Schoener - p. 2 
Schoener has for some years been studying the circumstances under which 
widespread Anolis species shift or fail to shift their habitats. At each of 
20 Caribbean localities, he measured the structural habitats utilized by all 
the diurnal arboreal lizard species (the only non-anoles were Leiocephalus) 
and the availability of these habitats. Schoener selected localities so as 
n include for the chosen four widespread Anolis species - A. carolinensis, 
. sagrei, A. distichus and A. grahami - nearly all of the species canbe ciions 
in which they occur, The data were fitted to equations that adjust for 
locality-specific differences in vegetation and that estimate the direction 
and intensity of apparent interaction between classes of the widespread 
species and the forms sympatric with them, 
Among the results are: 1, Carolinensis and sagrei show more instances 
of habitat shift,apparently because of competitors, than grahami. 2, Female- 
sized lizards show more such shift than adult males. 3, Pattern 2 is not 
independent of species but is most evident in sagrei, somewhat less so in 
grahami and entirely absent in carolinensis, 4. Locality-specific tendencies 
to shift or not shift exist within species, e.g. sagrei adult males. 5. The 
widespread species carolinensis, distichus and sagrei frequently negatively 
interact, On the other hand, angusticeps is rarely a competitor with 
carolinensis and opalinus (Jamaica only) rarely a competitor with sagrei. 
6, Males tend to respond more strongly to other males than to female-sized 
individuals, However, except in sagrei, female-sized individuals are more 
likely to respond to adult males than to their own class. 7. Climatic 
similarity is a major factor determining effect of a sympatric species upon 
one of the widespread species, 8. There are more cases where apparent 
competitors are similar in size than the reverse. Examined with regard to 
sex, the greatest effects appear to be against female-sized individuals of 
the widespread species. 9, Classes of larger size, on the other hand, seem 
to operate especially against adult males, 10, The most abundant classes 
are the apparent strongest competitors for distichus but not for the other 
widespread species. 
Indirect evidence implicates both behavioral and evolutionary adaptations 
in habitat shift. 
Thus carolinensis, where it co-occurs with three other species and its 
perch is most often on leaves, is often a vivid green, though it may 
facultatively turn to brown. On Crooked where two arboreal species are 
absent, perch shifts upward and is less often on leaves. Coloration is now 
brown with only the option of occasional olive tinges. On Acklins where 
over most of the island carolinensis is the only anole, perch height 
decreases and it is more terrestrial than elsewhere. (See figure for this 
remarkable habitat shift.) Here the coloration is a stony brown. Clearly 
genetic changes havetaken place which suit the colorationto the shift. 
Similar habitat and coloration shifts occur in distichus, but here less 
striking instances of habitat shift are accompanied by less striking color 
changes, 
