Research

Costs and benefits of facultative sex

The theory on the evolution of sex is quite mature, with many benefits and costs of sexual reproduction now identified. Less resolved is the prevalence of obligate sex in the face of facultative sex – theory and experiments predict that facultative sex is often the best strategy, but obligate sex is still ubiquitous among multicellular eukaryotes. What explains this conundrum? This is the current focus of my work, with Hanna Kokko and Yagmur Erten. I work on the short-term effects in the interaction between facultative and obligate sexuals, and on the larger-scale evolution of facultatively sexual organisms’ life-histories.

Endosymbiosis and the evolutionary transitions in individuality

The evolution of life, from molecular replicators to human societies, can be viewed as a sequence of diversifications punctuated by major events known as evolutionary transitions in individuality. In each of these transitions, initially autonomous – and potentially unrelated – individuals come together over evolutionary time to give rise to a more complex, higher-level entity. I am interested in understanding – both in these historical cases and more abstractly – the factors that lead to the emergence of higher levels of individuality. Eukaryogenesis is a prototypical example of a between-species transition, and endosymbiosis, more generally, is central to the origins of many complex biological systems. Why do only some symbioses undergo a full transition, and how does the host-symbiont relationship change during this process? During my master’s thesis, together with Chaitanya Gokhale and Pete Czuppon, I studied the evolution of the traits underlying two emergent collective-level properties of an endosymbiosis: host and symbiont survival as a collective (“mutual dependence”) and the level of synchronised reproduction (“reproductive cohesion”). Our results shed light on three aspects of endosymbioses: coevolution between the host and symbiont, coevolution between dependence and cohesion, and ultimately on the opportunity of undergoing an evolutionary transition.

The results of this work can be found in this paper:
Gaurav S. Athreya , Peter Czuppon, Chaitanya S. Gokhale. The evolution of dependence and cohesion in incipient endosymbioses. The American Naturalist (2025). https://doi.org/10.1086/737588

Antibiotic-mediated interactions and stability in microbial communities

Classic theories of ecology predict that the coexistence of species in a diverse community requires axes along which each pair is different, for example in terms of resource usage. Microbial communities are interesting in this respect since they are incredibly speciose, and it is difficult to imagine that no two strains compete over even one resource. Moreover, it is known that microbes in such communities are antagonistic towards each other, which should imply fewer species. So why is there coexistence? Questions framed as a “diversity paradox” like above have been around for a long time, and many bodies of work have arisen as potential resolutions, such as those focused on the effects of migration, eco-evolutionary feedbacks, priority effects, etc. An especially interesting one asks whether (and if so which) patterns of interactions between species can themselves give rise to community stability. With Prateek Verma and Chaitanya Gokhale, I worked on analysing the ecological consequences of microbes interacting via antagonistic toxins and other chemicals that degrade these toxins.

This work with resulted in a preprint currently under review. It can be found on biorXiv here:
Gaurav S. Athreya , Chaitanya S. Gokhale, Prateek Verma. Antibiotic-mediated interactions underlying microbial diversity. biorXiv (2023). https://doi.org/10.1101/2023.02.15.528676