Results:
Across the surveyed plot locations in Jamaica and Hispaniola the
combined probabilities of predatory bird species (essentially the
expected species richness of avian predators along a hypothetical 1km
transect) ranged from 2.36 to 8.00 (Figure 1). Predatory bird presence
in the Dominican Republic had a wider range (2.36 - 8.0) than Jamaica,
which showed less variation in predation pressure (3.67 - 6.71). On
average, however, predator presence was statistically indistinguishable
between islands (5.41 for Jamaica and 5.46 for the Dominican Republic;
p-value = 0.83).
Across all plots, abundances of lizards were ~21%
higher on average in Jamaica, with mean abundance in 15m radius (706
m2) plots of 65.39, compared to 53.95 in the Dominican
Republic (p-value<0.001). Both islands were similar when
comparing species richness of local communities. The average species
richness on both Jamaica and the Dominican Republic was slightly less
than 4 species (3.55 and 3.63, respectively, p-value = 0.83).
We first assessed the relationship between climate and the presence of
both anoles and bird predators individually. Species richness of anoles
was positively correlated with mean annual temperature (Spearman
correlation coefficient = 0.70, p-value<0.001, figure 4b) and
negatively with precipitation (Spearman correlation coefficient = -0.35,
p-value<0.001). Similar patterns existed for anole abundance:
a positive relationship with temperature (Spearman correlation
coefficient = 0.60, p-value,0.001) and a negative relationship with
precipitation (Spearman correlation coefficient = -0.29,
p-value<0.01). In contrast, predatory bird occurrence was
correlated only with mean annual temperature (Spearman correlation
coefficient = 0.64, effect of temperature on abundance = 0.12,
p-value<0.001, r2 = 0.50; Figure 2a) while
its correlation with mean annual precipitation trended negative, but was
non-significant (Spearman correlation coefficient = -0.14, p-value =
0.18, r2 = 0.01). While predation pressure correlated
with climate temperature, there was still substantial residual variation
in the relationship, allowing for the potential to detect independent
effects of predation and climate on lizard communities.