Disease (Conlnincd) 

 in cattle due to low calcium content 



of hay, 241 

 in elimination of eelgrass on 



Atlantic coast, 365 

 introduction of by man; 

 among field mice to control 



plagues, 235 

 in rabbit populations to control 

 plagues, 235 

 mortality of hosts and mutant 



organisms of, 228 

 occurrence of and theory of general 



cause of cycles, 241 

 physiological stress as factor in 



cycles, 241 

 physiological stress as state of, 



229 

 shock in snowshoe rabbit as state 

 of, 229, 241 

 Dispersal (see also Continents; 

 Dispersal Pathways; North 

 America): 

 accomplishment of primarily by 



young of species, 149 

 after changes in the environment, 



150 

 after changes in species, 150 

 and adaptive radiation, 266 

 and rate of gene flow from one 



locality to another, 259 

 as part of basis in establishment of 



new faunistic systems, 274-276 

 barrier(s) to: 

 changes in vegetation as, 149 

 classification of, 148 

 climatic, deserts as, 148-149 

 competition between species as, 



149 

 food- type availability as, 149 

 humidity as, to moist-skinned 



species, 148-149 

 land masses as, to fresh-water 



organisms, 148 

 length of season between spring 



and frosts as, 148-149 

 mountains as, to low- land 



species, 148 

 oceans as, to terrestrial 



organisms, 148 

 precipitation as, 148-149 

 predators as, 149 

 salt-water as, to fresh- water 



forms, 148 

 short photoperiods as, 148-149 

 solar radiation as, 148-149 

 valleys as, to mountain species, 



148 

 waterfalls as, to non-flying 



aquatic species, 148 

 wide rivers as, to mammals, 

 insects and birds, 148 



Dispersal (Coiiliiiuecl) 



broadcasting of eggs in and popu- 

 lation pressures, 150 



computing rate of outward diffusion 

 in, 149 



(letuicd. 145-146 



failure of food supply as reason 

 for, 150 



general laws governing, 145 



high altitude, vegetation, alpine 

 tundra and coniferous forest 

 as representing occurrence of 

 to south, 313 



in non- glacial areas, effect on of 

 pluvial and interpluvial peri- 

 ods, 284-285 



in North America as explained in 

 life- zone system, 274 



low altitude, vegetation as repre- 

 senting occurrence of to north, 

 313 



manner and means of: 

 as determined by directed move- 

 ments of animals, 147 

 attachment of eggs of aquatic 

 organisms to debris rafts as, 

 146 

 broadcasting of eggs, spores and 

 young in random manner as, 

 146 

 passive conveyance in broadcast- 

 ing as, 146 

 radiation in all directions from 



home area as, 146 

 river erosion as, 146 

 strong winds as, 146-147 

 trial and error as, 148 

 use of mild air currents by 



spiders as, 146-147 

 use of other animals as vehicles 

 in, 147 



northward due to amelioration of 

 climate in post- Pleistocene era, 

 291 



of animals with glacial advance, 

 286-288 



of arctic species southward in 

 post- Pleistocene era, 317 



of Asian species in North America 

 due to Pleistocene glaciation, 

 318 



of cold-blooded marine organisms 

 from tropics, 370 



of Eurasian bird element in North 

 America, 156, 308 



of Eurasian boreal forest biota, 

 307 



of Eurasian forms into South 

 America, 313 



of isolated fauna of coniferous 

 forest refugia during inter- 

 glacial period, 308 



Dispersal (CoiiliniaJ) 

 of isolated populations as hastened 



by man, 308 

 of North American alpine tundra 



species, 322 

 of organisms from extreme 



southern South America to 



Andes, 344-345 

 of southeastern North American 



forests into deciduous forests 



and forest- edge, 298 

 of species over continent and local 



differentiation centers, 259 

 of Tertiary era flora: 

 Arcto- tertiary, 282, 29 7 

 early, into favorable regions, 



281-282 

 Madro-tertiary, 283 

 of woodland, 311 

 population pressure as most 



potent reason for, 150 

 range expansion as result of 



generations of, 146 

 rate of: 

 as low in island forms, 155 

 as probably similar for all 



creatures once barriers 



passed, 145-146 

 as slow and covering short 



distances, 145-46 

 into area previously unoccupied 



by species, 150 

 rise of barriers after occurrence 



of and geographic isolation, 259 

 Tibet Plateau as important center 



of, 321 

 Dispersal Pathway(s) (see also 



Continents): 

 and continental drift theory, 150-51 

 corridors defined as, 151 

 determination of centers of origin 



of: 

 through continuity and conver- 

 gence of lines of dispersal, 154 

 through location of greatest diff- 

 erentiation of type, 154 

 filters, defined as, 151 

 formation of through connection of 



island to mainland, 155 

 from Asia to North America, 155 

 from Europe to North America, 



155 

 from South to North America, 155- 



156 

 in Australia-Papuan region, 269- 



270 

 in succession from sea to land, 



367-368 

 land bridges between continents 



as, 151 

 of mammals, Eurasia as point of 



origin of, 151 



Index 413 



