Estero to Fort Myers in Lee County (26.4°—26.5°N) and at nine sites in southeastern Florida ranging Delray Beach to Boynton Beach in Palm Beach County (26.4°—26.5°N). Although I found two well-established populations of C. novogranadensis at the same latitudes in southwestern and southeastern Florida, I did not find this species anywhere in the >150 km between. It is likely that C. novogranadensis will continue to spread in Florida, possibly impacting native ants.

Eastern Fence Lizards (Sceloporus undulatus) display an ontogenetic shift in relative consumption of native and invasive prey

Interactions between invasive prey and native predators can provide an opportunity to better understand predator–prey dynamics and how these may change through ontogeny. Eastern Fence Lizards (Sceloporus undulatus (Bosc and Daudin in Sonnini and Latreille, 1801)) are ant specialist, particularly as juveniles. Invasive red imported fire ants (Solenopsis invicta Buren, 1972) pose a lethal risk to S. undulatus that eat them, especially smaller-bodied juveniles. We examine ontogenetic shifts in S. undulatus consumption of toxic invasive fire ants versus palatable native pyramid ants (Dorymyrmex bureni (Trager, 1988)). We predicted that hatchlings should avoid eating fire ants in favor of native ants, whereas less-vulnerable adults should take advantage of both prey sources. However, when given the choice between fire ants and native ants, hatchlings consumed similar numbers of these species, whereas adults consumed nearly three times as many native ants as invasive fire ants. Increased consumption of fire ants in adulthood could be the result of lifetime experience, strategies to safely consume fire ants, ontogenetic shifts in the ability to distinguish between ants, or reduced costs to adults of eating venomous ants. Future research should aim to distinguish these alternative mechanisms and examine the long-term consequences of native species incorporating toxic invasive prey into their diets.

The Distribution of Ants in a Rwandan Coffee Plantation and Their Potential to Control Pests

Native ants are the oldest example of biological control agents used in tropical tree crops. Unfortunately, intensification of agricultural practices has led to a simplification of habitat and subsequent loss of native ant biodiversity. This paper describes an evaluation of the ants present in a Rwandan coffee plantation. The plantation was unshaded, intensively managed and regularly treated with pesticides. No herbicides or fertilisers were used, although the area had been mulched. Only five ant species were found in the plantation (Pheidole megacephala, Lepisiota depressa, Nesomyrmex angulatus and Camponotus (Myrmosericus) spp. (2 spp.). Pheidole megacephala dominated the plantation and occurred on 94 % of trees, while L. depressa, C. (Myrmosericus) spp. and N. angulatus each occurred on 13 % or less of trees. Pheidole megacephala and L. depressa were negatively associated, whereas C. (Myrmosericus) spp. were positively associated with L. depressa. Association between the coffee pests and ant species was not significant. We conclude that intensification of coffee production in this plantation and domination by P. megacephala has contributed to the low diversity of ants present and that those species that do occur there are not particularly efficient at reducing pest densities.

Unconscious Woman in Shock and Covered with Ants Pulled from an Abandoned Automobile

BackgroundA middle-aged woman was taken from an abandoned automobile unconscious and covered with ants in Tucson, Arizona. When hospitalized in July 2018, she had an extensive papular-pustular skin eruption on her abdomen and thigh and disseminated intravascular coagulation. She was stung innumerable times by native golden fire ants (Solenopsis aurea) while sleeping in the vehicle. The large amount of venom injected by stings into this individual may have triggered dissemnated intravascualar coagulation because the venom contains powerful hemolytic factors. MethodsThe patient history is presented and ants were captured and identified. ResultsClinical findings of fire ant stings are presented and the importance of recognizing the distinctive skin lesions that occur is emphasized. Stings of the red imported fire ant, Solenopsis invicta, and the black imported fire ant, Solenopsis richteri, cause skin lesions recognized by physicians and victims alike in the southern and southeastern United States. Native fire ant stings are documented much less often. However, there is significant cross-reactivity among the venoms of Solenopsis species. ConclusionIt is important for clinicians to recognize the characteristic skin lesions of fire ant envenomation as fire ant populations are expanding and they sting millions of people each year.

Humans and scavenging raptors facilitate Argentine ant invasion in Doñana National Park: no counter-effect of biotic resistance

Biotic resistance by native communities could have a role in the spread of invasive species. This seems to be the case in the invasion of the Argentine ant, Linepithema humile, but only when the environment is unfavorable for the survival of the invader. We studied the progress of Argentine ant invasion through favorable and unfavorable habitats of Donana National Park across three temporal snapshots covering three decades (1992, 2000, 2016). We assessed biotic resistance of the native community using species richness, as well as dominance and community structure. We also explored the role of abiotic factors (quality of surrounding habitat and spatial variables) and of potential vectors of Argentine ant dispersal across unfavorable areas. We found no evidence of biotic resistance after examining native ant species richness, proportion of native dominant ants, or community structure. On the contrary, invasion proceeded from trees with higher ant species richness, probably because those trees are larger and provide more resources and better protection from aridity. Furthermore, we found evidence that the invasion of new trees across a matrix of unfavorable habitat could be influenced not only by humans, but also by scavenging avian predators, which could act as vectors of ant dispersal through transport of carrion also exploited by the ants. Such leapfrog expansion through mobile predators could represent an overlooked mechanism that would enrich our understanding of invasion dynamics and provide potential opportunities for management of invasive species.

Ants as Predators of Diorhabda elongata (Chrysomelidae), a Biological Control Agent of Saltcedar (Tamarix spp.), in Texas

Four species of leaf beetles, Diorhabda spp, (Chrysomelidae), were introduced for biological control of saltcedar, Tamarix spp., an invasive small tree or shrub, in the US. In Texas, three species established at some sites but failed to establish or initially established but did not persist at other sites. Diorhabda larvae pupate in leaf litter on the soil surface and thus are exposed to ants and other soil-active predators. Predation by ants on Diorhabda pupa was evaluated as a potential factor in limiting establishment of Diorhabda populations at field sites in West Texas. Nighttime observations of pupae found that native ants represented 46-65% and pill bugs (Isopoda: Armadillidiidae) represented 8-51% of observed predation events. The predation rate of Diorhabda pupae by ants was significantly greater where red imported fire ant, Solenopsis invicta Buren, was present. When present, S. invicta was responsible for 93-100% of observed predation during the day. In the absence of S. invicta, native ants Monomorium spp., Crematogaster spp., and Formica perpilosa Wheeler were observed preying on Diorhabda pupae. Results suggested that predation by ants, especially red imported fire ant, could limit establishment of Diorhabda spp. released for biological control of saltcedar.

Previous diet affects the amount but not the type of bait consumed by an invasive ant.

Recent research on multiple invasive ant species has revealed the importance of carbohydrates for achieving high activity levels and outcompeting native ants. However, comparatively little is known about the role of diet and macronutrient preferences for uptake of insecticidal baits used to control invasive ants. We tested whether diet affected yellow crazy ant (Anoplolepis gracilipes Fr Smith) survival and behavior, and whether bait preference would be complementary to past diet. We found that colonies fed only crickets for 28 days had fewer live workers and queens, and less brood per live queen than colonies fed crickets + honeydew but did not differ significantly from colonies fed only honeydew. Colonies that had been fed only crickets were more active (as assessed by interaction with a novel object), retrieved 16-17 times more bait per worker overall, and consumed more of the six bait types than cricket + honeydew and honeydew-only fed colonies. However, prior diet did not affect bait choice. The two highest sugar bait formulations combined accounted for most of the bait consumed across all treatments (cricket-only 74.8% ± 28.1; cricket + honeydew 69.2% ± 12.4; honeydew-only 62.5% ± 30.4). Yellow crazy ant colonies fare better without protein than without carbohydrates. Yellow crazy ants ate the most bait when fed only crickets but did not choose baits complementary to their previous diet. Baits in a sugar-rich carrier may be most effective for the control of yellow crazy ants, regardless of the relative availability of macronutrients. © 2019 Society of Chemical Industry.

Aversion learning in response to an invasive venomous prey depends on stimulus strength

Learned avoidance can allow animals to survive the introduction of noxious prey. The effectiveness of aversion learning can depend on the intensity of the stimulus. The red imported fire ant, Solenopsis invicta, is a novel prey of the eastern fence lizard, Sceloporus undulatus, but can prove lethal especially to juvenile fence lizards. Thus, avoiding consumption of fire ants would increase survival for juveniles. We tested whether juvenile lizards would exhibit learned aversion of fire ants, and whether aversion would be longer lasting following exposure to greater numbers of fire ants. Lizards were exposed to one of three 8-ant treatments with varying relative proportions of fire ants for 5 days: (1) 100% fire ants, (2) 50% fire ants and 50% native ants, and (3) 0% fire ants (8 native ants). Juveniles in the 100% fire ant treatment showed clear aversion learning, consuming nearly two-thirds fewer fire ants after the first trial day. Juveniles exposed to the 50% fire ant treatment, consumed slightly fewer fire ants after day 1 of the trial, but recovered by day 5. Juveniles that received native ants only did not alter their consumption of ants over time. These results suggest that juveniles show species-specific aversion to fire ants, but this was dependent upon stimulus strength. When presented with both fire ants and native ants, lizards reduced their consumption of both species. Investigating whether exposure to noxious invasive prey alters the consumption of native prey would provide insight into long-term impacts of invasive species.

The vulnerability of leaflitter ants to forest disturbances in the island of Puerto Rico, Greater Antilles

Reduced biodiversity and high number of endemics characterize island ecosystems. Island natives and endemics are considered more vulnerable than continental species to exotic species invasions and habitat changes. The effect of replacing a native forest by an exotic wood plantation was studied on the assemblage of native and endemic ant species. The main hypothesis was that endemic and native ant species were more vulnerable to habitat changes than the exotic ant species. Nevertheless, it was found that native ants were more numerous and specious in both native and exotic plantations. Also, high numbers of two endemic ants were detected within exotic plantations, while only one exotic ant Hypoponera opacipeps was relatively abundant, particularly on native forest. In conclusion, exotic ant species did not dominate the communities studied nor the native and endemic ant assemblages seemed to be affected negatively by the forest replacement.

Do novel interactions with local fauna have reproductive consequences for exotic plants? A case study with thistles, ants, aphids, and pollinators

Exotic plants are involved in different interactions with the fauna of the invaded sites, which can facilitate or limit their successful establishment and spread. Here, we evaluated the impact of native aphid-tending ants on the reproductive consequences of the invasive thistle Carduus thoermeri in NW Patagonia, which is frequently infested by aphids. We estimated the number and proportion of viable seeds, seed weight, germination proportion, and mean germination time of thistles in the presence and absence of aphids and ants, and with or without pollinator access. Aphid-infested thistles had 57% less viable seeds and 29% lower seed weight than non-infested thistles. Although ants and aphids had no effect on germination proportion, the mean germination time was ca. 15% faster in seeds from aphid-infested thistles. Our results suggest that the potential indirect effects of aphid-tending ants on thistles (negative effects via pollinator deterrence and positive effects via driving away non-aphid herbivores) are less important than the direct negative effects of aphids. Interestingly, although harboring aphids and ants has negative reproductive consequences for C. thoermeri plants, it could also generate a competitive advantage by giving rise to small and fast germinated seeds. This study illustrates the complexity of novel interactions among exotic plants and native ants, reinforcing the need for more studies to fully understand the potential impact of ant–plant interactions mediated by Hemiptera on the invasion success of plants.

Myrmica rubra microhabitat selection and putative ecological impact

1. Myrmica rubra (European fire ant) has invaded northern latitude coastal areas in North America. This macroscale distribution suggests that M. rubra is moisture‐ and temperature‐limited, but the distribution of the invaded range may reflect the legacy of original introduction locations preserved by limited dispersal.2. This study examined a two‐decade population change in M. rubra (1994–2015) and the microscale abiotic (moisture and temperature), biotic (plants), anthropogenic (pesticide) and physiological (thermal tolerance) limits on the invasion at the Tifft Nature Preserve in Buffalo, NY (U.S.A.). Changes in the abundance of native ants and other invertebrates were also examined.3. Despite localised declines with pesticide treatments, overall M. rubra forager abundance increased 27% between 1994 and 2015. Abundance increased the most in the warmest areas (native ants were unaffected by temperature), but M. rubra colony locations were strongly linked to higher soil moisture and lower soil temperature. Myrmica rubra ants also exhibited relatively low thermal tolerances consistent with high‐latitude and high‐elevation ants.4. Where local M. rubra populations increased the most, native ant species decreased, and where local M. rubra populations declined, native ant species increased. Some arthropod species had lower abundance with M. rubra presence, but the impacts were less striking.5. Myrmica rubra population growth was promoted at the microhabitat scale where relatively higher temperatures prompted foraging, and relatively lower temperatures and high moisture supported nesting. These results suggest that macroscale M. rubra invaded‐range distributions in northern climates near coastal areas are replicated at the microscale where the ant prefers cooler, moister microsites.

Native and Exotic Ants Nesting in Red Mangroves of Jamaica

Red mangroves (Rhizophora mangle) grow in and adjacent to shallow brackish water in subtropical and tropical estuaries around the world, and provide a unique arboreal habitat, often completely isolated by water from any terrestrial habitat. I surveyed ants nesting in the dead hollow vegetation, including twigs, small branches, air roots, and prop roots, of red mangroves at 30 sites around Kingston Harbour and neighboring areas along the southeastern coast of Jamaica. I collected 18 ant species (13 native and 5 Old World exotics), including three Jamaican endemics (Camponotus fugax, Cephalotes jamaicensis, and Crematogaster vicina). The most common species in the 221 samples were three native species: Crematogaster steinheili (21 sites; 64 samples), Tapinoma litorale (18 sites; 40 samples), and C. fugax (18 sites; 33 samples). The only exotic ants collected at more than one site were Monomorium floricola (13 sites; 24 samples) and Tapinoma melanocephalum (4 sites; 5 samples). The most diverse site (with eight species) was part of an enormous continuous stand of red mangrove in Salt River, within the Portland Bight Protected Area. Two Salt River sites were the only places I found the Jamaican endemic Cephalotes jamaicensis. The sites with the greatest variety of ants were relatively free of trash, including all four Salt River sites, where I collected only native ant species. However, even at sites around Kingston Harbour that were littered with large amounts of trash washed in from the sea, the red mangrove stands generally seemed healthy and harbored primarily native Jamaican ants. Protecting red mangroves in Jamaica will help conserve native Jamaican species living in this unique habitat.