Habitat connectivity buffers extinction under extreme droughts in
experimental metapopulations
Abstract
Connectivity maintains the spatial dynamics of metapopulations by
promoting dispersal between habitat patches, potentially buffering
populations and communities against continued global change. However,
this function is threatened by habitats becoming increasingly
fragmented, and habitat matrices becoming increasingly inhospitable,
potentially reducing the resilience and persistence of populations. Yet,
we lack a clear understanding of how reduced connectivity interacts with
rates of environmental change to destabilise populations. Using
laboratory microcosms containing metapopulations of the Collembola
Folsomia candida, we investigate the impact of habitat
connectivity on metapopulation persistence under a range of simulated
droughts, a key stressor for this species. We manipulated both drought
severity and the number of patches affected by drought across landscapes
connected by either good or poor-quality corridors. We measured the time
of population extinction, the maximum rate of population decline, and
the variability of abundance among patches as criteria to evaluate the
persistence ability of metapopulations. We show that whilst drought
severity and number of drought-affected patches negatively influenced
population persistence, these results were mitigated by increased
habitat connectivity, which increased population persistence time and
decreased both how fast populations declined and the variability in
abundance among patches. Our results suggest that enhancing spatial
connectivity can increase the persistence of metapopulations, increasing
the time available for conservation actions to take effect, and/or for
species to adapt or move in the face of continued stress. Given that
fragmentation increases the isolation of habitats, improving habitat
connectivity by using good quality corridors may provide a useful
strategy to enhance the resistance of spatially structured populations.