Genetic differentiation at species level in the Neotropical army ant Labidus praedator

The nomadic, swarm-raiding army ant Labidus praedator (Smith, 1858) is an important arthropod predator in the Neotropics with a strong ecological impact on invertebrate communities. However, despite its high abundance and ubiquity over a large distribution range, it received relatively little scientific attention. Moreover, the taxonomic status is confusing because some morphological descriptions point towards the co-occurrence of several distinct taxa which are lumped together as L. praedator in most classical keys. Yet, clarifying genetic studies are lacking. Here, we show strong genetic differentiation within an L. praedator population in Mexico. Both microsatellite genotype patterns and phylogenetic analyses (concatenated nuclear and mtDNA sequences, including the coxI genetic barcoding region), reveal the occurrence of two strongly isolated lineages. Colonies from the very same location, clearly identified as the same species (L. praedator) according to classical morphological keys, exhibit an extremely high average sequence divergence (9.7–12.8 %), which was well in the range of divergence among GenBank sequences from other Labidus species. Thus, our data very likely show genetic differentiation at species level or cryptic speciation within L. praedator, which should be recognized when investigating biodiversity and ecological importance of army ants (or other arthropods) in the Neotropics.Finances were granted by the Graduate Scholarship of Saxony Anhalt (MBB) and the Mexican-European FONCICYT 94293 Grant “MUTUAL” for travel expenses.http://link.springer.com/journal/40hb2016Zoology and Entomolog

Superconductivity in the ternary ZrVGe compound

We report bulk superconductivity in ZrVGe withTc=6K determined by magnetization, electronic transport and specific heat measurements. From the analysis of magnetization and resistivity data we obtain the thermodynamic critical fieldsμ0Hc1andμ0Hc2, respectively. The heat capacity data deviate from conventional BCS theory suggesting possible unconventional superconducting behavior

Introgression asymétrique de gènes Africains dans les populations d'abeilles Apis mellifera L. du Mexique central

International audienceThe Africanization of the honeybee (Apis mellifera) in South America is one of the most spectacular examples of biological invasions. In this study, we analyzed the Africanization process in Central Mexico along an altitudinal transect from 72 to 2800 m, using both mitochondrial and nuclear DNA markers. The mitochondrial analysis revealed that the two high-altitude populations had a significantly greater percentage of African mitotypes (95%) than the three lowland populations (67%), indicating successful spreading of Africanized swarms to these altitudes. All populations (highland and lowland) had a similar overall proportion of African alleles at nuclear loci (58%). Thus, all populations showed an asymmetric introgression of African nuclear and mtDNA. Colonies with African mitotypes had, on average, significantly more African nuclear alleles (60%) than those with European mitotypes (51%). Furthermore, the three lowland populations showed clear signs of linkage disequilibrium, while the two high-altitude populations did not, indicating recent genetic introgression events into the lowland populations.L'africanisation des abeilles Apis mellifera en Amérique du sud est l'un des plus spectaculaires exemples d'invasion biologique. Nous avons analysé le processus d'africanisation dans des populations d'abeilles du Mexique central, au long d'un gradient altitudinal de 72 à 2800 mètres, sur la base de marqueurs de l'ADN nucléaire et mitochondrial. Au niveau mitochondrial, les deux populations d'altitude avaient un pourcentage de mitotypes Africains plus élevé (95%) que les trois populations de basse altitude, montrant une colonisation effective a haute altitude. Au niveau nucléaire, la proportion de gènes Africains étaient relativement constante (58%), quelque soit l'altitude. Toutes les populations présentaient donc une introgression asymétrique de gènes Africains. Cependant, les colonies au mitotype Africain présentaient plus d'allèles nucléaires Africains (60%) que les colonies au mitotype Européen (51%), et il y avait une différenciation significative entre ces populations. De plus, les populations de basse altitude montraient des signes clairs de déséquilibre de liaison, montrant des introgressions plus récente

L'expérience, mais pas la distance, influence la précision du recrutement chez l'abeille sans aiguillon, Scaptotrigona mexicana

International audienceAbstract Recruitment precision, i.e. the proportion of recruits that reach an advertised food source, is a crucial adaptation of social bees to their environment. Studies with honeybees showed that recruitment precision is not a fixed feature, but it may be enhanced by factors like experience and distance. However, little is known regarding the recruitment precision of stingless bees. Hence, in this study, we examined the effects of experience and spatial distance on the precision of the food communication system of the stingless bee Scaptotrigona mexicana. We conducted the experiments by training bees to a three-dimensional artificial patch at several distances from the colony. We recorded the choices of individual recruited foragers, either being newcomers (foragers without experience with the advertised food source) or experienced (foragers that had previously visited the feeder). We found that the average precision of newcomers (95.6±2.61%) was significantly higher than that of experienced bees (80.2±1.12%). While this might seem counter-intuitive on first sight, this “loss” of precision can be explained by the tendency of experienced recruits to explore nearby areas to find new rewarding food sources after they had initially learned the exact location of the food source. Increasing the distance from the colony had no significant effect on the precision of the foraging bees. Thus, our data show that experience, but not the distance of the food source, affected the patch precision of S. mexicana foragers.La précision du recrutement, c'est à dire la proportion de recrues trouvant une ressource alimentaire communiquée, est une adaptation cruciale des abeilles sociales à leur environnement. Les études avec les abeilles Apis mellifera ont montré que la précision n'est pas fixe, mais peut être améliorée par l'expérience ou la distance. Cependant, peu est connu à ce sujet chez les abeilles sans aiguillon. Nous avons donc examiné l'effet de l'expérience et de la distance sur la précision chez l'abeille sans aiguillon Scaptotrigona mexicana. Nous avons entraîné les abeilles sur un nourrisseur tri-dimensionnel à différentes distances de leur colonie, puis enregistré les choix des butineuses. Les butineuses novices choisissaient le nourrisseur communiqué avec une plus grande précision (95.6% ± 2.61%) que les butineuses expérimentées (80.2% ± 1.12%). Cette perte de précision pourrait s'expliquer par une tendance des butineuses expérimentées à explorer des nouvelles ressources autour d'une ressource connue. Par contre, l'augmentation de la distance à la colonie n'affecte pas la précision