Demographic Analysis 
241 
Table 11. Signature display complexity 
(number of units) and subjectively 
assessed vegetation density in several pop- 
ulations of the side-blotched lizard Uta 
stansburiana. 
of Units Vegetation 
Locality in the Display Density 
Lahonton Basin, 1 
Nevada 
low 
Mojave Desert, 2 
California 
low 
Bonneville Basin, 2 
Utah 
low-medium 
Colorado River Basin, 4 
Colorado 
medium 
Chihuahuan 4 
Desert-grassland 
medium-high 
Chaparral, 7 
California coast 
high 
mary, in the sparsely vegetated habitat, the 
balance of selection would favor a simple dis- 
play that would avoid detection by searching 
predators. In more heavily vegetated habi- 
tats, the balance of selection would favor a 
more complex display to facilitate adaptive 
conspecific communication. A similar model 
was proposed by Rand and Williams (1970) 
to explain complexity of Anolis lizard dis- 
plays. 
A Potential Test of the Model through 
Observation and Mark and Recapture 
Analysis 
With each generation, genetic recombina- 
tion should reconstitute less adapted geno- 
types so that the variance of a character with 
a high heritability should be greater in off- 
spring than in adults. Signature displays 
have a high heritability (Ferguson, in press). 
They are performed by lizards of all ages. 
Thus, one can observe changes in popula- 
tion variance of display characters through- 
out the life history. Because the mortality 
of side-blotched lizards is probably due to 
predation (Tinkle, 1967; Fox, 1973; Turner 
et. al., 1973), a greater loss of particular 
display types during ontogeny would be due 
to predation. Since an identified lizard’s home 
range and overlap of territory is easy to 
measure in the field, the exclusiveness of a 
male’s mating rights to one or more females 
can be determined. 
If the above model is correct, one would 
predict: (1) In the sparsely vegetated habi- 
tat, juvenile lizards with simple displays 
would disappear during their maturation 
period at a lower rate than lizards with 
complex displays. In the more heavily vege- 
tated habitat, the difference in the rate of 
disappearance would be less; (2) In the 
heavily vegetated habitat, males with simple 
displays would be less likely to prevent inva- 
sion of their mating territories and/or would 
fail to attract as many females into their 
territories as males with complex displays. 
An ideal location to perform such a study 
would be in the intergrade zone between 
simple and complex displaying populations 
of Uta (McKinney, 1971). In such zones 
combining sparsely and densely vegetated 
habitats, one finds large populations of side- 
blotched lizards with a wide variety of sig- 
nature displays. 
Conclusion 
The types of studies that have been dealt 
with in this paper, are illustrative of how it 
may be possible in the future to show how 
environment variability may affect individual 
fitness and natural selection. 
ACKNOWLEDGMENTS 
A number of Kansas State University faculty, 
students, and friends volunteered their time to assist 
in conducting censuses. These include Al Bissett, 
Tom Bowman, Bill Cooper, Ken Derickson, Becky 
Borland, Phil Elliot, Annetta Esser, Steve Fretwell, 
Tom Horst, Louis Huffman, John Johnson, Elaine 
Koski, Marilyn McGuire, Tracy Makovec, Ron 
Pearce, Chris Smith, John Tatschl, Alan Tubbs, Ira 
Yedlin. Special thanks go to Earl Francq and Pat 
Woolley for their dedicated help on phases of the 
projects. To all of these people we express deep grati- 
tude. We thank Mr. Henry Gehring from Paxico, 
Kansas, and Messers. Rex Wonderly, David Prickett, 
