Genetic basis of behavior in Temnothorax ants
Date issued
Authors
Editors
Journal Title
Journal ISSN
Volume Title
Publisher
License
Abstract
The transition to parasitism is a drastic lifestyle shift, characterized by rapid changes in gene structure, function, and expression. Combined with the co-evolutionary arms races common to parasite-host systems, recently-evolved or evolutionarily-'young' parasitic species represent an ideal system for elucidating the molecular underpinnings of parasite- and host-specific behavioral phenotypes. The repeated evolution of social parasitism and slavery among Temnothorax ants allows us to examine the molecular patterns characterizing the raiding phenotypes of slavemaking species within this taxon, as well as reciprocal host defensive phenotypes against their slavemakers. Previous studies of Temnothorax provide behavioral and chemical evidence for reciprocal adaptations between parasite and host, as well as diverging raiding strategies between slavemakers. Utilizing transcriptomics, gene expression, and selection analyses, we reveal that the slavemaker raiding phenotype and host response to these attacks are characterized largely by species-specific molecular patterns. Moreover, only a small number of genes share expression or selection patterns between slavemaking species. A number of candidate genes for slavemaker raiding behavior were identified, including Tyrpsin-7, Trypsin Inhibitor, and painless. Experimental down-regulation of Trypsin Inhibitor via RNAi resulted in an altered slave raiding pattern, shedding some light onto the role that single genes can play within complex behavioral phenotypes. Finally, an additional transcriptomic experiment investigated the molecular similarity between the externally-analogous slavemaker raiding recruitment and host tandem-running behavior of Temnothorax ants. We detected a number of genes differentially expressed in the brains of scouting and tandem-running individuals that are known to be involved in learning and memory formation in other insects. As such, our findings here reinforce previous conclusions: that molecular-specificity underlies externally similar behaviors. Taken together, the findings presented here suggest that Temnothorax slavemakers and hosts are on species-specific rather than convergent evolutionary trajectories, and that the evolution of social parasitism even among closely-related species may be reached in diverse ways.