How invasive species recognize novel competitors during range expansion remains poorly understood. We investigated this in the red imported fire ant (Solenopsis invicta, RIFA) during its northward spread in China. We assessed interspecific aggression toward three native ants using two geographic contexts: sampling native ants from different latitudes (testing Tetramorium bicarinatum and Polyrhachis dives) and comparing populations between species that occurred both within and outside their invaded range (testing Pheidole nodus and Polyrhachis dives). Results suggest aggression can be modulated by competitor identity, origin, and coexistence history. Aggression toward ground-dwelling T. bicarinatum decreased with increasing latitude, suggesting a "recognition lag" at the invasion front. Conversely, aggression toward arboreal Polyrhachis dives was higher in the non-invaded frontier than in the invaded core, indicating that the RIFA actively identifies novel threats but develops "neighborly tolerance" following coexistence. Furthermore, higher aggression toward ground-dwelling species (e.g., Pheidole nodus) confirmed that niche overlap may dictate competitive recognition. These findings highlight the RIFA's behavioral plasticity; the transition from proactive threat assessment to tolerance likely facilitates successful colonizing and gaining ecological dominance in newly invaded areas.
Strumigenys SMITH, 1860 is a diverse and cosmopolitan ant genus divided into several species groups. Among these, the Strumigenys gundlachiand Strumigenys louisianae-groups stand out for including some of the most widespread and commonly found Neotropical ants, many of which exhibit morphological variation suggestive of cryptic-species complexes. This study investigated the cytogenetics of six species from these groups. Chromosome numbers and karyotype formulae for the S. gundlachi-group were: 2n = 26 (20 m + 6sm) for Strumigenys crassicornis MAYR, 1887, 2n = 16 (8 m + 8sm) for Strumigenys aff. stenotes (BOLTON, 2000), 2n = 18 (16 m + 2sm) for Strumigenys denticulata MAYR, 1887, and 2n = 18 (18 m) for Strumigenys subedentata MAYR, 1887. For the S. louisianae-group, two populations of Strumigenys louisianae ROGER, 1863 exhibit cytogenetic variation (2n = 4, 4 m; 2n = 20, 18 m + 2sm) and distinct external morphologies from the type-locality populations. While all studied species revealed a single 18S rDNA-bearing chromosome pair, the localization of these clusters varied interspecifically. Repetitive sequences, including (TTAGG)n and (GA)n, are aligned with typical ant patterns. We combined a morphological study to our cytogenetic data to investigate the taxonomy of those populations currently within S. louisianae. Our results support the reinstatement of Strumigenys clasmospongia BROWN, 1953 stat.rev. (2n = 20) as a valid species and the description of a new species for the S. louisianae-group, Strumigenys mineira sp.n. (2n = 4). We also provide a taxonomic key for species of the S. louisianae-group. Our results underscore the effectiveness of integrative approaches in uncovering cryptic diversity within the genus.
Genetic and environmental cues have been suggested to affect cuticular hydrocarbon (CHC) profiles, in which the profile signature mediates aggressive behaviors in ants. Paradoxically, conflicting evidence exists, and none of these hypotheses has received decisive support. These cues have been studied independently without much attention to their potential mutual relationship. This study investigated the mutual relationships of cuticular hydrocarbons, genetics, and bacterial endosymbionts in mediating aggressive behavior in 14 colonies of the invasive African big-headed ant, Pheidole megacephala, in urban and forest areas of Taichung, Taiwan. Behavioral assays revealed that workers displayed aggression toward those from other colonies, indicating the absence of a supercolony in Taichung. However, urban ants did not necessarily exhibit aggression toward forest ants, indicating that environmental cues between these habitats play a minor role in mediating agonistic interactions. The aggression level corresponded to differences in dimethyl alkane. The dimethyl-alkane distances were significantly associated with genetic distances. Co-inertia analysis demonstrated a strong relationship between dimethyl alkanes and the bacterial endosymbionts of ants. In particular, colonies infected with Wolbachia exhibited a higher abundance of peaks corresponding to long-chain dimethyl alkanes ranging from carbon numbers C33 to C39. Based on these findings, we suggest that ant CHCs, shaped by heritable bacterial endosymbionts such as Wolbachia, lead to colony-level differences in dimethyl-alkane profiles and, thus, the observed agonistic interactions in P. megacephala regardless of habitat type.
Arboreal ants are ecologically dominant in tropical forests due to their primarily herbivorous diet and aggressive behavior. This aggression is known to be influenced by the availability of carbohydrate and protein resources. However, how nutrient availability interacts with habitat variation to shape ant behavior remains poorly understood. Here, we investigated the trophic positions of the Asian weaver ant, Oecophylla smaragdina (FABRICIUS, 1775), and tested how carbohydrate supplementation affects their behavior across different habitat types in tropical Xishuangbanna, China. We hypothesized that weaver ants exhibit different trophic positions across habitats, influencing their activity and aggression, and that carbohydrate supplementation enhances these behavioral traits. To test these hypotheses, we collected weaver ants from a natural habitat (rainforest) and two types of plantations (fruit garden and agroforestry with rubber trees) for nitrogen and carbon stable isotope analyses. Behavioral responses were assessed by offering sucrose solution and distilled water (control) in each habitat. This study found that: 1) Ants in the three habitats did not differ in trophic position, but their resource utilization varied; 2) ants in the fruit garden, where carbohydrates are likely less constrained, displayed lower foraging recruitments and reduced persistence at baits over time; and 3) short-term carbohydrate supplementation did not significantly alter ants` overall aggression across habitats but reduced activity levels, including foraging recruitments and persistence at baits. These findings challenge previous assumptions that sugar feeding consistently enhances the aggression and activity of ants. Our results offer new insights into how carbohydrate availability modulates the behavior of ecologically dominant arboreal ants across different habitats, with implications for their ecological roles and potential applications in biological control.
Ants are among the most abundant terrestrial animals and play key roles in ecosystems across the globe. Their taxonomic and ecological diversity makes them a prime taxon for contributing to our understanding of the patterns and processes of speciation. However, studies on ants, such as those on ant diversification or taxonomy, often do not explicitly consider how their results inform or update the broader framework of speciation and reproductive isolation. Yet, the wealth of taxonomic, biogeographical, behavioral, and genomic studies on ants could significantly contribute to our understanding of both micro- and macroevolutionary patterns of speciation. Here, we combine microevolutionary studies on reproductive isolation and hybridization with macroevolutionary work on ant diversification to review what is known about ant speciation. We also discuss how two key features, sociality and haplodiploidy, could impact speciation and hybridization in ants. We find that, although key innovations as drivers of ant diversification have been studied, gaps exist in our understanding of reproductive isolating mechanisms in ants. However, general population features or traits, such as co-evolution within mutualistic or parasitic relationships, suggest that reproductive isolating mechanisms studied in ants may be generalizable across the tree of life. We suggest that ants could serve as valuable systems to study open questions in speciation, especially hybridization and divergence with gene flow, the genomic basis of intrinsic postzygotic isolation, and species interactions as drivers of reproductive isolation between species.
Supercoloniality and unique reproductive strategies are critical factors driving the ecological dominance of invasive ant species. However, their role in the post-introduction success of species belonging to the Ponerinae subfamily remains largely unexplored. Odontomachus troglodytes, a ponerine ant native to sub-Saharan Africa, has been recently reported to have established populations in southern Taiwan. In the present study, we conducted behavioral assays and developed 11 novel polymorphic microsatellite markers to investigate the social organization, breeding system, and population structure of O. troglodytes in its introduced range. Genotypic analyses indicated sexual reproduction with no evidence of clonal propagation. Both field observations and genetic data revealed high levels of polygyny and polyandry, accompanied by a notable frequency of diploid males, likely resulting from inbreeding. Our findings suggest that the Kaohsiung population exhibits some supercolonial traits, including polygyny, polydomy, and the absence of inter-nest aggression across distances of several kilometers. This marks the first reported case of such a social structure in the Odontomachini tribe. While workers from different nests displayed tolerance, genetic data suggest incomplete homogenization across nests. The present study offers new insights into the colony structure and reproductive biology of O. troglodytes in an introduced context and highlights the potential role of social structure in supporting population persistence and spread.
Urban environments are known to significantly influence the ecological dynamics of ant communities, since some ant groups are strongly associated with cities. Although there is an increasing interest in identifying "urban phenotypes" in insects, the impact of urbanisation on morphological functional traits of ants remains poorly studied. This study investigates intraspecific variation in the morphology of the generalist arboreal ant Crematogaster scutellaris (OLIVIER, 1792) along a local urbanisation gradient within a metropolitan city in northern Italy. More than 500 workers were sampled, photographed, and functionally relevant morphological traits related to body size (pronotal and head width), defensive function (propodeal spines), and sensory abilities (antennae and eyes) were measured. The work aimed to show whether a shift in intraspecific functional traits is underway according to the urban functional trait space homogenisation hypothesis and / or the urban ecological filter hypothesis. The overall multi-dimensional trait space of ants from highly urbanised areas was reduced compared with those from less urbanised areas, indicating that morphological homogenisation is associated with increasing urbanisation. In addition, highly urbanised areas hosted smaller ants, with a higher density of ommatidia in the compound eyes, and with shorter antennae, suggesting that an ecological filter may be acting on the species. Possible urban environmental factors linked to these differences include increased temperatures (reduced body size), proportion of trees (positively correlated with antenna length), and proportion of cemented areas (positively correlated with ommatidia density). These findings highlight urbanisation as a significant driver of morphological variation in C. scutellaris.
Small organisms tend to lose water more rapidly than larger ones because of their high surface area relative to their body volume. In hot arid regions, desiccation resistance is an important trait for these organisms as they are exposed to high day temperatures and scarcity of water. For instance, Ocymyrmex ants have evolved physiological adaptations that enable them to survive the dry environments in which they live. These ants are adapted to forage at ground temperatures exceeding 50 degrees C. In this study, we investigated the physiological traits that enhance thermo-tolerance across selected Ocymyrmex species, collected from different climatic zones in South Africa. We measured and compared desiccation resistance, critical thermal limits, and cuticular hydrocarbon composition of these ants and tested whether these traits are evolutionary conserved or labile. We also investigated whether these adaptations are maintained by evolutionary constraints or environmental factors. Our results demonstrated that these ants have high thermal limits, are resistant to desiccation, and that their cuticular hydrocarbons are composed of long chains dominated by linear alkanes, which are believed to be beneficial for waterproofing. The results also showed a strong phylogenetic signal for desiccation tolerance, which could indicate that desiccation tolerance is an ancestral trait in this group of ants. In contrast, there was weak evidence for phylogenetic signal in critical thermal limits across all species, which could indicate that these traits are ubiquitous rather than varying across species from different environments.
A large geographically isolated hybrid population of the mound-building wood ants Formica aquilonia and Formica lugubris, living syntopically with a F. lugubris population at Mount Saana in subarctic Finland, is documented. Samples of both populations were identified with a numeric analysis of 10 morphological characters in a large data set published earlier. A principal component analysis (PCA) with nest averages placed all hybrid samples between the clusters of the parental species F. aquilonia and F. lugubris. A PCA using 16 morphological characters, including workers only from selected nests on Mt. Saana, clustered the hybrid individuals separately from those of F. lugubris. From one individual of a hybrid nest, genome-wide nuclear DNA was sequenced. When analysed together with a published genomic set of five Formica rufa group species, both principal component and ADMIXTURE analyses placed the hybrid individual between F. aquilonia and F. lugubris, thus corroborating the morphological classification. The morphological analyses also supported the hybrid status of the F. aquilonia x F. lugubris of three earlier single-nest samples, one from southern and another from eastern Finland, and one from mid Norway. Palaeoclimatic and palaeobotanic data suggest that populations of F. aquilonia and F. lugubris invaded Mt. Saana during the warm period of the Atlantic, about 7000 to 6000 years BP, but became isolated probably by 3600 years BP owing to declining temperatures and the subsequent disappearance of Scots pine (Pinus sylvestris). This isolation has persisted up to the present, despite local warming since about 1980: The nearest nests of the parental species F. aquilonia are currently found 35 km NW and that of F. lugubris 16 km NW from Mt. Saana. Thorough sampling of 177 wood-ant mounds on Mt. Saana revealed a large proportion of both hybrid and F. lugubris nests, but no F. aquilonia. Assuming that the primary colonisers were not themselves hybrids, the suggested evident disappearence of F. aquilonia is attributed to the post-glacial cooling of the climate and the retreat of pine forest (its main habitat in the north), and its subsequent long-lasting blockade of colonisation of F. aquilonia. While hybridisation between the two wood-ant species may be interpreted as a factor which has contributed to the local extinction of F. aquilonia, it may also help to understand how its evolutionary lineage has survived in spite of the adverse environment.
The common Mediterranean myrmicine ant Crematogaster scutellaris (OLIVIER, 1792) was suggested to represent a model of the mimetic formicine ant Camponotus lateralis (OLIVIER, 1792). Typically, both species share a reddish head, while large parts of the body are blackish. The adaptive value of this putative color-mimicry has not yet been understood. To test the aversion of predators against Crematogaster scutellaris and the mimicry in Camponotus lateralis, feces of South-Alpine wall-lizards (Podarcis muralis maculiventris (WERNER, 1891)), collected in a territory of Crematogaster scutellaris near Pula (Istria, Croatia), were investigated. Of 113 fecal pellets, 64 (57%) contained ant material of 18 species and 175 individuals, of which 104 were workers. At 48% of items, ants were by far the most frequently recorded preytaxon. While Crematogaster scutellaris represented 93% of all living ant workers visible on the substrate surface of the habitat (hereafter, substrate surface), its portion was with 4% strongly underrepresented in the feces. Of the four species of the genus Camponotus recorded in the habitat, all except C. lateralis were fully blackish and thus did not resemble the aposematic color of Crematogaster scutellaris. Camponotus lateralis represented 75% of all living Camponotus workers visible on the substrate surface but only 3% in the feces. Several hypotheses are discussed to explain the disharmony between trophic availability and consumption; among them, unpalatability in Crematogaster scutellaris as well as Batesian mimicry or trail sharing in Camponotus lateralis are most plausible.
Since ants are a prominent taxon of terrestrial food webs and significant ecosystem engineers, understanding ant community succession is important to understand ecosystem recovery after disturbance. We studied the succession of ant communities on brown coal mine spoil heaps in mixed deciduous forests of NW Czech Republic by censusing multiple sites in which assemblages differed in age between 1 and 50 years since initial spoil heap formation. We compared the species composition, ant traits, and habitat characteristics of chronosequences of reclaimed and unreclaimed sites and undisturbed reference sites in the surrounding landscape in the years 2001 and 2020. Although habitat characteristics such as canopy and bare soil cover were important, successional age was the single strongest predictor of ant species richness and composition, suggesting a similar successional trajectory of sites. The number of ant species, but not their total abundance, increased during succession. The composition of the ant community changed towards that of the referential surrounding landscape, where less aggressive species were common. During the early successional stages, the common species had queens which establish colonies independently by enclosing themselves in a founding chamber and relying on stored resources (claustral mode). During later successional stages, the common species had queens which establish colonies by leaving the founding chamber to forage for food (semi-claustral mode). Species of social parasites were also more common in late versus early successional stages. These results suggest that resource availability to ants increases during succession, which may enhance species coexistence. The rate of change in ant species richness and composition was high at young sites and slowed down with site age. As forest stands aged through the successional sequence, the abundance of forest ant species increased. We did not record differences in species richness between reclaimed and unreclaimed sites. Eurytopic species were the most numerous, but their abundance did not change significantly during succession. Collectively, these results suggest that as forest stands age and canopies close, ant species richness and composition consistently change, with potentially more resources and more complex species interactions in later stages.
Competition is one of the most intriguing ecological concepts as it is ubiquitous in nature but challenging to quantify. Tropical arboreal ants are known to compete for food resources and nesting space, with some species maintaining large colonies and territories. However, little is known about how elevation and forest stratification influence this competition at the community level. We hypothesize that ant competition is mediated by temperature and therefore expect it to increase in the warmer lowland rainforests compared with mid-elevations. We also expect that temperature should lead to higher competition in forest canopies compared with smaller understorey trees due to warmer microclimate. We measured resource competition by placing baits (food resource) and bamboo cavities (nesting resource) in the natural rainforest of Mt. Wilhelm, Papua New Guinea. These artificial resources were distributed in both canopy and understorey trees across four sites in each of two locations: lowland (ca. 200 m above sea level, a.s.l.) and mid-elevation (ca. 900 m a. s.l.) forests. We recorded a total of 89 ant species on the baits and 33 species inside the cavities, and each resource measured a complementary part of the community. Mid-elevation sites had significantly higher ant species diversity and species co- occurrence on baits but much lower occupation and abundance both on the baits and in the cavities. This indicated a stronger competition in the lowland than mid-elevation communities, despite the higher ant diversity in the latter. Canopies showed a higher competition than understorey, reflected by higher occupancies of both cavities and baits. Moreover, behaviourally dominant territorial species were much more common on baits in the lowlands than mid- elevations. While the two locations did not differ in the forest structure (i.e., tree size, lianas, and dead wood), the lowlands were ca. 4 degrees C warmer. We hypothesize that the lowland dominance of aggressive ants, possibly maintained by this warmer climate, plays an underappreciated role in elevational community assembly. We conclude that temperature-mediated competition is thus the most likely driver of the observed differences in ant community structure between the two elevations.
Temporary social parasitism is the most common type among four types of social parasitism and is known from more than 200 ant species. Queens of temporary social parasites invade a host ant colony, kill the host queen, and use the host workers as a workforce during the colony founding stage. In our study, we collected seven mixed colonies consisting of a Strumigenys mutica queen and its host species: Two included a queen of S. mutica and host workers, five included queens and workers of S. mutica and host workers. In contrast, we also found 14 mature pure S. mutica colonies which included a S. mutica queen and S. mutica workers. The pure colonies were extremely large (max. approx. 5000 workers per colony) compared with other species of this genus. Additionally, S. mutica queens had more ovarioles (10 - 17 in total) than those of other Strumigenys species. Associated with this, the abdomen of S. mutica queens were physogastric with developing ovaries. Behavioral observation of two mixed colonies revealed that S. mutica was highly integrated with their host ants. The foragers of captive S. mutica colonies hunted diverse soil arthropods but struggled to catch springtails, unlike congeneric species. The fact that workers collect food and care for brood is in line with temporary social parasitism but not with other types of social parasitism. Therefore, we confirmed that the rare species S. mutica is a temporary social parasite of other Strumigenys species such as S. lewisi and S. solifontis. Overall, we conclude that S. mutica is a temporary social parasite, showing a novel life history compared with other Strumigenys ants. Our study sheds light on how social parasitism can change the life history of an ant.
Holometabolous insects have evolved larvae distinct from adult forms, which is at the root of their ecological success and lifestyle diversity. Moreover, plasticity in larval development has yielded to different adult phenotypes in caste systems and sexual morphs, especially in ants. While understanding larval development and growth is crucial for many research questions, identification of larval instars remains challenging. Indeed, it has been recently suggested that studies based on size distribution alone have misjudged instar number in ant species. Here, we identified larval instars of Ectatomma tuberculatum (Olivier, 1792) by comparing the morphology and morphometry methods. We also searched for potential differences between female larvae that developed into reproductive or non-reproductive caste, that is, gynes or workers. Our results showed that chaetotaxy clearly differentiated four larval instars, whereas only three instars were separated by classical morphometric tools (i.e., size-frequency distribution, implementation of model, and test of Dyar's rule). This contradictory result comes from the partial overlapping of larval head sizes at first- and second-instar. Head growth rate was lower than expected at the first moult, and then not constant from instar to instar. Consequently, E. tuberculatum does not follow Dyar's rule. Furthermore, gyne larva size increased exponentially at the end of development, probably without adding instar. We confirmed that the first-instar larvae in ants could be inconspicuous and then easily ignored using morphometry alone. We hypothesized this early stage serves hatching and social functions. Overall, we recommend focusing initially on larval morphology and combining approaches in order to correctly identify larval instars in ants.
The larvae of ants are essential for colony organization and growth, yet knowledge of their internal anatomy is sparse, and the homologies of many larval structures remain uncertain. We therefore used synchrotron-radiation micro-computed tomography (SR-mu -CT) and scanning electron microscopy (SEM) to investigate, respectively, the internal and external morphology of the larva of the clonal raider ant, Ooceraea biroi (FOREL, 1907), a model species for experimental biology. The documented characters are compared with conditions found in other Formicidae and Hymenoptera, and more broadly with features of larvae of other orders of Holometabola. As in other groups of Aculeata (and Orussidae), the body of Ooceraea is grub-like and depigmented, with distinctly reduced cephalic structures, and a weakly sclerotized, strongly simplified, sausage-like postcephalic body. This larval pattern reflects a distinct simplification compared with immature stages in the symphytan grade, with completely reduced eyes, antennae, and extrinsic labral muscles, vestigial palps, and missing thoracic legs and abdominal prolegs. Despite a simplified and largely uniform body configuration in apocritan larvae, including ants, there is considerable variation. Larvae of Formicidae vary distinctly in external features, especially in the general body shape, setation, and mandibular teeth. We therefore summarize eight morphological characters from previous studies to contextualize our findings, highlighting the often-underestimated diversity of larval morphology, which provides fertile ground for future study. Our study extends the knowledge of the external and internal morphology of ant larvae by taking a multi-modal approach to phenotype sampling, particularly via mu -CT. These methods have the potential of rapidly increasing the knowledge of previously neglected larval morphology, facilitating deeper investigations of evolutionary transformations in immature stages and providing a more complete picture of the evolution of an ecologically paramount group of insects.
Ants play crucial roles in terrestrial ecosystems, especially in the tropics where they are abundant and speciose. Growing global demand for oil palm has resulted in extensive deforestation and modification of ecosystems. Due to their high abundance, tolerance of some species to change, and the various ecological functions they support, ants represent an important group to study in oil palm landscapes. However, comprehensive research on ants in oil palm systems is severely lacking. Here, we summarise the focus and scope of existing research on this topic and identify future research priorities. We reviewed 74 publications-80% of which were conducted in Southeast Asia, primarily in Malaysia and Indonesia, and 87% in industrial plantations. This contrasts with the rapidly increasing palm oil production in Africa and the Americas and the importance of smallholder systems globally. We also observed a lack of studies comparing oil palm with other vegetable oil crops, few tests of the effects of alternative oil palm management practices, and-apart from predation-a poor understanding of the role of ants in supporting ecosystem functioning in oil palm landscapes. Studies consistently show that oil palm plantations have lower ant diversity and different community compositions compared with forests-including significantly more non-native species; yet ants within oil palm landscapes can still be abundant and functionally important. Comparisons with other crops revealed more variable results, but with oil palm supporting higher ant diversity than annual crops like soybean or maize. Our findings demonstrate that conservation of ant diversity relies on preserving forest habitats for disturbance-intolerant species but indicates that many ant species can survive in oil palm environments, potentially supporting ecosystem processes and yield. To assess whether current findings are consistent across different ecological contexts and to maximise the ant species and functions that can be supported in plantation systems globally, future research should focus on regions other than Southeast Asia, smallholder plantations, and on a wider variety of oil palm management practices and their impacts on ant communities. The importance of ants in oil palm systems should also be highlighted specifically in best management practice advice given by certification bodies, such as the Roundtable on Sustainable Palm Oil, with guidelines being updated as new data emerges.
The ant colony is a life unit for ants consisting of different female castes and males. Workers are mainly responsible for feeding and defence, while the queen and males are mainly responsible for colony continuity. The queen is also rarely active away from the nest, let alone preserved as a fossil with other workers. Male ants develop from unfertilised ant eggs, and the vast morphological differences make identification of males so difficult and often neglected in fossils that they are known as the 'forgotten caste'. In this study, we introduce tGerontoformica priapos sp.n. based on a male specimen and report for the first time the discovery of an ant colony specimen that includes both morphologically differentiated queen and worker castes of stem ants in a single piece of mid-Cretaceous Kachin amber. The type specimen of tGeront-oformica priapos sp.n. features well-preserved genitalia and wing venation, filling a critical gap in our comparative studies of sexual morphological differentiation in stem-group ants. Additionally, the discovery of this ant colony provides new insights into the morphological differentiation among different castes of tGerontoformica females. To facilitate future research, we also provide detailed morphological diagrams for the various castes and sexes of tGerontoformica.
Myrmicinae LEPELETIER DE SAINT-FARGEAU, 1835, the largest subfamily within the Formicidae family, harbors a significant amount of undiscovered biodiversity. In this study, we describe a new genus, Unicumyrmex gen.n., represented by Unicumyrmex fushanensis gen.n. et sp.n., from the tribe Solenopsidini FOREL, 1893, in Taiwan. The classification at the genus level was corroborated by various forms of evidence, including the morphology of workers and males, as well as molecular data. Morphological comparisons between U. fushanensis gen.n. et sp.n. and both morphologically similar and phylogenetically related species were conducted using detailed photography, including scanning electron microscopy. Keys to Solenopsidini workers with 11 antennal segments, as well as known Solenopsidini males from 14 genera, were provided along with discussions. For the phylogenetic reconstruction, 10 nuclear gene segments from U. fushanensis gen.n. et sp.n. were extracted from the assemblies of shotgun sequencing. The result revealed that the species clusters with morphologically distinct genera distributed in the same bioregion. In addition, pairwise genetic distances in the barcoding region of the cytochrome c oxidase I gene for U. fushanensis gen.n. et sp.n. and other myrmicine ants were calculated to further support its genus-level classification.
Urban habitats represent an important challenge for many organisms. Besides the abiotic changes, urban habitats are also characterized by changes in the biotic conditions, such as a more uniform species composition and declining population sizes. For urban ants, this can result in dietary shortages. In our study, we tested whether urban ant colonies of the widespread species Lasius niger might suffer from dietary restrictions by carrying out a common garden experiment in which ant colonies from urban and rural habitats were exposed to high carbohydrate, protein, and fat + protein diets. We also investigated the body fat content of individuals from both habitat types. Our findings suggest a lower availability of high-quality carbohydrates in urban areas. Additionally, while not statistically significant, rural colonies tended to consume greater quantities of proteins and fat compared with urban colonies. This trend was in line with a higher body fat content observed in female sexuals (gynes) from rural colonies. These results might indicate the outcome of an evolutionary feedback process in which ant colonies adapt to nutritional constraints in urban environments. They achieve this by minimizing the investment in gynes, which might require fewer reserves for survival during colony foundation due to reduced competition for nesting sites within urban green spaces. Moreover, our results also suggest that the nutritional shortages might be connected to arthropod population decline in urban habitats due to the impact of nutritional shortages in the reproductive capacity in females of species with narrower ecological plasticity.
Foraging ants collect amino acids and proteins for developing larvae in their colony. Both essential amino acids (EAAs; some considered toxic to ants) and non-essential amino acids (non-EAAs) are important building blocks of proteins, but EAAs cannot be synthesized by animals and must be obtained from their diet. Whether ants specifically forage for EAAs, and how EAAs affect ant colony growth, has rarely been investigated. Using red ants, Myrmica rubra, and western carpenter ants, Camponotus modoc, as model species, we tested the hypotheses that (1) M. rubra and C. modoc colonies with brood preferentially forage for EAAs rather than non-EAAs; (2) M. rubra colonies provisioned with EAAs, instead of non-EAAs, have greater brood production and colony growth; and (3) M. rubra workers feeding on sucrose and EAAs die sooner than workers feeding on sucrose and non-EAAs (which are considered less toxic). In laboratory choice experiments, colonies of M. rubra and C. modoc preferentially foraged for EAAs rather than non-EAAs. Colonies of M. rubra that consumed both EAAs and non-EAAs produced more larvae but not more workers and queens than colonies that consumed only EAAs or non-EAAs. In a mortality experiment, isolated M. rubra workers that consumed sucrose and EAAs died sooner than workers that consumed sucrose and non-EAAs, possibly because they could not feed EAAs to larvae. Our results indicate that EAAs on their own, while critically important, are insufficient for ant colony growth. However, EAAs as key macro-nutrients in combination with sucrose could be offered as a new bait for pest ant control.
