Spatial sorting promotes the spread of maladaptive hybridization

• Hybridization between native and invasive species threatens biodiversity worldwide.
• Invasive hybridization can spread even when hybrids have reduced fitness.
• This paradox can be partially explained by spatial sorting.
• Spatial sorting allows genotypes to increase in frequency through space rather than time.
• Broader understanding of spatial sorting is needed to protect native biodiversity.

Invasive hybridization is causing loss of biodiversity worldwide. The spread of such introgression can occur even when hybrids have reduced Darwinian fitness, which decreases the frequency of hybrids due to low survival or reproduction through time. This paradox can be partially explained by spatial sorting, where genotypes associated with dispersal increase in frequency at the edge of expansion, fueling further expansion and allowing invasive hybrids to increase in frequency through space rather than time. Furthermore, because all progeny of a hybrid will be hybrids (i.e., will possess genes from both parental taxa), nonnative admixture in invaded populations can increase even when most hybrid progeny do not survive. Broader understanding of spatial sorting is needed to protect native biodiversity.