Population spatial structure and migration of three butterfly species within the same habitat network: consequences for conservation.
Abstract
In this study the question of the generalization of population viability analysis by comparing migration of different butterfly species in the same habitat network was addressed. The population spatial structure and the migration between local populations were compared in three butterfly specialist species living in the same habitat (chalk grassland in Belgium) within the same habitat network (eight patches) at the same time. For the three species, population structures within the study system were considered as metapopulations. However, their patch occupancy and migration patterns differed strongly, from a species with six small populations, one being apparently isolated (Cupido minimus), to a species with eight populations connected by individual movement with all others within the landscape (Melanargia galathea). Patch area of both donor and receiver sites affected migration rate in M. galathea. Patch quality may interfere with this area effect in Aporia crataegi. Increasing distance between patches decreased both the probability of movements between local population and the number of moving butterflies. The distribution of migration distances differed between A. crataegi and M. galathea: this distribution followed an inverse-power function for A. crataegi, and an exponential-negative function for M. galathea. These differences in population structure and migration patterns will have consequences for population viability analyses: the persistence of C. minimus cannot be expected if the habitat network is designed on the basis of the requirements of the two other species. Therefore, metapopulation persistence analyses have to remain species-specific. As such analyses are impossible to perform on every threatened species living in a given habitat, we propose a preliminary screening of the most fragile candidate based on its population structure and mobility.