Molecular signatures of resource competition: Clonal interference favors ecological diversification and can lead to incipient speciation*

Abstract

Microbial ecosystems harbor an astonishing diversity that can persist for long times. To understand how such diversity is structured and maintained, ecological and evolutionary processes need to be integrated at similar timescales. Here, we study a model of resource competition that allows for evolution via de novo mutation, and focus on rapidly adapting asexual populations with large mutational inputs, as typical of many bacteria species. We characterize the adaptation and diversification of an initially maladapted population and show how the eco-evolutionary dynamics are shaped by the interaction between simultaneously emerging lineages -clonal interference. We find that in large populations, more intense clonal interference can foster diversification under sympatry, increasing the probability that phenotypically and genetically distinct clusters coexist. In smaller populations, the accumulation of deleterious and compensatory mutations can push further the diversification process and kick-start speciation. Our findings have implications beyond microbial populations, providing novel insights about the interplay between ecology and evolution in clonal populations.

Digest: The complex interplay of phenotypic variation and diversifying selection *

“…Amicone and Gordo (2021) ask about the role of phenotypic variation in a familiar context—resource competition. Resource competition is perhaps the prototypical ecological interaction in which questions of diversity have been posed, as popularized by MacArthur and Levins (1964).…”

“…Amicone and Gordo (2021) move beyond these models by treating phenotypic variation as arising through the process of frequent, random mutations. Typically, frequent mutations speed up the pace of evolutionary change, even if they do not alter the ultimate evolutionary outcome.…”

“…But the nature of genetic and phenotypic variation is also critical because such variation provides the raw material on which selection acts. Amicone and Gordo (2021) ask about the role of phenotypic variation in a familiar context-resource competition. Resource competition is perhaps the prototypical ecological interaction in which questions of diversity have been posed, as popularized by MacArthur and Levins (1964).…”

Quantifying the Local Adaptive Landscape of a Nascent Bacterial Community

“…Despite the ubiquity of eco-evolutionary dynamics characterized by diversification and coevolution, we have limited theoretical understanding (26, 27) and experimental measurements of how mutational effects should depend on the (a)biotic environment, and how they drive evolutionary dynamics. Thus, we sought to (i) better understand how the spectrum of mutational effects changes over long evolutionary timescales and after ecological diversification, (ii) how mutational fitness effects depend on ecological conditions, and (iii) if and how they are correlated with evolutionary outcomes, i.e.…”

Competition dynamics in long‐term propagations of Schizosaccharomyces pombe strain communities

“…Moreover, evolution is likely to occur on timescales relevant for ecological dynamics, and thus, a complete understanding of the maintenance of diversity also requires assimilation of data about the evolutionary forces at work (Celiker & Gore, 2014;Lankau, 2011;Lawrence et al, 2012). On the one hand, novel mutations generate diversity which may be stably maintained (Amicone & Gordo, 2021;Dieckmann & Doebeli, 1999). On the other hand, evolution can also reduce the effectiveness of coexistence mechanisms through selection of the fittest, and thus, competitive exclusion occurs (Geritz et al, 1998;Shoresh et al, 2008).…”