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Color polymorphism and genetic structure in the sea star Pisaster ochraceus
C D G Harley1, M S Pankey, J P Wares
1University of British Columbia, Department of Zoology, Vancouver, British Columbia, Canada. harley@zoology.ubc.ca
The Biological Bulletin
|December 21, 2006
Summary
The sea star Pisaster ochraceus exhibits striking color variations across the Northeast Pacific. Regional differences in color frequencies are ecologically controlled, not solely due to genetics or past climate events.
Area of Science:
- Marine biology
- Ecology
- Evolutionary biology
Background:
- Pisaster ochraceus, a sea star species, displays significant color polymorphism along the Northeast Pacific coast.
- Color frequencies vary dramatically among populations, with some regions predominantly purple while others show a mix of orange, purple, and reddish-brown individuals.
Purpose of the Study:
- To investigate the factors maintaining color polymorphism in Pisaster ochraceus.
- To understand the causes of regional variation in sea star color frequencies.
Main Methods:
- Conducted a large-scale phylogeographic survey of Pisaster populations.
- Examined relationships between color frequencies and ecological variables (diet, salinity) and morphological variables (size, injury frequency).
Main Results:
- Found very low population genetic structure, indicating high gene flow and refuting Pleistocene glacial refugia as a cause for color variation.
- Color frequencies were unrelated to adult size or injury frequency.
- Suggestive relationships were observed between color frequencies and diet, and with areas of potentially low salinity.
Conclusions:
- Regional variation in Pisaster ochraceus color frequency is likely ecologically controlled, despite a potential underlying genetic component.
- Environmental factors such as diet and salinity may play a significant role in shaping sea star color patterns across different sites.
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