Particularities of seasonal activity of representatives of fungus gnats (Diptera, Sciaroidea) most popular genera in subtaiga of Western Siberia

While studying the ecology of fungus gnats (Diptera, Sciaroidea) in coniferous subtaiga of Western Siberia the dynamics of flight activity within the largest by number of species and the most popular genera (Bolitophila, Mycomya, Exechia, Trichonta, Phronia, Mycetophila) was examined. Structural analysis of the taxonomic composition of fungus gnats active imago during the season has shown that early in the season representatives of the Exechia dominate, in August – Mycetophila, in mid-summer the importance of Mycomya, Phronia, Trichonta genera grows. The maximum species diversity for genera Bolitophila, Trichonta and Mycetophila is observed in the third decade of May, Exechia – in the first decade of May, Phronia - in late June. Flying with two periods of activity is characteristic of typical inhabitants of fungi fruiting bodies at the beginning and end of the season, with a mandatory gap between them not less than one month. For species growing on wood-destroying fungi mycelium an extended flying period during the season or in its first half is more typical, with a maximum in the warmest decades. Within each genus several strategies of flight activity are observed, the analysis of which makes it possible to identify five types of flight strategies of Sciaroidea:
1. Species with one period of activity in the first half of the season. This type of flight activity is observed in many species of popular genera. In this group species with pre-dominantly short period of flying, from early May to early June, can be identified: the species of the genera Bolitophila, Exechia, Pseudexechia; and species with a long flight activity with a maximum in the summer months (representatives of Mycomya, Anatella, Rymosia, Phronia, Trichonta and Mycetophila).
2. Species with two short periods of activity – at the beginning and end of the season, with a gap between them not less than two months. This type of seasonal dynamics is most evident among a number of representatives of the genera Bolitophila and Exechia.
3. Species with two long periods of activity – at the beginning and end of the season, with a mandatory gap between them that is usually not less than one month. This type of activity is typical first of all for the representatives of the inhabitants of the fruiting bodies of fungi, especially the genus Mycetophila, as well as Phronia. The peculiarity of these fungus gnats is that the spring activity peak is more or less pronounced and occurs at the end of May and June; however, the maximum number is reached in the second half of the season and is associated with fungi fruiting. Decline usually occurs in the middle of summer: the second and third decade of July and early August.
4. The species flying throughout the summer season from mid-May till September. During this period several generations may change. This group includes many species of Phronia, Trichonta and Mycetophila.
5. The species active exceptionally in autumn, flying since the second half of August. It is a small group, including 3 species of the genera Mycetophila and Trichonta, as well as such species as Exechiopsis davatchii, Exechiopsis seducta, Exechiopsis indecisa, Pseudexechia trivittata, Rymosia affinis, Boletina gripha, Allodia ornaticollis.

Thus, in West Siberian coniferous subtaiga five types of fungus gnats’ flying strategy can be identified, while in the mid-taiga subzone of Karelia four types are distinguished, and in the mountain-taiga landscapes in the central part of the Kuznetsky Alatau only three types. In the Kuznetsky Alatau with its short summers and heavy rainfall, there are no species having two peaks of activity. In Karelia, with a cold and rainy summer, there is not a sharp decline in activity of adults in mid-season, which is characteristic of most species of subtaiga fungus gnats. Thus, it is shown that the strategies of flight activity of local faunas Sciaroidea reflect the characteristics of the landscape and climate conditions of a particular region.