标题： 缓慢扩张者通过在微生物菌落中形成凹陷前沿进行入侵 显示英文标题

标题： Slow expanders invade by forming dented fronts in microbial colonies

摘要： 大多数生物在空间中生长，无论是病毒在宿主组织内扩散还是入侵物种在新大陆定居。 进化通常会选择更高的扩展速率，但有研究表明，在某些条件下较慢的扩展者可能会占据优势。 在此，我们报告了这种种群动态的实验观察结果。 我们证明，较慢的突变体不仅在两种类型在前沿混合时获胜，而且在它们被空间分隔成区域时也能获胜。 后者曾被认为不可能，因为之前的研究仅关注由扩展速度介导的全局竞争，而忽略了区域边界处的局部竞争。 我们提出了一种区域几何理论，该理论考虑了局部和全局竞争，并描述了所有可能的区域形状。 特别是，该理论预测，一个较慢但更具竞争力的突变体会形成带有凹口的V形区域，从而占据扩展前沿。 这种区域确实在实验中被观察到，其形状与理论预测在数量上相匹配。 在模拟中，我们进一步探讨了几种可能为慢速扩展者提供局部竞争优势的机制，并表明它们都很好地被我们的理论所描述。 综合来看，我们的研究揭示了之前未探索的空间竞争结果，并建立了一个通用框架来理解扩展种群中的进化和生态动态。 显示英文摘要

摘要： Most organisms grow in space, whether they are viruses spreading within a host tissue or invasive species colonizing a new continent. Evolution typically selects for higher expansion rates during spatial growth, but it has been suggested that slower expanders can take over under certain conditions. Here, we report an experimental observation of such population dynamics. We demonstrate that the slower mutants win not only when the two types are intermixed at the front but also when they are spatially segregated into sectors. The latter was thought to be impossible because previous studies focused exclusively on the global competitions mediated by expansion velocities but overlooked the local competitions at sector boundaries. We developed a theory of sector geometry that accounts for both local and global competitions and describes all possible sector shapes. In particular, the theory predicted that a slower, but more competitive, mutant forms a dented V-shaped sector as it takes over the expansion front. Such sectors were indeed observed experimentally and their shapes matched up quantitatively with the theory. In simulations, we further explored several mechanism that could provide slow expanders with a local competitive advantage and showed that they are all well-described by our theory. Taken together, our results shed light on previously unexplored outcomes of spatial competition and establish a universal framework to understand evolutionary and ecological dynamics in expanding populations.