Constraints on the evolution of attractive traits: Natural selection, sexual selection and quantitative genetics in the zebra finch
Price, Donald Kevin
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Permalink
https://hdl.handle.net/2142/20944
Description
Title
Constraints on the evolution of attractive traits: Natural selection, sexual selection and quantitative genetics in the zebra finch
Author(s)
Price, Donald Kevin
Issue Date
1991
Doctoral Committee Chair(s)
Burley, Nancy
Department of Study
Biology
Discipline
Biology
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Biology, Ecology
Biology, Genetics
Biology, Zoology
Language
eng
Abstract
I investigated the causes and consequences of bill color (an attractive male trait) variation in zebra finches (Taeniopygia guttata). The primary objective of my research was to test several predictions of the good-genes and runaway sexual selection hypotheses. In a 19 month breeding experiment, I found that redder billed males have more offspring that survive to independence due to their high reproductive rate. In contrast, redder billed females had few offspring that survived to independence due to their low reproductive rate and survival. I also demonstrated that there was no correlation between male or female bill color and nestling weight or condition. These results indicate that redder bill color is advantageous to males but detrimental to females. In this same experiment, I also demonstrated that bill color is heritable and there is a high genetic correlation between the sexes. In addition, nestling or current condition did not affect offspring bill color at 120 days (adult age). These results indicate that females mated to redder billed males will produce male and female offspring with red bills but their survival and condition will be unaffected. I also showed that redder billed males and their mates spend less time in parental care and defensive activities primarily during the nestling stage. The reduced care provided by redder billed males may represent a cost to females mating with redder billed males. However, there is no indication that fewer offspring are produced due to the reduced time spent at the nest by the parents. Finally, I examined the genetic and environmental causes of bill color variation in a cross-fostering experiment. This experiment demonstrated that bill color is condition-dependent early in development but when the birds reach adult age (120 days) their bill color is heritable and no longer condition-dependent.
These results indicate that redder bill color in zebra finches is beneficial to males but detrimental to females. The genetic correlation between the sexes constrains males and females from evolving to their sex-specific optima as predicted by the runaway sexual selection hypotheses.
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