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Ashmole's hypothesis and the latitudinal gradient in clutch size
Carl G Lundblad1, Courtney J Conway2
1Idaho Cooperative Fish and Wildlife Research Unit, Department of Fish and Wildlife Sciences, University of Idaho, 875 Perimeter Drive MS 1141, Moscow, ID, 83844, U.S.A.
Biological Reviews of the Cambridge Philosophical Society
|March 23, 2021
Summary
Ecologists explore why avian clutch size varies with latitude. Ashmole's hypothesis links clutch size to resource seasonality, but its interpretation and testing remain debated.
Area of Science:
- Ecology
- Evolutionary Biology
- Ornithology
Background:
- Avian clutch size variation is a key ecological question.
- Clutch size generally increases with latitude, but underlying mechanisms are debated.
- N. Philip Ashmole's 1961 hypothesis links clutch size to resource seasonality.
Purpose of the Study:
- Clarify Ashmole's hypothesis on clutch size variation.
- Review and synthesize evidence for and against the hypothesis.
- Propose novel approaches to test the hypothesis and understand avian life-history evolution.
Main Methods:
- Literature review and synthesis of existing research.
- Analysis of historical and contemporary ecological studies.
- Conceptual clarification of hypothesis mechanisms and predictions.
Main Results:
- Ashmole's hypothesis is influential but often misinterpreted.
- Evidence supporting and refuting the hypothesis is mixed.
- Confusion exists regarding the precise predictions and tests of the hypothesis.
Conclusions:
- Revisiting Ashmole's hypothesis is crucial for understanding clutch size variation.
- Further research is needed to resolve debates and test predictions.
- Improved understanding can advance broader theories of life-history evolution.
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