  The rate of biological evolution depends on the fixation probability and on
the fixation time of new mutants. Intensive research has focused on identifying
population structures that augment the fixation probability of advantageous
mutants. But these `amplifiers of natural selection' typically increase
fixation time. Here we study population structures that achieve a trade-off
between high fixation probability and short fixation time. First, we show that
no amplifiers can have asymptotically lower absorption time than the well-mixed
population. Then we design population structures that substantially augment the
fixation probability with just a minor increase in fixation time. Finally, we
show that those structures enable higher effective rate of evolution than the
well-mixed population provided that the rate of generating advantageous mutants
is relatively low. Our work sheds light on how population structure affects the
rate of evolution. Moreover, our structures could be useful for lab-based,
medical or industrial applications of evolutionary optimization.
