Butterfly diversity (Lepidoptera: Papilionoidea) of Mt. Blegoš and Mt. Koprivnik (Škofjeloško hribovje, Slovenia)

. An overview of the surveys of butterfly fauna of Mt. Blegoš, Mt. Koprivnik and their surroundings is provided. In 2018, 14 surveys were performed and 80 butterfly species on eight transects recorded in the process. Additional surveys in 2019 and 2020 yielded 5 additional butterfly species. Among the butterflies observed, Parnassius mnemosyne, Lycaena hippothoe, Euphydryas maturna, Euphydryas aurinia, Melitaea britomartis, Melitaea diamina, and Pyrgus alveus are identified as vulnerable species, while both Phengaris arion and Phengaris alcon are classified as endangered species in Slovenia. The latter was found on two occasions in July 2018 and July 2020 on a single locality. Eggs of P. alcon were found on the host plant Gentiana cruciata at the same locality. Despite the fact that many species characteristic of higher altitudes were observed, like Aricia artaxerxes, Pyrgus alveus, Erebia stiria and Lasiommata petropolitana, other, which had still been present a few decades ago, were not found (Parnassius apollo and Boloria pales). In this article, the problem of loss of important butterfly habitats in the region due to overgrowing, and the negative impacts of overgrazing is also highlighted.


Introduction
Škofjeloško hribovje, a roughly 25 km long mountain chain, is one of the highest in Slovenia outside the Alps (Perko & Orožen-Adamič 2001).It is positioned in the southwestern part of the country in the Gorenjska region.Due to its location it forms a barrier between three different climates -continental to the east and south, alpine to the north and sub-Mediterranean to the southwest.Due to its specific geological structure and climate it has a very diverse morphology, with a plethora of different habitats, which is reflected in a diverse fauna and flora found in the region (Ilešič 1938(Ilešič , Šifrer 1974)).Due to the rich diversity and unique habitats, Mt.Blegoš is also a part of the Natura 2000 network (Blegoš; SI3000260; Ur. l.RS 2004a).
The two highest points of the mountain chain are Mt.Blegoš (1,562 m) and Mt.Koprivnik (1,393 m), which have been surveyed for butterflies since the first half of the 20 th century (Carnelutti 1980, Withrington 2003).However, apart from those general overviews, with only the most interesting species mentioned, there has been no extensive account of the butterfly fauna of the two mountains published.Nevertheless, Carnelutti (1980) provides some interesting observations, which can be used for the comparison with the current situation.He mentions several subalpine or alpine species for Mt.Blegoš, specifically Boloria pales, Parnassius apollo (already extinct at that time), Erebia euryale, E. medusa, and Pieris bryoniae.The only other faunistic survey, which only partially overlaps with our studied area, was done by Verovnik (2000), however, the aforementioned highest peaks were not visited at the time.
Given the lack of systematic research, our main objective was to survey the butterfly fauna of the region and check for potential habitats and presence of the interesting species mentioned in the previous studies.We also provide an evaluation of the conservation status and threats to the butterflies in the region.

Geographical characteristics of the region
Škofjeloško hribovje is a mountainous region between the Poljanska Sora River to the south and the Selška Sora River to the north.It is a diverse mountainous landscape which merges to the west, just north of Cerkno, with Cerkljansko hribovje and its highest mountain Porezen (1,630 m), and with Mt.Lubnik (1,025 m), just above Škofja Loka, reaches its easternmost point.Mt.Blegoš and its neighbour, Mt.Koprivnik, are located north of the villages of Volaka and Gorenja Žetina, respectively, and are the highest peaks of the region (Šifrer 1974).
The two mountains are surrounded with an old Paleozoic, presumably Silurian, shale and chives, while their peaks are predominantly composed of younger dolomites and shell limestone, which lie atop the Carboniferous layers.The limestone and dolomites are especially predominant at the top of Mt.Blegoš (Ilešič 1938, Šifrer 1974, Marinček & Wraber 1980).Due to the very complex geological structure composed of mainly impermeable rocks, which represents a transition point between the Alps and the Karst, the surrounding area of Mt.Blegoš is densely intersected with smaller gorges and ravines created by strong temporary torrents (Šifrer 1974).
Given the amount of precipitation and specific geology, the region is characterised by lush vegetation, especially dense mixed woods, consisting predominantly of Fagus sylvatica, Abies alba and Picea abies.F. sylvatica is especially common on the limestone and dolomite near the top of Mt.Koprivnik and in particular Mt.Blegoš, while the surrounding area is mostly covered by mixed woods (49 %) with a predominance of conifers.Those woods have the characteristics of sub-alpine mixed forest of Luzulo-Abieti-Fagetum praealpinum or Luzulo-Fagetum montanum praealpinum, depending on the altitude.Above 1,450 m they are considered as part of Fagetum subalpinum forests (Ilešič 1938, Marinček & Weber 1980).Ash, an important larval host plant of Euphydryas maturna, is also found in the area, especially around »Likar's hayfield« locality.
The highest parts of Mt.Blegoš are covered with extensive grasslands and pastures, which are present also on the southern slopes.These, despite showing the characteristics of a true alpine grasslands and pastures in some places, are of anthropogenic origin, which can be seen in an advanced overgrowing of uncut and un-grazed areas, as well as in a very high upper tree line limit, which nowadays reaches up to 1,500 m.Also typical of Paleozoic shales are low woodland shrubs and vegetation, like Vaccinium myrtillus, Calluna vulgaris and different species of ferns, which are especially common in the overgrown grasslands of Mt.Koprivnik (Ilešič 1938, Marinček & Weber 1980).
One of the main agricultural activities in the region and especially Mt.Blegoš is grazing.Before 1900, it was very widespread, also extending to other parts of the mountain chain (e.g.Mt.Koprivnik).After 1900, however, with the newly formed border between Italy and Slovenia, the grazing activity started to decline (Ilešič 1938).This has been even more prominent in recent decades when there was also a shift from sheep to now predominant cattle grazing (own observations).

Description of the surveys
Despite a few observations of butterflies around Mt. Blegoš, Mt.Koprivnik and their surroundings, no thorough research has ever been undertaken in this region.Thus, a more extensive survey was performed in order to determine the most important species and habitats NATURA SLOVENIAE 23(2): 65-79 from the conservation perspective.We established surveys on 8 transects/localities and, weather permitting, visited them at least once every second week from 27. 5. to 8. 9. 2018, counting the number of butterflies (species and individuals) in the process.The transect surveys were performed according to the Pollard walk method (Pollard 1977).In total, 14 surveys were conducted on all transects on the given dates: 27.5., 3.6., 10.6., 17.6., 26.6., 1.7., 7.7., 22.7., 30.7., 4.8., 13.8., 19.8., 28.8. and 8.9., all in 2018.The only exception is the transect No. 2 -Potok, where only 13 surveys were performed -the survey wasn't performed on 22.7.2018due to bad weather conditions.After extensive surveys in 2018, additional visits were made on some of the localities near the transects in 2019 and 2020, to check for additional expected species.In 2019, one additional survey was performed on localities near transects Nos. 1, 3, 6 (all on 2.6.) and 4 (14.7.), while in 2020, one additional survey was performed on localities near transects Nos. 1, 2, 6 (all 13.4.)and 8 (20.7.), two additional surveys on localities near transects No. 5 and 7 (4.7.and 20.7.), and three additional surveys on locality near transect No. 4 (11.4.,4.7. and 20.7.).Unlike in 2018, the Pollard walks were not carried out in 2019 and 2020.During this research, no major floristic surveys were performed and only certain larval host plants are pointed out in this article.
The selected transects included four main different habitat types (pastures, intensive grasslands, extensive grasslands and forest clearings) at different altitudes, in order to cover as many different ecotypes as possible.Two transects/localities were selected for each habitat type.The individual butterflies were caught (if necessary) with a butterfly net and determined using Tolman & Lewington's (2008) butterfly guide.

Data analysis
We calculated a population density of each species for each transect separately.The population density of species is expressed as number of individuals per survey per 100 m of transect, and was adapted from Čelik & Verovnik (2020) with slight alterations: Where X is the sum of all imagines of species observed in 2018 on a transects during all surveys, Y is the number of surveys performed on a transect (13 for locality »Potok«, and 14 for all other localities) and Z is the length of the transect in metres.

Results
Altogether, 80 species and 5,012 specimens were observed between 27.5.and 8.9.2018.Among these, 1,050 specimens and 52 species were observed on pastures, 890 specimens and 53 species in intensive grasslands, 763 specimens and 53 species inside forest clearings, and 2,309 specimens and 65 species in extensive grasslands.The complete butterfly survey of Mt.Blegoš, Mt.Koprivnik and their surroundings, which also included additional location-specific surveys in 2019 and 2020, yielded altogether 85 species (Tab.2).Of these, 9 species are listed as vulnerable, while two are considered endangered in either Slovenia or Europe (Tab.2).Most of those species were found on more than one occasion and in more than one locality.It is worth noting that the detailed data on exact dates of finding the species and their abundances were not included, due to the sheer amount of obtained information (eight tables were merged in one), but are available on request from the authors of the paper.Carnelutti (1980).
Since the latest records of biodiversity in 1980, agricultural activities became more intensive.Yet, while predominantly lowland habitats are mostly machined and fertilized, many habitats at higher altitudes are in the final overgrowth phase due to isolated intensive grazing (sheep, goats and cattle) and abandonment of mowing (Ilešič 1938).The most obvious is the overgrowing of the higher meadows of Mt.Koprivnik, where mowing or grazing is completely absent.Only the meadows by the macadam road leading to Črni Kal below Mt.Koprivnik are intensively mown.On the other hand, the intensification of agriculture impacted the grazing activity in the highest meadows of Mt.Blegoš.Due to isolated grazing with cattle, some larval food or host plants, such as Gentiana cruciata and once common Arnica montana, are being diminished in number.
Lower meadows are sparse and occur mainly in very steep and exposed areas, such as »Forest by the macadam« and »Likar's hayfield« transects.The latter presents the largest meadow area, where overgrowing is less problematic for the time being.Thus, habitat loss, due to rapid overgrowing and intensive grazing, is the greatest danger to the biodiversity of local butterflies.Some butterflies, like Parnassius apollo, have already disappeared presumably owing to this very reason.
Based on the uniqueness of the habitat and the diversity of butterflies found we defined 4 nature conservation important localities for butterflies in the region, based on the surveyed transect routes: »Mt.Koprivnik«, »Likar's hayfield«, »Forest by the macadam« and »Mt.Blegoš: meadow under the hilltop«.
Transects »Mt.Koprivnik« and »Likar's Hayfield« are the two most important sites with extensive meadows.Unfortunately, both localities, especially meadows of »Mt.Koprivnik«, are subject to overgrowing.Meadows of »Likar's hayfield« are especially characterised by the minor sub-Mediterranean influence as indicated by the presence of thermophilous species such as Satyrium spini, Lysandra coridon, Minois dryas, and Hipparchia fagi.The area consists of southfacing dry bushy grasslands, where in addition Libelloides macaronius is abundant, despite not being reported for the Škofjeloško hribovje (Devetak et. al. 2007).However, the find is not surprising, as it was also recently discovered in NW Slovenia on the Šentvid plateau (Torkar 2021).Both »Mt.Koprivnik« and »Likar's Hayfield« have the highest number of species recorded and are important for both -unique fauna and flora.
The »Forest by the macadam« represents the longest and most heterogeneous transect, consisting mainly of forest clearings, which is in the centre characterised by approximately 50 m of rocky cliffs.This unique habitat for the region hosts the two petrophilous species L. petropolitana and E. stiria.Despite not being listed as threatened in Slovenia or wider, their isolated occurrence on Mt.Blegoš is still of conservation importance.
The last among the important transects is »Mt.Blegoš: meadow under the hilltop«, which represents the largest open pasture partially intensively grazed by cattle.The impact of intensive grazing is manifested by trampled ground and low herbal height.The steeper rockier parts to the northeast of Mt.Blegoš peak are now mostly overgrown by trees.The locality is of particular conservation importance due to the presence of a small colony of P. alcon f. rebeli and its host plant G. cruciata.
From the conservation point of view, the presence of both Euphydryas species, Parnassius mnemosyne, Lopinga achine and P. arion, all included in the Annexes II and/or IV of the Habitats Directive, (OJ EC 1992) is of great importance.Their presence merits further investigations into their population size, distribution, threats and could provide foundations for long term conservation of their habitats and butterfly richness as a whole in both studied mountains.

Conclusions
The complete butterfly survey of Mt.Blegoš, Mt.Koprivnik and their surroundings, which took place between 27.5.and 8.9.2018 and included additional location-specific surveys in 2019 and 2020, yielded altogether 85 species, which amounts to 47 % of the butterfly fauna of Slovenia (Verovnik 2019).Among the surveyed species, 11 are defined as vulnerable or endangered in Slovenia or Europe (Ur. 1. RS 2002, Van Swaay et al. 2010).
The most interesting find is P. alcon f. rebeli, observed only in the high-lying pastures of Mt.Blegoš, not mentioned in the previous surveys.Abandonment of extensive farming, overgrowing of habitats and intensive grazing are the most likely causes for the absence of Boloria pales.The localities were also monitored for the presence of Sedum album, a larval food plant for the locally already extinct butterfly P. apollo (Carnelutti 1980), but unfortunately the plant has never been found.
The authors conclude that Mt.Blegoš and its wider surroundings are an important and biodiversity rich area worth preserving, and that its inclusion in the Natura 2000 conservation network is well deserved.The study also reveals some of the problems with the habitat loss which might arise in the future, due to the abandonment of mowing and grazing in certain areas.In order to preserve such habitats, the old farming practices should be re-implemented, wherever possible.

Table 1 .
The list of transects surveyed during the study.Coordinates are given in a WGS 84 projection.In the case of a broader locality, the observations were made near the transect location, but are sometimes not restricted to the indicated habitat type of the transect.Start/End refer to start and end points of each transect.Tabela 1. Seznam transektov, ki smo jih vzorčili med študijo.Koordinate so podane v WGS 84 projekciji.V primeru širše lokacije so bili popisi opravljeni v bližini transekta, a niso bili vedno omejeni le na habitatni tip, značilen za tisti transekt.Start/End se nanašata na začetno in končno točko transekta.

Table 4 .
(Verovnik et al. 2012ht transects and the number of butterflies/species found during 2018 surveys.Tabela 4. Primerjava vseh osmih transektov in števila metuljev/vrst, popisanih v letu 2018.Mt.Blegoš.Interestingly, there is a specimen of E. pronoe collected by Mate Hafner in 1911 in the collection of Slovenia NHM(Verovnik et al. 2012) from Mt. Blegoš, a record neglected in the overview by