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 2 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 changethreatened species are hampered due to its basic ecology being poorly understood. Here, we describe a study on the autecology of Mountain Ringlets 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.

Preserving Colias myrmidone in European cultural landscapes: requirements for the successful development from egg to higher larval stages at a Natura 2000 site in Romania

“…Other studies found similar results and draw a connection to the grazing regime at the sites. For the butterfly species Erebia epiphron, the Mountain Ringlet, Ewing et al (2020) found that the quantity of leaf litter influenced egg site selection. Females preferred sites with an intermediate amount of litter.…”

“…Females preferred sites with an intermediate amount of litter. The cover of litter is supposed to function as a microclimatic buffer that reduces temperature and humidity fluctuations and protects hibernating larvae from cold temperatures in winter (Stuhldreher and Fartmann 2014;Münsch et al 2018;Ewing et al 2020). Cold temperatures probably had no influence on the survival of the larvae of C. myrmidone in September, still it might be advantageous for their hibernation.…”

“…To design effective conservation strategies that halt or reverse declines of threatened butterfly species, detailed knowledge of their ecological requirements is needed (Ewing et al 2020). Most butterflies have very specific preferences regarding habitat quality (Münsch et al 2018;García-Barros and Fartmann 2009).…”

“…Due to their complex life cycle from egg through different larval stages to pupae and finally to adults, requirements of butterflies have to be met in all of those stages (García- Barros and Fartmann 2009). The larval stage is expected to be particularly limiting (Ewing et al 2020). Larval feeding is responsible for the accumulation of materials used for adult bodybuilding and egg production (Munguira et al 2009).…”

“…Most European butterfly species overwinter as larvae (Munguira et al 2009) which stresses the importance of the larval stage for the survival of those species. Larvae depend on ephemeral and narrow niches within their habitats, which have to contain their larval host plants in specific growth forms and have to provide specific microhabitats (Ewing et al 2020).…”