title: Lethal combat over limited resources: testing the importance of competitors and kin.
abstract: Although most animals employ strategies to avoid costly escalation of conflict, the limitation of critical resources may lead to extreme contests and fatal fighting. Evolutionary theories predict that the occurrence and intensity of fights can be explained by resource value and the density and relatedness of competitors. However, the interaction between these factors and their relative importance often remains unclear; moreover, few systems allow all variables to be experimentally investigated, making tests of these theoretical predictions rare. Here, we use the parasitoid waspMelittobiato test the importance of all these factors. In contrast to predictions, variation in contested resource value (female mates) and the relatedness of competitors do not influence levels of aggression. However, as predicted, fight intensity increased with competitor density and was not influenced by the greater cost of fighting at high density. Our results suggest that in the absence of kin recognition, indirectly altruistic behavior (spite) is unlikely to evolve, and in such circumstances, the scale of competition will strongly influence the amount of kin discrimination in the form of level of aggression as observed inMelittobiaspecies.
authors.affiliation: Institute of Evolutionary Biology, School of Biological Sciences, University of Edinburgh, EH9 3JT, UK.
authors.forename: Tabitha M
authors.initials: TM
authors.lastname: Innocent
authors.affiliation: Institute of Evolutionary Biology, School of Biological Sciences, University of Edinburgh, EH9 3JT, UK ; Department of Zoology, University of Oxford, OX1 3PS, UK.
authors.forename: Stuart A
authors.initials: SA
authors.lastname: West
authors.affiliation: Institute of Evolutionary Biology, School of Biological Sciences, University of Edinburgh, EH9 3JT, UK.
authors.forename: Jennifer L
authors.initials: JL
authors.lastname: Sanderson
authors.affiliation: Institute of Evolutionary Biology, School of Biological Sciences, University of Edinburgh, EH9 3JT, UK.
authors.forename: Nita
authors.initials: N
authors.lastname: Hyrkkanen
authors.affiliation: Institute of Evolutionary Biology, School of Biological Sciences, University of Edinburgh, EH9 3JT, UK ; Institute of Immunology and Infection Research, School of Biological Sciences, University of Edinburgh, EH9 3JT, UK.
authors.forename: Sarah E
authors.initials: SE
authors.lastname: Reece
keywords: Melittobia; fatal fighting; kin discrimination; relatedness; resource competition; spite