@article{RoemerRoces2014,
  author    = {R{\"o}mer, Daniela and Roces, Flavio},
  title     = {Nest Enlargement in Leaf-Cutting Ants: Relocated Brood and Fungus Trigger the Excavation of New Chambers},
  doi       = {10.1371/journal.pone.0097872},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-112860},
  year      = {2014},
  abstract  = {During colony growth, leaf-cutting ants enlarge their nests by excavating tunnels and chambers housing their fungus gardens and brood. Workers are expected to excavate new nest chambers at locations across the soil profile that offer suitable environmental conditions for brood and fungus rearing. It is an open question whether new chambers are excavated in advance, or will emerge around brood or fungus initially relocated to a suitable site in a previously-excavated tunnel. In the laboratory, we investigated the mechanisms underlying the excavation of new nest chambers in the leaf-cutting ant Acromyrmex lundi. Specifically, we asked whether workers relocate brood and fungus to suitable nest locations, and to what extent the relocated items trigger the excavation of a nest chamber and influence its shape. When brood and fungus were exposed to unfavorable environmental conditions, either low temperatures or low humidity, both were relocated, but ants clearly preferred to relocate the brood first. Workers relocated fungus to places containing brood, demonstrating that subsequent fungus relocation spatially follows the brood deposition. In addition, more ants aggregated at sites containing brood. When presented with a choice between two otherwise identical digging sites, but one containing brood, ants' excavation activity was higher at this site, and the shape of the excavated cavity was more rounded and chamber-like. The presence of fungus also led to the excavation of rounder shapes, with higher excavation activity at the site that also contained brood. We argue that during colony growth, workers preferentially relocate brood to suitable locations along a tunnel, and that relocated brood spatially guides fungus relocation and leads to increased digging activity around them. We suggest that nest chambers are not excavated in advance, but emerge through a self-organized process resulting from the aggregation of workers and their density-dependent digging behavior around the relocated brood and fungus.},
  language  = {en}
}
@misc{Wenzel2011,
  type      = {Master Thesis},
  author    = {Wenzel, Frank},
  title     = {Smell and repel: Resin based defense mechanisms and interactions between Australian ants and stingless bees},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-65960},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year      = {2011},
  abstract  = {Bees are subject to permanent threat from predators such as ants. Their nests with large quantities of brood, pollen and honey represent lucrative targets for attacks whereas foragers have to face rivalry at food sources. This thesis focused on the role of stingless bees as third party interactor on ant-aphid-associations as well as on the predatory potential represented by ants and defense mechanisms against this threat. Regular observations of an aphid infested Podocarpus for approaching stingless bees yielded no results. Another aim of this thesis was the observation of foraging habits of four native and one introduced ant species for assessment of their predatory potential to stingless bees. All species turned out to be dietary balanced generalists with one mostly carnivorous species and four species predominantly collecting nectar roughly according to optimal foraging theory. Two of the species monitored, Rhytidoponera metallica and Iridomyrmex rufoniger were considered potential nest robbers. As the name implies, stingless bees lack the powerful weapon of their distant relatives; hence they specialized on other defense strategies. Resin is an important, multipurpose resource for stingless bees that is used as material for nest construction, antibiotic and for defensive means. For the latter purpose highly viscous resin is either directly used to stick down aggressors or its terpenic compounds are included in the bees cuticular surface. In a feeding choice experiment, three ant species were confronted with the choice between two native bee species - Tetragonula carbonaria and Austroplebeia australis - with different cuticular profiles and resin collection habits. Two of the ant species, especially the introduced Tetramorium bicarinatum did not show any preferences. The carnivorous R. metallica predominantly took the less resinous A. australis as prey. The reluctance towards T. carbonaria disappeared when the resinous compounds on its cuticle had been washed off with hexane. To test whether the repulsive reactions were related to the stickiness of the resinous surface or to chemical substances, hexane extracts of bees' cuticles, propolis and three natural tree resins were prepared. In the following assay responses of ants towards extract treated surfaces were observed. Except for one of the resin extracts, all tested substances had repellent effects to the ants. Efficacy varied with the type of extract and species. Especially to the introduced T. bicarinatum the cuticular extract had no effect. GCMS-analyses showed that some of the resinous compounds were also found in the cuticular profile of T. carbonaria which featured reasonable analogies to the resin of Corymbia torelliana that is highly attractive for stingless bees. The results showed that repellent effects were only partially related to the sticky quality of resin but were rather caused by chemical substances, presumably sesqui- and diterpenes. Despite its efficacy this defense strategy only provides short time repellent effects sufficient for escape and warning of nest mates to initiate further preventive measures.},
  subject      = {Stachellose Biene},
  language  = {en}
}
@phdthesis{Geissler2008,
  author    = {Geissler, Oliver},
  title     = {Der Informationsfluss bei der Futtersuche von Ameisen : Spezielle Kommunikationsstrategien von Blattschneiderameisen und nektarsammelnden Ameisen},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-28878},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year      = {2008},
  abstract  = {Die komplexen Aktivit{\"a}tsmuster w{\"a}hrend der Futtersuche bei Ameisen sind kein Resultat einer einfachen Selbstorganisation mit starren Regeln sind, sondern diese Regeln werden vielmehr permanent durch den Informationsaustausch zwischen den Arbeiterinnen modifiziert. Die Furagier{\"o}kologie hat vor allem einen Einfluss auf die Rekrutierungsstrategie der Tiere. Blattschneiderameisen furagieren an großen und stabilen Nahrungsressourcen auf diese sie nach dem Auffinden sofort stark rekrutieren. Camponotus rufipes besucht hingegen Futterquellen, die in ihrer Ergiebigkeit schlecht vorhersagbar sind. Daher steigern die Tiere ihre Rekrutierungsintensit{\"a}t erst nachdem sie sich durch mehrmaliges Aufsuchen der Futterquelle von deren Best{\"a}ndigkeit {\"u}berzeugt haben.},
  subject      = {Nahrungserwerb},
  language  = {de}
}
@phdthesis{Endler2006,
  author    = {Endler, Annett},
  title     = {Regulation of reproductive division of labor in the ant Camponotus floridanus : behavioral mechanisms and pheromonal effects},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-18872},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year      = {2006},
  abstract  = {A hitherto unresolved problem is how workers are prevented from reproducing in large insect societies. The queen informs about her fertility and health which ensures sufficient indirect fitness benefits for workers. In the ant Camponotus floridanus, I found such a signal located on eggs of highly fertile queens. Groups of workers were regularly provided with different sets of brood. Only in groups with queen eggs workers refrain from reproducing. Thus, the eggs seem to inform the workers about queen presence. The signal on queen eggs is presumably the same that enables workers to distinguish between queen and worker-laid eggs, latter are destroyed by workers. Queen and worker-laid eggs differ in their surface hydrocarbons in a similar way as fertile queens differ from workers in the composition of their cuticular hydrocarbons. When I transferred hydrocarbons from the queen cuticle to worker eggs the eggs were no longer destroyed, indicating that they now carry the signal. These hydrocarbons thus represent a queen signal that regulates worker reproduction in this species. But the signal is not present in all fertile queens. Founding queens with low egg-laying rates differ in the composition of cuticular hydrocarbons from queens with high productivity. Similar differences in the composition of surface hydrocarbons were present on their eggs. The queen signal develops along with an increasing fertility and age of the queen, and this is perceived by the workers. Eggs from founding queens were destroyed like worker eggs. This result shows that founding queens lack the appropriate signal. In these little colony foundations chemical communication of queen status may not be necessary to prevent workers from reproducing, since workers may benefit more from investing in colony growth and increased productivity of large colonies rather than from producing male eggs in incipient colonies. If the queen is missing or the productivity of the queen decreases, workers start laying eggs. There is some evidence from correlative studies that, under queenless conditions, worker police each other because of differences in individual odors as a sign of social status. It can be expressed as either aggressive inhibition of ovarian activity, workers with developed ovaries are attacked by nest-mates, or destruction by worker-laid eggs. I found that in C. floridanus workers, in contrast to known studies, police only by egg eating since they are able to discriminate queen- and worker-laid eggs. Workers with developed ovaries will never attacked by nest-mates. This is further supported by qualitative and quantitative differences in the cuticular hydrocarbon profile of queens and workers, whereas profiles of workers with and without developed ovaries show a high similarity. I conclude that workers discriminate worker eggs on the basis of their hydrocarbon profile, but they are not able to recognize egg-laying nest-mates. Improving our knowledge of the proximate mechanisms of the reproductive division of labor in evolutionary derived species like C. floridanus will help to understand the evolution of extreme reproductive altruism involving sterility as a characteristic feature of advanced eusocial systems.},
  subject      = {Camponotus floridanus},
  language  = {en}
}