Contribució al coneixement de la taxonomia i la fenologia de les formigues (Hymenoptera : Formicidae) d'Andorra

Una trampa Malaise disposada a Santa Coloma, a 1.050 m de altitud, va capturar 1.413 formigues des d'agost 1992 fins desembre 1993. Hi havia 895 mascles (17 espècies), 137 reines (18 espècies) i 391 obreres (12 espècies). Ha estat possible la identificació específica de 582 mascles, 98 reines i totes les obreres. Entre mascles, reines i obreres hi ha 30 espècies, un resultat prou elevat per a una localitat dels Pirineus. D'aquestes, n'hi ha 18 que són mencionades a Andorra per primer cop. D'elles, n'hi ha un grup amb marcat significat biogeogràfic septentrional: Dolichoderus quadripunctatus, Formica fusca, Lasius brunneus, Lasius distinguendus, Myrmecina graminicola i Stenamma striatulum. D'altra banda, hi ha un component d'espècies de significat clarament mediterrani: (Aphaenogaster subterranea, Camponotus aethiops, Camponotus cruentatus, Camponotus truncatus, Crematogaster scutellaris, Messor structor, Pheidole pallidula, Pyramica tenuipilis, Plagiolepis pygmaea, Plagiolepis xene, Temnothorax rabaudi). Tres espècies més, capturades en un altre localitat 'Andorra, també són noves pel país: Formica gerardi, Myrmica spinosior i Temnothorax kraussei. Així, el nombre d'espècies de formigues que es coneix fins avui dia d'Andorra és de 58

A preliminary checklist of the ants (Hymenoptera, Formicidae) of Andorra

Within the last decade, checklists of the ant fauna of several European countries have been published or updated. Nevertheless, no ant checklists have hitherto been published for the principality of Andorra, a small landlocked country located in the eastern part of the Pyrenees. This work presents a critical list of the ant species of Andorra based on a review of the literature and on the biological material we collected during several field campaigns conducted in Andorra since the year 2005. Seventy-five species belonging to 21 genera of were recorded. Nine species were recorded for the first time in Andorra: Aphaenogaster gibbosa (Latreille, 1798), (Olivier, 1792), (Leach, 1825), Nylander, 1846, Seifert, 1992, Forel, 1895, (Bondroit, 1918), (Forel, 1894), (Mayr, 1855). The most speciose genera were Linnaeus, 1758 and Forel, 1890 with 14 and 12 species, respectively. The ant fauna of Andorra is mostly dominated by Central European species (some are typical cold climate specialists); however species belonging to the Mediterranean ant fauna were also found. This can be explained by the particular geographic situation of Andorra which is characterized by a high mountain Mediterranean climate

Resource sharing leads to the emergence of division of labour

Division of labour occurs in a broad range of organisms. Yet, how division of labour can emerge in the absence of pre-existing interindividual differences is poorly understood. Using a simple but realistic model, we show that in a group of initially identical individuals, division of labour emerges spontaneously if returning foragers share part of their resources with other group members. In the absence of resource sharing, individuals follow an activity schedule of alternating between foraging and other tasks. If non-foraging individuals are fed by other individuals, their alternating activity schedule becomes interrupted, leading to task specialisation and the emergence of division of labour. Furthermore, nutritional differences between individuals reinforce division of labour. Such differences can be caused by increased metabolic rates during foraging or by dominance interactions during resource sharing. Our model proposes a plausible mechanism for the self-organised emergence of division of labour in animal groups of initially identical individuals. This mechanism could also play a role for the emergence of division of labour during the major evolutionary transitions to eusociality and multicellularity

Does fungal infection produce cheaper workers?

Cuticle quality is of vital importance in insects. Amongst others, it prevents desiccation, and protects against pathogens. Therefore the development of thicker cuticle would be advantageous. The within-species variation of cuticle structure is affected by many factors, both physiological and ecological. Parasites can also affect the exoskeleton structure either to facilitate intrusion or to aid transmission to the next host. In the frame of our study we investigated the effect of an ectoparasitic fungus, Rickia wasmannii on the cuticle of its host. We measured the thickness of the exoskeleton in infected and uninfected ants originating from three European populations. Infected ants had thinner cuticle than uninfected ones, while there were also differences among populations. It is unclear though, whether this is the host’s response investing less into cuticle formation, or the fungus infects colonies with thin cuticle. Either way, within-species variation is linked to response to parasitic pressure

Oxidative stress and senescence in social insects:A significant but inconsistent link?

The life-prolonging effects of antioxidants have long entered popular culture, but the scientific community still debates whether free radicals and the resulting oxidative stress negatively affect longevity. Social insects are intriguing models for analysing the relationship between oxidative stress and senescence because life histories differ vastly between long-lived reproductives and the genetically similar but short-lived workers. Here, we present the results of an experiment on the accumulation of oxidative damage to proteins, and a comparative analysis of the expression of 20 selected genes commonly involved in managing oxidative damage, across four species of social insects: a termite, two bees and an ant. Although the source of analysed tissue varied across the four species, our results suggest that oxidative stress is a significant factor in senescence and that its manifestation and antioxidant defenses differ among species, making it difficult to find general patterns. More detailed and controlled investigations on why responses to oxidative stress may differ across social species may lead to a better understanding of the relations between oxidative stress, antioxidants, social life history and senescence. This article is part of the theme issue 'Ageing and sociality: why, when and how does sociality change ageing patterns

Oxidative stress and senescence in social insects : a significant but inconsistent link?

The life-prolonging effects of antioxidants have long entered popular culture, but the scientific community still debates whether free radicals and the resulting oxidative stress negatively affect longevity. Social insects are intriguing models for analysing the relationship between oxidative stress and senescence because life histories differ vastly between long-lived reproductives and the genetically similar but short-lived workers. Here, we present the results of an experiment on the accumulation of oxidative damage to proteins, and a comparative analysis of the expression of 20 selected genes commonly involved in managing oxidative damage, across four species of social insects: a termite, two bees and an ant. Although the source of analysed tissue varied across the four species, our results suggest that oxidative stress is a significant factor in senescence and that its manifestation and antioxidant defenses differ among species, making it difficult to find general patterns. More detailed and controlled investigations on why responses to oxidative stress may differ across social species may lead to a better understanding of the relations between oxidative stress, antioxidants, social life history and senescence. This article is part of the theme issue ‘Ageing and sociality: why, when and how does sociality change ageing patterns?’The German Research Foundation and the Technische Universität Dresden Zukunftskonzept funded from the Excellence Initiative by the German Federal and State Governments.http://rstb.royalsocietypublishing.orgam2022Zoology and Entomolog

Physical and land-cover variables influence ant functional groups and species diversity along elevational gradients

Of particular importance in shaping species assemblages is the spatial heterogeneity of the environment. The aim of our study was to investigate the influence of spatial heterogeneity and environmental complexity on the distribution of ant functional groups and species diversity along altitudinal gradients in a temperate ecosystem (Pyrenees Mountains). During three summers, we sampled 20 sites distributed across two Pyrenean valleys ranging in altitude from 1,009 to 2,339 m by using pitfall traps and hand collection. The environment around each sampling points was characterized by using both physical and land-cover variables. We then used a self-organizing map algorithm (SOM, neural network) to detect and characterize the relationship between the spatial distribution of ant functional groups, species diversity, and the variables measured. The use of SOM allowed us to reduce the apparent complexity of the environment to five clusters that highlighted two main gradients: an altitudinal gradient and a gradient of environmental closure. The composition of ant functional groups and species diversity changed along both of these gradients and was differently affected by environmental variables. The SOM also allowed us to validate the contours of most ant functional groups by highlighting the response of these groups to the environmental and land-cover variables

Does substrate coarseness matter for foraging ants? An experiment with Lasius niger (Hymenoptera; Formicidae)

International audienceWe investigated whether workers of the ant species Lasius niger are able to sense and discriminate the coarseness of the substrate on which they walk. First, we studied the way in which substrate coarseness affects the ants' locomotory behaviour. Second, we investigated the spontaneous preference of ants for substrates of different coarseness. And third, we tested with a differential conditioning procedure the ants' capacity to learn to associate a given coarseness with a food reward. The locomotory behaviour of ants differed according to substrate coarseness: ants moved significantly faster and had more sinuous trajectories on a fine than on a coarse substrate. No spontaneous preference for a substrate of a given coarseness was observed and, even after 20 successive conditioning trials, there was little evidence of the effect of experience on substrate coarseness discrimination. Overall however, ants trained on fine sand made significantly more correct choice than those trained on coarse sand. We discuss these results and argue that in L. niger substrate coarseness may be more important at the collective level, by interacting with the chemical properties of the pheromone trail used in mass recruitment to food source, than at the individual level