Clonal interference and Muller's ratchet in spatial habitats

Abstract

Competition between independently arising beneficial mutations is enhanced in spatial populations due to the linear rather than exponential growth of clones. Recent theoretical studies have pointed out that the resulting fitness dynamics is analogous to a surface growth process, where new layers nucleate and spread stochastically, leading to the build up of scale-invariant roughness. This scenario differs qualitatively from the standard view of adaptation in that the speed of adaptation becomes independent of population size while the fitness variance does not. Here we exploit recent progress in the understanding of surface growth processes to obtain precise predictions for the universal, non-Gaussian shape of the fitness distribution for one-dimensional habitats, which are verified by simulations. When the mutations are deleterious rather than beneficial the problem becomes a spatial version of Muller's ratchet. In contrast to the case of well-mixed populations, the rate of fitness decline remains finite even in the limit of an infinite habitat, provided the ratio $U_d/s^2$ between the deleterious mutation rate and the square of the (negative) selection coefficient is sufficiently large. Using again an analogy to surface growth models we show that the transition between the stationary and the moving state of the ratchet is governed by directed percolation.

References in corpus (6)

• Genetic drift at expanding frontiers promotes gene segregation
• Growing interfaces uncover universal fluctuations behind scale invariance
• The traveling wave approach to asexual evolution: Muller's ratchet and speed of adaptation
• Radial Domany-Kinzel Models with Mutation and Selection
• Muller's ratchet with overlapping generations
• Upper bound on the rate of adaptation in an asexual population

Cited by in corpus (9)

• On integrable directed polymer models on the square lattice
• The crossing probability for directed polymers in random media
• Crossing probability for directed polymers in random media: exact tail of the distribution
• Critical Fitness Collapse in Three-Dimensional Spatial Population Genetics
• Mutually avoiding paths in random media and largests eigenvalues of random matrices
• Bridging Wright-Fisher and Moran models
• Shape of population interfaces as an indicator of mutational instability in coexisting cell populations
• Rare beneficial mutations cannot halt Muller's ratchet in spatial populations
• Absolute negative mobility in evolution