Deconstructing collective building in social insects : implications for ecological adaptation and evolution

Funding: John Templeton Foundation as part of the research collaboration grant “Putting the extended evolutionary synthesis to the test” (Grant no. 60501).Nests built by eusocial insect species are often complex structures consisting of multiple effectively integrated and functionally distinct substructures. Stigmergy, self-assembly and self-organisation have been proposed as the mechanisms that translate simple individual behaviour into coordinated collective activity. Here, we consider these processes focusing on their implications for the generation of new structures, nest adaptiveness and the evolution of building rules. We discuss in particular how self-organisation and stigmergy may guide the shift between substructures during building and generate new elements, either as an indirect result of building rule sets evolved for other purposes and under direct selection. The same mechanisms generate local, short-term adaptation through exploration of the phenotype space of the construction. Finally, we introduce the hypothesis that feedback dynamics create evolutionary transition between collective level phenotypes when mutations arise in the worker line, thus facilitating colony survival and affecting the evolution of collective building rules and of nest shape. This smooth transition is possible only when the new and the old rule variant are compatible. We call for new research that investigates self-organisation in collective building from an evolutionary perspective.Publisher PDFPeer reviewe

Large-scale profiling of noncoding RNA function in yeast

Noncoding RNAs (ncRNAs) are emerging as key regulators of cellular function. We have exploited the recently developed barcoded ncRNA gene deletion strain collections in the yeast Saccharomyces cerevisiae to investigate the numerous ncRNAs in yeast with no known function. The ncRNA deletion collection contains deletions of tRNAs, snoRNAs, snRNAs, stable unannotated transcripts (SUTs), cryptic unstable transcripts (CUTs) and other annotated ncRNAs encompassing 532 different individual ncRNA deletions. We have profiled the fitness of the diploid heterozygous ncRNA deletion strain collection in six conditions using batch and continuous liquid culture, as well as the haploid ncRNA deletion strain collections arrayed individually onto solid rich media. These analyses revealed many novel environmental-specific haplo-insufficient and haplo-proficient phenotypes providing key information on the importance of each specific ncRNA in every condition. Co-fitness analysis using fitness data from the heterozygous ncRNA deletion strain collection identified two ncRNA groups required for growth during heat stress and nutrient deprivation. The extensive fitness data for each ncRNA deletion strain has been compiled into an easy to navigate database called Yeast ncRNA Analysis (YNCA). By expanding the original ncRNA deletion strain collection we identified four novel essential ncRNAs; SUT527, SUT075, SUT367 and SUT259/691. We defined the effects of each new essential ncRNA on adjacent gene expression in the heterozygote background identifying both repression and induction of nearby genes. Additionally, we discovered a function for SUT527 in the expression, 3’ end formation and localization of SEC4, an essential protein coding mRNA. Finally, using plasmid complementation we rescued the SUT075 lethal phenotype revealing that this ncRNA acts in trans. Overall, our findings provide important new insights into the function of ncRNAs

Building models : developing the behavioural model of <i>Temnothorax</i> collective wall building to study the evolutionary robustness of self-organised algorithms

This thesis focuses on wall building behaviour in Temnothorax ants as a case study of self-organised collective behaviour. It contains a progressing series of research packages, building towards one evolutionary question: how eusocial insect nest building algorithms successfully make the transition between two rule variants. I start by revising the existent behavioural model of Temnothorax wall building. By replicating the original agent-based model, I identify two issues: 1. the behavioural model performs poorly in conditions of low building material availability; and 2. the behavioural model lacks behavioural termination. I then introduce a revised version of the behavioural model (the gradual model) in which high stone density at building sites triggers a decrease in building activity, eventually leading to behavioural termination. I then compare the fit of both models to empirical data using laboratory observations of T. rugatulus wall building, applying a hidden Markov model framework to interpret the data. The gradual model provides the best match to the observed data. Finally, I use the revised model to test, in an agent-based model setting, how wall quality responds to different types of inter-worker variation in the building rule used: the presence of a mutant variant spreading within the colony; the co-existence of multiple variants; and widespread epigenetic individual variation. I find wall quality to be very robust to nearly any degree and frequency of variants. With additional simulations, I identify the two key elements of the building algorithm that provide robustness: the positive feedback effect, co-localising worker effort despite starting individual variation; and the existence of an area of overlap where activity occurs with high frequency under all variants (a buffer zone). I predict that these two components have been under selection for evolvability in wall building Temnothorax ants."This work was supported by the John Templeton Foundation as part of the research programme 'Putting the Extended Evolutionary Synthesis to the test' [grant number 60501]. EI’s training and conference travels were partially supported by the Santander-St Leonard’s College Research Mobility Scholarship and by the Sir Ken Murray Endowment Fund." --Fundin

Identifying cues for self-organised nest wall building behaviour in the rock ant, Temnothorax rugatulus

Seeking empirical support for the behavioural model of Temnothorax collective wall building. Analysis of laboatory data