Home – Home – Jornals – Contemporary Problems of Ecology 2021 number 3

As a model species to study the geographic variation of cold hardiness in insects, we used ants Lasius flavus from the populations in the regions separated by thousands of kilometers (southern Finland, Moscow Region, Amur Province) with contrasting climates - from maritime variants to those, differing in the degree of continentality. We measured the temperatures of maximal supercooling ( SCP ) as well as the limits of tolerated negative temperatures ( LT _{50 %}), and evaluated the overwintering conditions. The data on L. flavus were compared to similar data obtained on L. niger , аs well as to similar measurements in separate nests of L. alienus , L. psammophilus and L. fuliginosus , which were published earlier. The workers of L. flavus and L. niger have close values of cold hardiness ( LT _{50 %} -13 to -15 °C, minimal average SCP -24 to -25 °C), although these species inhabit different climatic zones and place their overwintering chambers at a different depth. Such resistance to long-term exposure to negative temperatures is more than sufficient even for overwintering in the coldest of the studied areas (Arkhara village, Amur Province), where the average minimal temperature in January in the ant overwintering chambers at 50 cm of depth does not fall below -6 °C. The variation of cold hardiness and higher values of its parameters, in other studied ant species is due to their insufficient preparation for overwintering. However, the narrow range of SCP (-27 to -29 °C) in the most cold resistant individuals of all studied species allows to confidently assume that their average Т _p and threshold LT _{50 %} correspond to those of L. flavus and L. niger. Similar (or maybe identical) cold hardiness of the studied ant species appears to be a stable trait of the genus Lasius , as was demonstrated for another ant genus, Myrmica , and as opposed to the genus Formica , where different species have individual characteristics of cold resistance. Such cold hardiness that is excessive for overwintering in warmer climate (southern Finland, Estonia) appears to have no adaptive value. It can be considered as a byproduct of the diapause, which is manifested in preadaptation to withstand negative temperature. However, it was this cold hardiness that made possible the colonization of the giant territory of the southern Siberia and Far East by the discussed ant species.