Phenotypic integration and independence: Hormones, performance, and response to environmental change
Ellen D Ketterson1, Jonathan W Atwell, Joel W McGlothlin
1Department of Biology and Center for the Integrative Study of Animal Behavior, Indiana University, Bloomington, Indiana, USA. ketterso@indiana.edu
Integrative and Comparative Biology
|June 14, 2011
Summary
Hormones link traits, but how they evolve together remains unclear. This review explores whether hormonal changes promote trait integration or independent evolution, focusing on testosterone in songbirds.
Area of Science:
- Evolutionary biology
- Endocrinology
- Animal behavior
Background:
- Hormones coordinate multiple traits, creating integrated phenotypes.
- The evolution of these hormone-mediated traits depends on changes in hormone systems.
- It is unknown if these changes occur independently or together, impacting evolutionary pathways.
Purpose of the Study:
- To explore the implications of hormonal correlations for the evolution of hormone-mediated traits.
- To investigate whether hormones promote tight phenotypic integration or allow independent trait evolution.
- To examine the relative importance of integration versus independence in trait evolution.
Main Methods:
- Review of existing studies on hormone-mediated trait evolution.
- Comparison across sexes, individuals, and populations.
- Focus on testosterone (T) and the dark-eyed junco (Junco hyemalis) as a model system.
Main Results:
- Hormonally mediated traits can evolve through changes in hormone secretion, carrier protein affinity, degradation rates, or target tissue interactions.
- The degree of phenotypic integration (tightly linked vs. loosely associated traits) influences adaptive modification.
- Selection may favor either coordinated or independent changes in hormone-regulated traits.
Conclusions:
- Understanding the interplay between hormone signal variation and target tissue sensitivity is crucial for predicting evolutionary trajectories.
- Further research is needed to determine the relative contributions of integration and independence in shaping hormone-mediated phenotypes.
- The study highlights the complex evolutionary dynamics of hormone-influenced traits, using testosterone in songbirds as a key example.
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