PopuhltlOll(s) (LOIltllllUll) 



levels ol affected by different 

 species demands for space, 

 food, shelter, 230 

 liniitm^; factors in described as 



physical, 220 

 maintenance of health and vigor in 



through predation, 226 

 mean longevity of and density, 219- 



220 

 mean survival rates in, 216 

 necessity for measurement of, 31 

 number of age classes in and 



survival rates, 216 

 ol ants during sand sere, 107-109 

 of benthos, in lakes, 69-73 

 of birds: 

 breeding, in forests, 135 

 differentiation in of North 



American boreal forests, 305 

 highest level of in autumn, 156- 



157 

 level of in North American 



deciduous forests, 296 

 non-breeding, in forests, 135 

 of Basin sagebrush biociation, 



337 

 on arctic tundra, 319 

 of bison in North America, 328 

 of fish: 

 factors in density of, 55 

 in dystrophic lakes, 64 

 in eutrophic lakes, 64 

 in oligotrophic lakes, 64 

 replacement of in fish manage- 

 ment, 58 

 of grasshoppers during sand sere, 



107 

 of host species, factors in regula- 

 tion of by particular parasitoid, 

 226-227 

 of insects: 

 as varying with season, 55 

 density of in air, 147 

 in abandoned field sub- seres, 115 

 of invertebrates in Basin sage- 

 brush biociation, 337 

 of invertebrates in grassland 



communities, 124 

 of lemmings, curtailment of 



through emigration, 231 

 of mammals; 

 in forest as affected by seasonal 



changes, 137 

 level of in North American 



deciduous forest biociation, 296 

 small, in forest communities, 



135-136 

 small, in Michigan coniferous 

 forest, 308-309 

 of marine plankton, 358 

 of mice and rats in mesquite vege- 

 tation of New Mexico, 335-336 



Population(s) (Coiiliiiiicil) 

 of muskrats, stabilizing factors m, 



232-233 

 of nekton, m lakes, 73-74 

 of parasitoids, increase in and 



duplicate infestation, 226-227 

 of plankton, in lakes, 66-69 

 of primitive pronghorn antelopes, 



328 

 of soil animals in forest commun- 

 ity, 130, 131-134, 134-135 

 of spiders during sand sere, 109 

 of spiders in grassland communi- 

 ties, 124 

 of trophic levels, and predatory 



consumption of energy, 202 

 order of occurrence of regulatory 



mechanisms in, 231 

 predation as a density-dependent 



factor in, 220-221 

 predation pressure shifts in species 



and locality as density stablizing 



factor in, 226 

 presence of non- breeding animals 



in, 215 

 pressure of as most potent reason 



for dispersal, 150 

 prevalence of cycles of and number 



of species in, 226 

 progressive variations in. 



described. 234 

 proportional effects of density- 

 dependent factors in, 220-221 

 ratios of individuals per hectare 



between different animal 



groups, 130 

 recognition of characteristic 



species in, 20 

 reduction in as causing withdrawal 



of species to optimum habitat, 



150 

 reduction in level of before limits 



of range are reached, 11 

 regulation of through emigration, 



228 

 regulatory factors in, importance 



of time of occurrence of in life 



of organism, 230 

 relation between density-limiting 



and density-stabilizing factors 



in, 229-230 

 relaxation in intensity of action of 



density-dependent factors with 



reduction in, 229 

 reproduction as stabilizing factor 



in: 

 average growth rate of tadpoles 



and, 224 

 density and fecundity of great 



tit and, 223 

 disturbance of females and, 224 

 effects of overcrowding on 



fecundity of salmon and, 223 



Populatu)n(s) f( iiiitdtitcd) 



fecundity of house mice and, 223- 



224 

 fecundity of laboratory mice and, 



223 

 fecundity of voles and, 223- 

 fertility of egg and, 224 

 flour beetle fecundity, 223 

 necessity for distinguishing 

 between fecundity and survival 

 in, 224-225 

 optimum intermediate density of 



grain weevils and, 224 

 Paramecium fecundity and sur- 

 vival and, 222 

 reduction in fecundity of fruit 



flies and, 223 

 sheep blow-fly, 223 

 snowshoe rabbit cycle and, 224 

 survival rates of Dioso/jliila 

 and, 224 

 resiliency of after depletion, 219- 



220 

 role of buffer species in para- 

 sitoidism and level of, 227 

 size of in community classifica- 

 tion, 29 

 stabilization of as occurring only 

 in innermost zone of abundance, 

 233 

 stabilized, age ratios in, 216-217 

 described. 219-220 

 term defined by geneticists, 257 

 term defined in taxonomy, 257 

 threshold of vulnerability for 



particular factors affecting, 231 

 upper limit of vulnerability for 

 particular factors affecting, 

 231 

 variations in abundance in accord- 

 ing to fertility of habitat, 255 

 wild, mean length of life for, 215- 

 216 

 Post- Pleistocene Era: 

 amelioration of climate in and 

 northward movement of fauna, 

 291 

 analysis of pollen in bogs and 

 determination of climate in, 

 288-289 

 climatic optimum in and extension 



of animal ranges, 289-290 

 climatic optimum in and forest 



growth, 289-290 

 conditions of flora and fauna during 



xerothermic period of, 290-291 

 distribution of tundra species 



during, 317 

 early forest growth in, 289 

 evidence for emergence of warmer, 



drier climate during, 289 

 existence of tundra in, 289 

 first plants to appear during, 289 



Index 435 



