Komarova Natalia L, Shahriyari Leili, Wodarz Dominik
Department of Mathematics, University of California Irvine, , Irvine, CA 92697, USA.
J R Soc Interface. 2014 Mar 26;11(95):20140014. doi: 10.1098/rsif.2014.0014. Print 2014 Jun 6.
The evolution of complex traits requires the accumulation of multiple mutations, which can be disadvantageous, neutral or advantageous relative to the wild-type. We study two spatial (two-dimensional) models of fitness valley crossing (the constant-population Moran process and the non-constant-population contact process), varying the number of loci involved and the degree of mixing. We find that spatial interactions accelerate the crossing of fitness valleys in the Moran process in the context of neutral and disadvantageous intermediate mutants because of the formation of mutant islands that increase the lifespan of mutant lineages. By contrast, in the contact process, spatial structure can accelerate or delay the emergence of the complex trait, and there can even be an optimal degree of mixing that maximizes the rate of evolution. For advantageous intermediate mutants, spatial interactions always delay the evolution of complex traits, in both the Moran and contact processes. The role of the mutant islands here is the opposite: instead of protecting, they constrict the growth of mutants. We conclude that the laws of population growth can be crucial for the effect of spatial interactions on the rate of evolution, and we relate the two processes explored here to different biological situations.
复杂性状的进化需要多个突变的积累，相对于野生型而言，这些突变可能是不利的、中性的或有利的。我们研究了适应性山谷跨越的两种空间（二维）模型（恒定种群莫兰过程和非恒定种群接触过程），改变了所涉及的基因座数量和混合程度。我们发现，在中性和不利的中间突变体的情况下，由于形成了增加突变谱系寿命的突变岛，空间相互作用加速了莫兰过程中适应性山谷的跨越。相比之下，在接触过程中，空间结构可以加速或延迟复杂性状的出现，甚至可能存在一个最优混合程度，使进化速率最大化。对于有利的中间突变体，在莫兰过程和接触过程中，空间相互作用总是会延迟复杂性状的进化。这里突变岛的作用则相反：它们不是起到保护作用，而是限制突变体的生长。我们得出结论，种群增长规律对于空间相互作用对进化速率的影响可能至关重要，并且我们将这里探讨的两个过程与不同的生物学情况联系起来。
