Chapter V — 79 — Tsrpes of Areas 



times it had a much wider distribution there. The latter fact has been 

 definitely established by the finding, far to the north of the present dis- 

 tribution of the birch in the Crimea, of fossil remains of birch charcoal 

 from the bonfires of prehistoric man. The birch was crowded out by 

 the beech in the post-glacial period (Wulff, 1931). 



The second type are the geomorphological relics, to which belong 

 plants which are connected in their habitat with definite ecological con- 

 ditions but which, due to geological and other historical causes, do not 

 find themselves provided with the conditions of growth to which they 

 are accustomed, e.g., marine plants in fresh-water lakes, shore plants 

 along the edges of former gulfs that are now dried up, species which 

 have become isolated on islands formerly forming part of the mainland, 

 etc. A very characteristic example of a geomorphological relic area is 

 that of Pinus eldarica. This pine belongs to the group of Mediterra- 

 nean species to which also belong P. halepensis and P. brutia, species 

 characteristic of the Mediterranean region, and P. pityusa, growing in 

 Asia Minor, the Caucasus, and the Crimea (ssp. Stankevici), to which 

 last-mentioned P. eldarica is very close. These two species are, in turn, 

 undoubtedly closely connected with the Tertiary pine, P. sarmalica, 

 fossil remains of which have been found in Sarmatian deposits on the 

 Kerch Peninsula. All these species grow for the most part along the 

 seashore, with the exception of P. eldarica, which has a very limited 

 area on slopes along the edge of the Eldar steppe in Transcaucasia. 

 This steppe undoubtedly occupies the bed of a former sea, and the 

 Eldar pines mark a shore line existing in an earher geological epoch 

 (SosNOVSKY, 1928). 



As another example of geomorphological relic areas we may take the 

 isolated, islet-like habitats of Quercus Ilex on the southern slopes of the 

 Alps near Lago di Garda, Trient, and Gemona, reaching to an altitude 

 of 550 meters. The finding here, deep in the Alps, of this distinctly 

 Mediterranean oak, ordinarily linked with marine climatic conditions, 

 may be explained only by the relic character of these alpine habitats, 

 preserved from a more extensive area existing in the Tertiary period, 

 when the entire Po basin formed a gulf of the Adriatic Sea and the 

 southern slopes of the Alps the shores of this gulf (Trotter, 1927). 

 This type of relic may arise solely as a result of geomorphological 

 changes unaccompanied by climatic changes. 



Lastly, the third type of rehcs are climatic relics, i.e., plants which, 

 while growing now under certain climatic conditions, give evidence 

 beyond any doubt that their origin and distribution took place under 

 other climatic conditions. There are many such relics. 



Due to the great diversity of types of relic species in nature, any 

 rigid classification of them would, in our opinion, be artificial, and, 

 hence, we do not consider it advisable to attempt to elaborate one. 

 We wish merely here, in summing up, to emphasize that the basic 

 factors determining the character of a relic species are its age, origin, 

 and ecological t3rpe. The causes giving rise to the relic character of a 

 species may be cHmatic, geomorphological, edaphic, or biotic. Accord- 

 ing to their age and origin, relic species may be subdivided into: 

 (/) pre -Tertiary; (2) Tertiary (including (a) tropical and subtropical, 

 (b) temperate, and (c) alpine-arctic); (j) glacial; (4) inter-glacial; 

 and (5) post-glacial relics. 



