Evolutionary Game Theory and the Adaptive Dynamics Approach: Adaptation where Individuals Interact

Evolutionary game theory and the adaptive dynamics approach have made invaluable contributions to understand how gradual evolution leads to adaptation when individuals interact. Here, we review some of the basic tools that have come out of these contributions to model the evolution of quantitative traits in complex populations. We collect together mathematical expressions that describe directional and disruptive selection in class- and group-structured populations in terms of individual fitness, with the aims of bridging different models and interpreting selection. In particular, our review of disruptive selection suggests there are two main paths that can lead to diversity: (i) when individual fitness increases more than linearly with trait expression; (ii) when trait expression simultaneously increases the probability that an individual is in a certain context (e.g. a given age, sex, habitat, size or social environment) and fitness in that context. We provide various examples of these and more broadly argue that population structure lays the ground for the emergence of polymorphism with unique characteristics. Beyond this, we hope that the descriptions of selection we present here help see the tight links among fundamental branches of evolutionary biology, from life-history to social evolution through evolutionary ecology, and thus favour further their integration

Life history and mutation rate joint evolution

The cost of germline maintenance gives rise to a trade-off between lowering the deleterious muta-tion rate and investing in life history functions. Therefore, life history and the mutation rate evolve jointly, but this coevolution is not well understood. We develop a mathematical model to analyse the evolution of resource allocation traits affecting simultaneously life history and the deleterious mutation rate. First, we show that the invasion fitness of such resource allocation traits can be approximated by the basic reproductive number of the least-loaded class; the expected lifetime pro-duction of offspring without deleterious mutations born to individuals without deleterious mutations. Second, we apply the model to investigate (i) the joint evolution of reproductive effort and germline maintenance and (ii) the joint evolution of age-at-maturity and germline maintenance. This analysis provides two biological predictions. First, under higher exposure to environmental mutagens (e.g. oxygen), selection favours higher allocation to germline maintenance at the expense of life history. Second, when exposure to environmental mutagens is higher, life histories tend to be faster with individuals having shorter life spans and smaller body sizes at maturity. Our results suggest that mutation accumulation via the cost of germline maintenance is a major force shaping life-history traits

Evolutionary Game Theory and the Adaptive Dynamics Approach: Adaptation where Individuals Interact

Evolutionary game theory and the adaptive dynamics approach have made invaluable contributions to understand how gradual evolution leads to adaptation when individuals interact. Here, we review some of the basic tools that have come out of these contributions to model the evolution of quantitative traits in complex populations. We collect together mathematical expressions that describe directional and disruptive selection in class- and group-structured populations in terms of individual fitness, with the aims of bridging different models and interpreting selection. In particular, our review of disruptive selection suggests there are two main paths that can lead to diversity: (i) when individual fitness increases more than linearly with trait expression; (ii) when trait expression simultaneously increases the probability that an individual is in a certain context (e.g. a given age, sex, habitat, size or social environment) and fitness in that context. We provide various examples of these and more broadly argue that population structure lays the ground for the emergence of polymorphism with unique characteristics. Beyond this, we hope that the descriptions of selection we present here help see the tight links among fundamental branches of evolutionary biology, from life-history to social evolution through evolutionary ecology, and thus favour further their integration

New insights on the role of ecology and life-history in social evolution

Biological altruism, defined as a behaviour that benefits others at an apparent cost to the focal individual, is found abundantly across different levels of biological organization. While kin selection has been useful for explaining both cooperation and conflict in specialized cooperative societies, more theoretical work has to be done to develop models for realistic ecological and life-history contexts. This thesis aims to fill this gap by providing several new insights on the role of ecology and life-history in various social systems. Firstly, I propose a model that incorporates realistic ecological mechanisms of population regulation and study how different population regulation mechanisms affect the evolution of helping behaviour. I show that nest-site limitation strongly favours evolution of helping behaviour even if the helpers are relatively inefficient. I also find that interactions between density dependent mechanisms and life-history traits affect the evolution of social behaviour. Secondly, I consider a resource allocation model for eusocial insect colonies that incorporates the dynamics of colony growth and the conflict between the queen and the workers over the sex ratio. I show that conflict over sex allocation gives rise to a suboptimal pattern of colony growth, while the queen wins the sex allocation conflict. Thirdly, I study optimal reproductive tactics in facultatively cooperative wasps. I show that co-foundress nests and costly helping can evolve even with a low average relatedness between co-foundresses, but only during the initial stages of the nesting cycle. Costly helping during the reproductive phase can only evolve if the relatedness between co-foundresses is high. In conclusion, this thesis demonstrates the importance of considering ecological and life-history aspects in the study of social interactions from early stages of helping behaviour to resolving conflicts in eusocial insect colonies

No Synergy Needed: Ecological Constraints Favor the Evolution of Eusociality

In eusocial species, some individuals sacrifice their own reproduction for the benefit of others. It has been argued that the evolution of sterile helpers in eusocial insects requires synergistic efficiency gains through cooperation that are uncommon in cooperatively breeding vertebrates and that this precludes a universal ecological explanation of social systems with alloparental care. In contrast, using a model that incorporates realistic ecological mechanisms of population regulation, we show here that constraints on independent breeding (through nest-site limitation and dispersal mortality) eliminate any need for synergistic efficiency gains: sterile helpers may evolve even if they are relatively inefficient at rearing siblings, reducing their colony’s per-capita productivity. Our approach connects research fields by using hypotheses developed for cooperative breeding to explain the evolution of eusociality. The results suggest that these hypotheses may apply more generally than previously thought.peerReviewe

Role of Phosphatidic Acid in the Coupling of the ERK Cascade*S⃞

The production of phosphatidic acid plays a crucial role in the activation of the ERK cascade. This role was linked to the binding of phosphatidate to a specific polybasic site within the kinase domain of Raf-1. Here we show that phosphatidate promotes ERK phosphorylation in intact cells but does not activate Raf in vitro. The kinase suppressor of Ras (KSR) contains a sequence homologous to the phosphatidate binding site of Raf-1. Direct binding of phosphatidate to synthetic peptides derived from the sequences of the binding domains of Raf-1 and KSR was demonstrated by spectroscopic techniques. The specificity of these interactions was confirmed using synthetic lipids and mutated peptides in which the core of the phosphatidic acid binding domain was disrupted. Insulin and exogenous dioleoyl phosphatidate induced a rapid translocation of a mouse KSR1-EGFP construct to the plasma membrane of HIRcB cells. Mutation of two arginines located in the core of the putative phosphatidate binding site abolished dioleoyl phosphatidate- and insulin-induced translocation of KSR1. Overexpression of the mutant KSR1 in HIRcB cells inhibited insulin-dependent MEK and ERK phosphorylation. The addition of dioleoyl phosphatidate or insulin increased the co-localization of KSR1 and H-Ras and promoted the formation of plasma membrane patches enriched in both proteins and phosphatidic acid. These results, in conjunction with our previous work, suggest the formation of phosphatidate-enriched membrane microdomains that contain all components of the ERK cascade. We propose that these domains act as molecular scaffolds in the coupling of signaling events