Speaker
Description
Multilevel selection in host-associated microbiomes has important implications for understanding the origin and evolution of these complex associations. To date, we do not have a clear understanding of the different levels that can affect selection on microbial communities. There is evidence that the higher level of selection provided to the microbiome by the host has a significant impact on the evolution of microbial lineages and enhances beneficial interactions [1, 2]. At the individual level, microbial lineages within each host experience selection favoring individuals with higher reproduction rates. Conversely, hosts may have their health status and reproductive success enhanced depending on their microbiome, which, in turn, increases the likelihood of proliferation of the microbiome individuals. For example, let's consider two types of individuals: cooperators and defectors. At the individual level, defectors dominate over cooperators, while at the group level, purely cooperator groups have an advantage over defector groups. Thus, the direction of selection at both levels is in opposite directions - for instance, cooperation is beneficial at a higher level but detrimental for an individual at a lower level.
Although previous studies [1, 2] have investigated the role of a higher level of selection, they focus on the evolution of interactions between a few microbial types. When considering several microbial types, how does multilevel selection influence the selection of interactions? This study aims to understand the possible role of multilevel selection in shaping host-microbiome interactions and how the population structure influences the selection of interactions when there are multiple types of individuals. Does it promote higher microbial diversity in the population? Are microbial lineages more likely to evolve beneficial interactions with their host and other microbes when subjected to multilevel selection? Here, we address these questions structuring a population of individuals into groups. Individuals interact with other group members through an evolutionary game that determines their fitness. Individuals reproduce according to a fitness-dependent Moran process. When the group reaches a certain size, it can split into two groups, while another group is eliminated, or an individual from the group will be eliminated at random. Multilevel selection emerges as a consequence of individual reproduction and constraint from the population structure.
[1] Traulsen, Nowak, PNAS 103, 10952-10955 (2006)
[2] van Vliet, Doebeli, PNAS 116, 20591-20597 (2019)
