Butterfly species differing in mobility show different structures of dispersal-related syndromes in the same fragmented landscape


S. Ducatez, Muséum National d’Histoire Naturelle, Dépt Ecologie et Gestion de la Biodiversité, 57 rue Cuvier, FR-75005 Paris cedex 5, France. SD also at: Dept of Biology, McGill Univ., 1205 Avenue Docteur Penfield, Montréal, QC H3A 1B1, Canada. E-mail: simon.ducatez@mail.mcgill.ca


Mobility varies strongly between and within species, reflecting different dispersal strategies. Within species, such differences can imply suites of traits associated in syndromes. Different syndrome structures have been found within species among populations differing in the selective pressures they are exposed to. Similarly, we expect species differing in mobility to show different syndrome structures in response to similar selective pressures such as landscape fragmentation. Using butterflies originating from the same fragmented landscape, we investigated the differences in mobility syndrome between four common butterflies (Pyronia tithonus, Pararge aegeria Maniola jurtina, Pieris rapae) known to differ in their mobility. We expected individuals from the less mobile species to display a resident strategy because of high dispersal cost in this fragmented landscape, and individuals from the more mobile species to display a larger range of movement strategies. Moreover, as syndromes can only be detected whenever individuals differ in their dispersal strategies, we expected mobility syndromes to be observable only in populations where dispersal polymorphism is maintained. We thus expected stronger correlations between mobility-related traits in more mobile species. Using three mobility tests in controlled conditions designed to measure different components of mobility, we showed that mobility-related traits were indeed correlated only in the most mobile species. The absence of correlation in the less mobile species may be explained by a low variation in movement strategies, dispersal being counter-selected.