On the time and routes of the penetration of the Caucasian black grouse's ancestor into the Caucasus

The Caucasian black grouse Lyrurus mlokosiewiczi is the unique species of the family Tetraonidae, associated with subalpine and alpine zones of high mountains of the Caucasus and adjacent high mountain territories of Turkey and Iran. At present, it is the single representative of the family in this region. Some time ago, I proposed a possible way of penetration of the ancestor of this species into the Caucasus from the place of its origin (Balkan hills and mountains) and the time of this event. In my opinion, the route from Balkans to the Caucasus along mountain ranges running along the northern edge of the Anatolian Peninsula was a single possible way (Potapov 1985, 2004). During one or several epochs of Tertiary glaciations, when the timberline descended down to 700-800 m, it could possibly reach foothills and subalpine ecosystems connected with semi-exposed plain landscapes. This hypothesis was based on the recording of the first representatives of the genus Lyrurus in late Pliocene in Bulgarian foothills (nearly 2.5 MA) and on the date of the first bones of L. mlokosiewiczi found in the Caucasus (about 500 KA). At present, the latter date was corrected, constituting about 350±70 KA. Recently, another hypothesis appeared, assuming quite different route of penetration via the plains of the southern Ukraine and Russia in the late Miocene. The following three reasons demonstrate impossibility of this process, namely: 1) Landscape of these plains at that time resembled the African savannah with corresponding climate and fauna (elephants, rhinoceroses, giraffes, ostriches etc.); in any way, these conditions were unfavorable for all the grouses, adopted to the cold climate with the pronounced winter season. 2) subalpine and alpine belts in the Caucasian mountains appeared only in the lower Pleistocene and were always isolated from plains by the strong and vast forest belt improper for the ancestors of black grouses, adopted to semi-exposed landscapes of the forest-steppe zone. 3) All the palaeontological data revealed the absence of Lyrurus in these plains as far as the late Pleistocene (20 - 22 KA).