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Environmental component of morphological differentiation in birds
Science (New York, N.Y.)
|July 8, 1983
Summary
Bird nestling development shows significant regional differences due to nongenetic factors, not just genetic adaptations. This challenges the assumption that natural selection alone drives geographic character variation in bird populations.
Area of Science:
- Avian biology
- Evolutionary biology
- Ecology
Background:
- Geographic variation in bird traits is typically explained by natural selection favoring locally adapted genetic differences.
- Phenotypic differences observed in adult birds are often assumed to stem from distinct genetic adaptations to specific environments.
Purpose of the Study:
- To investigate the role of nongenetic factors in geographic character variation in birds.
- To determine the proportion of regional differences in nestling development attributable to non-genetic influences.
Main Methods:
- Experimental cross-fostering of red-winged blackbird eggs between geographically distinct populations (northern and southern Florida; Colorado and Minnesota).
- Analysis of nestling development to assess phenotypic differences in relation to the experimental manipulation.
Main Results:
- A significant portion of regional variation in red-winged blackbird nestling development was found to be nongenetic.
- Experimental transplants demonstrated that environmental or maternal effects, rather than solely genetic differences, contribute substantially to observed phenotypic clines.
Conclusions:
- Nongenetic factors play a crucial role in shaping geographic character variation in birds, alongside natural selection.
- For natural selection to maintain observed clines in adult phenotypes, genetic and nongenetic components of phenotypic variation must exhibit covariation.
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