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Host-parasite arms races and rapid changes in bird egg appearance
Claire N Spottiswoode1, Martin Stevens
1Department of Zoology, University of Cambridge, Downing Street, Cambridge CB2 3EJ, United Kingdom. cns26@cam.ac.uk
The American Naturalist
|April 17, 2012
Summary
Bird egg color and pattern evolution demonstrates rapid coevolutionary arms races. African tawny-flanked prinia and cuckoo finch eggs show diversification driven by host-parasite interactions and frequency-dependent selection.
Area of Science:
- Evolutionary Biology
- Behavioral Ecology
- Ornithology
Background:
- Coevolutionary arms races drive adaptation and diversification.
- Phenotypic polymorphisms can hinder parasite or predator exploitation.
- Egg polymorphisms in birds may serve as a defense against brood parasites.
Purpose of the Study:
- To analyze avian egg appearance evolution in a host-parasite system.
- To investigate rapid phenotypic changes in egg traits over time.
- To understand the selective pressures driving host-parasite coevolution in egg appearance.
Main Methods:
- Utilized models of avian visual perception.
- Analyzed egg color and pattern data from prinia (Prinia subflava) and cuckoo finch (Anomalospiza imberbis) over 40 years.
- Applied models of frequency-dependent and directional selection.
Main Results:
- Observed rapid changes and diversification in egg color and pattern traits for both host and parasite.
- Egg colors expanded within avian color space, consistent with negative frequency-dependent selection.
- Egg patterns exhibited signatures of both frequency-dependent and directional selection, evolving independently.
- Cuckoo finch eggs showed closer color mimicry of contemporaneous prinia eggs, indicating tracking of host evolution.
Conclusions:
- Correlational evidence suggests an ongoing coevolutionary arms race in egg appearance between prinia and cuckoo finches.
- Constant shifts in selective advantages drive rapid phenotypic change in this host-parasite system.
- Coevolutionary arms races can lead to remarkably swift evolutionary adaptations in interacting species.
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