Many of plant and animal species extend in their distribution to NE Asia only to the coastal parts of the Sea of Okhotsk. This narrow corridor, which has great importance for understanding of the genesis of flora and fauna of Beringia, seems to have the climate connected with the influence of sea, while certain mechanisms of such sway was newer studied.

Formica aquilonia and F.lugubris, a typical inhabitants of the forest zone in Eurasia, are the helpful subjects for investigations of the ecological nature of this biogeographical boundary. Only distribution of these two species limited by the seaside on the Northeast Asia. Meanwhile, the great ranges of these species reflect their great ecological tolerance.

The subject of our work is an investigation of factors which limit distribution of two species. Spatial distribution, species composition of other ant species occurring in the same biotopes, hydrothermic's, soil's and permafrost's affinities of the biotopes, as well as temperature in hibernation cells and cold resistance (populations both from seaside ecosystems and extreme continental parts) have been examined.

While temperatures in the nests (with the snow cover about 55-80 cm) of F.aquilonia do not go down below - 1.5-4¸C , or in the nest of F.lugubris do not reach lower than -4-5¸C, their resistance to low temperatures quite big. 50% mortality during 24 hours cooling was observed in both species when the temperatures were -13-16¸C. Same cold resistance is known for species occurring in continental parts of Northeast Asia as well. Hence it follows that F.aquilonia and F.lugubris, due to their cold resistance can exist in areas with continental climate.

Competition with other species, most probably, have no great importance, because, from one side: there are no species in continental parts which can be a real competitors, and from other side: in the coastal parts 2 study species coexist with all species known from continental parts.

The main factor which limits the distribution of study species, is a distribution of permafrost. Continental areas have almost continuous impermeable permafrost, closely separated from the soil surface. This permafrost do not allow to built deep (1.5-2 m) nests for F.aquilonia and F.lugubris. In the seashore forests, where there is discontinuous permafrost, study species inhabit only sites which have no permafrost.

Berman Daniil
Institute of Biological Problems of the North
K.Marx Pr., 24
Magadan 685010, Russia
Telephone number: (41322) 53463(h)
Fax:  (41322)  20166 (w)
E-mail:  ibpn@ibpn.magadan.su