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

Abstract

The endangered and declining butterfly species Colias myrmidone is sensitive to land-use changes and vulnerable in its immature stages. The requirements for its larval habitats are still largely unknown, which hinders appropriate management in protected areas. We examined the relation between the larval development of C. myrmidone and environmental variables at a Natura 2000 site in Romania. Individuals that reached higher larval stages had a higher cover of litter as well as a lower cover of forbs around their host plants than individuals that died in early larval stages or as eggs. Surviving individuals had less other host plants in their surrounding and were found on larger host plants. Surviving individuals were found further away from the tip of their hosts than individuals that were lost due to grazing. The grazing regime is of particular importance to ensure the successful development of C. myrmidone from egg to higher larval stages. There seems to be a trade-off between positions at the tip of the shoot with palatable leaves and positions further down that protect against grazing. Especially sheep grazing may cause high direct mortality. The higher amount of litter around surviving larvae indicates a better survival when the grazing pressure is very low, but still present to keep the habitat open. However, occasional heavy grazing events may reduce the cover of forbs. Implications for insect conservation The designation of the investigated Natura 2000 site offers a great opportunity to implement the insights on larval development of C. myrmidone into a management plan, which can support low-intensity grazing regimes preferably with cattle.

Endangered Oarisma poweshiek larvae vary their graminoid forage in Manitoba, Canada

“…Disturbances such as a cutting actionhayingand prescribed burns may improve the suitability of habitats for butterflies (Swengel 1996;Thom and Daniels 2017) but ought to be compatible with the life history of these same butterflies to reduce mortality (Swengel andSwengel 1999, 2015). Our findings regarding seasonal larval positioning of Poweshiek skipperlings suggest that haying in late summer or fall, when larvae are relatively closer to the ground, instead of in midsummer, when the eggs or larvae are located in the vegetative canopy, may positively influence the vegetative components of habitats without directly displacing or destroying larvae (e.g., grazing for Pieridae; Nippen et al 2021). To determine conservation disturbances that create or maintain the intersection of microhabitat attributes that are suggested by our study and are compatible with other species at risk, we encourage future research.…”

Mosaic landscapes provide conservation pockets for an endangered species: Colias myrmidone in Romania

“…However, given the general trend of abandonment of small‐scale pastoralism (Erős et al, 2020; Fischer et al, 2012), the accelerating scrub encroachment may soon turn into a dense woodland, which is unsuitable not only for C. myrmidone but also potentially for other species that occur in transition zones between grasslands and forests (Baur et al, 2006). Hence, we evaluate the survival probability as low (Nippen et al, 2021) and emphasise the need for landscape‐scale management for conservation success in cultural landscapes (Bergman et al, 2004).…”

“…While both our models on hostplant and butterfly occurrence revealed mostly negative relationships with slopes in general, the question on why these avoidances might happen can be related to less intensive grazing on the slopes. Without grazing, natural succession may lead to a lack of sun‐exposed hostplants that might be necessary for oviposition and successful larval development (Nippen et al, 2021).…”

“…Compared to mowing or any other type of land use in these landscapes, management regimes that involve grazing of different livestock species, including cattle or buffalo (Hartel & von Wehrden, 2013), create and maintain spatial heterogeneity, which is an important asset for C. myrmidone . However, the stock density of animals needs to be low to prevent severe damages at the larval foodplants (Nippen et al, 2021). Grazing by cattle may be the most appropriate management form for conservation of C. myrmidone as cattle seem to avoid feeding on the hostplant Chamaecytisus sp.…”

Movements of a Specialist Butterfly in Relation to Mowing Management of Its Habitat Patches

“…In the short term, mowing produces a series of negative effects, with direct mortality caused by various machinery used in the process and indirect impact through the reduction of available host plants for caterpillars and nectar sources for adult butterflies or changing the habitat microclimate [ 27 , 28 , 29 ]. In contrast, in the long term, mowing saves meadow habitats from overgrowing, prevents the succession of vegetation, promotes plant species diversity and provides young host plant shoots required by some caterpillars [ 21 , 30 , 31 , 32 , 33 ]. Thus, the overall long-term effects of mowing are highly positive for grassland butterflies.…”