Permeability of habitat edges for Ringlet butterflies (Lepidoptera, Nymphalidae, Erebia Dalman 1816) in an alpine landscape

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.

The isolated Erebia pandrose Apennine population is genetically unique and endangered by climate change

“…To reduce clustered occurrences due to unbalanced sampling, we filtered the occurrence dataset by selecting points at a minimum distance of 2 kilometres to each other with the ‘thin’ function of the ‘spThin’ R package (Aiello‐Lammens et al ., 2015) in R v. 4.0.3 (R Core Team, 2020). We chose the minimum distance of 2 km taking into account the limited dispersal propensity of Erebia species (Kuras et al ., 2003; Grill et al ., 2020). This reduced the final dataset for species distribution modelling to 166 records (Fig.…”

Low winter precipitation, but not warm autumns and springs, threatens mountain butterflies in middle-high mountains

“…All constituent species develop on grasses, overwinter as larvae, and either form a single annual brood, or prolong their development across multiple seasons ( Sonderegger, 2005 ). They display remarkable diversity in larval cold hardiness ( Vrba et al, 2017a ) and adult thermoregulation ( Kleckova, Konvicka & Klecka, 2014 ), resulting in a diversity of micro-habitat use ( Sonderegger, 2005 ) and diverse species assemblages in high mountains ( Grill et al, 2020 ; Polic et al, 2016 ). Lower-altitude mountains host lower Erebia diversity but allow exploring the effects of climatic variability on sub-alpine butterflies on the margins of their climatic tolerances.…”

Modelling the scope to conserve an endemic‐rich mountain butterfly taxon in a changing climate

“…To protect all endemic Erebia species, protection will be needed in a wide set of mountain ranges (Figures 5 and 6), not only to cover interspecific and intraspecific diversity but to spread the risk that the regional variation in climate change imposes to the conservation of individual species. Additional threats to these areas (such as building of new infrastructures and mountain roads) should be minimised (Grill et al, 2020; Polic et al, 2014). Erebia caterpillars feed on grasses: therefore, while the distribution of host plants may not be a limiting factor in distribution shifts (Schweiger et al, 2008, 2012), the habitats where the grasses grow may be vital, with some species requiring plants growing among bare ground or rocky terrain, and others damp grassland or woodland clearings.…”

“…Additional threats to these areas (such as building of new infrastructures and mountain roads) should be minimised (Grill et al, 2020;Polic et al, 2014). Erebia caterpillars feed on grasses: therefore, while the distribution of host plants may not be a limiting factor in distribution shifts (Schweiger et al, 2008(Schweiger et al, , 2012, the habitats where the grasses grow may be vital, with some species requiring plants growing among bare ground or rocky terrain, and others damp grassland or woodland clearings.…”