Klára Bezděčková, Pavel Bezděčka: Muzeum Vysočiny Jihlava, Masarykovo náměstí 55, CZ-586 01 Jihlava; e-mail: bezdecka@muzeum.ji.cz; bezdeckova@muzeum.ji.cz

Abstract: We present here the results of a survey into a polydomous colony of the rare and strongly endangered ant species Formica foreli Bondroit, 1918 in a former pasture with communities of dry grasslands near the village of Štěměchy (Czech Republic, District of Vysočina). This colony containing 654 nests in 2014 was the largest known supercolony in the Czech Republic. However, then this positive trend reversed, probably due to effects of fertilizers entering the site after application on neighbouring fields in combination with several invasions of wild boars. Eutrophication and mechanic disturbance probably facilitated an expansion of the grass Calamagrostis epigejos and other competitive plants, obviously deteriorating the condition of the colony. The succession was not even stopped by the ongoing management (mosaic mowing). An inventory of nests in 2020 revealed that only a small remnant of the colony – 86 nests, i.e. 13 % of the original number – had survived at the site. The species diversity of the ant assemblage decreased from 25 to 13 species in comparison with 2014. The habitats at the location have dramatically changed and the state of the F. foreli colony is alarming. Since F. foreli is critically endangered in the Czech Republic and has a similar status in all other countries of Central Europe, the planned conservation interventions are aimed primarily at rescuing its habitat. In 2020, the area with nests was cut more vigorously than in the past. Future monitoring will show whether and to what extent the F. foreli colony will be able to regenerate.

Key words: ants, Formica foreli, Formicidae, Hymenoptera, supercolony, polydomous colony

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