Ant-partners play a minor role on occurrence of the myrmecophilous butterfly <Emphasis Type="Italic">Leptotes cassius</Emphasis> in its host plant

Ant-related oviposition in facultatively myrmecophilous lycaenid butterflies is common, but not universal. In fact, our knowledge of ant-related oviposition in lycaenids is based on some common species (e.g., Rekoa marius, Allosmaitia strophius, Parrhasius polibetes), which limits generalizations about these systems. In this study, we experimentally investigated whether the oviposition pattern of the florivorous lycaenid Leptotes cassius was influenced by the presence of Camponotus ants and whether larvae were attended, rather than attacked, by ants. This might be evidence of myrmecophily. Both L. cassius and Camponotus ants occur on Bionia coriacea, an extrafloral nectaried legume shrub that grows in the Brazilian cerrado. Plants were randomly assigned to ant-present and ant-excluded treatments and were observed twice throughout the short reproductive season. Larvae of L. cassius were tended by ants, whose attendance was characterized by active antennation on the last body segments of the caterpillars. Therefore, Camponotus can be considered a partner of L. cassius. Lycaenid abundance was on average 1.9- and 1.21-fold higher in plants with ants in each sampling period, respectively, indicating a tendency of L. cassius to occur in plants with ants. Nonetheless, results were not statistically significant, suggesting that in this case ants are not a major cue for lycaenid oviposition. In many ant–lycaenid mutualisms, butterfly immatures benefit from reduced parasitism rates. However, no L. cassius immature, regardless of ant presence or absence, was parasitized. Furthermore, larvae may occur inside flower buds that may provide protection from natural enemies; thus, ants may not be required for immature protection.     

Host plant preference in the protected myrmecophilous Transylvanian Blue (<Emphasis Type="Italic">Pseudophilotes bavius hungarica</Emphasis>) butterfly (Lepidoptera: Lycaenidae) and its relationship with potential ant partners

When selecting specific host plants, caterpillars of many lycaenid butterflies, such as the protected Pseudophilotes bavius hungarica, are known to engage in various interactions with ants, which help them survive. Although P. bavius is a protected species, data about its host plant selection is very scarce, and little information is available on its myrmecophilous relationships. Our aim was to identify the host plant characteristics that determine the occurrence of the caterpillar and to clarify the specificity of its myrmecophily. We conducted a series of field surveys regarding host plant characteristics. Laboratory experiments were carried out to investigate the nature of interactions between the caterpillar and its potential ant partners. Control experiments involving non-visiting ants were also performed. On the basis of our findings, the physical characteristics of host plants do not seem to influence host plant choice, but the absence of aphids and the presence of different ant species proved important. According to the results of behavioural assays, neutral reactions to the caterpillars were recorded in the case of ant species that regularly visited the host plant (Lasius paralienus, Camponotus aethiops), in contrast to Tapinoma subboreale, which was not observed at all on the host plants and which behaved aggressively towards the larvae. Therefore, the caterpillar is expected to show a certain ant host selectivity. The study constitutes an essential contribution to our knowledge of the natural history of a protected butterfly species, which can be used as a basis for more appropriate management strategies, while also shedding light on aspects of myrmecophilous relationships in Lycaenidae in general.     

Invasive goldenrods affect abundance and diversity of grassland ant communities (Hymenoptera: Formicidae)

Goldenrods (Solidago sp.) are currently one of the most invasive plant species in Central Europe. They threaten abandoned semi-natural wet grasslands which are extremely vulnerable to plant succession and invasions. We assessed whether Solidago invasion affects ants, keystone organisms essential to proper ecosystem functioning and to the existence of myrmecophilous Phengaris butterflies. Ten meadows containing 60 plots with and without goldenrods were studied. We found a strong, negative dependence between the presence of goldenrod cover and the number of ant nests (more than 50 % reduction compared to control) as well as the number of species, and changes in species composition. Myrmica ants, essential hosts for Phengaris larvae, were among the most affected species by goldenrod invasion. Immediate action should be undertaken for restoration and maintenance of biodiversity hotspots affected by goldenrod invasion.     

Mortal combat between ants and caterpillars: an ominous threat to the endangered Schaus swallowtail butterfly (<Emphasis Type="Italic">Heraclides aristodemus ponceanus</Emphasis>) in the Florida Keys,USA

The federally endangered Schaus swallowtail butterfly (Heraclides aristodemus ponceanus) has reached critically low numbers. Exotic ants are a potential threat to H. a. ponceanus and other rare butterflies as they can attack immature stages. Ant surveys conducted in subtropical dry forests in Biscayne National Park documented ant species diversity and relative abundance. A caterpillar predator exclusion experiment using physical barriers in different combinations evaluated caterpillar survivorship of both early and late instar caterpillars exposed to different threats. Ant-caterpillar interactions were also documented by placing caterpillars on plants and observing physical interactions between caterpillars and ants. A total of 1418 ants comprising 25 ant species was captured and identified. In canopies of H. a. ponceanus host plants, 243 ants comprising 12 species were found. The four most common ants collected in the host plant canopies were Pseudomyrmex gracilis, Camponotus planatus, Cremastogaster ashmeadi, and Camponotus floridanus. The predator exclusion experiment revealed survivorship was significantly lower for early and late instar caterpillars without any physical barrier, as well as for early instars not protected by a mesh cage. Pseudomyrmex gracilis and C. floridanus were more aggressive towards caterpillars in comparison to other ant species; these two species ranked first and second in the “ant danger index” ranking predatory abilities of the four most common ant species. Pseudomyrmex gracilis is a common arboreal exotic ant in Biscayne National Park and presents a major threat to caterpillars during their earliest life stages.     

Host ant use of the Alcon blue butterfly at the northern range margin

In myrmecophilous insects, interactions with ants are often a key factor determining persistence of their populations. Regional variation in host ant use is therefore an essential aspect to consider to provide adequate conservation practices for such species. In this study, we examined this important facet of species’ ecology in an endangered myrmecophilous butterfly Phengaris (=Maculinea) alcon (Lepidoptera, Lycaenidae). The investigations conducted in peripheral populations in Estonia allowed us to expand the knowledge of its host ant use to the northern distribution limit of the species. Our data indicate that in its northernmost populations, the xerophilous ecotype of Phengaris alcon is primarily parasitizing a single host ant species, Myrmica schencki. The data collected are in line with the emerging evidence suggesting that peripheral and core populations of P. alcon use different host ants, and peripheral populations tend to display higher host ant specificity. We also show that, at its northern range margin, P. alcon might be more limited by the availability of its sole larval food plant in the region, Gentiana cruciata, than the densities of its host ant. Finally, we found a strong negative correlation between Myrmica spp. and Lasius spp. colony densities, suggesting that interspecific competition between ants could have a substantial influence on host ant availability of Phengaris butterflies, and thus should be taken into account in conservation plans of these species.     

Larvae of the exotic predatory ladybird <Emphasis Type="Italic">Platynaspidius maculosus</Emphasis> (Coleoptera: Coccinellidae) on citrus trees: prey aphid species and behavioral interactions with aphid-attending ants in Japan

An aphidophagous ladybird, Platynaspidius maculosus (Weise) (Coleoptera: Coccinellidae), is originally distributed in China, Taiwan, and Vietnam. The ladybird has recently intruded into the southern and central parts of Japan. The present study found that the larvae of this ladybird preyed on three aphid species, Aphis spiraecola, Aphis gossypii, and Toxoptera citricidus (all Hemiptera: Aphididae), feeding on young shoots of various Citrus species in August to early October in Shizuoka Prefecture, central Japan. Laboratory rearing of the sampled larvae confirmed that the larvae completed their development (adult emergence) by consuming each of the three aphid species. The ladybird larvae were observed foraging in aphid colonies attended by one of the four ants, Lasius japonicus, Pristomyrmex punctatus, Formica japonica, and Camponotus japonicus (all Hymenoptera: Formicidae). Field observations revealed that the foraging/feeding larvae were almost completely ignored by honeydew-collecting ants even when they physically contacted each other. Thus, in Japan, the larvae of the exotic ladybird exploit colonies of the three aphid species attended by one of the four ant species on many Citrus species. On the basis of the results, I discuss the possibility of the ladybird’s reproduction on citrus trees in Japan, probable adaptations of the ladybird larvae to aphid-attending ants, and potential impacts of the ladybird on native insect enemies attacking ant-attended aphids on citrus.     

Reduced ant defenses in <Emphasis Type="Italic">Macaranga</Emphasis> myrmecophytes (Euphorbiaceae) infested with a winged phasmid <Emphasis Type="Italic">Orthomeria cuprinus</Emphasis>

Macaranga is a tree genus that includes many species of myrmecophytes, which are plants that harbor ant colonies within hollow structures known as domatia. The symbiotic ants (plant–ants) protect their host plants against herbivores; this defense mechanism is called ‘ant defense’. A Bornean phasmid species Orthomeria cuprinus feeds on two myrmecophytic Macaranga species, Macaranga beccariana and Macaranga hypoleuca, which are obligately associated with Crematogaster ant species. The phasmids elude the ant defense using specialized behavior. However, the mechanisms used by the phasmid to overcome ant defenses have been insufficiently elucidated. We hypothesized that O. cuprinus only feeds on individual plants with weakened ant defenses. To test the hypothesis, we compared the ant defense intensity in phasmid-infested and non-infested M. beccariana trees. The number of plant–ants on the plant surface, the ratio of plant–ant biomass to tree biomass, and the aggressiveness of plant–ants towards experimentally introduced herbivores were significantly lower on the phasmid-infested trees than on the non-infested trees. The phasmid nymphs experimentally introduced into non-infested trees, compared with those experimentally introduced into phasmid-infested trees, were more active on the plant surface, avoiding the plant–ants. These results support the hypothesis and suggest that ant defenses on non-infested trees effectively prevent the phasmids from remaining on the plants. Thus, we suggest that O. cuprinus feeds only on the individual M. beccariana trees having decreased ant defenses, although the factors that reduce the intensity of the ant defenses remain unclear.     

Consequences of the arms race between <Emphasis Type="Italic">Maculinea teleius</Emphasis> social parasite and <Emphasis Type="Italic">Myrmica</Emphasis> host ants for myrmecophilous butterfly conservation

The arms race between Maculinea butterflies and Myrmica host ants leads to local host-parasite adaptations. In our study, we assessed whether sympatric and allopatric Myrmica scabrinodis populations exhibit behavioural differences towards Maculinea teleius larvae during the adoption-period when butterfly larvae need to be taken inside the Myrmica nest. The second aim was to assess the butterfly survival rate inside ant colonies from different populations. We used one sympatric host population and three allopatric populations: one infested by M. teleius and two uninfested populations. We found that ants from the sympatric population showed a higher number of positive behaviours toward M. teleius larvae during adoption than ants from the allopatric populations. There were no differences in the number of inspection or negative behaviour events. The survival of butterfly larvae was highest inside sympatric host colonies and differed from the survival of M. teleius reared by ants from the allopatric, uninfested populations. No difference was found for the survival rate of M. teleius raised by infested, allopatric host colonies compared to sympatric host populations. Our results suggest the lack of behavioural counter-adaptations of local hosts of M. teleius that more easily adopt and rear butterfly caterpillars compared to naive M. scabrinodis colonies. Our results may also have implications for Maculinea butterfly conservation, especially for reintroduction programmes. We suggest that the existence of behavioural host defences should be checked for the source host population, as well as for the Myrmica population from the reintroduction site. It may also be reasonable to introduce several Myrmica host colonies from the source butterfly host population.     

Plant–insect interactions: gentians,seed predators and parasitoid wasps

While studying breeding systems and pollination ecology of nine Gentiana species (G. lutea, G. punctata, G. asclepiadea, G. pneumonanthe, G. cruciata, G. pyrenaica, G. verna, G. utriculosa, and G. nivalis) in the Bulgarian mountains, we recorded number of insects that feed on their maturing seeds. In addition, parasitoid wasps in connection to these seed predators were detected. Insects are identified and the impact on the seed set of afore mentioned Gentiana species is estimated. Fruit capsules of Gentiana spp. from different populations in the mountains in Bulgaria were investigated for the presence or absence of damage by larvae during the period of 16 years. The seed destruction varies among the nine investigated Gentiana species. The insects whose larvae damaged the seed/fruit set belonged mainly to Coleoptera and Diptera. The larvae of lycaenid butterflies, Maculinea spp. (Lepidoptera), were recorded only in seeds of G. asclepiadea, G. pneumonanthe and G. cruciata. Parasitoid wasps from the families Ichneumonidae, Braconidae, and Pteromalidae were identified, some of them new for the fauna of Bulgaria.     

Ants (Hymenoptera: Formicidae) as potential egg predators of lepidopteran pests of sweet potato, <Emphasis Type="Italic">Ipomoea batatas</Emphasis> (Solanales: Convolvulaceae), in Japan

The sweet potato Ipomoea batatas (L.) Lam., which has extrafloral nectaries, was visited by nine indigenous ant species in south Kyushu, Japan. These ant species were evaluated for their ability to remove the eggs of two lepidopteran species—Aedia leucomelas (Linnaeus) and Spodoptera litura (Fabricius)—through ant-exclusion experiments. The results showed that Tetramorium bicarinatum (Nylander), one of the dominant ant species, is an efficient predator of lepidopteran eggs. This ant species removed A. leucomelas eggs from ant-visited plants in six trials conducted from mid-July to mid-October, with high removal rates (90–100%) occurring from mid-September onward. On ant-excluded plants, only 0–18% of exposed eggs were removed by ants that accidentally invaded the plants. Tetramorium bicarinatum also removed egg masses and the hatchlings of S. litura. The mean percent area of egg-laden leaves eaten by S. litura larvae was lower on ant-visited plants (0.9%) than on ant-excluded plants (57.3%). In contrast, Formica japonica Motschulsky, another dominant ant species, was not observed removing the eggs or larvae of the lepidopteran species. These results show that certain indigenous ant species are efficient as biocontrol agents. Thus, individual ant species need to be investigated for their ability to control insect pests in various crops.     

Ant–aphid relations in the south of Western Siberia (Hymenoptera: Formicidae; Hemiptera: Aphididae)

Aphids, the main suppliers of energy-rich honeydew, play an important role in the life of ants. However, the data on the trophobiotic ant–aphid associations in the majority of regions are still limited. We present the first data on the ant–aphid relations in the south of Western Siberia. Investigations were carried out in the most typical biotopes of forest-steppe and steppe zones in the territory of Novosibirsk and Kurgan regions (Russia) during 1993–2014. There were revealed 35 species of ants and 198 species of aphids. Detected 456 ant–aphid associations involved 28 ant species and 134 myrmecophilous aphids. Seven ant species were found to consume honeydew of 9 non-myrmecophilous aphids, scraping it from the plant. This behaviour is typical of subdominant and subordinate ants which do not protect their foraging areas. Ants associate with various numbers of aphid species. About 36% of ants attended aphid colonies of less than 5 species. The largest number of myrmecophilous aphids is associated with L. niger (Linnaeus, 1758) (103 species), Formica pratensis Retzius, 1783 (50), Formica rufa group (25–33), F. (Serviformica) fusca Linnaeus, 1758 (26) and F. (S.) cunicularia Latreille, 1798 (27). Different ants play unequal roles in the formation of trophobiotic interactions with aphids. Due to complex territorial and foraging behaviour, including high functional specialization among honeydew collectors, dominant ants of Formica s. str. are one of the leaders in this process. The role of L. niger and Formica ants of the subgenus Serviformica requires further detailed investigation.     

Ants Do Not Traverse the Silk of Adult Female <Emphasis Type="Italic">Nephila clavipes</Emphasis> (Linnaeus) Webs

Many organisms use chemicals to deter enemies. Some spiders can modify the composition of their silk to deter predators from climbing onto their webs. The Malaysian golden orb-weaver Nephila antipodiana (Walckenaer) produces silk containing an alkaloid (2-pyrrolidinone) that functions as a defense against ant invasion—ants avoid silk containing this chemical. In the present study, we test the generality of ants’ silk avoidance behavior in the field. We introduced three ant species to the orb webs of Nephila clavipes (Linnaeus) in the tropical rainforest of La Selva, Costa Rica. We found that predatory army ants (Eciton burchellii Westwood) as well as non-predatory leaf-cutting ants (Atta cephalotes Linnaeus and Acromyrmex volcanus Wheeler) avoided adult N. clavipes silk, suggesting that an additional species within genus Nephila may possess ant-deterring silk. Our field assay also suggests that silk avoidance behavior is found in multiple ant species.     

Complex flowers and rare pollinators: Does ant pollination in <Emphasis Type="Italic">Ditassa</Emphasis> show a stable system in Asclepiadoideae (Apocynaceae)?

If on one hand, ant pollination is rare, on the other Asclepiadoideae flowers are the most complex among Eudicots. Both themes are exciting in pollination biology. Although there are records of ants with the ability to remove the pollinarium on this subfamily, the role of these insects as pollinators is not yet known. Therefore, we investigated the interaction between flowers and ants, as well as the associated features in two species of Asclepiadoideae, Ditassa capillaris and D. hastata. The studied species were both visited by Cephalotes inaequalis and Dorymyrmex thoracicus. We analyzed the common traits of ant pollination of the plant species, recorded the number of visit by ants, and carried out experiments of selective pollination, developing an effectivity index. Both Ditassa species have common traits of ant pollination, such as small bright flowers with exposed floral resource. The pollinarium is clip-shaped and resistant to the metapleural gland, which ensures effective pollination. Dorymyrmex thoracicus is a very frequent but not very efficient pollinator, whereas Cephalotes inaequalis is more efficient though at a lower frequency. Therefore, the total contributions of both ants to the pollination of both Ditassa species are similar. The features of both Ditassa species which favor ant pollination, include some synapomorphies within Asclepiadoideae. Furthermore, the efficiency of the ants as pollinators to the reproductive success of the plants was similar despite the different behaviors observed in both ant species. Hence, we suggest that the role of ants in pollination within this subfamily has been neglected.     

Two ways to be a myrmecophilous butterfly: natural history and comparative immature‐stage morphology of two species of Theope (Lepidoptera: Riodinidae)

Symbiotic interactions between butterfly larvae and ants, termed myrmecophily, require a range of behavioural and morphological adaptations (ant‐organs). Here, using light and scanning electron microscopy, we describe the complete life cycle of two species of Theope (Lepidoptera: Riodinidae) that have contrasting ways of life. Theope thestias larvae are facultatively tended by several ant species, whereas Theope pieridoides have obligate symbiotic interactions with Azteca ants that inhabit a myrmecophytic tree. Morphological differences associated with their different degrees of intimacy with tending ants are visible from hatching. In T. thestias, the untended first‐instar larva has elongated bifurcated setae and a few tiny perforated cupola organs (PCOs), whereas in T. pieridoides, the ant‐tended first instar has short dendritic setae, larger and more numerous PCOs, and functional tentacle nectary organs (TNOs). Throughout ontogeny, T. pieridoides always shows more conspicuous ant‐organs than T. thestias, with the exception of balloon setae, which are larger and more numerous in T. thestias. In addition, mature T. pieridoides larvae have an anterior set of ant‐organs, including a new type, here described and termed anterior glandular openings (AGOs). Based on the behavioural responses of ants in contact with these structures, a new interpretation for the mechanism whereby Theope larvae can manipulate the behaviour of their tending ants is proposed. Until now, three ecological syndromes can be defined among Theope species: (1) oligophagous larvae with facultative myrmecophily; (2) monophagous larvae with obligate myrmecophily; and (3) polyphagous larvae with obligate myrmecophily. These results suggest that differences in the degree of specificity in the ant–plant interactions may have an important role in the evolution of host‐plant use in Theope. © 2013 The Linnean Society of London     

Mass Occurrence and Dominant Behavior of the European Ant Species <Emphasis Type="Italic">Formica fuscocinerea</Emphasis> (Forel)

Recently, masses of the ant Formica (Serviformica) fuscocinerea (Forel) have been occurring at numerous sites in Southern Germany. Although F. fuscocinerea is native to Southern Germany, these mass occurrences resemble ant invasions in density and dominance. This study aimed to investigate the underlying mechanisms that promote sudden mass occurrence of a previously inconspicuous ant species within its native range. To estimate the competitive dominance of F. fuscocinerea, species occurrence and abundance considering biotic and abiotic parameters were studied in a natural habitat where F. fuscocinerea co-occurred with two other common ant species, Myrmica ruginodis (Nylander) and Lasius niger (Linnaeus). To understand the species’ distribution in the field, laboratory experiments on interspecific competition were conducted. Finally, the colony structure of F. fuscocinerea was investigated with intraspecific aggression tests. Formica fuscocinerea dominated an area that, as indicated by strongly frequented foraging trails on the trees, provided important food sources, e.g. trophobionts, to the ants. Other ant species coexisted only at the periphery of the F. fuscocinerea range. Laboratory experiments revealed F. fuscocinerea as highly dominant species. Additionally, F. fuscocinerea showed a complete lack of intraspecific aggression between ants originating from distances up to 58 km, indicating weak or nonexistent behavioral boundaries among ants of physically separated nests. Since extraordinarily high worker densities, strong interspecific dominance and a lack of colony boundaries within supercolonies are considered to be important traits of several invasive ant species we conclude that the same traits also promote the dominance of F. fuscocinerea.     

Patterns of floral resource use by two dominant ant species in a biodiversity hotspot

Ecological dominance in ants is often fuelled by carbohydrate intake. Most studies have focused on the importance of invasive ant mutualistic associations with trophobionts whereas few studies have investigated the importance of floral nectar on invasion success. In this study, utilisation of temporarily available floral nectar by the invasive Argentine ant, Linepithema humile, was compared to that of the dominant native ant, Anoplolepis custodiens, within the Cape Floristic Region (CFR), a biodiversity hotspot. The effect of these two focal ant species on species composition and abundance of ground foraging ants as well as floral arthropod visitors in inflorescences of Proteacea species was assessed. Foraging activity, and trophic ecology inferred from the abundance of natural stable isotopes of Carbon (δ¹³C) and Nitrogen (δ¹⁵N), and the ratio of Carbon to Nitrogen (C:N) were compared between the two ant species during three flowering periods. Linepithema humile significantly reduced the abundance and species diversity of both above-ground and floral arthropod species abundance and composition. Linepithema humile increased its foraging activity with increasing nectar availability, switching its diet to a more herbivorous one. Anoplolepis custodiens did not respond as effectively to increasing floral nectar or negatively impact floral arthropod visitors. This study showed that the availability of floral nectar and ability of L. humile to more effectively utilise this temporarily available resource than native ants, can contribute significantly to the further spread and persistence of L. humile in natural environments in the CFR.     

Ants Associated with <Emphasis Type="Italic">Turnera subulata</Emphasis> (Turneraceae): Elaiosome Attraction,Seed Dispersion and Germination

Symbiosis between plants and ants include examples in which the plant provides shelter and/or food for ants that, in turn, act in the defense or in the dispersion of seeds from the host plant. Although traditionally referred as mutualistic, the results of these interactions may vary with the ecological context in which patterns are involved. A range of species have facultative association with Turnera subulata (Turneraceae). Here, using behavioral bioassays, we investigated the effects of the most frequent ant species associated with T. subulata (Brachymyrmex sp.1, Camponotus blandus (Smith), Dorymyrmex sp.1, Crematogaster obscurata Emery, and Solenopsis invicta Buren) in the dispersion of plant host seeds and in the number of seedlings around the associated ant nests. We also evaluated the effects of these ant species in the germination of T. subulata seeds, in the consumption of elaiosome, and in the attractiveness to elaiosome odor. Our results showed that the ant species associated with T. subulata presented variation in the attraction by the odor and in the rate of consumption of the elaiosomes. However, none of the ant species studied contributed significantly to the increase of seed germination and seedling growth. Our results suggest that the consumption of the elaiosome by ant species is not a determinant factor to the success of germination of T. subulata. However, such species could contribute indirectly to seed germination by carrying seeds to sites more fertile to germination. In general, our results help to elucidate the results of ecological interactions involving ants and plants.     

Differences in Aggressive Behaviors between Two Ant Species Determine the Ecological Consequences of a Facultative Food-for-Protection Mutualism

Ant-hemipteran mutualisms are widespread interactions in terrestrial food webs with far-reaching consequences for arthropod communities. Several hypotheses address the behavioral mechanisms driving the impacts of this mutualism, but relatively few studies have considered multiple ant species simultaneously as well as interspecific and intraspecific variation in ant behavior. In a series of field experiments that manipulated ant diet, this work examines the role of induced behaviors of forest ant species actively engaged in mutualism with Hemiptera. Based on other work in ant mutualisms, we predicted a higher frequency of aggressive behaviors towards prey and competitors by ants in the presence of honeydew-producing Hemiptera. We specifically compared Camponotus chromaoides and Formica neogagates (Formicidae), two abundant species in temperate forests of the northeastern U.S.A. After manipulating ant diet and interactions with sap-feeders experimentally, we observed 494 one-on-one interactions between ants and competitors, ladybird beetles and caterpillar prey. We found that C. chromaoides, exhibited behavioral dominance over F. neogagates, and C. chromaoides was more likely to attack ladybird beetles, competing ants, and caterpillar prey. However, contrary to other work in ant-Hemipteran mutualisms, we observed no evidence that food rewards provided by sap-feeders induced changes in ant behavior for either ant species examined. These results reveal the importance of considering interspecific differences in behavior as a mechanism underlying the ecological impacts of ant-Hemipteran protection mutualisms.     

Interaction between a threatened endemic plant (<Emphasis Type="Italic">Anchusa crispa</Emphasis>) and the invasive Argentine ant (<Emphasis Type="Italic">Linepithema humile</Emphasis>)

Seed dispersal mutualisms are essential to ensure the survival of diverse plant species and communities worldwide. Here, we investigated whether the invasive Argentine ant can replace native ants by fulfilling their functional role in the seed dispersal of the rare and threatened endemic myrmecochorous plant, Anchusa crispa, in Corsica (France). Our study addressed the potential of Linepithema humile to disperse elaiosome-bearing seeds of A. crispa, examining L. humile’s effects on (1) the composition of communities of ants removing seeds, (2) the number of seed removals, (3) seed preference, (4) the distance of seed dispersion, and (5) seed germination. We caught seven native species at the control site, but only the Argentine ant at invaded sites. L humile removed A. crispa seeds in greater numbers than did native ants, respectively 66 and 23%, probably due to their higher worker density. The invader was similar to native ants with respect to distance of seed transport. Finally, rates of seed germination were not significantly different between seeds previously in contact with either Argentine ants or not. Taken all together, these results suggest that the Argentine ant is unlikely to pose a threat to A. crispa population. These results have important implications for the management of this rare and threatened endemic plant and provide an example of non-negative interactions between invasive and native species.