Native Ants Research Articles

The native ant, Tapinoma melanocephalum, improves the survival of an invasive mealybug, Phenacoccus solenopsis, by defending it from parasitoids.

Mutualistic ants can protect their partners from natural enemies in nature. Aenasius bambawalei is an important parasitoid of the the invasive mealybug Phenacoccus solenopsis. We hypothesized that mutualism between native ants and mealybugs would favor survival of mealybugs. To test this, we examined effects of tending by the native mutualistic ant Tapinoma melanocephalum on growth of P. solenopsis colonies on Chinese hibiscus, Hibiscus rosa-sinensis, in a field setting. Ant workers with access to honeydew of mealybugs lived much longer than those provisioned only with water in the laboratory, and number of ant workers foraging increased significantly with growth of mealybug colonies in the field. In later observations, there were significant differences in densities of mealybugs between ant-tended and -excluded treatments. Survival rate of mealybugs experiencing parasitoid attack was significantly higher on ant-tended plants than on ant-excluded plants. When the parasitoid was excluded, there was no difference in survival rate of mealybugs between ant-tended and -excluded plants. In most cases, ants directly attacked the parasitoid, causing the parasitoid to take evasive action. We conclude that native ants such as T. melanocephalum have the potential to facilitate invasion and spread of P. solenopsis in China by providing them with protection from parasitoids.

Testing the effects of ant invasions on non-ant arthropods with high-resolution taxonomic data.

Invasions give rise to a wide range of ecological effects. Many invasions proceed without noticeable impacts on the resident biota, whereas others shift species composition and even alter ecosystem function. Ant invasions generate a broad spectrum of ecological effects, but controversy surrounds the extent of these impacts, especially with regard to how other arthropods are affected. This uncertainty in part results from the widespread use of low-resolution taxonomic data, which can mask the presence of other introduced species and make it difficult to isolate the effects of ant invasions on native species. Here, we use high-resolution taxonomic data to examine the effects of Argentine ant invasions on arthropods on Santa Cruz Island, California. We sampled arthropods in eight pairs of invaded and uninvaded plots and then collaborated with taxonomic experts to identify taxa in four focal groups: spiders, bark lice, beetles, and ants. Spiders, bark lice, and beetles made up ~40% of the 9868 non-ant arthropod individuals sampled; the majority of focal group arthropods were putatively native taxa. Although our results indicate strong negative effects of the Argentine ant on native ants, as is well documented, invaded and uninvaded plots did not differ with respect to the richness, abundance, or species composition of spiders, bark lice, and beetles. One common, introduced species of bark louse was more common in uninvaded plots than in invaded plots, and including this species into our analyses changed the relationship between bark louse richness vs. L. humile abundance from no relationship to a significant negative relationship. This case illustrates how failure to differentiate native and introduced taxa can lead to erroneous conclusions about the effects of ant invasions. Our results caution against unqualified assertions about the effects of ant invasions on non-ant arthropods, and more generally demonstrate that accurate assessments of invasion impacts depend on adequate information about species identity.

Effects of a Native Ant, Pristomyrmex pungens (Hymenoptera: Formicidae) on the Population Dynamics and Spatial Distribution of the Invasive Mealybug Phenacoccus solenopsis (Hemiptera: Pseudococcidae)

The mealybug Phenacoccus solenopsis has been recently reported as a serious invasive insect pest in China. Earlier investigations suggest that some species of native ants may tend P solenopsis in the field, and affect the population number and spatial distribution of P solenopsis. To confirm this, we studied the relationship between P solenopsis and the native ant Pristomyrmex pungens on Dendranthema morifolium plants in a garden spot. We found there was a significant positive correlation between population numbers of P solenopsis and P pungens, and the less the distance from nest, the greater the quantity of P solenopsis. Additionally, the mean number of P solenopsis increased significantly in the presence of P pungens. P solenopsis and P pungens had strong crowding tendencies and these individuals were attracted to each other on all investigated dates except on August 6. Our results suggest the presence of P pungens has effects on the population numbers and spatial distribution of P solenopsis on D. morifolium plants, and this relationship between them may have an important effect on the population explosion and dispersal of the invasive mealybug.

Fatty Amines from Little Black Ants, Monomorium minimum, and Their Biological Activities Against Red Imported Fire Ants, Solenopsis invicta.

Red imported fire ants, Solenopsis invicta, are significant invasive pests. Certain native ant species can compete with S. invicta, such as the little black ant, Monomorium minimum. Defensive secretions may contribute to the competition capacity of native ants. The chemistry of ant defensive secretions in the genus Monomorium has been subjected to extensive research. The insecticidal alkaloids, 2,5-dialkyl-pyrrolidines and 2,5-dialkyl-pyrrolines have been reported to dominate the venom of M. minimum. In this study, analysis of defensive secretions of workers and queens of M. minimum revealed two primary amines, decylamine and dodecylamine. Neither amine has been reported previously from natural sources. Toxicity and digging suppression by these two amines against S. invicta were examined. Decylamine had higher toxicity to S. invicta workers than dodecylamine, a quicker knockdown effect, and suppressed the digging behavior of S. invicta workers at lower concentration. However, the amount of fatty amines in an individual ant was not enough to knockdown a fire ant or suppress its digging behavior. These amines most likely work in concert with other components in the chemical defense of M. minimum.

Ant communities in native sage scrub, non-native grassland, and suburban habitats in Los Angeles County, USA: conservation implications

Southern California’s sage scrub (SS) ecosystem is severely threatened by suburban development and invasion by non-native grasses, but how these threats impact the arthropod community is poorly understood. Native ants, which face the additional threat of being displaced by non-native Argentine ants, may be particularly at risk of local and regional extirpation. In this study, we surveyed the ant communities in the SS and non-native grassland habitats at the Robert J Bernard Biological Field Station (BFS) and surrounding suburban habitat, and compared patterns of species richness and composition among habitat types. We also compared ant richness and composition at the BFS to 40 coastal SS fragments previously surveyed in San Diego County to better understand how ant communities in interior and coastal SS fragments differ. Ant composition significantly differed among all three habitat types at and surrounding the BFS, but species richness did not. Comparisons between the BFS and coastal fragments indicate that interior SS fragments harbor unique ant species and more species relative to fragment area. Increased richness and unique ant assemblages are probably associated with the limited ability of invasive Argentine ants to colonize the non-native grassland and SS at the BFS. Because many southern California invertebrates are narrowly endemic to low elevation areas, patterns of habitat specificity seen with ants highlight that maintaining a mosaic of SS and non-native grassland habitat, particularly in interior areas where activity and diversity of non-native invertebrate species may be restricted, may be critical to preserving biodiversity.

The fire ant Solenopsis saevissima and habitat disturbance alter ant communities

The fire ant Solenopsis saevissima is a major pest frequent in human-disturbed areas of its native range where it forms ‘supercolonies’. We determined that its natural habitat in French Guiana is likely the sporadically flooded riparian forest and aimed to evaluate this ant’s impact on the abundance and diversity of other ants by comparing different habitats at two sites. We noted a significant decrease in ant species richness between the rainforest and human-disturbed habitats (but not between the former and the naturally disturbed riparian forest), and between extreme habitats and all others. The number of ant nests per surface unit (i.e., quadrats of equal surface area), a proxy of ant abundance, globally followed this pattern. S. saevissima was absent from pristine rainforest (as expected) and from extreme habitats, showing the limits of its adaptability, whereas some other native ants can develop in these habitats. Ant species richness was significantly lower in the presence of S. saevissima in the riparian forest, forest edges and meadows, illustrating that this ant species has a negative impact on the ant communities in addition to the impact of natural- and man-made disturbances. Only some ant species can develop in its presence, and certain of these can even thrive. Because it has been recorded in Africa, Guadeloupe and the Galápagos Islands, we concluded that, due to the increasing volume of global trade and forest destruction, S. saevissima could become a pantropical invasive species.

Infiltration of a facultative ant–plant mutualism by the introduced Argentine ant: effects on mutualist diversity and mutualism benefits

1. Ant–plant mutualisms have been the focus of considerable empirical research, but few studies have investigated how introduced ants affect these interactions. Using 2 years of survey data, this study examines how the introduced Argentine ant [Linepithema humile (Mayr)] differs from native ants with respect to its ability to protect the extrafloral nectary‐bearing coast barrel cactus (Ferocactus viridescens) in Southern California.2. Eighteen native ant species visited cacti in uninvaded areas, but cacti in invaded areas were primarily visited by the Argentine ant. The main herbivore of the coast barrel cactus present at the study sites is a leaf‐footed bug (Narnia wilsoni).3. Herbivore presence (the fraction of surveys in which leaf‐footed bugs were present on individual cacti) was negatively related to ant presence (the fraction of surveys in which ants were present on individual cacti). Compared with cacti in uninvaded areas, those in invaded areas were less likely to have herbivores and when they did had them less often.4. Seed mass was negatively related to herbivore presence, and this relationship did not differ for cacti in invaded areas versus those in uninvaded areas.5. Although the Argentine ant might provide superior protection from herbivores, invasion‐induced reductions in ant mutualist diversity could potentially compromise plant reproduction. The cumulative number of ant species on individual cacti over time was lower in invaded areas and was associated with a shortened seasonal duration of ant protection and reduced seed mass. These results support the hypothesis that multiple partners may enhance mutualism benefits.

Southern toads alter their behavior in response to red-imported fire ants

We used the southern toad (Anaxyrus terrestris) as a model species to explore how an invasive species, the red-imported fire ant (Solenopsis invicta; hereafter RIFA), influences amphibian predator avoidance and movement behaviors. Our objective was to determine if toads spent less time near and moved more frequently in the presence of RIFAs compared to pyramid ants by comparing behavioral reactions of toads to RIFAs versus a control and pyramid ants versus a control. Laboratory experiments involved three treatments including no ants, RIFAs, and native pyramid ants (Dorymyrmex bureni) within an experimental arena. We randomly placed ants into one of two containers located at each end of the arena. For each trial we placed a toad into the experimental arena, allowed the toad to acclimate and then recorded its behavior. We calculated the proportion of time the toad spent near ants and the number of movements completed by each toad. Comparing the RIFA treatment to the pyramid ant treatment, toads spent 35 % less time on the half of the experimental arena near RIFAs (P = 0.0304). Toad movements were 1.5 times more frequent in trials with RIFAs than pyramid ants (P = 0.0488). We propose that southern toads associate RIFAs either with increased predation risk or risk of injury compared to pyramid ants. Although the behaviors we observed might lessen the direct effects of RIFAs on southern toads via predation and injury, the indirect effects of increased movement and avoidance of RIFAs could also influence toad fitness by decreasing reproductive and foraging success.

Solenopsis invicta virus 3: Further Host-Specificity Tests with NativeSolenopsisAnts (Hymenoptera: Formicidae)

A thorough understanding of host specificity is essential before pathogens can be used as biopesticides or self-sustaining biocontrol agents. In order to better define the host range of Solenopsis invicta virus 3 (SINV-3), we collected and exposed colonies of 2 native fire ants (Solenopsis aurea Wheeler, Solenopsis xyloni McCook) and 2 native thief ants (Solenopsis carolinensis Forel, Solenopsis molesta [Say]) (Hymenoptera: Formicidae) to the SINV-3 virus. Despite extreme exposure to the virus, active, replicating infections resulted only in colonies of the red imported fire ant (Solenopsis invicta Buren). These results, combined with a previous study of ants from 13 other genera, strongly support the proposition that the SINV-3 virus can be used safely as either a biopesticide or a self-sustaining biocontrol agent in parts of California, the Caribbean, and other regions of the world where this virus does yet not occur.

Mutualism between co-introduced species facilitates invasion and alters plant community structure

Generalized mutualisms are often predicted to be resilient to changes in partner identity. Variation in mutualism-related traits between native and invasive species however, can exacerbate the spread of invasive species ('invasional meltdown') if invasive partners strongly interact. Here we show how invasion by a seed-dispersing ant (Myrmica rubra) promotes recruitment of a co-introduced invasive over native ant-dispersed (myrmecochorous) plants. We created experimental communities of invasive (M. rubra) or native ants (Aphaenogaster rudis) and invasive and native plants and measured seed dispersal and plant recruitment. In our mesocosms, and in laboratory and field trials, M. rubra acted as a superior seed disperser relative to the native ant. By contrast, previous studies have found that invasive ants are often poor seed dispersers compared with native ants. Despite belonging to the same behavioural guild, seed-dispersing ants were not functionally redundant. Instead, native and invasive ants had strongly divergent effects on plant communities: the invasive plant dominated in the presence of the invasive ant and the native plants dominated in the presence of the native ant. Community changes were not due to preferences for coevolved partners: variation in functional traits of linked partners drove differences. Here, we show that strongly interacting introduced mutualists can be major drivers of ecological change.

Floral visitation by the Argentine ant reduces bee visitation and plant seed set.

Ants often visit flowers, but have only seldom been documented to provide effective pollination services. Floral visitation by ants can also compromise plant reproduction in situations where ants interfere with more effective pollinators. Introduced ants may be especially likely to reduce plant reproductive success through floral visitation, but existing experimental studies have found little support for this hypothesis. Here, we combine experimental and observational approaches to examine the importance of floral visitation by the nonnative Argentine ant (Linepithema humile) on plant species native to Santa Cruz Island, California, USA. First, we determine how L. humile affects floral visitor diversity, bee visitation rates, and levels of pollen limitation for the common, focal plant species island morning glory (Calystegia macrostegia ssp. macrostegia). Second, we assess the broader ecological consequences of floral visitation by L. humile by comparing floral visitation networks between invaded and uninvaded sites. The Argentine ant and native ants both visited island morning glory flowers, but L. humile was much more likely to behave aggressively towards other floral visitors and to be the sole floral occupant. The presence of L. humile in morning glory flowers reduced floral visitor diversity, decreased rates of bee visitation, and increased levels of pollen limitation. Network comparisons between invaded and uninvaded. sites revealed differences in both network structure and species-level attributes. In. invaded sites, floral visitors were observed on fewer plant species, ants had a higher per-plant interaction strength relative to that of other visitors, and interaction strengths between bees and plants were weaker. These results illustrate that introduced ants can negatively affect plant reproduction and potentially disrupt pollination services at an ecosystem scale.

Secretions of Dufour's Gland in Some Ants (Hymenoptera: Formicidae)

The ant Pachycondyla sennaarensis (Mayr) (Hymenoptera: Formicidae: Ponerinae) is a small dark ant, a recent accidental introduction into Saudi Arabia. It tends to be found in or near human habitations, and it is particularly unpleasant because its sting can cause severe reaction in some individuals, and there are reports of fatal effects. Analysis of the poison apparatus of P. sennaarensis, locally known as the samsum ant, and comparison with two other native small black ants, Messor meridionalis and M. foreli (Hymenoptera: Formicidae), have shown distinct differences in the materials in their Dufour glands and clearly distinguish P. sennaarensis from the two Messor species. Pachycondyla sennaarensis showed only hydrocarbons in its Dufour gland dominated by nonadecene, nonadecane and heneicosane. The powerful venom revealed no volatile compounds. The Dufour glands of M. meridionale and M. foreli had characteristic mixtures of hydrocarbons, but no venom gland volatile compounds. Pentadecane and hepadecane were the major compounds of the gland in M. meridionalis while nonadecane and heneicosane were the major in M. foreli.

Effects of Red Imported Fire Ants (Solenopsis invicta) on the Species Structure of Ant Communities in South China

We evaluated the effects of invasive red imported fire ants (RIFAs), Solenopsis invicta Buren, on native ant communities at three habitats in South China. By using paired control and treatment plots, the change in diversity and community structure of native ants due to the invasion of red imported fire ants could be observed. Ant species richness was reduced by 46 and 33% at RIFA-infested lawn and pasture habitats, respectively; however, the ant species richness in the lichee orchard was not affected by red imported fire ants. Our results indicated that red imported fire ants became one of several dominant species or the only dominant species in all three habitats in South China.

Interspecific competition between the red imported fire ant, Solenopsis invicta Buren and ghost ant, Tapinoma melanocephalum Fabricius for honeydew resources produced by an invasive mealybug, Phenacoccus solenopsis Tinsiley

In natural as in agricultural ecosystems, interactions between ants and honeydew-producing hemipterans are commonly observed. Mutualisms between invasive ants and hemipterans have been extensively studied in recent years. However, native ant species can equally exploit the honeydew excreted by hemipterans, and establish close relationships with them. Up till present, little is known about the competition between exotic ants (such as Solenopsis invicta) and its co-occurring species (e.g., Tapinoma melanocephalum) for this food resource. In this study, we compared the competitive ability of the invasive ant S. invicta and its co-occurring species T. melanocephalum in the laboratory. We also determined whether the two ant species could coexist and share honeydew resource. Our results indicate that the foraging activity of T. melanocephalum was restrained by S. invicta. Mortality of S. invicta and T. melanocephalum was significantly higher in T. melanocephalum colony case than that in other cases. The invasive ability between the two ant species was significantly different. These results suggest that S. invicta suppresses exploitation of honeydew-producing hemipterans by native ants and occupies most of honeydew resource. S. invicta could not completely drive T. melanocephalum out of honeydew competition, with small numbers of T. melanocephalum workers coexisting and sharing the honeydew with S. invicta. This finding permits a better understanding of the invasion success of S. invicta, and its ability to occupy new habitats.

Landscape corridors can increase invasion by an exotic species and reduce diversity of native species.

Landscape corridors are commonly used to mitigate negative effects of habitat fragmentation, but concerns persist that they may facilitate the spread of invasive species. In a replicated landscape experiment of open habitat, we measured effects of corridors on the invasive fire ant, Solenopsis invicta, and native ants. Fire ants have two social forms: polygyne, which tend to disperse poorly but establish at high densities, and monogyne, which disperse widely but establish at lower densities. In landscapes dominated by polygyne fire ants, fire ant abundance was higher and native ant diversity was lower in habitat patches connected by corridors than in unconnected patches. Conversely, in landscapes dominated by monogyne fire ants, connectivity had no influence on fire ant abundance and native ant diversity. Polygyne fire ants dominated recently created landscapes, suggesting that these corridor effects may be transient. Our results suggest that corridors can facilitate invasion and they highlight the importance of considering species' traits when assessing corridor utility.

Effect of broadcast baiting on abundance patterns of red imported fire ants (Hymenoptera: Formicidae) and key local ant genera at long-term monitoring sites in Brisbane, Australia.

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.

The ants of remote Polynesia revisited

The islands of remote Polynesia (east of Rotuma, Samoa, Tonga and New Zealand) have long been thought to contain few, if any, native ants. The findings of recent sediment core studies, however, challenge this conventional wisdom and indicate some species may be native. The majority of ant species in remote Polynesia, however, are introductions from tropical and subtropical regions around the world. Despite this diversity of origins, and the lack of a common coevolutionary history in the region, patterns of organization in remote Polynesian ant communities are generally similar to those observed in coevolved continental areas. The distribution of ant species across Polynesia is consistent with a primary mechanism of anthropogenic introductions, with the availability of suitable habitat as a secondary mechanism. The species-area relationship for better-collected Polynesian islands reveals these islands are depauperate compared to Melanesian islands with endemic species. Four out of five of the “world’s worst” invasive ant species are present in remote Polynesia. Recent studies have documented how range expansions of such ant species have had detrimental effects on native arthropod populations, although the overall effects of introduced ants per se on naive endemic island arthropods may never be known with certainty. Considering the relatively fragile nature of island ecosystems, and the potential transformative effects of invasive ants on arthropod communities, vigilance is required to prevent the spread of invasive ant species across Polynesia.

Density-dependent effects of an invasive wasp on the morphology of an endemic New Zealand ant

Invasive species can cause extinction, but perhaps more commonly they compete for resources, resulting in subtle life history modification in native species. Changes in food quantity and quality as a result of biological invasions have the potential to influence the size and morphology of native species. The invasive wasp Vespula vulgaris reaches its highest known population densities in the honeydew beech forests of New Zealand, where it competes with native ants (Prolasius advenus) for food. We tested the hypothesis that this competition would reduce ant worker size in areas of high wasp density. A significant reduction in worker size was found with increasing invasive wasp density, after accounting for site and environmental covariate effects. However, this significant average reduction in size was small. For example, an increase of 10 wasp nests ha−1 was associated with an average decrease of only 1.2 % in the Weber’s length of native ant workers. We also examined scaling of morphological relationships in ants to test the hypothesis that scaling would vary between ant populations at differing wasp densities. Scaling relationships for six out of eight measured morphological characters significantly differed in ants when subject to high wasp densities, relative to areas of low wasp abundance. These results indicate that invasive wasps can potentially reduce native ant size, and alter scaling relationships, likely by limiting resource availability during ant development. Such subtle effects of an invasive species may be common in situations where invasive species exert strong competitive pressure.

Does Prescribed Fire Facilitate Fire Ant Invasions in Coastal Prairies or Aid Management by Improving Mound Search Efforts?

Abstract We established a high-intensity prescribed-fire experiment in shrub-dominated coastal prairie to quantify (1) the proportion of Red Imported Fire Ant mounds that are likely to be missed by applicators of individual mound-based chemical treatments in prairie, based on the number of mounds found in unburned prairie compared to recently burned areas, and (2) to track changes in the densities of Red Imported Fire Ant and native Red Harvester Ant mounds in response to growing-season prescribed fires conducted during drought. First, our data suggest insecticide applicators are likely to miss 48% of Red Imported Fire Ant mounds when applying individual mound treatments in shrub-infested prairie. Second, fire treatments did not increase Red Imported Fire Ant or decrease Red Harvester Ant populations. Prescribed fire may therefore provide an advantageous management option for prairie managers that does not increase densities of Red Imported Fire Ants, and maintains mound densities of Red Harvester Ants, w...

Argentine Ant Affects Ant-Mimetic Arthropods: Does Argentine Ant Invasion Conserve Colouring Variation of Myrmecomorphic Jumping Spider?

Argentine ant invasion changed colour-polymorphic composition of ant-mimetic jumping spider Myrmarachne in southwestern Japan. In Argentine ant-free sites, most of Myrmarachne exhibited all-blackish colouration. In Argentine ant-infested sites, on the other hand, blackish morph decreased, and bicoloured (i.e. partly bright-coloured) morphs increased in dominance. Invasive Argentine ant drives away native blackish ants. Disappearance of blackish model ants supposedly led to malfunction of Batesian mimicry of Myrmarachne.