title: Population fluctuations and synchrony of grassland butterflies in relation to species traits.
abstract: Population fluctuations and synchrony influence population persistence; species with larger fluctuations and more synchronised population fluctuations face higher extinction risks. Here, we analyse the effect of diet specialisation, mobility, length of the flight period, and distance to the northern edge of the species' distribution in relation to between-year population fluctuations and synchrony of butterfly species. All butterfly species associated with grasslands were surveyed over five successive years at 19 grassland sites in a forest-dominated landscape (50 km(2)) in southern Sweden. At both the local and regional level, we found larger population fluctuations in species with longer flight periods. Population fluctuations were more synchronous among localities in diet specialists. Species with a long flight period might move more to track nectar resources compared to species with shorter flight period, and if nectar sources vary widely between years and localities it may explain that population fluctuations increase with increasing flight length. Diet generalists can use different resources (in this case host plants) at different localities and this can explain the lower synchrony in population fluctuations among generalist species. Higher degree of synchrony is one possible explanation for the higher extinction risks that have been observed for more specialised species. Therefore, diet specialists are more often threatened and require more conservation efforts than generalists.
authors.affiliation: Department of Community Ecology, UFZ, Helmholtz Centre for Environmental Research, Halle, Germany ; Department of Biology, Biodiversity and Conservation Biology, Lund University, Lund, Sweden.
authors.forename: Markus
authors.initials: M
authors.lastname: Franzén
authors.forename: Sven G
authors.initials: SG
authors.lastname: Nilsson
authors.forename: Victor
authors.initials: V
authors.lastname: Johansson
authors.forename: Thomas
authors.initials: T
authors.lastname: Ranius
mesh_terms: D000818:Animals; D044822:Biodiversity; D002080:Butterflies / Q000502:physiology*; D017753:Ecosystem; D065948:Grassland; D011153:Population; D011157:Population Dynamics; D013045:Species Specificity; D013548:Sweden