BRADFORD C, LISTER (Department of Biology, Princeton University, Princeton, 
New Jersey 08540) has been trying to answer two questions concerning the 
ecology and evolution of Anolis lizards: (1) what are the ecological conse- 
quences of reduced competition?; (2) how do these species adjust their niche 
widths, i.e. to what extent are changes in niche width and niche position 
evolutionary or behavioral events? To answer the first question he has 
compared the structural, thermal and food niches of Anolis populations, 
primarily insular populations of A. sagrei, where they coexist with varying 
numbers of congeners. The major results RI; this ecological study are: 
(1) Mean perch height and the diversity of perch heights utilized by 
male and female sagrei (measured as 1/2P;?) decrease monotonically as the 
number of co-occurring Anolis species increases, Adult males in the solitary 
populations on Swan Island and Cayman Brac have twice the niche width along 
the perch height dimension, females four times the niche width, of male and 
female sagrei on Jamaica, A. monensis, a solitary anole on Mona Island, was 
also found to occupy a broader range of perch heights than its mainland" 
counterpart on Puerto Rico, A. cooki. In fact, monensís and Swan Island and 
Cayman Brac sagrei have virtually identical perch height distributions. 
(2) On islands where more shade-tolerant competitors are absent, sagrei 
populations occupy habitats with high and low insolation. Populations in 
closed habitats were found to have body temperatures several degrees Centi- 
grade lower than populations in open habitats, Due to habitat expansion, 
then, sagrei populations in the Bahamas and the Cayman Islands have a much 
broader thermal range than Jamaican sagrei which are excluded from forests 
and shady patches within habitats by A. lineatopus. A similar expansion of 
thermal niche was found to occur in AT monensis. 
(3) In adult male sagrei populations, niche width along the prey size 
resource axis increases with an increase in mean head length. Unexpectedly, 
niche width with respect to prey taxa was not found to increase on islands 
where sagrei occurs without more arboreal competitors. 
The evolutionary component of these niche shifts was studied by comparing 
the means and variances of characters adaptively important along the perc 
height, thermal and food niche dimensions. The results of this morphological 
analysis are: 
(1) Lamellae number in adult male sagrei was closely and positively 
correlated with mean perch height. The coefficient of variation of lamellae 
number, however, showed no tendency to increase with an increase in the 
range of perch heights utilized by a population. 
(2) Dorsal scale size of sagrei populations on Little Cayman and Cayman 
Brac were convergent and intermediate between Cuban forest anoles (ahli and 
allogus) and sagrei populations on Jamaica and Cuba. Within the roquet 
group, the solitary species roquet and luciae were also convergent and inter- 
