Abstract
The breakdown of the transhumant grazing system in the Spanish Pyrenees has led to a severe decline in the area of pastures. However, in the high mountain zone there are still large areas of species-rich grasslands. The aim of this study was to assess the oviposition preferences of the shrub-feeding Blue-spot hairstreak, Satyrium spini (Denis & Schiffermuller, 1775), in montane common pastures in the Spanish Pyrenees and recommend a way of managing these grasslands that favours this species. Our study showed that females of S.spini laid their eggs on Dwarf buckthorn (Rhamnus pumila Turra) and Alpine buckthorn (R. alpina L.), which are novel host plant records for Spain. A warm microclimate was of crucial importance for egg-laying. Occupied plants grew mostly at sparsely vegetated grassland sites where there were large patches of bare rocks, stones or gravel. Most egg batches were laid close to the ground and 75% consisted of only one egg. The number of batches per R. pumila plant was higher on east-, south- and west-facing slopes than on north-facing slopes. Presence of eggs and the number of egg batches per R. pumila plant were best explained by a long sunshine duration. At high altitudes particularly warm microhabitats seem to be more important for S.spini than at lower altitudes in Central Europe. We assume that the preference for unusually warm microhabitats is explained by the cold climatic conditions near the altitudinal range limit of the species. That most of the eggs were laid singly and not in small batches as in Central Europe might be a risk-spreading strategy to cope with the harsh climatic conditions and the high inter-annual variation in weather conditions in the high mountain zone in the Pyrenees. The best way to maintain open grasslands for S. spini and other thermophilous grassland species in the high mountain zone of the Pyrenees is to use the traditional combination of sheep and cattle grazing.
Highlights
During recent decades, the worldwide rate of species extinctions has risen continuously and is estimated to be 100 to 1000 times higher than the natural background extinction (Pimm et al, 1995)
Our study showed that females of S. spini laid their eggs on Dwarf buckthorn (Rhamnus pumila Turra) and Alpine buckthorn (R. alpina L.), which are novel host plant records for Spain
Presence of eggs and the number of egg batches per R. pumila plant were best explained by a long sunshine duration
Summary
The worldwide rate of species extinctions has risen continuously and is estimated to be 100 to 1000 times higher than the natural background extinction (Pimm et al, 1995). The most important driver of this process is land-use change (Sala et al, 2000). The transition from traditional land-use to modern agriculture mostly entails two contrasting processes: intensified use of productive sites that can be cultivated mechanically and abandonment of marginal land (Foley et al, 2005; Henle et al, 2008; Kleijn et al, 2009). Both phenomena often have adverse effects on species richness. Declines in habitat and species diversity due to cessation of traditional land use have been reported for several European mountain ranges (MacDonald et al, 2000; Tasser & Tappeiner, 2002; Bezák & Halada, 2010)
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