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Limitations of methods to test density-dependent fecundity hypothesis
1ERENA, Ordenamento e Gestão de Recursos Naturais, Rua Robalo Gouveia, 1-1 A, 1900-392 Lisboa, Portugal. pbeja@erena.pt
The Journal of Animal Ecology
|February 8, 2008
Summary
Statistical artifacts can mimic relationships between fecundity and its variation, making it difficult to distinguish between the habitat heterogeneity hypothesis (HHH) and the individual adjustment hypothesis (IAH) in population studies.
Area of Science:
- Ecology
- Population Dynamics
- Behavioral Ecology
Background:
- Density dependence in fecundity is explained by two main hypotheses: habitat heterogeneity (HHH) and individual adjustment (IAH).
- Previous methods to differentiate these hypotheses have limited validation with real or model populations.
Purpose of the Study:
- To test the adequacy of methods used to discriminate between HHH and IAH.
- To investigate if statistical artifacts can influence the interpretation of density dependence mechanisms.
Main Methods:
- A simulation study using a stochastic territory-based approach.
- Model populations were parameterized using data from an increasing Bonelli's eagle population (1992-2006).
- Analysis focused on relationships between mean fecundity and its coefficient of variation (CV) and skewness.
Main Results:
- Both HHH and IAH produced indistinguishable relationships between mean fecundity and its CV and skewness.
- Strong negative correlations between mean fecundity and its CV/skewness can arise as statistical artifacts.
- These correlations may be inadequate for inferring density dependence mechanisms.
Conclusions:
- The proposed methods are largely inadequate for distinguishing between HHH and IAH.
- Statistical artifacts can confound the interpretation of density dependence in demographic parameters.
- Further research is needed to develop robust methods for understanding population regulation.
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