Shifts from pulled to pushed range expansions caused by reduction of landscape connectivity

Range expansions are key processes shaping the distribution of species; their ecological and evolutionary dynamics have become especially relevant today, as human influence reshapes ecosystems worldwide. Many attempts to explain predict range assume, explicitly or implicitly, so-called ‘pulled' expansion dynamics, in which low-density edge populations provide most ‘fuel' for species advance. Some expansions, however, exhibit very different with high-density behind front ‘pushing' forward. These two types predicted effects on e.g. genetic diversity habitat quality sensitivity. However, empirical studies lacking due challenge generating reliably pushed versus pulled laboratory, discriminating them field. We here propose that manipulating degree connectivity among may prove a more generalizable way create expansions. demonstrate this individual-based simulations well replicated experimental (using parasitoid wasp Trichogramma brassicae model). By analyzing velocities neutral diversity, we showed reducing led dynamics. Low alone, i.e. without density-dependent dispersal, can only lead ‘weakly pushed' where invasion speed conforms expectations, but decline does not. In low some cases also adjustments dispersal-density function, recreating ‘classical' current context loss fragmentation, need better account relationship between regimes successfully consequences