Vegetation composition and structure are important predictors of oviposition site selection in an alpine butterfly, the Mountain Ringlet Erebia epiphron

Abstract

Knowledge of species’ ecological requirements is key for designing effective conservation management. In butterflies, the needs of larval stages are often the most specialised part of the life-cycle, but for many species information on this is lacking. The Mountain Ringlet Erebia epiphron is a cold-adapted butterfly found in alpine grasslands in mountainous regions of Europe. Efforts to devise conservation strategies for this climate change-threatened species are hampered due to its basic ecology being poorly understood. Here, we describe a study on the autecology of Mountain Ringlets at sites across its British distribution, focusing on the habitat preferences of egg-laying females as a proxy for larval preferences. Female Mountain Ringlets placed their eggs predominantly on Nardus stricta and Festuca ovina, but also on several other host plant species, suggesting larvae may be more broadly polyphagous than previously realised. Sites chosen for eggs had higher abundance of larval host plants, intermediate leaf litter cover, and lower cover of grass tussocks than random locations, as well as a shorter and sparser grass sward. Although the main host plant is ubiquitous in upland areas of Britain, our findings suggest that this butterfly’s egg and larval stages have specialised ecological requirements, requiring specific microhabitat features characterised by a narrow range of vegetation composition and structural characteristics. Many habitat associations are liable to be explicable as adaptations to ensure placement of eggs and larvae in sites within optimal (warm or buffered) microclimates. We tentatively suggest that the distribution of Mountain Ringlets in the landscape is thermally-constrained.