Showing papers on "Lasius published in 2008"

Specificity and transmission mosaic of ant nest-wall fungi

Abstract: Mutualism, whereby species interact to their mutual benefit, is extraordinary in a competitive world. To recognize general patterns of origin and maintenance from the plethora of mutualistic associations proves a persisting challenge. The simplest situation is believed to be that of a single mutualist specific to a single host, vertically transmitted from one host generation to the next. We characterized ascomycete fungal associates cultured for nest architecture by the ant subgenera Dendrolasius and Chthonolasius. The ants probably manage their fungal mutualists by protecting them against fungal competitors. The ant subgenera display different ant-to-fungus specificity patterns, one-to-two and many-to-one, and we infer vertical transmission, in the latter case overlaid by horizontal transmission. Possible evolutionary trajectories include a reversal from fungiculture by other Lasius subgenera and inheritance of fungi through life cycle interactions of the ant subgenera. The mosaic indicates how specificity patterns can be shaped by an interplay between host life-cycles and transmission adaptations.

Avoidance responses of an aphidophagous ladybird, Adalia bipunctata, to aphid‐tending ants

Abstract: 1. Insect predators often aggregrate to patches of high prey density and use prey chemicals as cues for oviposition. If prey have mutualistic guardians such as ants, however, then these patches may be less suitable for predators. 2. Ants often tend aphids and defend them against predators such as ladybirds. Here, we show that ants can reduce ladybird performance by destroying eggs and physically attacking larvae and adults. 3. Unless ladybirds are able to defend against ant attacks they are likely to have adaptations to avoid ants. We show that Adalia bipunctata ladybirds not only move away from patches with Lasius niger ants, but also avoid laying eggs in these patches. Furthermore, ladybirds not only respond to ant presence, but also detect ant semiochemicals and alter oviposition strategy accordingly. 4. Ant semiochemicals may signal the extent of ant territories allowing aphid predators to effectively navigate a mosaic landscape of sub-optimal patches in search of less well-defended prey. Such avoidance probably benefits both ants and ladybirds, and the semiochemicals could be regarded as a means of cooperative communication between enemies. 5. Overall, ladybirds respond to a wide range of positive and negative oviposition cues that may trade-off with each other and internal motivation to determine the overall oviposition strategy.

Ant-seed interactions: combined effects of ant and plant species on seed removal patterns

Abstract: Seed dispersal by ants (i.e. myrmecochory) is usually considered as a mutualism: ants feed on nutritive bodies, called elaiosomes, before rejecting and dispersing seeds in their nest surroundings. While mechanisms of plant dispersal in the field are well documented, the behaviour of the ant partner was rarely investigated in details. Here, we compared in laboratory conditions the foraging behaviour of two ant species, the omnivorous Lasius niger and the insectivorous Myrmica rubra to which seeds of two European myrmecochorous plants (Chelidonium majus and Viola odorata) were given. Ant colonies were simultaneously presented three types of items: entire seeds with elaiosome (SE), seeds without elaiosome (S) and detached elaiosomes (E). The presence of elaiosomes on seeds did not attract workers from a distance since ants first contact equally each type of items. Although ants are mass-recruiting species, we never observed any recruitment nor trail-laying behaviour towards seeds. For ants having contacted seed items, their antennation, manipulation and seed retrieval behaviour strongly varied depending on the species of each partner. Antennation behaviour, followed by a loss of contact, was the most frequent ant-seed interaction and can be considered as a “hesitation” clue. For both plant species, insectivorous Myrmica ants removed items in larger number and at higher speed than Lasius. This fits with the hypothesis of a convergence between odours of elaiosomes and insect preys. For both ant species, the small Chelidonium seeds were retrieved in higher proportion than Viola ones, confirming the hypothesis that ants prefer the higher elaiosome/diaspore-ratio. Thus, in these crossed experiments, the ant-plant pair Myrmica/Chelidonium was the most effective as ants removed quickly almost all items after a few antennations. The presence of an elaiosome body increased the seed removal by ants excepting for Myrmica which retrieved all Chelidonium seeds, even those deprived of their elaiosome. After 24 h, all the retrieved seeds were rejected out of the nest to the refuse piles. In at least half of these rejected items, the elaiosome was discarded by ants. Species-specific patterns and behavioural differences in the dynamics of myrmecochory are discussed at the light of ant ecology.

The Structure of Ant Assemblages in an Urban Area of Helsinki, Southern Finland

Abstract: We collected ants in ten replicated habitat types of an urban island and described their assemblages using Non-metric Multidimensional Scaling and Multivariate Regression Trees. Lasius niger was the most abundant species, followed by Myrmica rubra, Formica fusca, L. flavus and L. platythorax; these species comprised 87% of all 1133 nests of the 16 species found. Ant assemblages changed gradually from open habitats to sites with closed tree canopy. Species most tolerant to urban pressure were L. niger, L. flavus and M. rugulosa, whereas forest-associated species were scarce or absent. Successful urban species had extensive (Palaearctic) or more limited (Euro-Siberian) distribution. Common and abundant habitat generalists were overrepresented relative to rural areas; these were also efficiently dispersing pioneer species with independent colony founding. Lack of suitable (micro)habitat apparently hampered colonization of many species. Competitively superior, territorial species were rare or absent, as were species dependent on dead wood, and many species depending on other ants. The indicated reorganization of interspecific competitive relationships may be due to selective impoverishment of the urban species pool. Comparison with other urban studies suggested that in ants, faunal homogenization has not taken place on a European scale.

A DNA and morphology based phylogenetic framework of the ant genus Lasius with hypotheses for the evolution of social parasitism and fungiculture.

Abstract: Ants of the genus Lasius are ecologically important and an important system for evolutionary research. Progress in evolutionary research has been hindered by the lack of a well-founded phylogeny of the subgenera, with three previous attempts disagreeing. Here we employed two mitochondrial genes (cytochrome c oxidase subunit I, 16S ribosomal RNA), comprising 1,265 bp, together with 64 morphological characters, to recover the phylogeny of Lasius by Bayesian and Maximum Parsimony inference after exploration of potential causes of phylogenetic distortion. We use the resulting framework to infer evolutionary pathways for social parasitism and fungiculture. We recovered two well supported major lineages. One includes Acanthomyops, Austrolasius, Chthonolasius, and Lasius pallitarsis, which we confirm to represent a seventh subgenus, the other clade contains Dendrolasius, and Lasius sensu stricto. The subgenus Cautolasius, displaying neither social parasitism nor fungiculture, probably belongs to the second clade, but its phylogenetic position is not resolved at the cutoff values of node support we apply. Possible causes for previous problems with reconstructing the Lasius phylogeny include use of other reconstruction techniques, possibly more prone to instabilities in some instances, and the inclusion of phylogenetically distorting characters. By establishing an updated phylogenetic framework, our study provides the basis for a later formal taxonomic revision of subgenera and for studying the evolution of various ecologically and sociobiologically relevant traits of Lasius, although there is need for future studies to include nuclear genes and additional samples from the Nearctic. Both social parasitism and fungiculture evolved twice in Lasius, once in each major lineage, which opens up new opportunities for comparative analyses. The repeated evolution of social parasitism has been established for other groups of ants, though not for temporary social parasitism as found in Lasius. For fungiculture, the independent emergence twice in a monophyletic group marks a novel scenario in ants. We present alternative hypotheses for the evolution of both traits, with one of each involving loss of the trait. Though less likely for both traits than later evolution without reversal, we consider reversal as sufficiently plausible to merit independent testing.

Soil engineering ants increase grass root arbuscular mycorrhizal colonization

Abstract: The role of edaphic factors in driving the relationship between plant community structure and ecosystem processes is a key issue of the current debate on functional implications of biodiversity. In this study, we draw a direct link between aboveground/belowground relationships, vegetation structure, and aboveground management. We used ground nesting ants and arbuscular mycorrhizal fungi (AMF) as an example for quantifying the role of biotic interactions in soil. Although both groups are known to have a major impact on grasslands, the interactive effect of these taxa on vegetation structure and its sensitivity to grassland management is poorly understood. We show that the ant Lasius flavus increases the root arbuscular mycorrhizal colonization (AMC) of grasses by modifying biotic and abiotic soil properties. As a possible consequence, the shoot length of grass growing on ant mounds was shorter and shoot N and P concentrations were higher than in grass growing off of the mounds. In addition, management affected ant nest architecture and soil and, in turn, AMC. These results emphasize the need to consider the interactions between plants, soil microorganisms, soil fauna, and aboveground management to increase the understanding of the drivers of biodiversity and ecosystem functioning in grasslands both aboveground and belowground.

How ants find each other; temporal and spatial patterns in nuptial flights

Abstract: Reproduction is a key factor in understanding population ecology and therefore species occurrence. However, patterns in reproductive behaviour for distinct ant species remain insufficiently known. In this paper strategies in mate finding are studied for six ant species (Lasius niger, Lasius umbratus, Temnothorax nylanderi, Myrmica rubra, Myrmica ruginodis, Stenamma debile) in a forest – forest edge – agricultural field gradient. Using window traps, we studied whether these species had a restricted nuptial flight season, displayed swarming behaviour, and whether the alates aggregated at the forest edge. The flight season was limited to one month or less for L. niger, T. nylanderi, M. rubra, M. ruginodis and S. debile. Swarming behaviour occurred in all but one (L. umbratus) species. Although none of the six species seemed to have highest nest density at the forest edge, three of them, M. rubra, M. ruginodis and S. debile, showed male aggregations there, indicating this to be the main reproduction site. This last finding could be due to a more suitable micro-climate, but most likely, edges are conspicuous land marks which are used by ants to meet mates. The behavioural patterns of ant sexuals at the forest edge can influence dispersal possibilities in fragmented landscapes, reproductive success and nest densities.

Potential positive effect of the ant species Lasius niger on linyphiid spiders

Abstract: Ants are highly abundant generalist predators and important ecosystem engineers which can strongly affect the composition of animal communities. We manipulated the density of the ant species Lasius niger with baits in a small-scale field experiment to study the role of intraguild predation, top-down control and bottom-up effects of ants in a dry grassland surrounded by agricultural fields. Two different kinds of baits (honey and tuna) were presented near to the nests and at a distance of 2 m from six L. niger colonies in a dry grassland habitat, where L. niger was a highly abundant, omnipresent species. The experiments were performed for 1 month in spring. Additionally, the natural abundance of L. niger varying with the distance to their nests was used to study the effects on spiders and potential prey groups. The activity of L. niger was significantly higher at tuna baits compared with that at honey baits and empty control dishes. We found no effects of higher activity of L. niger on the arthropod community. However, there is evidence for a facilitation effect of ants on Collembola near to their colonies, probably due to habitat modification, which also influenced the density of Linyphiidae. Both groups had up to four times higher denisities next to L. niger colonies than at a distance of 2 m. Furthermore, d 13 C values demonstrated that linyphiid spiders and L. niger predominantly feed on Collembola. We conclude that there is no evidence of top-down effects of L. niger in a grassland in spring, but we found a facilitation of linyphiid spiders and their prey by the ants, which acted as ecosystem engineers.

Investigations of the associated between aphids and ants on wild plants in ankara province (turkey)

Abstract: Differences in feeding position consequently affect the benefits of myrmecophily for different aphid species. Tending also seems to be associated with differences in the honeydew quality and quantity of the aphids. This study yielded 16 ant species associated with 19 aphid species. The most encountered ant species that associated with many aphid species were Camponotus aethiops (Latreille), Camponotus piceus (Leach), Formica glauca Ruzsky, Lasius paralienus Seifert, Crematogaster sordidula (Nylander). On the other hand, the ant species that associated with only 1 aphid species were Aphis chloris Koch, Aphis euphorbiae Kaltenbach, Aphis fabae ssp. circiiacanthoidis Scopoli, Aphis gossypii Glover, Aphis nasturtii Kaltenbach, Aphis verbasci Schrank, Brachcaudus helicrysi (Kaltenbach), Hyadaphis foeniculi (Passerini), Hydaphias hofmanni Borner and Protaphis terricola Rondani. The results indicated that the ant-aphid interaction is important on biological control.

Spatial organization in ants’ nests: does starvation modify the aggregative behaviour of Lasius niger species?

Abstract: Ant colonies that undergo long starvation periods have to tune their exploratory and foraging responses to face their food needs. Although the number of foragers is known to increase with food deprivation in the ant Lasius niger, such enhanced food exploitation is not related to a more intense recruitment by successful scouts. We thus suggest that the colony’s response to a food shortage could result from changes at the level of the ant recruits, in particular from changes in their spatial organization inside the nest. Since aggregation plays a key role in the social organization of ants, we assume that the colony’s response to starvation could be due to changes in the aggregative behaviour of L. niger nestmates.We thus compared the aggregation dynamics of inner-nest workers and foragers having undergone either a short or a long-lasting starvation period. Whatever the ethological group (foragers or inner-nest workers), there was no significant influence of starvation on the aggregation dynamics nor on any feature of the observed clusters. This result shows that an increased foraging response to food shortage cannot be explained by changes in the tendency of nestmates to aggregate within the nest. Finally, we discuss other behavioural mechanisms, in particular changes in behavioural thresholds that could underlie the adaptive changes seen in colony foraging after long starvation periods.

A Phylogenetic Analysis of North American Lasius Ants Based on Mitochondrial and Nuclear DNA

Abstract: The ant genus Lasius (Formicinae) arose during the early Tertiary approximately 65 million years ago Lasius is one of the most abundant and widely distributed ant genera in the Holarctic region, with 95 described species placed in six subgenera: Acanthomyops, Austrolasius, Cautolasius, Chthonolasius, Dendrolasius and Lasius Many species of Lasius have been central to numerous species-level studies and the focus of many ecological, agricultural, and behavioral investigations The focus of this study was to use molecular phylogenetic analysis of 781 base pairs of the mitochondrial gene cytochrome oxidase I (COI) and 251 base pairs of an anonymous nuclear gene (ANG) to address questions about the evolutionary relationships of North American Lasius species and subgenera These relationships were used to better understand the biological and evolutionary complexities associated with these species given their North American distributions The resulting hypotheses generated in this study from the analyses of these genes produced unexpected patterns of phylogenetic placement of Lasius species and subgenera A number of biological processes alone or together could explain these patterns, including interspecific hybridization and gene introgression, incomplete lineage sorting, and the presence of multiple cryptic species

Social context predicts recognition systems in ant queens

Abstract: Recognition of group-members is a key feature of sociality. Ants use chemical communication to discriminate nestmates from intruders, enhancing kin cooperation and preventing parasitism. The recognition code is embedded in their cuticular chemical profile, which typically varies between colonies. We predicted that ants might be capable of accurate recognition in unusual situations when few individuals interact repeatedly, as new colonies started by two to three queens. Individual recognition would be favoured by selection when queens establish dominance hierarchies, because repeated fights for dominance are costly; but it would not evolve in absence of hierarchies. We previously showed that Pachycondyla co-founding queens, which form dominance hierarchies, have accurate individual recognition based on chemical cues. Here, we used the ant Lasius niger to test the null hypothesis that individual recognition does not occur when co-founding queens do not establish dominance hierarchies. Indeed, L. niger queens show a similar level of aggression towards both co-foundresses and intruders, indicating that they are unable of individual recognition, contrary to Pachycondyla. Additionally, the variation in chemical profiles of Lasius and Pachycondyla queens is comparable, thus informational constraints are unlikely to apply. We conclude that selection pressure from the social context is of crucial significance for the sophistication of recognition systems.