Eleven remarkable Diptera species, emerged from fallen aspens in Kivach Nature Reserve, Russian Karelia

Abstract Background In 2016, saproxylic Diptera associated with aspen (Populus tremula L.) logs were studied in the Kivach Nature Reserve, Russian Karelia, using trunk emergence traps. New information Eleven rare species of Diptera (families Limoniidae, Scatopsidae, Axymyiidae, Mycetophilidae, Sciaridae, Platypezidae, Syrphidae and Clusiidae) with poorly known distribution and ecology were recorded. For each species, basic diagnostic characteristics were provided along with the information on microhabitats. An attempt was also undertaken to outline possible associations with wood-decaying macrofungi using nonparametric correlation.


Introduction
Saproxylic Diptera have never been specially studied in Russian Karelia, except for certain groups partly associated with wood-decaying fungi (Yakovlev 1988, Yakovlev 1993, Yakovlev 1995, Jakovlev 2011. Only a few works provide information on abundance and microhabitats for some rare or red-listed species associated with dead wood (Humala and Polevoi 2015, Siitonen et al. 1996, Polevoi and Salmela 2014, Yakovlev et al. 2000. In 2015, research which aimed to study the insect fauna on fallen logs of different tree species, was started. As a result, a number of remarkable species of Coleoptera, Hymenoptera and Diptera were recorded Pilipenko 2016, Polevoi et al. 2017). In 2016, trapping was continued concentrating on fallen aspens with different degrees of decomposition. In total, 105 species of Diptera were collected, including a range of poorly known taxa Suppl. material 1. Here the most remarkable findings are presented.

Materials and methods
The trapping was undertaken in the Kivach Nature Reserve, Republic of Karelia. The biotope was Oxalis acetosella-Vaccinium myrtillus type spruce forest, over 150 years old (for details see Shorohova et al. 2016). Trunk emergence traps (Polevoi and Pilipenko 2016) were used as a collecting method. Fourteen traps were set on the fallen aspens, which had died from 1 to 16 years ago. The time since death was determined using dendrochronological methods (Shorohova et al. 2016). The traps were installed on 25 April 2016 and kept until 28 September 2016, with monthly checking. Diameter at the breast height, decay class (Shorohova et al. 2016) and the tree mortality mode (windthrow or windbreak) were recorded for each tree. The species composition of wood-decaying macromycetes was identified as well. The inventory of the fruitbodies was conducted in May, June, August and October, 2015 as well as in July and September, 2016. The presence-absence was recorded for all species on each log, counting one or several fruitbodies of a particular species on an individual dead tree as one occurrence. Remarkable Diptera species were recorded in 10 of the 14 installed traps (Table 1).
Association with fungi was analysed using Pearson's non-parametric rank-order correlation coefficient (RS) calculated with PAST software (Hammer et al. 2001   Occurrence of remarkable Diptera species and wood-decaying macromycetes on fallen aspens in Kivach Nature Reserve (DBH -diameter at breast height; WB -windbreak; WT -windthrow).

Diagnosis
Medium sized dark species, distinguished from other Gnophomyia by the structure of male and female genitalia (

Ecology
Saproxylic species, associated with different deciduous trees (Krivosheina 2008). In Finland and Karelia, so far collected exclusively on aspen (Hancock 2008, Halme et al. 2012). According to the authors' data, this species prefers huge wind-broken aspens with a diameter over 70 cm, fallen 7 years ago (

Distribution
Palaearctic and Oriental regions (Oosterbroek 2017). Karelian record is the northernmost one. Closest locations are in Poland, Lithuania and Moscow province in Russia.

Ecology
Saproxylic species. Larvae develop under the bark of various trees (Krivosheina 2010). This species was collected from a wind-broken aspen, colonised by 13 species of macrofungi (Table 1).

Diagnosis
Distinguished from other Discobola by more heavily marked wings and the structure of the male genitalia (Fig. 3), see also (Starý 1974, fig. 5, 6) .

Distribution
Palaearctic (Oosterbroek 2017). Karelian record is the northernmost one. Closest locations are in Poland, Lithuania and the Republic of Bashkortostan in Russia.

Ecology
Poorly known, though associations with dead wood and wood-destroying fungi were reported (Ševčík 2006(Ševčík , Wiedenska 2007. This species was collected from a windthrown aspen, colonised by 15 species of macrofungi (Table 1).

Diagnosis
Distinguished from other Limonia by the structure of the male genitalia (Fig. 4) as well as wing pattern and the shape of the tarsal claws (Starý and Salmela 2004, fig. 1, 2).

Ecology
Saproxylic species, associated with dead aspen wood (Halme et al. 2012). According to the authors' data, this species prefers wind-broken aspens with a diameter over 50 cm, fallen 6 years ago

Ecology
Larvae develop under the bark of aspen and poplar (Krivosheina 2002). According to the authors' data, the species prefers huge wind-broken aspens (diameter 70 cm. and more) fallen 7-10 years ago

Distribution
Europe. Known by a few records from the European part of Russia, Ukraine and Slovakia (Humala and Polevoi 2009, Jakovlev and Polevoi 1997, Martinovský and Roháček 1993.

Ecology
Poorly known. Larvae were collected from spruce wood (Mamaev and Krivosheina 1966) and adults found sitting on very damp fir logs (Martinovský and Roháček 1993). According to Krivosheina (1991), larvae of Axymyiidae may colonise newly fallen trunks and stay there for several years. This species was collected from a wind-broken aspen, colonised by 7 species of macrofungi Table 1.

Ecology
Poorly known. Some specimens were caught with light traps (Plassmann 1980, Kurina 2003. This species was collected from a wind-broken aspen, colonised by 15 species of macrofungi Table 1.

Diagnosis
Gnats of the genus Zygoneura are distinguished from other Sciaridae by widely curved fork of wing vein M and long neck of flagellomeres (Fig. 9a). Zygoneura bidens can be recognised by the two dark spines on a shared lobe in the middle of gonostylus ( Fig.  9b; see also Shin et al. (2014), fig. 1: A, B). a b Figure 9.

Ecology
Evidently saproxylic as other species of the subgenus Pharetratula. In Korea, collected at a shiitake farm with oak trunks used as a substrate for shiitake culture (Shin et al. 2014). According to the authors' data, the species prefers wind-broken aspens with a mean diameter of ca. 40 cm and having died 9 years ago

Ecology
Virtually unknown. Other Agathomyia species assumed to develop internally in polypore fungi (Chandler 2001). In the Czech Republic, adults were registered in pyramidal (emergence) traps (Tkoč and Barták 2013). This species was collected from aspens fallen 8-10 years ago. The species did not show any preferences either to the trunk size or tree mortality mode (windfall vs. windbreak)

Distribution
Palaearctic. Few specimens are known from Finland and Leningrad province of Russia (Kerppola 2011). In East Russia, recorded from the republic of Tyva to Primorje region (Krivosheina 2003).

Ecology
Saproxylic species, associated with deciduous trees (Krivosheina 2003). This fly was collected from a wind-broken aspen, colonised by 7 species of macrofungi Table 1.

Conservation
Red-listed in Leningrad province of Russia (Krivokhatsky and Kuznetsov 2002).

Diagnosis
The only representative of the genus Clusiodes with no darkening along the costal vein and entirely black scutum (Fig. 12). Male surstylus figured by Mamaev (1974)

Distribution
Known only by the type specimens from East Russia, Primorje region (Lonsdale andMarshall 2007, Mamaev 1974). First record for Europe.

Ecology
Unknown, but most probably similar to other species of Clusiodes, which develop in dead wood in an advanced state of decay, preferring fallen bark-covered trunks or stumps (Rotheray and Horsfield 2013). According to the authors' data, this species prefers wind-broken aspens of average diameter (ca. 40 cm) fallen 9 years ago (Table  1). It favoured the trunks colonised by Peniophora incarnata (RS=0.61, P<0.05).

Discussion
Trunk emergence traps have some benefits in comparison with other methods traditionally used for collection of wood-living Coleoptera and Diptera (Alinvi et al. 2006, Halme et al. 2012. They, however fail in some cases (e.g. when larvae need to migrate to the soil for pupation) and usually cannot provide exact information about microhabitat preferences (Økland 1999). These traps were shown to be effective in detecting rather diverse insect communities, including a range of rare and otherwise remarkable species, which are difficult to find using commonly used techniques . This study once more demonstrates the effectiveness of the method and also shows the importance of large dead aspens for supporting diverse saproxylic insect communities. It is realised that indirect association of Diptera species with certain trunk parameters or fungi, e.g. correlation, may be questionable because of the relatively small number of replicates. However, in case of species with poorly known biology, such information may be of great importance. Initial knowledge about species preferences may help to outline directions for future studies and conservation measures.