V NATURAL SELECTION 111 



stomach adupted to digest vegetable matter alone, or flesh 

 alone, draws more nutriment from these substances. So, in 

 the general economy of any land, the more Avidely and 

 perfectly the animals and plants are diversified for different 

 habits of life, so Avill a greater number of individuals be 

 capable of there supporting themselves." ^ 



The most closely allied Species inhabit distinct Areas. 



One of the curious results of the general action of this 

 principle in nature is, that the most closely allied species — 

 those whose differences though often real and important are 

 hardly j^erceptible to any one but a naturalist — are usually 

 not found in the same but in Avidely separated countries. 

 Thus, the nearest allies to our European golden plover are 

 found in North America and East Asia ; the nearest ally 

 of our European jay is found in Japan, although there are 

 several other species of jays in Western Asia and North 

 Africa; and though we have several species of titmice in 

 England they are not very closely allied to each other. 

 The form most akin to our blue tit is the azure tit of 

 Central Asia (Parus azureus) ; the Parus ledouci of Algeria 

 is very near our coal tit, and the Parus lugubris of South- 

 Eastern Europe and Asia Minor is nearest to our marsh tit. 

 So, our four species of wild pigeons — the ring-dove, stock- 

 dove, rock-pigeon, and turtle-dove — are not closely allied to 

 each other, but each of them belongs, according to some 

 ornithologists, to a separate genus or subgenus, and has its 

 nearest relatives in distant parts of Asia and Africa. In 

 mammalia the same thing occurs. Each mountain region of 

 Europe and Asia has usually its own species of A\ald sheep 

 and goatj and sometimes of antelope and deer ; so that in 

 each region there is found the greatest diversity in this 

 class of animals, while the closest allies inhabit cjuite distinct 

 and often distant areas. In plants we find the same 

 phenomenon prevalent. Distinct species of columbine are 

 found in Central Europe (Aguilegia vulgaris), in Eastern 

 Europe, and Siberia (A glandulosa), in the Alps (A. Alpina), 

 in the Pyrenees (A. pyrenaiea), in the Greek mountains (A. 

 ottonis), and in Corsica (A. Bernardi), but rarely are two 

 ^ Origin of Species, p. 89. 



