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Selection for rapid embryo development correlates with embryo exposure to maternal androgens among passerine birds

American Naturalist

By:
, , and
DOI: 10.1086/519397

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Abstract

Greater offspring predation favors evolution of faster development among species. We hypothesized that greater offspring predation exerts selection on mothers to increase levels of anabolic androgens in egg yolks to achieve faster development. Here, we tested whether (1) concentrations of yolk androgens in passerine species were associated with offspring predation and (2) embryo and nestling development rates were associated with yolk androgen concentrations. We examined three androgens that increase in potency along the synthesis pathway: androstenedione (A4) to testosterone (T) to 5??- dihydrotestosterone (5??-DHT). Concentrations of none of these steroids were related to clutch size; only A4 was allometrically related to egg volume. Species that experience greater predation showed higher yolk concentrations of T and 5??-DHT. Higher concentrations of T and particularly 5??-DHT were strongly correlated with faster development during the embryo period and less so during the nestling period. Development rates were most strongly correlated with 5??-DHT, suggesting that potency increases along the androgen synthesis pathway and that effects are mediated by the androgen receptor pathway. These results are consistent with the hypothesis that selection for faster development by time-dependent offspring mortality may be achieved epigenetically by varying embryo exposure to maternal anabolic steroids. ?? 2007 by The University of Chicago. All rights reserved.

Additional Publication Details

Publication type:
Article
Publication Subtype:
Journal Article
Title:
Selection for rapid embryo development correlates with embryo exposure to maternal androgens among passerine birds
Series title:
American Naturalist
DOI:
10.1086/519397
Volume
170
Issue:
2
Year Published:
2007
Language:
English
Larger Work Type:
Article
Larger Work Subtype:
Journal Article
Larger Work Title:
American Naturalist
First page:
196
Last page:
206
Number of Pages:
11