Andrews - p. 2 
1. The size classes within island species appear to be dividing food 
resources more finely, i.e. show lower within phenotype variance in the 
sense of Roughgarden, hence are greater specialists than the size classes 
of the mainland species which show higher within phenotype variance, hence 
are greater generalists. 
2. Lower growth rates in insular populations result from greater 
pressure from these populations on the total food supply. 
Survival rates are higher on islands and individuals are more abun- 
dant. Predation keeps the survival and abundance of mainland populations low. 
. Sexual dimorphism in size is greater in insular populations. 
Presumably several factors are involved, including specialization by the 
sexes on different size prey as well as dominance relationships, both more 
important in the resource-limited, relatively predator free ecology of the 
islands than in the contrasting ecology of the mainland, 
A parallel manuscript by Andrews on growth rates in 15 populations of 
13 species of Anolis finds comparable differences between mainland and 
island lizards. The rate constant G of the logistic equation for the 
fastest growing species is almost five times that of the slowest growing 
species. Males and females of a given species have very similar rate con- 
stants with those of females generally higher. 
Differences in food availability had a marked effect on the growth of 
juveniles of an island species, A. oculatus, both in the field and especially 
in the laboratory (.10 mm and .17 mm/day under moderate and excellent field 
food availability respectively, and .27 mm/day with food ad libitum in the 
laboratory). In contrast, a mainland species, A. limifrons, did not increase 
growth under conditions of high food availability. The rate of growth was 
the same in field and laboratory (.17 mm/day). 
When comparable species of the lowland tropics are considered, West 
Indian Anolis are characterized by relatively low growth rates (G = .005-.011) 
and Central American species by relatively high rates (G = .016-.023). As 
a group the mainland populations grow 2-3 times faster than island populations. 
Andrews interprets these contrasting data as implying that island anoles are 
food limited and that mainland anoles are not, 
Two giant species - one mainland (A. frenatus) and one insular (A. 
garmani) - have similar rate constants intermediate between those of the 
smaller mainland and smaller island species. (Actually, A. frenatus females 
have a daily growth rate of .3 mm - larger than any rate cited above - but 
A. frenatus has to grow more to achieve the same proportional change in 
length as a smaller species, and this requires more time, reducing the value 
of G.) 
