Various ramifications become apparent when thinking about simple invasion scenarios not just in time, but in space. For example, during invasion, individuals at the range edge are presumably more likely to disperse into unexploited habitat than those at the centre of the metapopulation. Over time, this would create strong drift at the leading edge of an expanding population. As a consequence, a subset of low-frequency mutations that arise at the range edge will propagate over space and reach high frequencies simply as a consequence of population expansion (Edmonds, Lillie, & Cavalli-Sforza, 2004). This phenomenon is known as genetic surfing (or ‘allele surfing’), and is more likely to occur in small, fast-expanding populations, which could include many invasive species (Klopfstein, Currat, & Excoffier, 2006). Below, a mutation at the expanding range edge spreads to high frequency over a large area through genetic surfing (adapted from Foutel-Rodier & Etheridge, 2020).