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Insularity and the determinants of lizard population density
Lauren B Buckley1, Walter Jetz
1Santa Fe Institute, Santa Fe, NM 87501, USA. lbuckley@santafe.edu
Ecology Letters
|May 15, 2007
Summary
Island lizard populations are 10 times more abundant than mainland ones due to reduced predators and competitors, not just resources. This highlights the impact of insularity on animal population density and community sensitivity.
Area of Science:
- Ecology
- Zoology
- Conservation Biology
Background:
- Understanding factors controlling animal population density is crucial for ecology and conservation.
- The roles of resource availability versus biotic interactions (predation, competition) remain debated.
- Species-depauperate islands provide unique natural experiments to study these dynamics.
Purpose of the Study:
- To investigate the primary drivers of lizard population density on islands versus mainlands.
- To determine the relative importance of resource availability, predator richness, and competitor richness.
- To assess the impact of insularity on ecological community structure and stability.
Main Methods:
- Analyzed data from 643 lizard populations globally.
- Compared lizard abundances between island and mainland populations.
- Controlled for variations in resource availability.
- Correlated lizard densities with predator and competitor richness.
Main Results:
- Lizard populations on islands were approximately one order of magnitude more abundant than those on mainlands.
- Resource availability did not fully explain the difference in abundance between islands and mainlands.
- Reduced predator and competitor richness were the dominant factors driving higher lizard abundances on islands.
Conclusions:
- Insularity dramatically alters the balance between biotic and abiotic factors controlling animal populations.
- Island ecosystems are highly sensitive to changes in species composition, with significant implications for conservation.
- Species loss and introduction on islands can have disproportionately large effects on community dynamics.
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