After the Cut: Sizes and Stability of Populations Decline After Disconnecting Experimental Habitat Networks

ABSTRACT

Individual habitat patches may be connected by movement pathways to create habitat networks for resident organisms. Theory predicts that restrictions to movement among patches of these networks will impact population size and temporal stability at patch and network scales, but there have been few experimental tests of this prediction. We conducted laboratory experiments to explore the effect of reduced population connectivity on population outcomes in artificial habitat networks. We used populations of Daphnia carinata in replicate habitat networks of six increasingly complex topologies. With populations at dynamic equilibrium, all habitat networks were cut into two by removing the most central connections, disrupting population connectivity. The results showed that reduced population connectivity led to significantly reduced population sizes at both network and patch scales, but mainly in dendritic networks, most likely because of their topological differences. Linear and lattice networks maintained populations because they experienced minimal structural change and retained high connectivity post cut, respectively. At the patch scale, the magnitude of this decrease was significantly affected by the position of the patch within the network. The cut significantly reduced population temporal stability at network scales. Reduced habitat connectivity, causing population decline and destabilization, may lead to greater extinction risk, particularly for populations inhabiting less complex habitat networks with few inter‐patch connections. Our study delivered a rare empirical test. Our results support existing conservation strategies that prioritize central dispersal pathways to reconnect habitats. By prioritizing population connectivity, managers can increase population size and stability, reducing extinction risk.