Population spatial structure and migration of three butterfly species within the same habitat network: consequences for conservation

1. In this study we addressed the question of the generalization of populat ion viability analysis by comparing migration of different butterfly specie s in the same habitat network. We compared (i) the population spatial struc ture and (ii) the migration between local populations in three butterfly sp ecialist species living in the same habitat (chalk grassland) within the sa me habitat network (eight patches) at the same time. 2. For the three species, population structures within the study system wer e considered as metapopulations. However, their patch occupancy and migrati on patterns differed strongly, from a species with six small populations, o ne being apparently isolated (Cupido minimus), to a species with eight popu lations connected by individual movement with all others within the landsca pe (Melanargia galathea). 3. Patch area of both donor and receiver sites affected migration rate in M . galathea. Patch quality may interfere with this area effect in Aporia cra taegi. Increasing distance between patches decreased both the probability o f 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. crat aegi, and an exponential-negative function for M. galathea. 4. These differences in population structure and migration patterns will ha ve consequences for population viability analyses: the persistence of C. mi nimus cannot be expected if the habitat network is designed on the basis of the requirements of the two other species. Therefore, metapopulation persi stence analyses have to remain species-specific. As such analyses are impos sible 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.