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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