Many natural populations are spatially distributed, forming a network of subpopulations linked by migration. Migration patterns are often asymmetric and heterogeneous, with important consequences on the ecology and evolution of the species. Here we investigate experimentally how asymmetric migration and heterogeneous structure affect a simple metapopulation of budding yeast, formed by one strain that produces a public good and a non-producer strain that benefits from it. We study metapopulations with star topology and asymmetric migration, finding that all their subpopulations have a higher fraction of producers than isolated populations. Furthermore, the metapopulations have lower tolerance to challenging environments but higher resilience to transient perturbations. This apparent paradox occurs because tolerance to a constant challenge depends on the weakest subpopulations of the network, while resilience to a transient perturbation depends on the strongest ones.
Over evolutionary time, bacteria face changing environments, which may require different sets of genes for survival. As they adapt to a specific constant environment, some genes are modified and lost, which can increase fitness while also modulating the effects of further gene losses. However, whether evolutionary specialization leads to systematic changes in robustness to gene loss is largely unexplored. Here, we compare the effects of insertion mutations in Escherichia coli between ancestral and 12 independently derived strains after 50,000 generations of growth in a simple, uniform environment. We find that epistasis between insertion mutations and genetic background is common, but the overall distribution of fitness effects is largely unchanged. In particular, we see systematic changes in gene essentiality, with more genes becoming essential over evolution than vice versa. The resulting changes often occurred in parallel across the independently evolving populations. A few of the changes in gene essentiality are associated with large structural variations, but most are not. Taken together, our results demonstrate that gene essentiality is a dynamic, evolvable property, and they suggest that changes in gene essentiality are a result of natural selection in this long-term evolution experiment, rather than a mere byproduct of structural changes.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.