Distribution of two rare taxa of caddisflies (Trichoptera: Rhyacophilidae, Polycentropodidae) from the Republic of Kosovo

Abstract Background The knowledge about distribution, ecology and species composition of caddisflies of the Balkan Peninsula is still not complete. The ongoing investigations of the last years highlight this area as an important hotspot of caddisfly diversity. Polycentropus ierapetra slovenica has been considered a narrow range endemic of Slovenia and surrounding areas. Rhyacophila aurata, a species known from many parts of Europe, according to the current knowledge, is absent from a large part of the Balkan Peninsula. New information In this paper, we present records of these two rare taxa of Trichoptera from the Republic of Kosovo with exact distribution data, based on sampling carried out randomly during 2014 and 2017. Polycentropus ierapetra slovenica was found in several streams in Bjeshkët e Nemuna Mountains and Karadak Mountains. Rhyacophila aurata was found during this investigation at a single locality in Bjeshkët e Nemuna Mountains. The unexpected finding of these two taxa in Kosovo greatly enlarges their known distribution area and makes a contribution towards the better knowledge of distributional patterns of these rare taxa of caddisflies in this part of Europe.


Introduction
The knowledge about distribution, ecology and species composition of caddisflies in the Balkan Peninsula is still not complete. The recent and ongoing investigations in this area (e.g. Bilalli et al. 2018, Ibrahimi and Vehapi 2017, Oláh et al. 2018, Previšić et al. 2014, Rimcheska et al. 2015) make possible the better understanding of distribution patterns and ecological features and consequently increase conservation efforts for these species and their associated habitats.
Until recently, there were only few registered records of caddisfly species in Kosovo, but the list has significantly increased during the past decade, with several new species being described (e.g. , Ibrahimi and Vehapi 2017, Ibrahimi et al. 2012, Ibrahimi et al. 2016, Karaouzas et al. 2018). However, some areas, especially the high altitude mountains of Bjeshkët e Nemuna, Sharr, Karadak and Kopaonik, have still not been fully investigated. Caddisflies of large lowland rivers and downstream freshwater ecosystems are also not very well known.
The main goal of this study was to contribute to the list of caddisfly taxa in the Republic of Kosovo and improve the knowledge about geographic distribution of rare taxa of caddisflies in the Balkan Peninsula, to assist in proper conservation of freshwater ecosystems.

Materials and methods
Sampling was carried out occasionally during 2014 and 2017 at six sampling stations, three of them being located in Bjeshkët e Nemuna and the other three in Karadak Mountains in the Republic of Kosovo (Table 1). Adult caddisflies were collected by using ultraviolet light traps during the night and entomological nets during the day. UV light traps (according to Malicky 2004) were placed on stream banks immediately after dusk and operated throughout the night. Collected samples were preserved in 75% ethanol. The specimens were identified under a stereomicroscope using appropriate keys (Kumanski 1985, Kumanski 1988, Malicky 2004

Ecology
We found that the flight period of this subspecies is from May to September. The subspecies is present at different altitudes, from 620 m up to 1307 m.

Taxon discussion
The shape of male genitalia and especially of parts which are important for subspecies identification (length, shape and curvature of intermediate appendages, shape and size of dorsal and ventral lobes of inferior appendages and shape of inner basal projections) clearly point to the slovenica subspecies (Malicky 2004

Discussion
One species of the Rhyacophilidae family is reported for the first time and one subspecies of Polycentropodidae is documented for the first time with the exact data from the Republic of Kosovo: Rhyacophila aurata and Polycentropus ierapetra slovenica.
The species Polycentropus ierapetra is endemic to South-eastern Europe and Turkey, with several known subspecies which are narrow endemics of certain areas (Malicky 2019, Neu et al. 2018. Currently, the highest-known number of subspecies is from Turkey ( Polycentropus ierapetra anatolica Sipahiler, 1989, Polycentropus ierapetra isparta Sipahiler, 1996, Polycentropus ierapetra adana Sipahiler, 1996, Polycentropus ierapetra milikuri Malicky, 1975 andPolycentropus ierapetra baroukus Botosaneanu andDia, 1983) and Greece (Polycentropus ierapetra ierapetra, Polycentropus ierapetra ikaria Malicky, 1974, Polycentropus ierapetra dirfis Malicky, 1974 and Polycentropus ierapetra kalliope Malicky, 1976). In Bulgaria, only one subspecies (Polycentropus ierapetra septentrionalis Kumanski, 1986) is known. The only subspecies with wider distribution is Polycentropus ierapetra slovenica, which was described from Slovenia but was later found in Italy and Bosnia and Herzegovina as well , Stanić-Koštroman 2009, Valle 2001. During 2014, a single female specimen of Polycentropus ierapetra was found in Kosovo ), but it was impossible to identify up to the subspecies level, due to the fact that females of all subspecies are similar. During the current investigation, we found a large number of males in several localities in Bjeshkët e Nemuna and Karadak mountains and were able to identify them as Polycentropus ierapetra slovenica. Considering the narrow distribution of other subspecies, this was somehow unexpected. Our findings make this subspecies one of the most widely distributed. Currently, our findings are the southernmost records of this subspecies. At the same time, these findings are the first reported with exact data for this subspecies for Ecoregion 6. It has been reported by Neu et al. 2018 as present at a single locality in Bjeshkët e Nemuna and here we give exact locality data for several other localities in this area and Karadak Mountains as well.
Rhyacophila aurata was found during this investigation in one locality only in Bjeshkët e Nemuna National Park and with only one specimen. This species, although present in many countries in Europe, it is not found frequently in Western Balkans and is absent from neighbouring countries of Kosovo (Malicky 2019, Neu et al. 2018). The species is quite abundant in Central Europe and becomes scarcer towards the Balkan Peninsula. In Southeastern Europe, it is present in numerous localities in Slovenia and Croatia and in only one locality in Bosnia and Herzegovina (Neu et al. 2018) Finding this species during this investigation greatly enlarges its known distribution area.
The number of Rhyacophila species has now been increased to fifteen and the number of Polycentropodidae species to ten in the Republic of Kosovo.
Finding of several other rare species during this investigation (such as: Rhyacophila loxias, Rhyacophila palmeni, Polycentropus excicus, Plectrocnemia mojkovacensis, Psychomyia klapaleki, amongst others) greatly enlarges their known distribution area. Previously, they have been reported from only few localities in the Balkans. It is only the second time that Psychomyia klapaleki and the third time that Plectrocnemia mojkovacensis have been reported from Kosovo. This investigation shows that both mountainous areas where this investigation was conducted harbour a collection of rare caddisfly taxa, many of which are known only from a limited number of localities in the area, based on current knowledge. Further investigations of this area will most certainly increase the number of known species in Kosovo and improve the knowledge about this order of insects in the Balkans.