Native Ant Species Research Articles

The underdog invader: Breeding system and colony genetic structure of the dark rover ant (Brachymyrmex patagonicus Mayr).

Ants are among the most successful species at invading new environments. Their success undeniably comes from their various modes of reproduction and colony breeding structures, which influence their dispersal ability, reproductive potential, and foraging strategies. Almost all invasive ant species studied so far form supercolonies, a dense network of interconnected nests comprising numerous queens, without aggression toward non‐nestmates. This strategy results in invasive colonies that are able to grow extremely fast and large while avoiding intraspecific competition, allowing them to monopolize environmental resources and outcompete native species.Here, we developed and used 10 microsatellite markers to investigate the population structure and breeding system of the dark rover ant Brachymyrmex patagonicus Mayr in its introduced range. We determined whether this species exhibits a supercolonial structure by assessing whether different nests belonged to the same genetic colony. We inferred its dispersal ability by investigating isolation by distance and estimated the numbers of queens per colonies and mating per queen through parent‐offspring inferences. We found that most of the colonies of B. patagonicus were comprised of a single nest, headed by a single queen. Each nest was distinct from one another, without isolation by distance, which suggests strong dispersal ability through nuptial flights. These features are commonly observed in noninvasive and native ant species, but they are surprising for a successful invasive ant, as they strongly differ from other invasive ants. Overall, we discuss how this seemingly unfavorable strategy for an invasive ant might favor the invasive success of the dark rover ant in the United States.

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.

Differences in exploitation and interference ability between two dominant ants: the invasive Argentine ant (Linepithema humile) and Tapinoma magnum

The Argentine ant is a highly invasive species that can cause significant ecosystem alterations. Its spread in the invaded areas is usually associated with the displacement of native ant species by means of strong interference competition mechanisms. According to recent studies, Tapinoma nigerrimum s.l., a native Mediterranean ant, can potentially limit the expansion of the Argentine ant. The aim of the present study is to determine the ethological features that discriminate against the ability of L. humile and T. magnum (nigerrimum complex) to exploit a trophic resource both in the presence and in the absence of the competitor. We conducted behavioural assays on experimental colonies using foraging arenas in a laboratory experiment. Linepithema humile colonies showed the ethological profile typical of the species, as they carried out more intense recruitment, initially concentrated on the whole foraging site rather than on the bait. Linepithema humile workers were more aggressive and fought cooperatively during inter-specific interactions. Tapinoma magnum colonies apparently showed a more food-oriented profile as they were faster in the search for food and concentrated the recruitment on it rather than on the whole foraging site. Tapinoma magnum workers tried to avert the competitor using threat postures rather than physical aggression. Tapinoma magnum colonies were systematically excluded by L. humile colonies from the trophic resource and underwent a visible reduction in surface activity. These results suggest that L. humile used a different and more effective interference competition strategy compared to T. magnum.

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.

Predicting future invaders and future invasions

Invasive alien species are a great threat to biodiversity and human livelihoods worldwide. The most effective way to limit their impacts and costs is to prevent their introduction into new areas. Identifying invaders and invasions before their occurrence would arguably be the most efficient strategy. Here, we provide a profiling method to predict which species-with which particular ecological characteristics-will invade, and where they could invade. We illustrate our approach with ants, which are among the most detrimental invasive species, as they are responsible for declines of numerous taxa, are involved in local extinctions, disturb ecosystem functioning, and impact multiple human activities. Based on statistical profiling of 1,002 ant species from an extensive trait database, we identify 13 native ant species with an ecological profile that matches that of known invasive ants. Even though they are not currently described as such, these species are likely to become the next global invaders. We couple these predictions with species distribution models to identify the regions most at risk from the invasion of these species: Florida and Central America, Brazil, Central Africa and Madagascar, Southeast Asia, Papua New Guinea Northeast Australia, and many islands worldwide. This framework, applicable to any other taxa, represents a remarkable opportunity to implement timely and specifically shaped proactive management strategies against biological invasions.

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.

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.

Exotic ants from the Maghreb (Hymenoptera, Formicidae) with first report of the hairy alien ant Nylanderia jaegerskioeldi (Mayr) in Algeria

We compiled 16 exotic ant species found in the Maghreb in wild ecosystems, gardens and urban areas. Five of these introduced species are considered major ecological and agricultural household pest species that have become established above all in Morocco. During our investigation in a citrus orchard of ITMAS Heuraoua, Algiers, we detected two exotic ants, Nylanderia jaegerskioeldi (Mayr, 1904) and Strumigenys membranifera Emery, 1869, plus nine native ant species. The Formicinae ant N. jaegerskioeldi is recorded for the first time in Algeria, taking the number of exotic ants in the country to 11. This is the fourth known record in North Africa. A brief comparison between the exotic ant fauna of Algeria, Morocco, Tunisia and neighboring countries highlights the need to improve the limited knowledge of ants in North Africa.

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.

Lasius neglectus Van Loon et al. (Hymenoptera, Formicidae), an Invasive Ant Species in Crimea

Data on distribution of Lasius neglectus Van Loon et al. in Crimea are reported. The structure of foraging areas of 111 monocalic and polycalic colonies, the daily activity rhythm, and the visiting of 26 species of trees by L. neglectus workers were studied; over a third of the visited tree species were conifers. Most colonies of L. neglectus in Crimea are monocalic. No replacement of the 12 native ant species present in the territories of the monocalic and polycalic colonies of L. neglectus was observed. Invasion of L. neglectus to Crimea probably started in the early 1970s.

Foraging behavior and locomotion of the invasive Argentine ant from winter aggregations.

The collective behavior of ant colonies, and locomotion of individuals within a colony, both respond to changing conditions. The invasive Argentine ant (Linepithema humile) thrives in Mediterranean climates with hot, dry summers and colder, wet winters. However, its foraging behavior and locomotion has rarely been studied in the winter. We examined how the foraging behavior of three distinct L. humile colonies was related to environmental conditions and the locomotion of workers during winter in northern California. We found that colonies foraged most between 10 and 15°C, regardless of the maximum daily temperature. Worker walking speed was positively associated with temperature (range 6–24°C) and negatively associated with humidity (range 25–93%RH). All colonies foraged during all day and night hours in a predictable daily cycle, with a correlation between the rate of incoming and outgoing foragers. Foraging activity was unrelated to the activity of a competing native ant species, Prenolepis imparis, which was present in low abundance, and ceased only during heavy rain when ants left foraging trails and aggregated in small sheltered areas on trees.

Native and Exotic Ants (Hymenoptera: Formicidae) Nesting in Red Mangroves (Malpighiales: Rhizophora mangle) of Eastern Florida

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 collected ants nesting inside the hollow dead twigs, small branches, air roots, and prop roots of red mangroves at 98 sites in 9 counties along the east coast of Florida, from Volusia County in the north to the Upper Keys of Monroe County in the south. I found a total of 22 ant species nesting in red mangroves, including ten native species, eight exotic species (four Old World, four New World), and four New World species whose status in Florida is uncertain. The most common species by far were two native species (Tapinoma litorale and Xenomyrmex floridanus). The next three most common species, however, were exotics (Monomorium floricola, Pseudomyrmex gracilis, and Technomyrmex difficilis). I also collected the first Florida specimens of Crematogaster steinheili, a species that is very common in red mangroves of the West Indies, but may be exotic to Florida. Several native and exotic species show strikingly similar ecologies. For example, native X. floridanus and exotic M. floricola are both tiny, thin, short-legged, slowmoving myrmicine ants that cling tenaciously to surfaces. Earlier studies indicate that native ant species compete for resources in red mangroves. It seems likely that exotic ant species in the red mangroves also compete with and may threaten the native ant species.

Long-term record of Argentine ant invasions reveals enduring ecological impacts.

The ecological effects of species introductions can change in magnitude over time, but an understanding of how and why they do so remains incompletely understood. Clarifying this issue requires consideration of how temporal variation in invader traits affects invasion impacts (e.g., through differential effects on the diversity and composition of native species assemblages). We examine the temporal dynamics of Argentine ant invasions in northern California byresurveying 202 sites first sampled 30-40yr ago. To test how invasion impacts change over time, we estimated native ant richness and species composition at 20 riparian woodland sites that span a 30-yr invasion chronosequence. We then use these data to test how variation in two invader traits (aggression and relative abundance) is related to time since invasion and invasion impact. Native ant assemblages along the chronosequence exhibited reduced native ant richness and altered species composition (compared to uninvaded control sites), but the magnitude of these impacts was independent of time since invasion. These results are corroborated by additional temporal comparisons of native ant assemblages at riparian sites sampled 20-30yr ago. Our findings together illustrate that the impacts of invasions can persist undiminished over at least a 30-yr time frame and remain evident at regional scales. Although neither invader trait varied with time since invasion, native ant richness declined as the relative abundance of the Argentine ant increased. This latter result supports the hypothesis that factors reducing invader abundance at particular sites can decrease invasion impacts, but also that such changes may be due to site-specific factors (e.g., abiotic conditions) that affect invader abundance rather than time since invasion per se. Future studies should attempt to differentiate factors that are intrinsic to the process of invasion (e.g., changes in invader populations) from long-term environmental changes (e.g., climate change) that represent extrinsic influences on the dynamics of invasion.

Variable responses of non-native and native ants to coarse woody debris removal following forest bioenergy harvests

Timber harvests may facilitate ant invasions of forested landscapes, fostering interactions between non-native and native ants. Harvests that include removal of low-value woody biomass as forest bioenergy feedstock may reduce residual coarse woody debris, thereby altering food and cover resources for ant species. We manipulated: (1) volume and distribution of coarse woody debris in stand-scale treatments ranging from intensive coarse woody debris removal to no coarse woody debris removal; and (2) coarse woody debris availability at microsite locations within stand-scale treatments, including piles of hardwood stems, piles of conifer stems, and no pile locations in North Carolina, USA and windrows (i.e., long, linear piles of harvest residues) and no windrows in Georgia, USA, in recently clearcut pine plantations (n = 4 per state). We captured ants in regenerating stands and tested treatment- and location-level effects on non-native and native ant relative abundances. Invasive ants represented 19% of ant taxa richness, but comprised 94% of total ant captures. Red imported fire ant (Solenopsis invicta Buren, hereafter “RIFA”) dominated the ant community in young plantations. RIFA avoided windrows, but its relative abundance did not differ among stand-scale treatments. Coarse woody debris retention in stand-scale treatments and at microsite locations favored non-RIFA ants, including Asian needle ant (Brachyponera chinensis Emery) and several native ant species. Dual invasions of RIFA and Asian needle ant in young plantations of the eastern United States may commonly occur because the two species may not compete for resources on the forest floor. Reduction of coarse woody debris via intensified woody biomass harvesting may negatively affect non-RIFA ant species and promote RIFA colonization, thereby indirectly increasing deleterious effects of RIFA on other wildlife.

Verification of Argentine ant defensive compounds and their behavioral effects on heterospecific competitors and conspecific nestmates

The invasive Argentine ant (Linepithema humile) has become established worldwide in regions with Mediterranean or subtropical climates. The species typically disrupts the balance of natural ecosystems by competitively displacing some native ant species via strong exploitation and interference competition. Here we report that Argentine ants utilize glandular secretions for inter and intra-specific communications during aggressive interactions with a heterospecific competitor, California harvester ant (Pogonomyrmex californicus). Chemical analyses indicated that Argentine ants deploy glandular secretions containing two major volatile iridoids, dolichodial and iridomyrmecin, on the competitor’s cuticular surface during aggressive interactions. Bioassays indicated that the glandular secretions function as a defensive allomone, causing high levels of irritation in the heterospecific. Furthermore, the same glandular secretions elicited alarm and attraction of conspecific nestmates, potentially enabling more rapid/coordinated defense by the Argentine ants. Two major volatile constituents of the glandular secretion, dolichodial and iridomyrmecin, were sufficient to elicit these responses in conspecifics (as a mixture or individual compounds). The current study suggests that invasive Argentine ants’ superior exploitation and interference competition may rely on the species’ effective semiochemical parsimony.

Intra- and inter-specific variation in alarm pheromone produced by Solenopsis fire ants.

Some fire ants of the genus Solenopsis have become invasive species in the southern United States displacing native species by competition. Although the displacement pattern seems clear, the mechanisms underlying competitive advantage remain unclear. The ability of ant workers to produce relatively larger amount of alarm pheromone may correspond to relative greater fitness among sympatric fire ant species. Here we report on quantitative intra-specific (i.e. inter-caste) and inter-specific differences of alarm pheromone component, 2-ethyl-3,6-dimethylpyrazine (2E36DMP), for several fire ant species. The alarm pheromone component was extracted by soaking ants in hexane for 48 h and subsequently quantified by gas chromatography-mass spectrometry at single ion monitoring mode. Solenopsis invicta workers had more 2E36DMP than male or female alates by relative weight; individual workers, however, contained significantly less pyrazine. We thus believe that alarm pheromones may serve additional roles in alates. Workers of Solenopsis richteri, S. invicta, and hybrid (S. richteri × S. invicta) had significantly more 2E36DMP than a native fire ant species, Solenopsis geminata. The hybrid fire ant had significantly less 2E36DMP than the two parent species, S. richteri and S. invicta. It seems likely that higher alarm pheromone content may have favored invasion success of exotic fire ants over native species. We discuss the potential role of inter-specific variation in pyrazine content for the relationship between the observed shifts in the spatial distributions of the three exotic fire ant species in southern United States and the displacement of native fire ant species.

The beginning of the invasion of Lasius neglectus (Hymenoptera, Formicidae) in Kiev (Ukraine)

Research conducted in August and September 2016 in the city of Kiev (Ukraine). A total of 8 places of the possible location of invasive garden ant Lasius neglectus Van Loon, Boomsma & Andrasfalvy, 1990 were observed. Only one monocalic colony of L. neglectus was discovered. The forage area of L. neglectus is bounded by asphalted area on three sides. We consider that the invasion of L. neglectus at an early stage can be successful under the following conditions: (a) Favorable temperature. Mitigating of the climate during the winter months in recent years contributed to the consolidation of L. neglectus in Kiev. (b) Spatial separation of nests and foraging trails of native dominant ant species. In our case, L. neglectus colony was found on the site free of other ants. (c) Visiting trees, where native ant species are few or absent. This one partially overlaps with the previous condition.

Assessing the impacts of tramp and invasive species on the structure and dynamic of ant-plant interaction networks

Ants are among the most widespread and damaging of introduced organisms. In the last decade, many studies have documented the negative impact of tramp and invasive ant species (TIS) on native ant species mainly through competitive displacement and behavior. However, despite the great advances in the knowledge of TIS, still little is known about the impacts of these ants on the trophic cascade. In this study we used an approach based on network theory to explore the impact of TIS on the structure and ecological dynamic of a well-sampled and well-known community of ant–plant interactions in a tropical environment in coastal Veracruz, Mexico. We observed that of all the ant-plant interactions recorded, only 15% involved TIS and the ant Paratrechina longicornis (Formicinae) was the unique tramp species to be part of the central core of highly interacting species. We also found that TIS had little impact on the structure and dynamic ant-plant interactions in our study area, although possible indirect effects for specific TIS are also discussed. This study represents a valuable tool to conservation planners, mainly because we show the vulnerability and robustness of a tropical system rich in species and interactions to biological invasions.