The importance of recognition and aggression in the coevolution between ant social parasites and their hosts
Loading...
Files
Date issued
Authors
Editors
Journal Title
Journal ISSN
Volume Title
Publisher
Reuse License
Abstract
In my dissertation I investigate host defense and parasite offense strategies in different species of Temnothorax slavemaking ants (social parasites) and their hosts. The thesis is mainly divided into two parts: (1) The evolution of host defense behaviors in relation to parasite pressure and (2) The evolution of slavemaker counter-adaptations. Temnothorax host colonies are able to recognize the slavemaker T. americanus as a threat and respond with high aggression towards it. During raids, having recent contact with a slavemaker worker yields fitness benefits, but only for those colonies that have a high aggressive potential. Hence, Temnothorax hosts are able to utilize information of an upcoming attack to better defend themselves, when being aggressive (Chapter 1). But this was only true for aggression towards conspecifics – baseline aggression - which was moreover positively related to parasite abundance in a population. This indicates that parasites select for more aggressive host colonies. The correlation was found for two host species of T. americanus, pointing to convergent evolution of aggression as a defense strategy (Chapter 2). Aggression towards a living and potentially manipulative parasite decreased with parasite pressure, instead host colonies switched to an alternative defense mechanism – evacuation (Chapter 3). Populations that were less aggressive towards the parasite were also less resistant to chemical manipulation and slavemakers benefitted from it, as the likelihood of parasite survival and the parasites abundance increased (Chapter 4). One of the three slavemaker species evolved a different strategy – chemical camouflage – to steal adult host ants, known as eudulosis (Chapter 5-6). Hosts of this slavemaker do recognize the two slavemaker species T. americanus and T. duloticus, but are unable to identify their sympatric slavemaker T. pilagens. However, if they do recognize the slavemaker, aggression is costly as most workers die during raids, and evacuation although utilized in confrontations with T. americanus, seems to not be employed during raids of T. pilagens (Chapter 6). The three slavemaker species, although of different evolutionary origin, moreover show convergent evolution of a specific chemical profile that may undermine host recognition (Chapter 7).
We detected an intricate suite of adaptations and counter-adaptations in Temnothorax hosts and slavemakers. I aimed to shed light on the diverse roles of recognition and aggression within this system and found evidence for convergent evolution of both, possibly due to their similar lifestyles of slavemakers and hosts, respectively. Studying different host populations with differences in reciprocal selection, based on variation in parasite abundance, allowed for the elucidation of the selective forces that shape host behavior. Comparing different slavemaker species within the same genus, each representing different origins of slavery and evolutionary age, moreover allows delineating trends in the evolution of parasitic lifestyle.