New findings of the butterfly Phengaris teleius at the border between Hungary and Serbia (Lepidoptera: Lycaenidae)

Abstract Background Due to its interesting life cycle, vulnerability and conservation importance, the butterfly Phengaris teleius is one of the most studied insects in Europe. It was discovered in Serbia only in 2012 and there were no data on its distribution from the south of Hungary. New information Phengaris teleius was recorded for the first time in four localities in Hungary and in additional locality in Serbia. This suggests that the local populations are more interconnected than previousely thought and that conservation efforts should be done in collaboration between the two countries. All localities are inside protected areas and management measures for preserving several target species already exist. This represents a solid base for the conservation of newly discovered populations of P. teleius.


Introduction
The Scarce Large Blue, Phengaris teleius (Bergsträsser, 1779), is distributed from Central Europe to Asia. The European part of its range is well known as the species received great attention over the last few decades due to its extraordinary myrmecophilous life cycle making it sensitive to habitat changes and therefore in risk of extinction , Wynhoff 1998). The species is now assessed as vulnerable in Europe (Van Swaay et al. 2010) and listed in Annex II and IV of the Habitats Directive (European Commission, No. 92/43/EEC). European Union member states have the obligation to monitor the status of this species, the size of its populations and its distribution range. Hungary has already designated Natura 2000 sites for the conservation of P. teleius, but none in the southeastern part of the country, where the presence of the butterfly has not been recorded yet (Haraszty 2014). Serbia, as a candidate country, has an obligation to study the distribution and population trend of target species and to propose SCI areas (Sites of Community Importance) for its upcoming Natura 2000 network. P. teleius was discovered in 2012 in the very north of the country, some 50 km from the nearest known populations in Hungary (Popović et al. 2014). This triggered a more detailed study on the distribution of this species around the border between Hungary and Serbia and the results are summarised here.

Materials and methods
Potential habitats of Phengaris teleius, containing the food plant of the butterfly (Sanguisorba officinalis L.) were identified using Google Earth satellite images and with the help of local rangers. In order to check whether P. teleius lives on the Hungarian side of the border, we visited four localities inside of the National Park Kiskunság on 6th of August 2015: 1. Rívó-erdő és semlyék, 2. Ásotthalmi láprét (Csodarét), 3. Csipak semlyék and 4. Domaszéki canal (north of Zákányszék). The distribution of P. teleius in Serbia has been studied since 2012 and here the results are summarised, wtih the addition of the recently discovered location.

Distribution
During this survey, Phengaris teleius was recorded in all visited localities in Hungary (Figs 1, 2). They are situated inside the National Park Kiskunság and are mown once a year to help sustaining populations of protected plants and animals (Figs 3, 4). In Serbia, the single unpublished observation is located on a motorbike polygon, close to the known populations at Ludaš lake (Fig. 1). The Serbian populations are also located inside nationally protected areas and are managed in similar manner to the Hungarian ones.

Discussion
The new records of Phengaris teleius in Hungary and Serbia shows that the local populations may be more interconnected than previously thought (Popović et al. 2014). This could have great conservation importance, knowing the small migration distances and sedentary character of this butterfly species . As maximal migrations reach up to 5 km, at least some exchange of individuals is possible between local populations (Nowicki et al. 2014. The distribution of P. teleius in Serbia is probably limited only to the study area and is now well known due to the considerable research efforts made since its discovery in 2012. However, more detailed studies are required in south-eastern Hungary for mapping its range and habitats. These populations are on the southern border of the species distribution in Europe (Wynhoff 1998), thus more conservation importance and efforts is required for their conservation (Bourn and Thomas 2002).
On some sites hosting P. teleius, we also observed the Large Copper, Lycaena dispar (Haworth 1802), another Natura 2000 species that can be found in wetland habitats. This increases the conservation value of the remaining wet meadow fragments. Such meadows are now among the most important habitats for the survival of threatened butterflies in Europe and the persistence of P. teleius depends on their appropriate management, including mowing regimes ). In addition, the survival of this butterfly is highly dependent on the presence of host plant and host ants, both being sensitive to management practice. Recent study has shown that the local populations in Serbia are still exceptionally numerous, although a few local extinctions are recorded on a small scale (Popović, unpublished data). There is a need for additional research on ecology of P. teleius in order to adapt habitat management to the local needs of present butterfly populations. For example, in similar habitats in Hungary, low grazing was indicated as adequate management practice (Batáry et al. 2007) and mowing regimes have been proven important for its conservation in Serbia (Popović et al. 2014).
The results of scientific studies should be applied in joint conservation plans for P. teleius in both Serbia and Hungary, especially because the species conservation status is known to be unfavourable. This is easy to achieve since the studied populations are located inside of the protected areas, where some active management practice already exsist. The present locations of the species should be urgently included into the official ecological network of the Republic of Serbia and planned for inclusion within the upcoming Natura 2000 areas. Special attention should be given to preserve current water regimes inside the protected areas, create better connection between isolated habitats and monitor remaining populations of P. teleius.