Abstract
We tracked the movements of adult Ringlet butterflies (Lepidoptera, Nymphalidae, Erebia Dalman, 1816) in high-elevation (> 1800 meters a.s.l.) grasslands in the Austrian Alps in order to test if an anthropogenic boundary (= an asphalt road) had a stronger effect on butterfly movement than natural habitat boundaries (trees, scree, or dwarf shrubs surrounding grassland sites). 373 individuals (136 females, 237 males) belonging to 11 Erebia species were observed in one flight season (July–August 2013) while approaching or crossing habitat edges. Erebia pandrose (Borkhausen, 1788) was the most abundant species with 239 observations. All species studied were reluctant to cross habitat boundaries, but permeability was further strongly affected by the border type. Additional variables influencing movement probability were species identity and the time of the day. In E. pandrose, for which we had sufficient observations to analyse this, individuals were more likely to cross a boundary in the morning and in the late afternoon than at midday. Erebia euryale (Esper, 1805) and E. nivalis Lorković & de Lesse, 1954 were more likely to leave a habitat patch than their studied congeners. The key result of our study is that the paved road had the lowest permeability among all edge types (0.1 likelihood of crossing when approaching the edge). A road cutting across a conservation area (viz. a national park) thus hinders inter-patch exchange among Ringlet butterflies in the alpine zone, even though theoretically they ought to be able to fly across.
Highlights
An “edge” can be defined as any boundary between two ecosystems inhabited by different biological communities or as “transitional zones between adjoining ecosystems or habitats” (e.g., Magura et al 2017 and references therein)
All studied species avoided crossing habitat boundaries, natural and anthropogenic ones, similar to findings in other studies on the behaviour of butterflies at habitat edges (Polic et al 2014; Mair et al 2015). Another key result from our study was that the likelihood of crossing habitat boundaries differed between species within the genus Erebia: E. euryale and E. nivalis were clearly more likely to leave a habitat patch than the other species
In former mark-release-recapture work that compared the movement of six different Erebia species (eriphyle, epiphron, pharte, gorge (Hübner, 1803–1804), pandrose, nivalis) we found only E. pharte to be more likely to change between plots than the other Ringlet species (Polic et al 2014)
Summary
An “edge” can be defined as any boundary between two ecosystems inhabited by different biological communities or as “transitional zones between adjoining ecosystems or habitats” (e.g., Magura et al 2017 and references therein). In alpine landscapes, which are the focus of this study, natural edges exist, for instance, where grasslands border scree, shrubs, or woodland. There are anthropogenic edges, like roads crossing a habitat or the borders to areas under different modes of land-use. Most anthropogenic edges are characterized by sharper environmental contrasts and have been described to be less permeable than natural ones in a number of studies (e.g., Ascensão et al 2017 for mammals; Magura et al 2017 for beetles; Baguette and Van Dyck 2007 for insects; Ries and Debinski 2001 and Polic et al 2014 for butterflies). Various animal groups living in vegetated habitats, such as small mammals (Ascensão et al 2017), amphibians (Matos et al 2017) and elephants (Wadey et al 2018) have
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