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Probing the Limits of Egg Recognition Using Egg Rejection Experiments Along Phenotypic Gradients
Published on: August 22, 2018
How to evade a coevolving brood parasite: egg discrimination versus egg variability as host defences
Claire N Spottiswoode1, Martin Stevens
1Department of Zoology, University of Cambridge, Downing Street, Cambridge CB2 3EJ, UK. cns26@cam.ac.uk
Proceedings. Biological Sciences
|April 15, 2011
Summary
Avian brood parasite hosts evolve defenses against egg mimicry through either increased egg pattern variation (polymorphism) or better discrimination. Both strategies offer similar fitness benefits, representing alternative evolutionary paths.
Area of Science:
- Evolutionary Biology
- Animal Behavior
- Ornithology
Background:
- Avian brood parasitism involves a co-evolutionary arms race where parasites mimic host eggs to avoid rejection.
- Host defenses against brood parasitism can evolve via enhanced egg discrimination or increased egg appearance polymorphism.
Purpose of the Study:
- To compare the egg discrimination and polymorphism strategies in three Afrotropical cuckoo finch host species.
- To model the fitness consequences of different host defense strategies against brood parasitism.
Main Methods:
- Egg rejection experiments were conducted with three host species of the cuckoo finch (Anomalospiza imberbis).
- Avian color and pattern vision models were used to analyze visual cues in egg rejection.
- Simulations modeled parasitic laying and host rejection to assess fitness advantages.
Main Results:
- Host species varied in their degree of egg polymorphism and discrimination ability.
- The most polymorphic host species exhibited the least discrimination, while the least polymorphic species was most discriminating.
- A non-parasitized species showed intermediate levels of both defenses.
Conclusions:
- Two distinct host defense strategies against brood parasitism exist: high polymorphism with low discrimination, or low polymorphism with high discrimination.
- Both strategies confer similar fitness advantages, indicating alternative evolutionary trajectories for host defenses.
- Understanding these alternative strategies is crucial for comprehending host-parasite co-evolution.
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