New sector morphologies emerge from anisotropic colony growth

Expanding populations are of central interest in population genetics because range expansion can have lasting consequences on genetic diversity. Bacterial colonies in a Petri dish are a common model system of range expansion, and the enhanced effect of drift at the expanding front generates spatially segregated domains known as sectors. Typically, these colonies are grown on a uniform substrate which naturally produces an isotropic growth pattern. The effects of anisotropy on colony growth and sector establishment remain understudied. In this work, we use a simple model to analyze the influence of anisotropy on bacterial range expansion, with specific focus on sector morphology. Our results indicate that pronounced anisotropy introduces a unique sector morphology not achievable in standard isotropic conditions.