Conclusion
Our study utilized a large dataset of bird detections spanning several
years, and combined this with local scale Anolis community
surveys at several locations in a variety of habitat types on two large
Caribbean islands. This method allowed us to examine community
properties across individual islands, at a scale in which individual
species co-occur. Despite the large sample size of predator and lizard
observations across these islands, our results fail to detect a strong
or consistent signal of predators diminishing lizard abundance or
diversity. Instead, correlations between predation pressure and lizard
community diversity tended to be positive, which could suggest that
predators decrease competition in the community and facilitate higher
lizard species richness and greater lizard evenness. Ultimately,
experimental approaches that manipulate predator density or access to
lizard communities may be needed to tease apart potential mechanisms.
Regardless, the patterns in predator and lizard abundance that we
document within islands stand in contrast to past assessments of the
importance of predators on both small experimental islands, and
macroecologically across islands. This finding points to an important
knowledge gap related to the way that predation pressure manifests at
different scales. Irrespective of predation, climate repeatedly emerges
as a significant predictor of diversity, both of lizards and their avian
predators, suggesting that bottom-up, rather than top-down control of
communities is the primary driver of variation in diversity on these
islands. While species interactions may play a role in structuring some
aspects of communities, our data suggest that ultimately resource
availability is required for high levels of biodiversity.
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