NATURAL SELECTION 



661 



by the survival of relict types in geographi- 

 cally or ecologically peripheral regions 

 where competitors are absent or reduced in 

 number (Cole, 1946). The reptile Spheno- 

 don (p. 680) survived in New Zealand in 

 the absence of terrestrial mammals. New 

 World marsupials have withstood the pres- 



relatives that apparently could not compete 

 after the Pleistocene arrival of the dingo 

 dog, but survived in Tasmania in the ab- 

 sence of this carnivore. 



The primitive termite genus, Kalotermes, 

 (Fig. 241), exists in subtropical region? 

 over the world, and in ecologically periph- 



Fig. 242. Distribution of the termite genus, Neotermes. Note the occurrence in central con- 

 tinental regions of high competition in comparison with its ancestral genus, Kalotermes, in 

 Figure 241. 



Fig. 243. Distribution of Glyptotermes, a genus of dry-wood termites with a phragmotic 

 soldier-head. Note the distribution in central continental regions with high competition in con- 

 trast to its ancestral genus, Kalotermes, in Figure 241. 



sure of competition from superior placental 

 mammals, possibly through the restriction of 

 their activities to nocturnal periods (O. 

 Park, 1940, p. 522), while the Austrahan 

 marsupials, remaining diurnal in many in- 

 stances, radiated into a great variety of 

 habitats in the absence of such placental 

 competitors (p. 666). The Tasmanian wolf 

 and the Tasmanian devil had Australian 



eral tropical regions, such as oflFshore is- 

 lands, mangrove swamps, and oceanic is- 

 lands, while the derived genera (Neotermes, 

 Fig. 242, and Glyptotermes, Fig. 243) 

 are better able to survive in areas of great 

 competition such as are found in the con- 

 tinental tropical rain forests (p. 725). 



Cowles and Bogert (1944) emphasize 

 the well-known fact that relicts are more 



