Does dispersal drive extinction risk for lizards in a 25 year fragmentation experiment?

Background/Question/Methods

Habitat fragmentation is considered a major threat to biodiversity because it often results in smaller, more isolated populations with a higher risk of extinction. If these populations are connected by the migration of individuals, the assemblage comprises a metapopulation whose persistence is driven by the balance between local extinctions and recolonizations. In metapopulation models, one component of the colonization parameter is dispersal rate, which varies greatly between species and can increase metapopulation resilience when local extinction rates are high. Thus, species with high dispersal rates are expected to persist longer in fragmented landscapes because they can offset local losses. However, despite a well-developed theoretical foundation for the relationship between metapopulation persistence and dispersal rates, experimental support for these ideas is lacking. We hypothesize that incorporating long-term population data and measures of dispersal ability from morphological features will allow us to develop comprehensive, spatially explicit metapopulation models that can help clarify this relationship.

Results/Conclusions

Coupling population data with measures of dispersal ability, we tested the prediction that species with limited dispersal have a greater risk of local and metapopulation extinction when examined 25 years after the experimental fragmentation of their habitat at Wog Wog in southeastern Australia. We used abundance data on 3 species of common terrestrial lizards in a long-term, large-scale fragmentation experiment to measure two population parameters: 1) metapopulation persistence time for each species and 2) dispersal ability both within and between patches. Initial results suggest the feasibility of developing a predictive framework for the relationship between connectivity and metapopulation persistence time using these two parameters. Applications of our model to other systems within the fragmentation experiment will help clarify its predictive power. By coupling long-term abundance data with measures of dispersal ability, this study helps clarify the relationship between dispersal and extinction risk to provide insight into the importance of connectivity when designing nature reserves and wildlife management strategies that combat biodiversity loss.