Later this week, many of you may gather together with family around a table adorned with a turkey. In a grocery store or on a farm, turkeys are remarkably uniform, but wild turkeys have remarkably diverse appearances and behaviors. One striking example of this is the decorative displays of male (or “tom”) turkeys, which includes iridescent feathers, a brightly colored head and neck, and enlarged beard, caruncles, wattle and snood. These features are used to attract females, but surprisingly many toms don’t mate, and these subordinate males actually look and act different from dominant males.
Once dominance is established within a family of toms, subordinate turkeys develop less vivid coloration and smaller wattles, caruncles and snoods. These turkeys help their one dominant brother to attract mates, and serve as bodyguards to fight off other groups of males, but the subordinate toms don’t attempt to mate.
The basis for the existence of these two male phenotypes is a fascinating example of epigenetics and gene expression plasticity. Transcriptome analysis shows genome-wide changes in gene activity after establishment of dominance, with subordinate males expressing fewer male-biased genes and more female-biased genes. Almost definitely these differences are caused exclusively by the behavior and the social environment of the different male birds, meaning that the male turkey phenotype can exist in two stable states, independent of genotype. Also fascinating is that when a dominant tom dies, a subordinate male quickly develops a dominant phenotype, even late in life, emphasizing the remarkable plasticity of the turkey transcriptome.
Just some science to ponder while you’re gobbling your turkey.
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1. Pointer MA, Harrison PW, Wright AE, Mank JE. (2013) Masculinization of gene expression is associated with exaggeration of male sexual dimorphism. PLoS Genet. 9:e1003697
2. Krakauer AH. (2005) Kin selection and cooperative courtship in wild turkeys. Nature. 434:69-72.
Image courtesy of Tuomas_Lehtinen at FreeDigitalPhotos.net