Hierarchical networks of food exchange in the black garden ant Lasius niger.

In most eusocial insects, the division of labor results in relatively few individuals foraging for the entire colony. Thus, the survival of the colony depends on its efficiency in meeting the nutritional needs of all its members. Here, we characterize the network topology of a eusocial insect to understand the role and centrality of each caste in this network during the process of food dissemination. We constructed trophallaxis networks from 34 food-exchange experiments in black garden ants (Lasius niger). We tested the influence of brood and colony size on (i) global indices at the network level (i.e., efficiency, resilience, centralization, and modularity) and (ii) individual values (i.e., degree, strength, betweenness, and the clustering coefficient). Network resilience, the ratio between global efficiency and centralization, was stable with colony size but increased in the presence of broods, presumably in response to the nutritional needs of larvae. Individual metrics highlighted the major role of foragers in food dissemination. In addition, a hierarchical clustering analysis suggested that some domestics acted as intermediaries between foragers and other domestics. Networks appeared to be hierarchical rather than random or centralized exclusively around foragers. Finally, our results suggested that networks emerging from social insect interactions can improve group performance and thus colony fitness.

[What science can do against biodiversity loss]. / La science face à l'érosion de la biodiversité.

The earth is currently facing an unprecedented biodiversity loss, which is taking such proportions that it is sometimes considered to be the sixth mass extinction. Human activities are the main cause of this alarming ecological crisis and threaten this biodiversity yet essential to mankind. It is thus necessary to learn more about the different living species, in order to protect and preserve them. In particular, three key scientific fields give us a better insight on biodiversity and its characteristics: ecology, focusing on living species interacting with their environment; ethology, focusing on animal behaviour; and ecophysiology, linking changes at the physiological scale to environmental changes. Together, they allow us to work in favor of biodiversity, by giving us a better understanding of animal species and their ways of life, thus allowing us to act accordingly.

TITLE: La science face à l'érosion de la biodiversité. ABSTRACT: Aujourd'hui, le monde fait face à une érosion importante de sa biodiversité ; le déclin des populations animales est si important qu'il est considéré par certains comme la sixième extinction de masse de la terre. L'homme, au travers de ses actions, est la cause principale de cette crise écologique et menace une biodiversité qui lui est pourtant indispensable. Agir pour la préserver devient donc primordial et passe par une meilleure connaissance des espèces à protéger. Ainsi, la science joue un rôle essentiel, notamment via trois disciplines spécifiques : l'écologie, qui étudie les êtres vivants en relation avec leur milieu naturel, l'éthologie, axée sur le comportement animal, et l'écophysiologie, qui s'intéresse aux adaptations physiologiques des êtres vivants aux changements de leur environnement. Ensemble, celles-ci permettent d'œuvrer pour la protection de la biodiversité grâce à une meilleure compréhension des espèces animales et de leur mode de vie qui conduit à mettre en place des actions de conservation spécifiques et réfléchies.