Will refaunation by feral horse affect five checkerspot butterfly species (Melitaea Fabricius, 1807) coexisting at xeric grasslands of Podyji National Park, Czech Republic?

Abstract In connection with the broad refaunation/rewilding movement, free-range grazing by native ungulates is being increasingly used as a management option for diverse habitat types, including xeric grasslands of temperate Europe. Prior to the establishment of such grazing by Exmoor ponies, an analogue of the wild horse for European grasslands, we surveyed the demography, mobility and habitat use of five species of checkerspot butterflies (Melitaeini) co-occurring at two grasslands of the Podyji National Park, Czech Republic: Melitaea athalia, M. aurelia, M. britomartis, M. cinxia and M. didyma. We combined mark-recapture, adults distribution models and larval nests surveys to describe co-occurrence patterns of the five butterflies and to predict impacts of the horses on their populations. All five species co-occurred at grassland M, a former military training range. M. aurelia and M. britomartis were absent from grassland H, a former village commons, the latter due to a recent local extinction. Four species conformed to adult demography patterns typical for univoltine Melitaeini, while M. didyma formed multiple generations. Mobility inversely reflected current distribution ranges in the Czech Republic: the widespread M. athalia and M. cinxia were most mobile, the currently expanding M. didyma was intermediate, and the range-restricted and endangered M. britomartis and M. aurelia were least mobile. Habitat requirements followed a gradient from wooded structures (M. athalia), through long-sward shrubby sites (M. britomartis), short-sward grasslands (M. cinxia) to open-turf sites (M. aurelia, M. didyma). Based on our findings, we predict that natural grazing by the ponies will benefit M. aurelia, M. cinxia and M. didyma, and will be neutral for M. athalia. It may pose a risk for M. britomartis, rather an open woodlands dweller, which likely benefited from successional overgrowth of the grasslands. As its conservation is a top priority, we recommend measures to mitigate the negative impacts.