Mechanical and Evolutionary Constraints on Hyphal Shape and Growth

During pathogenesis fungal hyphae grow invasively through host tissue. It has been proposed that the tapered apical shape of fungi promotes invasive growth. I will demonstrate, rather, that the tapered shape results from an instability in the mechanical mechanism of" inflationary" growth common to all tip growing cells. This instability leads directly to a bifurcation in the fitness landscape of tip growth whereby naturally occurring shapes, including tapered shapes, grow faster than hypothetical non-natural shapes. More broadly, our study illustrates a paradigm for how evolutionary dynamics emerge from physical and developmental constraints to sculpt biological form.