The evolution of social traits and biodiversity in the ants.

Cooperation has shaped the evolution of life on Earth. The ants are the most numerically diverse of the eusocial Hymenoptera, and display wide variation in social complexity. This positions the ants as an ideal taxon in which to study social evolution in a comparative framework. Social evolution theory has generated many hypotheses that are testable in ants, however the lack of comprehensive or complete phylogenies, and the decentralised and scattered nature of trait data, has been an obstacle to these types of study. In this thesis I construct a large species-level, and a complete genus-level, phylogeny of the ants, and draw together a large dataset of social traits from the literature in order to test hypotheses concerning the evolution of social traits in the ants. I find evidence that the earliest ant was large bodied, and lived in small highly related colonies. I show that group size is a significant trait in the evolution of sociality in ants, predicting the probability of a species having polymorphic workers, or of being polyandrous. I also show that the change in these traits is correlated between ancestral nodes on the phylogeny. Furthermore, in the Attini, colony size correlates closely with non-reproductive and reproductive division of labour. Together these results cement group size as a driving force of social evolution in the ants, and this has interesting implications for social evolution in general. Finally, I report the first evidence that intermediate colony sizes, the presence of discrete worker castes and polygyny are associated with increased diversification rates in ants. This thesis provides a valuable tool for the study of comparative hypotheses in the ants in the form of a complete genus-level phylogeny, and offers significant evidence to support several key hypotheses in social evolution. Furthermore, these results generate hypotheses regarding the evolution of social traits for future research.

Name dc:type.qualificationname

phd

Level dc:type.qualificationlevel

doctoral

Grantor dc:publisher.institution

University of East Anglia

Year dc:date.issued

2014

Author dc:creator

• Ferguson-Gow, Henry

Language dc:language

en