Androgens, interspecific competition and species replacement in hybridizing warblers

The steroid hormone testosterone regulates aggressive behaviour in many vertebrates and is important for territorial defence among males of the same species. However, its role in mediating interspecific competition, and ultimately species distributions, is unknown. We show that testosterone may infl...

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Bibliographic Details
Published in:Proceedings of the Royal Society. B, Biological sciences Biological sciences, 2004-12, Vol.271 (Suppl 6), p.S498-S500
Main Authors: Owen-Ashley, Noah T., Butler, Luke K.
Format: Article
Language:English
Subjects:
Aggression
Analysis of Variance
Androgens
Androgens - blood
Animal aggression
Animals
Demography
Dendroica occidentalis
Dendroica townsendi
Extinction
Geography
Hermit lifestyle
Human aggression
Hybrid Zone
Hybridity
Hybridization
Hybridization, Genetic
Interspecific Competition
Male
Male animals
Mating behavior
Population Dynamics
Radioimmunoassay
Selection, Genetic
Songbirds - genetics
Songbirds - metabolism
Songbirds - physiology
Species Specificity
Territoriality
Testosterone
Warbler
Warblers
Washington
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Summary:The steroid hormone testosterone regulates aggressive behaviour in many vertebrates and is important for territorial defence among males of the same species. However, its role in mediating interspecific competition, and ultimately species distributions, is unknown. We show that testosterone may influence the geographical replacement of one species by another. Townsend's warblers (Dendroica townsendi) have replaced hermit warblers (D. occidentalis) over a vast portion of their historical range, partly because Townsend's males are more aggressive than hermit males and outcompete them for territories in areas of sympatry. We report differences in plasma androgen levels that parallel these aggressive asymmetries and the historical pattern of species replacement between Townsend's and hermits. Using hybrids, we provide evidence that these hormonal differences are partially genetically based and thus may have evolved through sexual selection during Pleistocene glacial maxima. Hormone-behaviour mechanisms can therefore have important effects on species distributions and can even influence the pathways underlying extinction.
ISSN:0962-8452
1471-2954
DOI:10.1098/rsbl.2004.0230