Present address: Evolutionary Biology Centre/Animal Ecology, Norbyvägen 18d, University of Uppsala, 752 36 Uppsala, Sweden.
PRONOUNCED WITHIN-INDIVIDUAL PLASTICITY IN SPERM MORPHOMETRY ACROSS SOCIAL ENVIRONMENTS
Version of Record online: 10 DEC 2009
© 2010 The Author(s). Journal compilation © 2010 The Society for the Study of Evolution
Volume 64, Issue 6, pages 1634–1643, June 2010
How to Cite
Immler, S., Pryke, S. R., Birkhead, T. R. and Griffith, S. C. (2010), PRONOUNCED WITHIN-INDIVIDUAL PLASTICITY IN SPERM MORPHOMETRY ACROSS SOCIAL ENVIRONMENTS. Evolution, 64: 1634–1643. doi: 10.1111/j.1558-5646.2009.00924.x
- Issue online: 2 JUN 2010
- Version of Record online: 10 DEC 2009
- Received April 27, 2009Accepted November 18, 2009
- Corticosteroid hormones;
- phenotypic plasticity;
- social hierarchy;
- sperm competition;
- sperm morphometry
Sperm morphometry (i.e., size and shape) and function are important determinants of male reproductive success and are thought to be under stabilizing selection. However, recent studies suggest that sperm morphometry can be a phenotypically plastic trait, which can be adjusted to varying conditions. We tested whether different behavioral strategies in aggression between aggressive red and nonaggressive black males of the color polymorphic Gouldian finch (Erythrura gouldiae) can influence sperm morphometry. We show pronounced within-individual phenotypic plasticity in sperm morphometry of male Gouldian finches in three different social environments. Both red and black males placed in intermediate to high competitive environments (high frequency of red males) increased the relative length of their sperm midpiece. By contrast, red males placed in low to intermediate competitive environments (higher frequency of black males) increased the length of the sperm flagellum. Significant changes in stress and sex steroid hormone levels (in response to the competitive environment) appear to influence sperm traits in red but not in black males, suggesting that changes in hormonal levels are not solely responsible for the observed changes in sperm morphometry. These findings imply that males can adjust sperm morphometry across social environments.