Browsing by Subject "nestmate recognition"

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  • Huusari, Noora (Helsingin yliopisto, 2020)
    Social insects such as ants live in societies and have a strict division of labor between reproductive and worker castes. A colony can consist of even millions of individuals and the number of queens can vary a lot. Populations where each colony comprises just one or few queens are often called kin structured because the relatedness between nestmates is high. Colonies that have lots of queens and the society lives in many connected nests (polydomy) in are referred to as supercolonies. In these colonies relatedness between individuals is low and the workers represent many genetic lineages. Depending on species and the environment where the colony lives societies can behave aggressively towards individuals from other nests to protect their own nest. Ants must be able to recognize members of their own colony from the intruders to be able to protect the nest. Nestmate recognition is a key element in the interaction between nests and species and makes it possible for the workers in the colony to favour their own nestmates in form of care, defence or food acquisition to gain inclusive fitness benefits. To recognise nestmates ants must be able to sense chemical cues. Ants detect these chemical signals through the proteins expressed mainly in their antennas. In this thesis I studied gene expression of genes related to chemosensation in seven Formica species using the RT qPCR method. My study species were kin structured Formica exsecta, F. pratensis and F. fusca and supercolonial F. truncorum, F. pressilabris, F. cinerea and F. aquilonia. My study genes belong to gene families that code for odorant binding proteins (OBP), chemosensory proteins (CSP) and gustatory reseptors (GRT). I want to find out whether the expression of these genes differs between castes, and whether the caste difference varies between kin structured and supercolonial species. Workers have many tasks in the ant colony and to take care of them, they need to have a sophisticated sensory system. For that reason, I expect to find out that the study genes are expressed more in the worker than the queen caste. In addition, I expect the caste difference in gene expression to be higher in the kin structured species than in the supercolonial species. That is because kin structured species behave more aggressively towards intruders and possibly confront intruders more often than the individuals living in supercolonies. Furthermore, in the supercolonies low relatedness between individuals sometimes lead to conflicts inside the nest. For that reason, I suppose queens of the supercolonies express chemosensory genes more than the queens from the kin structured colonies. Overall expression level was the highest for the OBP and the lowest for GRT. The expression level of CSP was in between these extremes. In accordance with my hypothesis gene expression of OBP and CSP was higher in workers in all the study species. GRT expression was worker biased in six of the seven species. Caste difference in expression of chemosensory genes was similar in kin structured and supercolonial species. The expression level varied between species but did not show a pattern depending on the degree of the polygyny. The study revealed that the expression of OBP and CSP is correlated. My results revealed expected worker biased pattern in the expression. The result might be a consequence of better olfactory or taste abilities in the worker caste compared to queens or it may even be consequence of more sophisticated nestmate recognition skills of the workers. This study reveals valuable information about the gene expression of chemosensory genes related to the recognition system in the ants and awakes many new study questions. Chemical sensory system has been studied a lot in the ants, but in the field of expression studies there is still lot to reveal.
  • Hakala, Sanja M.; Ittonen, Mats; Seppä, Perttu; Helanterä, Heikki (2020)
    Abstract Understanding how social groups function requires studies on how individuals move across the landscape and interact with each other. Ant supercolonies are extreme cooperative units that may consist of thousands of interconnected nests, and their individuals cooperate over large spatial scales. However, the inner structure of suggested supercolonial (or unicolonial) societies has rarely been extensively studied using both genetic and behavioral analyses. We describe a dense supercolony-like aggregation of more than 1,300 nests of the ant Formica (Coptoformica) pressilabris. We performed aggression assays and found that, while aggression levels were generally low, there was some aggression within the assumed supercolony. The occurrence of aggression increased with distance from the focal nest, in accordance with the genetically viscous population structure we observe by using 10 DNA microsatellite markers. However, the aggressive interactions do not follow any clear pattern that would allow specifying colony borders within the area. The genetic data indicate limited gene flow within and away from the supercolony. Our results show that a Formica supercolony is not necessarily a single unit but can be a more fluid mosaic of aggressive and amicable interactions instead, highlighting the need to study internest interactions in detail when describing supercolonies.