International Union for the Study of Social Insects (IUSSI2018), August 5-10, 2018 in Guarujá, Brazil.

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Direct fitness of workers in a Temnothorax ant

Author(s):
Julia Giehr, Julia Giehr , Jürgen Heinze
Institution(s):
Department of Zoology/Evolutionary Biology, University of Regensburg, Regensburg, Germany; Department of Zoology/Evolutionary Biology, University of Regensburg, Regensburg, Germany ; Department of Zoology/Evolutionary Biology, University of Regensburg, Regensburg, Germany
Sociality evolved several times throughout the history of life, but the degree of cooperation and altruism varies among taxa. Hamilton’s theory of inclusive fitness provides the fundament of our understanding of social evolution. It suggests that an individual’s fitness consists of its own reproductive success (direct fitness) and the additional offspring its relatives can produce because of the help provided by the individual, weighted by the relatedness between helper and recipient (indirect fitness). In cooperatively breeding birds and mammals, the experience, safety, and resources gained by non-reproductive helpers might result in an increased direct fitness when they themselves start to produce offspring later in live. In contrast, helpers in eusocial Hymenoptera (e.g., bees and ants), are usually not capable of mating and do normally not gain direct fitness by replacing a fully fertile queen. However, they are often capable of producing unfertilized eggs in the absence of a reproductive. How important these direct fitness benefits are has rarely been quantified. Previous studies in the monogynous ant Temnothorax crassispinus revealed that after the loss or death of the queen workers form a hierarchy, in which the highest-ranking workers gain direct fitness by producing sons under laboratory conditions. Our current study shows that many workers in both queenright and queenless natural colonies have elongated ovaries with eggs in development. Microsatellite analyses revealed that a considerable proportion of males in queenright colonies are not produced by the queen. Currently, we compare whether queen- and worker-produced males differ in fitness-relevant aspects. So far our findings reveal a considerable direct fitness component for workers of this species under natural conditions.Supported by DFG (He 1623/39)
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