Predators reduce extinction risk in noisy metapopulations.
BACKGROUND
Spatial structure across fragmented landscapes can enhance regional population persistence by promoting local "rescue effects." In small, vulnerable populations, where chance or random events between individuals may have disproportionately large effects on species interactions, such local processes are particularly important. However, existing theory often only describes the dynamics of metapopulations at regional scales, neglecting the role of multispecies population dynamics within habitat patches.


RESULTS
By coupling analysis across spatial scales we quantified the interaction between local scale population regulation, regional dispersal and noise processes in the dynamics of experimental host-parasitoid metapopulations. We find that increasing community complexity increases negative correlation between local population dynamics. A potential mechanism underpinning this finding was explored using a simple population dynamic model.


CONCLUSIONS
Our results suggest a paradox: parasitism, whilst clearly damaging to hosts at the individual level, reduces extinction risk at the population level.
Bull
James C
JC
Populations and Disease Group, Department of Biological Sciences, University of Warwick, Coventry, United Kingdom.
Bonsall
Michael B
MB
D000818:Animals; D001517:Coleoptera / Q000254:growth & development* / Q000502:physiology; D007887:Fabaceae / Q000254:growth & development* / Q000469:parasitology; D006790:Host-Parasite Interactions / Q000502:physiology*; D008962:Models, Theoretical; D011157:Population Dynamics; D048889:Weevils / Q000254:growth & development / Q000502:physiology