Modelling mortality and dispersal: consequences of parameter generalisation on metapopulation dynamics

Modelling dispersal is a fundamental step in the design of population viability analyses. Here, we address the question of the generalisation of population viability analysis models across landscapes by comparing dispersal between two metapopulations of the bog fritillary butterfly ( Proclossiana eunomia ) living in similar highly fragmented landscapes (<1% of suitable habitat in 9 km²). Differences in dispersal patterns were investigated using the virtual migration (VM) model, which was parameterised with capture–mark–recapture data collected during several years in both landscapes. The VM model allows the estimation of 6 parameters describing dispersal and mortality as well as the simulation of dispersal in the landscapes. The model revealed large differences in the VM parameter estimates between the two landscapes and consequently, simulations indicated differential rates of emigration and dispersal mortality. Furthermore, results from crossed-simulations i.e. simulations performed in one of the landscape but using parameter estimates from the other landscape emphasize that dispersal parameters are very specific to each metapopulation and to their landscape. Hence, we urge conservation biologists to be cautious with such parameter generalisations, even for the same species in comparable landscapes.