Sebastian Pohl


 

 

Department Biologie II

Ludwig-Maximilians-Universität München

Großhaderner Str. 2

82152 Planegg-Martinsried

GERMANY

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Tel:  +49 (0)89 2180 74 216

Fax: +49 (0)89 2180 74 221

 

 

 

 

 

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 Nationality                                 German

 Place and Date of Birth             Idar-Oberstein, 26.05.1981

 

 Education

 2006                                            Diploma in Biology at the Albert-Ludwigs-Universität Freiburg

                                                     Topics:       Evolution and ecology

                                                                       Neurobiology / Physiology of animals

                                                                       Biochemistry

                                                                       French

                                                     Thesis title (translated):  "The influence of different factors on the production of a replacement clutch in the burying beetle

                                                                                          Nicrophorus vespilloides HERBST (Coleoptera: Silphidae)"

 2000                                            "Abitur" at the Gymnasium an der Heinzenwies, Idar-Oberstein

 

 Grants

 2010                                            Research and travel grant IRT 3 trial of the Munich Graduate Program for Evolution, Ecology and Systematics

 2009                                            Research Grant of the E. N. Huyck Preserve and Biological Research Station, Rensselaerville, NY, USA

                                                             Title:  "Host-parasite interactions in slavemaking ants and their slaves"

                                                     Research and travel grant IRT 3 trial of the Munich Graduate Program for Evolution, Ecology and Systematics

 2008                                            Research Grant of the E. N. Huyck Preserve and Biological Research Station, Rensselaerville, NY, USA

                                                             Title:  "Different fronts in the coevolutionary arms race of slavemaking ants and their hosts"

                                                     Research and travel grant IRT 3 trial of the Munich Graduate Program for Evolution, Ecology and Systematics

 2007                                            Research Grant of the E. N. Huyck Preserve and Biological Research Station, Rensselaerville, NY, USA

                                                             Title:  "Risk evaluation and decision making in slavemaking ants"

 

 Publications

 Pohl S, Foitzik S, 2011. Slave-making ants prefer larger, better defended host colonies. Animal Behaviour, 81:61-68.

 

 Presentations

 Pohl S, Foitzik S, 2011. Scouting behaviour and host worker response in slave making ants. 7th Ecology & Behaviour Meeting, Rennes

 Pohl S, Foitzik S, 2010. Raid organisation and division of labour in slave-making ants.
 13th International Behavioral Ecology Congress of the International Society for Behavioral Ecology (ISBE), Perth

 Pohl S, Foitzik S, 2010. Raid organisation and task allocation in slave-making ants.
 15th Graduate Meeting of the Section Evolutionary Biology of the German Zoological Society, Freiburg

 Pohl S, Foitzik S, 2010. Raid organisation and division of labour in slave-making ants.
 6th Ecology & Behaviour Meeting, Tours

 Pohl S, Foitzik S, 2009. Decision making and host nest choice in the slavemaking ant Protomognathus americanus.
 1st Central European Meeting of the International Union for the Study of Social Insects, Frauenchiemsee

 Pohl S, Foitzik S, 2009. Risk evaluation and decision making in slavemaking ants.
 5th Ecology & Behaviour Meeting, Lyon

 Pohl S, Foitzik S, 2009. Risk evaluation and decision making in slavemaking ants.
 14th Graduate Meeting of the Section Evolutionary Biology of the German Zoological Society, Munich

 Pohl S, Konrad M, Foitzik S, 2008. Behavioural and chemical changes in orphaned Temnothorax ant workers.
 13th Graduate Meeting of the Section Evolutionary Biology of the German Zoological Society, Hamburg

 

 Poster contributions

 Pohl S, Foitzik S, 2010. Raid organisation and division of labour in slave-making ants.
 XVI Congress of the International Union for the Study of Social Insects, Copenhagen

 Pohl S, Foitzik S, 2009. Cost-benefit evaluation and host nest choice in the slavemaking ant Protomognathus americanus.
 102nd Conference of the German Zoological Society, Regensburg

 Pohl S, Steiger S, Müller JK, 2007. On the benefit of filial infanticide in burying beetles.
 12th Graduate Meeting of the Section Evolutionary Biology of the German Zoological Society, Bayreuth

 Pohl S, Müller JK, 2006. The effect of potential risk and potential benefit on the behaviour of widowed burying beetles.
 11th International Behavioral Ecology Congress of the International Society for Behavioral Ecology (ISBE), Tours

 

 Media coverage

 Science news websites:
 BBC online
 Encyclopaedia Britannica Blog
 Bayerischer Rundfunk online

 Radio programs:
 Adelaide Breakfast, 891 ABC Adelaide

 Newspapers:
 Süddeutsche Zeitung, November 10th, 2010; available online

 

 Organization experience

 Member of the Organization Board of the
      1st Central European Meeting of the International Union for the Study of Social Insects and the
      3rd Central European Workshop in Myrmecology, Frauenchiemsee, October 8 - October 12, 2009

 

 

 

Work


 

Risk evaluation and decision making in slavemaking ants

 

Parasitism is an interesting research field as it provides a possibility to study interactions between different species and may reveal some of the mechanisms of the course of evolution. Social parasites provide the opportunity to investigate some basic questions of parasitism under controlled conditions. The term "social parasite" denominates social insects in which the members of a colony exploit the worker force of other colonies (Hölldobler and Wilson 1990). These host colonies may be formed by conspecifics or heterospecifics, but a single parasitic species often uses only one or very few species as hosts. This allows the evolution of adaptations by the parasite to improve the hosts' exploitation as well as the occurrence of counter-adaptations on the side of the hosts to lower the impact of parasites on their own colony, which may result in a coevolutionary arms race (Dawkins and Krebs 1979; Foitzik et al. 2001).
               In slavemaking ants, a whole range of different life history varieties exists, from species that only facultatively take advantage of other colonies' workers to inquiline species in which the worker caste is completely reduced and only a parasitic queen remains (Hölldobler and Wilson 1990; Brandt et al. 2005). The North American myrmicine species
Protomognathus americanus is an obligate, dulotic social parasite (Wesson 1939). During the whole colony life cycle, it relies on slaves of the genus Temnothorax: T. longispinosus, T. curvispinosus and T. ambiguus. The slavemaker colonies are small; beside the queen, a single colony comprises a mean number of four to five slavemaker workers and 30 slaves (Herbers and Foitzik 2002). They can be found in hollow acorns, twigs and hickory nuts on the ground of mixed deciduous forests in the northeast of the United States and the adjacent Canadian regions. A young, mated slavemaker queen enters a host colony and kills or expels the resident queen and adult workers, whereas the host pupae are allowed to hatch. Freshly emerged workers are imprinted on the intruder and perform ordinary tasks like foraging or brood care. Slavemaker workers, in contrast, are specializing in raiding new host colonies to keep supplies of new slaves coming and thus securing the survival of the colony. A quite similar host-parasite system exists in European forests. The parasitic myrmicine Harpagoxenus sublaevis depends on the worker force of its host species Leptothorax acervorum and L. muscorum. Unlike in the North American slavemaker species, the nests of H. sublaevis contain on average more than 20 slavemaker workers and more than 75 slaves (Buschinger 1966; Buschinger 1974; Fischer and Foitzik 2004).
               When a slavemaker colony is in need of new slaves, some slavemaker workers, the so called "scouts", leave the nest and look for a nearby host colony. Having found a nest of one of the host species, a scout may enter the host nest before returning to her own nest and recruiting other workers by tandem-running. When the number of recruited workers is large enough, they start to attack the host colony, kill or expel the host workers and transport the pupae and larvae to their own nest (Wesson 1939). The host workers on their part defend their brood and often immobilize and kill attacking slavemaker workers. Therefore, the scouts should weigh the potential benefit they may gain in the form of raided larvae and pupae against the potential risk of losing nestmates due to the hosts' defense before they start recruiting. The ability to estimate the consequences of an attack will be particularly necessary if a single scout discovers two different host nests before she returns to her own nest, allowing her to recruit her nestmates to the host nest which provides the highest benefit-per-cost ratio. Additionally, when two scouts find two different host nests, they have to exchange their information in order to come to a decision whether and which nest to raid. Studies on decision making in social insects focused mainly on the nest finding behavior in ants and honey bees. In slavemaking ants, the slave raids additionally contain a risk component that is not present in nest site choices, as large host nest are able to injure or kill attacking slavemaking workers. Hence, the study of dulotic social parasites offers new possibilities to investigate the process of collective decision making in insects.
               In my PhD thesis, I want to study the mechanisms of risk evaluation and decision making in slavemaking ants. To conduct a successful slave raid, the slavemakers have to make several decisions. Firstly, they have to note a need of new slaves to start the search for new host nests. Possible factors leading to the onset of this behavior may be that the number of slaves reaches a lower threshold, or that the slavemaker : slave ratio exceeds the tolerable limits. When a scout then left its nest and found a host colony, it will be of particular interest which demographic factors of the host nest influence the scout's decision whether this nest is worth to be raided or not and how this information is gained. Does she decide on the basis of the potential benefit, e.g. the number of host brood item that may be stolen, or the number of defending host workers which are responsible for the potential costs of a slave raid by means of killed slavemaker workers, or does she take both elements into account, computing the ratio of both factors? Are chemical cues inside the host nest sufficient transmitters of information to the scout or does she need additional tactile contacts to get a picture of the situation inside the host nest? It will be interesting to compare the decisions of the North American social parasite
Protomognathus americanus with those of its European counterpart Harpagoxenus sublaevis. Protomognathus americanus colonies comprise fewer slavemaker workers than the nests of H. sublaevis, so I suggest that the former will show a rather risk-avoiding strategy compared to the latter, as a loss of some slavemaker workers in fights with the defending host workers has a greater impact on the fitness of the smaller nests of the American social parasite. Finally, before a slave raid can be started, the scouts have to recruit other slavemaker workers to the host nest. I want to gain insight into the process from individual information to collective decision making. Which mechanisms, chemical or tactile ones, are used to transmit the information about the chosen host nest? Are cuticular hydrocarbons or gland secretions involved in this process? Additionally, I want to know how an unambiguous decision will be reached if two scouts discovered two different host nests.

 

A worker of Harpagoxenus sublaevis.

A worker of Protomognathus americanus.

Y-shaped raiding arena with three artificial nest sites.
A: Position of the slavemaker's nest. B, C: Position of the host nests.