NATURA SLOVENIAE 23(1): 21-33 Prejeto / Received: 4. 5. 2021 SCIENTIFIC PAPER Sprejeto / Accepted: 9. 8. 2021 Biotehniška fakulteta Univerze v Ljubljani in Nacionalni inštitut za biologijo, Ljubljana, 2021 Local host ant usage of scarce large blue Phengaris teleius and dusky large blue P. nausithous (Lepidoptera: Lycaenidae) at Goričko Nature Park (NE Slovenia) Valerija ZAKŠEK1, Barbara ZAKŠEK2, Gregor BRAČKO1, Marijan GOVEDIČ2, Rudi VEROVNIK1 1Department of Biology, Biotechnical Faculty, University of Ljubljana, Jamnikarjeva 101, SI-1000 Ljubljana, Slovenia; E-mail: valerija.zaksek@bf.uni-lj.si, gregor.bracko@bf.uni-lj.si, rudi.verovnik@bf.uni-lj.si 2Centre for Cartography of Fauna and Flora, Antoličičeva 1, SI-2204 Miklavž na Dravskem polju; E-mail: barbara.zaksek@ckff.si, marijan.govedic@ckff.si Abstract. In our contribution we report on the local host ants of two threatened and protected butterfly species, the scarce large blue (Phengaris teleius) and the dusky large blue (P. nausithous) at Goričko (NE Slovenia), which hosts one of the largest and the most important metapopulation for both species of large blues in Slovenia. Larvae of both species are developing in Myrmica ant nests and different ant species may be used as larval hosts in different parts of the species range. During our study, seven species of potential host ants of the genus Myrmica were found at 12 selected sampling sites. A total of 142 ant nests were examined for the presence of Phengaris larvae. Larvae of P. teleius were found in 25 nests of three ant species: M. scabrinodis, M. rubra and M. gallienii, while larvae of P. nausithous were found in 9 nests, all of M. rubra. The results of the present study provide the first insight into the local host ants of the two Phengaris species in Slovenia and could serve as an important source for active conservation of both species in Slovenia. Key words: Phengaris, Slovenia, host ants, Goričko, Myrmica Izvleček. Gostiteljske vrste mravelj strašničinega mravljiščarja Phengaris teleius in temnega mravljiščarja P. nausithous (Lepidoptera: Lycaenidae) v Krajinskem parku Goričko (SV Slovenija) – V prispevku predstavljamo rezultate prve raziskave gostiteljskih vrst mravelj dveh ogroženih in zavarovanih vrst dnevnih metuljev, strašničinega (Phengaris teleius) in temnega mravljiščarja (P. nausithous) v Sloveniji. Mravljišča in potencialne gostiteljske vrste mravelj smo vzorčili na Goričkem (SV Slovenija), kjer je središče razširjenosti obeh vrst v Sloveniji. Na dvanajstih lokacijah smo našli sedem vrst mravelj iz rodu Myrmica, ki so potencialne gostiteljske vrste gosenic mravljiščarjev. Prisotnost gosenic mravljiščarjev smo preverili v 142 mravljiščih. V 25 mravljiščih vrst Myrmica scabrinodis, M. rubra in M. gallienii smo našli gosenice strašničinega mravljiščarja, v devetih mravljiščih, vsa vrste M. rubra, pa gosenice temnega mravljiščarja. Rezultati raziskave dajejo prvi vpogled v gostiteljske vrste mravelj strašničinega in temnega mravljiščarja v Sloveniji in bodo lahko rabili kot pomembno izhodišče pri aktivnem ohranjanju teh dveh ogroženih vrst metuljev. Ključne besede: mravljiščarji, Phengaris, Slovenija, gostiteljske mravlje, Goričko, Myrmica 22 Valerija ZAKŠEK et al.: Local host ant usage of scarce large blue and dusky large blue ... / SCIENTIFIC PAPER NATURA SLOVENIAE 23(1): 21-33 Introduction Butterflies of the genus Phengaris Doherty, 1891 (syn. Maculinea van Ecke, 1915) are among the most studied insects in Europe, mainly due to their highly specific myrmecophilous life cycle, vulnerability and endangerment (e.g. Settele et al. 2005). All four European Phengaris species, i.e. P. arion (Linnaeus, 1758), P. alcon (Denis & Schiffermüller, 1775), P. teleius (Bergsträsser, 1779) and P. nausithous (Bergsträsser, 1779), live in Slovenia (Verovnik et al. 2012). The scarce large blue (P. teleius) and the dusky large blue (P. nausithous) occur sympatricaly in northeastern Slovenia, where they often live syntopically. The range of the P. nausithous in Slovenia is limited to the northeastern part of the country, while the range of the P. teleius also extends to the western parts. Both species live on extensively used humid meadows that are among the most threatened habitats, mainly due to agricultural intensification, fragmentation and abandonment of traditional management (e.g. van Swaay et al. 2012). As such, they have become flagship species for nature conservation and both are protected by the Habitats’ Directive (Annex II, IV) as a key instrument for biodiversity conservation in Europe (OJ EC 1992). Although both species use the same host plant, the great burnet (Sanguisorba officinalis L.), and share some general characteristics of their habitat, there are differences in their ecology, including lifecycle, microhabitat preferences and use of host ants (e.g. Nowicki et al. 2005). The females lay their eggs only on the S. officinalis and the early instar of larvae feed on host plant’s flowers and seeds. When the larvae reach the fourth instar, they leave the host plant. On the ground, they have to be adopted by ants of the genus Myrmica Latreille, 1804, which take the larvae into the ant nest. There they predate on ant brood and/or mimic ant larvae and are fed by ant workers (Elmes et al. 1992). They overwinter (one or two winters) in ant nests and pupate in late spring (Thomas et al. 1998). Pioneering work on the adoption by Myrmica ants had suggested that each Phengaris species parasitizes a specific Myrmica species (Thomas et al. 1989). Later, it was shown that larvae can be adopted by different Myrmica species (the so-called primary and secondary host: Elmes et al. 1998) and host species and colony size have an important impact on larval survival (Witek et al. 2010). However, several recent studies raise doubts on a high host ant specialization of Phengaris species across Europe (e. g. Pech et al. 2007, Tartally et al. 2019). The most recent and comprehensive survey across Europe (Tartally et al. 2019) showed that each Phengaris species is predominantly specialised to a single, basically the most abundant Myrmica species found on Phengaris site. However, there is a geographic mosaic as a difference; populations of the same Phengaris species, sometimes in close proximity, often use different host ant species. Most data on the host specificity of Phengaris were obtained in Central and Eastern Europe, especially in Poland, Hungary and Romania (e.g. Stankiewicz et al. 2005, Tartally & Varga 2008, Witek et al. 2008, Pech & Sedlachek 2016). The term host specificity usually refers to the ability of Phengaris butterflies to develop within the nests of particular host ant species. To quantify specificity, ideally the number of Phengaris larvae adopted by each Myrmica ant species, should be known, as well as the number that survive in ant nests and develop into adults (Thomas et al. 2005). Although the level of specialisation and the character of the Phengaris–Myrmica host system is now better understood, local data on hosts are still needed, and are useful for site Valerija ZAKŠEK et al.: Local host ant usage of scarce large blue and dusky large blue ... / SCIENTIFIC PAPER 23 NATURA SLOVENIAE 23(1): 21-33 management and species conservation at the local scale. Knowledge of host ant specificity is essential for the conservation of these two butterfly species. Although the host ant specificity of Phengaris species (especially for P. teleius and P. nausithous) is relatively well known in Europe, there are no published data on this topic for Slovenia. Only a basic survey of Myrmica ants in the habitat of P. teleius and P. nausithous was conducted in the central area of Slovenske Gorice in 2003 and 2004 (Zakšek 2004). The study revealed that M. scabrinodis and M. rubra are the commonest species in the vicinity of S. officinalis, although none of the ant nests were opened and examined for the presence of Phengaris larvae. To fill this gap, we studied host ant specificity of P. teleius and P. nausithous in the Goričko region and the pattern of their local variability. Our results are of high importance for establishing site-specific management of the habitat of the two threatened butterfly species in the region. Materials and methods Study area and study sites Goričko is a predominantly rural hilly countryside in NE Slovenia and most of it is included at Goričko Nature Park and the Goričko Natura 2000 site (SI3000221) designated to maintain a favourable conservation status of P. teleius and P. nausithous and other selected species and habitat types (Ur. l. RS 2004). Humid meadows in the valleys are home to the largest populations of P. teleius and P. nausithous in Slovenia (Zakšek et al. 2005). Twelve sampling sites were selected in the eastern part of Goričko NP (Fig. 1), where the population density of both species is the highest (Zakšek et al. 2012). All sampling sites hosted P. teleius, while P. nausithous was present at ten of the selected sites (see Tab. 1 for details). 24 Valerija ZAKŠEK et al.: Local host ant usage of scarce large blue and dusky large blue ... / SCIENTIFIC PAPER NATURA SLOVENIAE 23(1): 21-33 Table 1. Detailed information on study sites in the Goričko region, NE Slovenia, together with occurrence data of Phengaris teleius and/or P. nausithous prior to the sampling in 2011. Tabela 1. Podrobnejše informacije vzorčnih lokacijah na Goričkem skupaj s podatki o prisotnosti strašničinega (Phengaris teleius) in/ali temnega mravljiščarja (P. nausithous), zabeleženih pred vzorčenjem v letu 2011. Study site code Locality Coordinates (WGS84) Presence of Phengaris species Lat (°N) Long (°E) NER1 Ženavlje, meadow at Koritiški potok, 600 m NW from hamlet Vreja 46.844218 16.180123 P. teleius, P. nausithous NER2 Neradnovci, meadow 460 m NE from village Ženavlje, on the left bank of Koritiški potok 46.838818 16.185550 P. teleius, P. nausithous ČEP Čepinci, meadow 440 m SW from hamlet Smodin Breg 46.840992 16.215897 P. teleius, P. nausithous STAN Gornji Petrovci, meadow 320 m SE from hamlet Džešarni 46.804415 16.205508 P. teleius, P. nausithous KUŠ Kuštanovci, meadow at Kmetov potok 200 m NE from homestead Dirdin 46.779013 16.190457 P. teleius, P. nausithous DOL Dolenci, meadow 550 NE from hamlet Šoštarne Grabe 46.852637 16.271801 P. teleius, P. nausithous ŠAL Šalovci, meadow at Krplivniški potok SE from hamlet Vrvji Breg 46.804811 16.280853 P. teleius IVAN1 Ivanjševci, meadows between hamlets Kotov Kraj in Balaškin Kraj 46.766287 16.292941 P. teleius, P. nausithous IVAN2 Ivanjševci, meadow 400 m NE from hamlet Kotov Kraj 46.763510 16.296618 P. teleius, P. nausithous MOT1 Motvarjevci, meadow NE from house Motvarjevci 73 46.706049 16.351857 P. teleius, P. nausithous MOT2 Motvarjevci, left bank of the stream Kobilje affluent at Motvarjevci 46.704889 16.353332 P. teleius, P. nausithous KOB Kobilje, meadow 640 m SW from gravel pit at the western part of Kobilje village 46.689622 16.375921 P. teleius Valerija ZAKŠEK et al.: Local host ant usage of scarce large blue and dusky large blue ... / SCIENTIFIC PAPER 25 NATURA SLOVENIAE 23(1): 21-33 Figure 1. Map of Goričko Nature Park (dark line represents its southern border) showing the position of the sampling sites of our study in 2011 and 2012. The proportion of Myrmica species ant nests at each sampling site is shown with pie charts. The size of the circle corresponds to the number of examined Myrmica ant nests (see Tab. 3 for details). The small circles »localities« represents accurate location of sampling site, as the position of pie charts is moved to avoid their overlap. Slika 1. Zemljevid Krajinskega parka Goričko (temna linija ponazarja njegovo južno mejo) z lokacijami vzorčnih mest v tej raziskavi v letih 2011 in 2012. Delež mravljišč mravelj iz rodu Myrmica na vsakem vzorčnem mestu je prikazan s tortnim grafikonom. Velikost kroga je sorazmerna številu pregledanih mravljišč mravelj iz rodu Myrmica. Majhne točke lokalitet prikazujejo natančne lokacije vzorčnih lokacij (v primerih prekrivanja so prikazi deležev mravljišč nekoliko premaknjeni). Field work Field sampling was carried out in 2011 and 2012, from mid-May to mid-June when Phengaris larvae were at the pre-pupal stage. At selected sites, we searched for Myrmica ant nests within one-metre radius of S. officinalis, which is likely within a foraging distance of Myrmica ants (Elmes et al. 1998). All Myrmica ant nests found were marked and carefully excavated. The nest material was placed on a white sheet, where the nests were opened to check for the presence of Phengaris larvae. After excavation, the nest material and vegetation were restored to their original condition as much as possible. Five to ten ant workers were collected from each nest and preserved in 70% ethanol for later identification. In addition, a random sample of foraging 26 Valerija ZAKŠEK et al.: Local host ant usage of scarce large blue and dusky large blue ... / SCIENTIFIC PAPER NATURA SLOVENIAE 23(1): 21-33 Myrmica ant species was collected on sampling sites when searching for ant nests using the hand collection method. Myrmica species were identified according to Seifert (2018) and Radchenko & Elmes (2010). Phengaris larvae were identified at the site using a 20× magnifier lens and determination key by Śliwińska et al. (2006) and afterward returned to the nests. Results Ant species on the study sites A total of 142 Myrmica nests were surveyed revealing presence of seven species at twelve sites hosting P. teleius and/or P. nausithous in the eastern Goričko NP: M. curvithorax Bondroit, 1920, M. gallienii Bondroit, 1920, M. rubra (Linnaeus, 1758), M. ruginodis Nylander, 1846, M. sabuleti, Meinert, 1861, M. scabrinodis Nylander, 1846 and M. schencki Viereck, 1903 (Tab. 2). The total number of Myrmica nests found on each locality varied from 4 at MOT 2 to 35 at KOB (Tab. 3). Myrmica scabrinodis was the commonest species of the genus found on ten sites with 105 recorded nests. It was followed by M. rubra, found on eight sites (22 nests), and M. gallienii, found on four sites (6 nests) (Tab 3). On all sites where it occurred, M. scabrinodis had the highest proportion of the total nests found (Fig. 1). Table 2. All Myrmica ant species recorded on selected sampling sites at Goričko Nature Park during this study in years 2011 and 2012. For codes of sampling sites see Tab. 1. In species marked with asterisk only individual ant workers were recorded on the study site (no nests were found and excavated). Tabela 2. Vse vrste mravelj iz rodu Myrmica najdene na izbranih vzorčnih mestih v Krajinskem parku Goričko tekom te raziskave v letih 2011 in 2012. Oznake vzorčnih mest so enake kot v Tab. 1. Pri vrstah označenih z zvezdico so bi le med vzorčenjem najdene samo posamezne delavke na vzorčnem mestu. Sampling site Myrmica species found NER1 M. rubra, M. scabrinodis, M. schencki NER2 M. rubra ČEP M. ruginodis, M. scabrinodis STAN M. gallienii, M. rubra, M. scabrinodis KUŠ M. rubra, M. scabrinodis DOL M. gallienii, M. rubra, M. scabrinodis ŠAL M. rubra, M. ruginodis, M. scabrinodis IVAN1 M. curvithorax, M. scabrinodis, M. schencki* IVAN2 M. curvithorax, M. gallienii, M. rubra, M. sabuleti*, M. scabrinodis, M. schencki* MOT1 M. sabuleti*, M. scabrinodis MOT2 M. rubra KOB M. gallienii, M. rubra*, M. ruginodis, M. sabuleti, M. scabrinodis Valerija ZAKŠEK et al.: Local host ant usage of scarce large blue and dusky large blue ... / SCIENTIFIC PAPER 27 NATURA SLOVENIAE 23(1): 21-33 Table 3. Number of Myrmica ant nests and number of Phengaris teleius and P. nausithous larvae found in nests at each sampling site in Goričko Nature Park during our study in 2011 and 2012. For codes of sampling sites see Tab. 1. Tabela 3. Število mravljišč rodu Myrmica in število najdenih gosenic strašničinega (Phengaris teleius) in/ali temnega mravljiščarja (P. nausithous) na posameznih vzorčnih mestih v Krajinskem parku Goričko tekom te raziskave v letih 2011 in 2012. Oznake vzorčnih mest so enake kot v Tab. 1. Sampling site Myrmica species No. of nests No. of nests with P. teleius No. of P. teleius larvae No. of nests with P. nausithous No. of P. nausithous larvae NER 1 M. scabrinodis 6 1 1 0 0 M. rubra 2 0 0 0 0 M. schencki 1 0 0 0 0 NER 2 M. rubra 6 3 6 5 57 ČEP M. scabrinodis 12 2 2 0 0 M. ruginodis 1 0 0 0 0 STAN M. scabrinodis 10 3 10 0 0 M. rubra 3 1 2 0 0 M. gallienii 2 0 0 0 0 KUŠ M. scabrinodis 9 2 2 0 0 M. rubra 1 1 1 0 0 DOL M. scabrinodis 8 2 3 0 0 M. rubra 2 2 4 2 4 M. gallienii 1 1 1 0 0 ŠAL 1 M. scabrinodis 8 0 0 0 0 M. rubra 2 0 0 0 0 M. ruginodis 1 0 0 0 0 IVAN 1 M. scabrinodis 6 1 2 0 0 M. curvithorax 1 0 0 0 0 IVAN 2 M. scabrinodis 6 0 0 0 0 M. rubra 2 0 0 0 0 M. gallienii 2 0 0 0 0 M. curvithorax 1 0 0 0 0 MOT 1 M. scabrinodis 10 4 10 0 0 MOT 2 M. rubra 4 1 11 2 26 KOB M. scabrinodis 30 1 1 0 0 M. gallienii 1 0 0 0 0 M. ruginodis 2 0 0 0 0 M. sabuleti 2 0 0 0 0 Total 142 25 56 9 87 28 Valerija ZAKŠEK et al.: Local host ant usage of scarce large blue and dusky large blue ... / SCIENTIFIC PAPER NATURA SLOVENIAE 23(1): 21-33 Host ants P. teleius larvae were found in 25 Myrmica ant nests and P. nausithous in 9 nests (Tab. 3). Altogether, 56 larvae of P. teleius and 87 larvae of P. nausithous were found (Tab. 3). P. nausithous larvae were found exclusively in M. rubra nests, while P. teleius larvae were recorded in ant nests of three Myrmica species: M. scabrinodis, M. rubra and M. gallienii. The highest proportion of all infested nests with P. teleius was in M. scabrinodis (64%), while the proportion of infestation with P. teleius per investigated ant nest and species was the highest in M. rubra. A different species of host ants were found on three locations. The co-occurrence of both butterfly species larvae in the same ant nest was observed in six ant nests, in all cases M. rubra was a host species. In general, P. teleius was recorded in a larger number of ant nests compared to P. nausithous, while P. nausithous larvae were found in a larger number per ant nest. The median value of P. teleius larvae found per ant nest is 1, while the median value of P. nausithous larvae number found per ant nest is 3. In three M. rubra nests, larger numbers of larvae (more than 20) per nest were found. The largest number of larvae in a single nest was counted in M. rubra nest in the locality MOT2 – a total of 35 larvae, 11 larvae of P. teleius and 24 larvae of P. nausithous. In the locality NER2, 26 and 22 larvae of P. nausithous were found, respectively, accompanied by a single P. teleius larva in each nest. Altogether, more than half of all larvae of both species were found in the three M. rubra nests mentioned above. Discussion During our study, a total of seven species of Myrmica ants were recorded in meadows with P. teleius and/or P. nausithous at Goričko Nature Park, which is half of all Myrmica ant species known for Slovenia (Bračko 2007). The fact that 19.7% of all Myrmica nests examined contained Phengaris larvae and most of these contained only a few larvae, follows the pattern of ant nests infestation on Phengaris sites across Europe (e.g. Witek et al. 2010). As ant nests vary greatly in their susceptibility to larval parasitism, typical Phengaris sites include many uninfested nests, several with moderate infestation, and a few with high infestation (Tartally et al. 2008). According to our results, we can consider M. rubra as the primary and most important ant host of P. nausithous at Goričko. A high specificity in relationship of P. nausithous with M. rubra has also been reported across Europe (Witek et al. 2008, 2010), including western Hungary, which is closest to our Goričko study region (Tartally & Varga 2005, Tartally et al. 2019). For P. teleius, M. rubra and M. scabrinodis can be considered as primary hosts at Goričko. P. teleius has the most diverse hosts among European Phengaris species and often uses the locally most abundant Myrmica species (e.g. Tartally & Varga 2008, Witek et al. 2010, Tartally et al. 2019). This is in line with our observations, as the two primary host Myrmica species were also the most abundant in our study area, and with observations at the Őrség National Park in Hungary (Tartally & Varga 2008). Among the other five Myrmica species recorded, we found only one larva of P. teleius in an ant nest of M. gallienii. Larvae of P. teleius were found in nests of M. gallienii also in Poland (Stankiewicz & Sielezniew 2002). Valerija ZAKŠEK et al.: Local host ant usage of scarce large blue and dusky large blue ... / SCIENTIFIC PAPER 29 NATURA SLOVENIAE 23(1): 21-33 Although the number of M. scabrinodis nests discovered was much higher than that of M. rubra (105 vs. 22), the percentage of nests parasitized by Phengaris was higher in M. rubra (41% vs. 24%), as was the total number of larvae detected (111 in M. rubra vs. 31 in M. scabrinodis). Three nests of M. rubra contained more than 20 Phengaris larvae. Moreover, co-occurrence of both Phengaris species larvae was detected exclusively in M. rubra nests. We found six cases of co-occurrence out of total 8 or 9 nests found infected by P. teleius or P. nausithous, respectively. The large number of larvae and co-occurrence of the two Phengaris species in M. rubra nests was previously reported by Tartally & Varga from western Hungary (2005). In their study, they found a M. rubra colony with 36 larvae of both Phengaris species, which is comparable to our colony from MOT2 (35 larvae). Since M. rubra forms the most populous colonies of all Central European Myrmica species (Seifert 2018), the highest numbers of parasitizing larvae in their colonies is not surprising. Such large colonies have a higher carrying capacity to host and survive a large number of Phengaris larvae. Although M. scabrinodis nests were parasitized in lower percentage and contained lower total number of larvae, this species still represents an important host for Phengaris larvae at Goričko, mostly as it is the most frequent ant species in Phengaris sites. It is particularly important host for P. teleius, which as mentioned above, often uses locally most abundant Myrmica species. Conservation implications The nest of Myrmica rubra hosting the largest number of Phengaris larvae was found at Motvarjevci (MOT2), along an abandoned road verge. This finding indicates and confirms the importance of road verges and grassland margins as larval habitat for P. teleius and, in particular, for P. nausithous (e.g. Wynhoff et al. 2011). Myrmica rubra, as the main host ant of P. nausithous, is known to be less thermophilic than M. scabrinodis, preferring sheltered and more overgrown habitat for its nests (Wynhoff et al. 2011). According to Seifert (2018), M. rubra gains optimum in mesophilic to moist conditions, and is absent only from most xerothermic and sparsely-vegetated habitats. It is often the only ant in very high-grassy lowland meadows and tall herb communities. Therefore, it is important to maintain parts of more dense vegetation with the larval host plant along meadow margins, which could be beneficial for M. rubra and both target butterfly species (see also Tartally & Varga 2005). Myrmica scabrinodis is a hygrophilous to moderately thermophilic species and reaches highest densities in meadows or ecotones with moderate height of grasses (Seifert 2018). Each host ant species has its own niche and, according to current knowledge, the two Myrmica species require different mowing regimes (Wynhoff et al. 2011), which should be taken into consideration in practical management, especially on smaller, isolated sites where both ant species occur together. Myrmica scabrinodis seems to benefit from mowing in early June, while M. rubra benefits from mowing in late autumn which should be combined with some annually unmown parts/verges that are alternated among years to prevent overgrowing especially by invasive plants (Wynhoff et al. 2011). The general recommendation for habitat management should thus consider mosaic mowing offering many different microhabitat opportunities. However, at least in the last decade, the habitat and populations of both species in NE Slovenia have been declining (Zakšek et al. 2020), so moving towards more active conservation of both species is essential for their long term survival. With basic knowledge on their larval ecology in hand, potential restoration of new habitats or focusing on a conservation of the most important parts of the larval habitat of both species will enable a first step to halt their decline. It should be emphasised that there is no active habitat restoration possible without knowledge and monitoring of ant communities (e.g. Wynhoff et al. 2017). 30 Valerija ZAKŠEK et al.: Local host ant usage of scarce large blue and dusky large blue ... / SCIENTIFIC PAPER NATURA SLOVENIAE 23(1): 21-33 Povzetek Strašničin (Phengaris teleius) in temni mravljiščar (P. nausithous) sta ozko specializirani vrsti dnevnih metuljev. Gosenice obeh vrst se razvijajo v mravljiščih mravelj iz rodu Myrmica, izbira gostiteljskih vrst mravelj pa se lahko geografsko (npr. v različnih delih Evrope) ali lokalno razlikuje. Njun razvoj je vezan na zdravilno strašnico (Sanguisorba officinalis), na katero samice odlagajo jajčeca in kjer se razvijajo prvi stadiji gosenic. Po posvojitvi, od četrtega larvalnega stadija naprej, se gosenice obeh vrst razvijajo v mravljiščih mravelj iz rodu Myrmica. Tam se prehranjujejo na dva načina: plenijo zarod mravelj ali pa jih hranijo mravlje kot svoj zarod (t.i. kukavičji način prehranjevanja); ali pa uporabljajo kombinacijo obojega. Zaradi specifičnega razvojnega cikla in življenja na mokrotnih travnikih sta vrsti tako v Sloveniji kot drugod v Evropi ogroženi in tudi zavarovani. V letih 2011 in 2012 smo na Goričkem v severovzhodni Sloveniji ugotavljali, katere so gostiteljske vrste mravelj strašničinega in temnega mravljiščarja. To je prva raziskava gostiteljskih vrst mravelj v Sloveniji. Gostiteljske mravlje smo vzorčili na dvanajstih lokacijah na Goričkem, ki je eno največjih in najpomembnejših območij razširjenosti za obe vrsti mravljiščarjev v Sloveniji. Na območju raziskave smo zabeležili sedem vrst mravelj iz rodu Myrmica, kar je polovica vseh znanih vrst tega rodu v Sloveniji. Prisotnost gosenic mravljiščarjev smo preverjali v 142 mravljiščih mravelj iz rodu Myrmica. Gosenice strašničinega mravljiščarja smo našli v mravljiščih treh različnih vrst mravelj, M. scabrinodis, M. rubra in M. gallienii, medtem ko so bile gosenice temnega mravljiščarja najdene izključno v mravljiščih M. rubra. Skupaj smo gosenice strašničinega mravljiščarja našli v 25 mravljiščih, gosenice temnega pa v devetih mravljiščih. Kljub manjšemu številu mravljišč je bilo skupno število najdenih gosenic temnega mravljiščarja višje, saj so bile gosenice te vrste v mravljiščih številnejše. Razlogov za to je lahko več: M. rubra je znana po svojih velikih kolonijah in kot take lahko gostijo večje število gosenic; temni mravljiščar v nasprotju s strašničinim, ki se hrani izključno plenilsko, uporablja obe strategiji prehranjevanja. Zanimivo je, da je bilo najvišje število najdenih gosenic v enem mravljišču M. rubra kar 35, zastopane pa so bile gosenice tako strašničinega kot temnega mravljiščarja. O tako visokem številu gosenic v enem mravljišču so v literaturi podatki tudi iz sosednje zahodne Madžarske. Rezultati naše raziskave dajejo prvi vpogled v gostiteljske vrste mravelj za strašničinega in temnega mravljiščarja v Sloveniji. Ugotavljamo, da je temni mravljiščar tudi v Sloveniji glede izbire gostiteljskih mravlje ozko specifičen, medtem ko je za strašničinega mravljiščarja značilna večja plastičnost glede gostiteljskih vrst mravelj. Glede na to, da se ohranitveno stanje obeh vrst v Sloveniji slabša, bodo rezultati lahko pomembna osnova pri aktivnem ohranjanju teh dveh ogroženih vrst mravljiščarjev v Sloveniji. Acknowledgements The study was part of the project »Krajina v harmoniji« (Teritorialno sodelovanje, SLO-HU: 2007-2013). We are grateful to Primož Presetnik (CKFF) for his help during field work, to Kristjan Malačič (Goričko NP) for communicating with the land owners and to Ali Šalamun (CKFF) for preparation of the map. Nest disturbance was in accordance with the licence (35603-3/2010-4) issued by the Slovenian Environment Agency of the Ministry of Environment and Spatial Planning of the Republic of Slovenia to CKFF. The study was partially supported by the Slovenian Research Agency (Program P1-0184). Valerija ZAKŠEK et al.: Local host ant usage of scarce large blue and dusky large blue ... / SCIENTIFIC PAPER 31 NATURA SLOVENIAE 23(1): 21-33 References Bračko G. (2007): Checklist of the ants of Slovenia (Hymenoptera: Formicidae). Nat. Slov. 9(1): 15-24. Elmes G.W., Thomas J.A. (1992): Complexity of species conservation in managed habitats: interaction between Maculinea butterflies and their ant hosts. Biodivers. Conserv. 1: 155-169. Elmes G.W., Thomas J.A., Wardlaw J.C., Hochberg M.E., Clarke R.T., Simcox D.J. (1998): The ecology of Myrmica ants in relation to the conservation of Maculinea butterflies. J. Insect Conserv. 2: 67-78. Nowicki P., Witek M., Skorka P., Settele J., Woyciechowski M. (2005): Population ecology of the endangered butterflies Maculinea teleius and M. nausithous and the implications for conservation. Popul. Ecol. 47: 193-202. OJ EC (1992): Council Directive 92/43/EEC of 21 May 1992 on the conservation of natural habitats and of wild fauna and flora. Official Journal of the European Communities L 206, 22. 7. 1992: 7-50. Pech P., Sedlachek O. (2016): Records of host ant use of Phengaris Doherty, 1891 (Lepidoptera, Lycaenidae) in the Czech Republic. Nota Lepid. 39: 85-91. Pech P., Friz Z., Konvicka M. (2007): Species-Specificity of the Phengaris (Maculinea) – Myrmica Host System: Fact or myth? (Lepidoptera: Lycaenidae; Hymenoptera: Formicidae). Sociobiology 50: 983-1003. Radchenko A., Elmes G.W. (2010): Myrmica ants (Hymenoptera, Formicidae) of the Old World. Natura Optima Deux, Warszaw, 789 pp. Seifert B. (2018): The ants of Central and North Europe. Lutra Verlags- und Vertriebsgesellschaft, Tauer, 408 pp. Settele J., Kühn E., Thomas J. (eds.) (2005): Studies on the ecology and conservation of butterflies in Europe: Maculinea butterflies as a model, Vol. 2, Pensoft, Sofia, Bulgaria, 289 pp. Stankiewicz A.M., Sielezniew M. (2002): Host specificity of Maculinea teleius Bgstr. and M. nausithous Bgstr. (Lepidoptera: Lycaenidae): the new insight. Anna. Zool. 52: 403-408. Stankiewicz A.M., Sielezniew M., Švitra G. (2005): Myrmica schencki (Hymenoptera: Formicidae) rears Maculinea rebeli (Lepidoptera: Lycaenidae) in Lithuania: new evidence for geographical variation of host-ant specificity of an endangered butterfly. Myrmecol. Nachr. 7: 51-54. Śliwińska E.B., Nowicki P., Nash D.R., Witek M., Settele J., Woyciechowski M. (2006): Morphology of caterpillars and pupae of European Maculinea species (Lepidoptera: Lycaenidae) with an identification table. Entomol. Fenn. 17: 351-358. Tartally A., Varga Z. (2005): Myrmica rubra (Hymenoptera: Formicidae): the first data on host-ant specificity of Maculinea nausithous (Lepidoptera: Lycaenidae) in Hungary. Myrmecol. Nachr. 7: 55-59. Tartally A., Varga Z. (2008): Host ant use of Maculinea teleius in the Carpathian Basin (Lepidoptera: Lycaenidae). Acta Zool. Acad. Sci. H. 54(3): 257-268. Tartally A., Nash D.R., Lengyel S., Varga Z. (2008): Patterns of host ant use by sympatric populations of Maculiea alcon and M. ‘rebeli’ in the Carpathian Basin. Insect. Soc. 55: 370-381. 32 Valerija ZAKŠEK et al.: Local host ant usage of scarce large blue and dusky large blue ... / SCIENTIFIC PAPER NATURA SLOVENIAE 23(1): 21-33 Tartally A., Thomas J.A., Anton C., Balletto E., Barbero F., Bonelli S., Bräu M., Casacci L.P., Csősz S., Czekes Z., Dolek M., Dziekańska I., Elmes G., Fürst M.A., Glinka U., Hochberg M.E., Höttinger H., Hula V., Maes D., Munguira M.L., Musche M., Nielsen P.S., Nowicki P., Oliveira P.S., Peregovits L., Ritter S., Schlick-Steiner B.C., Settele J., Sielezniew M., Simcox D.J., Stankiewicz A.M., Steiner F.M., Švitra G., Ugelvig L.V., van Dyck H., Varga Z., Witek M., Woyciechowski M., Wynhoff I., Nash D.R. (2019): Patterns of host use by brood parasitic Maculinea butterflies across Europe. Phil. Trans. R. Soc. B 374: 20180202. Thomas J.A., Elmes, G.W., Wardlaw J.C., Woyciechowski M. (1989): Host specifity among Maculinea butterflies in Myrmica ant nests. Oecologia 79: 425-457. Thomas J.A., Elmes G.W., Wardlaw J.C. (1998): Polymorphic growth in larvae of the butterfly Maculinea rebeli, a social parasite of Myrmica ant colonies. Proc. R. Soc. Lond. B. 265: 1895- 1901. Thomas J.A., Elmes, G.W., Schönrogge K., Simcox D.J., Settele J. (2005): Primary hosts, secondary hosts and ‘non host’: common confusion in the interpretation of host specificity in Maculinea butterflies and other social parasites of ants. In: Settele J., Kühn E. (Eds.), Studies on the Ecology and Conservation of Butterflies in Europe, Species Ecology along a European Gradient: Maculinea Butterflies as a Model, Vol. 2. Pensoft, Sofia, Bulgaria, pp. 99-104. Ur. l. RS (2004): Uredba o posebnih varstvenih območjih (območjih Natura 2000). Uradni list RS 14(49): 13173-13395. Van Swaay C., Collins S., Dušej G., Maes D., Munguira M.L., Rakosy L., Ryrholm N., Šašić M., Settele J., Thomas J.A., Verovnik R., Verstrael T., Warren M., Wiemers M., Wynhoff I. (2012): Dos and don’ts for butterflies of the habitats directive of the European Union. Nature Conservation 1: 73-153. Verovnik R., Rebeušek F., Jež M. (2012): Atlas dnevnih metuljev (Lepidoptera: Rhopalocera) Slovenije, Atlas of butterflies (Lepidoptera: Rhopalocera) of Slovenia. Atlas faunae et florae Sloveniae 3. Center za kartografijo favne in flore, Miklavž na Dravskem polju, 456 pp. Witek M., Śliwińska E.B., Skórka P., Nowicki P., Wantuch M., Vrabec V., Settele J., Woyciechowski M. (2008): Host ant specificity of large blue butterflies Phengaris (Maculinea) (Lepidoptera: Lycaenidae) inghabiting humid grasslands in East-central Europe. Eur. J. Entomol. 105: 871-877. Witek M., Nowicki P., Śliwińska E.B., Skórka P., Settele J., Schönrogge K., Woyciechowski M. (2010): Local host ant specifity of Phengaris (Maculinea) teleius butterfly, an obligatory social parasite of Myrmica ants. Ecol. Entomol. 35: 557-564. Wynhoff I., van Gestel R., van Swaay C., van Langevelde F. (2011): Not only the butteflies: managing ants on road verges to benefit Phengaris (Maculinea) butterflies. J. Insect Conserv. 15: 189-206. Wynhoff I., Kolvoort A.M., Bassignana C.F., Berge M.P., van Langevelde F. (2017): Fen meadows on the move for the conservation of Maculinea (Phengaris) teleius butterflies. J. Insect Conserv. 21: 379-392. Zakšek B., Govedič M., Kogovšek N., Rebeušek F., Šalamun A., Verovnik R. (2012): Kartiranje dnevnih metuljev v Krajinskem parku Goričko v letih 2010 in 2011. Center za kartografijo favne in flore, Miklavž na Dravskem polju, 141 pp. Zakšek B., Verovnik R., Zakšek V., Kogovšek N., Govedič M. (2020): Monitoring izbranih ciljnih vrst metuljev v letu 2020. Center za kartografijo favne in flore, Miklavž na Dravskem polju, 109 pp. Valerija ZAKŠEK et al.: Local host ant usage of scarce large blue and dusky large blue ... / SCIENTIFIC PAPER 33 NATURA SLOVENIAE 23(1): 21-33 Zakšek V. (2004): Izbira habitata in ogroženost metuljev Maculinea teleius in M. nausithous (Lepidoptera: Lycaenidae) v osrednjih Slovenskih goricah. Diplomsko delo, Biotehniška fakulteta, Univerza v Ljubljani, Ljubljana, 140 pp. Zakšek V., Malačič K., Rebeušek F., Verovnik R. (2005): Distribution and autecology of Maculinea teleius and M. nausithous (Lepidoptera: Lycaenidae) in Northeast Slovenia. In: Settele J., Kühn E. (Eds.), Studies on the ecology and conservation of butterflies in Europe: Maculinea butterflies as a model, Vol. 2. Pensoft, Sofia, Bulgaria, pp. 253-256