Abstract
Considerable theoretical and empirical effort has been focused on the potential of continuously variable sexual traits to honestly indicate male quality, but relatively little effort has been devoted to a similar evolutionary role for dimorphic traits. Male dimorphisms, associated with conditionally expressed alternative reproductive tactics, represent extreme phenotypic plasticity. Evidence suggests that considerable heritable variation exists in the 'liability' underlying many threshold traits; if this liability is correlated with the genetic quality of males, dimorphic traits have the potential to be reliable indicators. We investigated the genetic architecture of phenotypically plastic morph expression in the context of condition-dependent signalling theory. Male morph in the mite Sancassania berlesei is condition dependent: 'fighters' armed with thickened and sharp third pairs of legs emerge from heavier nymphs than unarmoured 'scramblers'. We selected on male morph in three replicate 'fighter' and 'scrambler' lines and recorded a significant response to selection over seven generations; this was due to a shift in the threshold reaction norm but the lines showed no correlated response in condition. This is inconsistent with models predicting a substantial genetic correlation between condition and sexual trait expression. We discuss why dimorphic sexual traits may show more condition-independent genetic variance than continuous sexual traits.
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Selected References
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- Emlen D. J., Nijhout H. F. Hormonal control of male horn length dimorphism in Onthophagus taurus (Coleoptera: Scarabaeidae): a second critical period of sensitivity to juvenile hormone. J Insect Physiol. 2001 Sep;47(9):1045–1054. doi: 10.1016/s0022-1910(01)00084-1. [DOI] [PubMed] [Google Scholar]
- Emlen D. J., Nijhout H. F. Hormonal control of male horn length dimorphism in the dung beetle Onthophagus taurus (Coleoptera: Scarabaeidae). J Insect Physiol. 1999 Jan;45(1):45–53. doi: 10.1016/s0022-1910(98)00096-1. [DOI] [PubMed] [Google Scholar]
- Greeff JM, Ferguson JW. Mating ecology of the nonpollinating fig wasps of Ficus ingens. Anim Behav. 1999 Jan;57(1):215–222. doi: 10.1006/anbe.1998.0954. [DOI] [PubMed] [Google Scholar]
- Hazel W. N., Smock R., Johnson M. D. A polygenic model for the evolution and maintenance of conditional strategies. Proc Biol Sci. 1990 Dec 22;242(1305):181–187. doi: 10.1098/rspb.1990.0122. [DOI] [PubMed] [Google Scholar]
- Houle D. Comparing evolvability and variability of quantitative traits. Genetics. 1992 Jan;130(1):195–204. doi: 10.1093/genetics/130.1.195. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Johnstone R. A. Sexual selection, honest advertisement and the handicap principle: reviewing the evidence. Biol Rev Camb Philos Soc. 1995 Feb;70(1):1–65. doi: 10.1111/j.1469-185x.1995.tb01439.x. [DOI] [PubMed] [Google Scholar]
- Knülle W. Genetic and environmental determinants of hypopus duration in the stored-product mite Lepidoglyphus destructor. Exp Appl Acarol. 1991 Feb;10(3-4):231–258. doi: 10.1007/BF01198653. [DOI] [PubMed] [Google Scholar]
- Knülle Wilhelm. Interaction between genetic and inductive factors controlling the expression of dispersal and dormancy morphs in dimorphic astigmatic mites. Evolution. 2003 Apr;57(4):828–838. doi: 10.1111/j.0014-3820.2003.tb00294.x. [DOI] [PubMed] [Google Scholar]
- Kokko Hanna, Brooks Robert, McNamara John M., Houston Alasdair I. The sexual selection continuum. Proc Biol Sci. 2002 Jul 7;269(1498):1331–1340. doi: 10.1098/rspb.2002.2020. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Kotiaho J. S., Simmons L. W., Tomkins J. L. Towards a resolution of the lek paradox. Nature. 2001 Apr 5;410(6829):684–686. doi: 10.1038/35070557. [DOI] [PubMed] [Google Scholar]
- Radwan J. Male morph determination in Rhizoglyphus echinopus (Acaridae). Exp Appl Acarol. 2001;25(2):143–149. doi: 10.1023/a:1010688516704. [DOI] [PubMed] [Google Scholar]
- Radwan Jacek. Heritability of male morph in the bulb mite, Rhizoglyphus robini (Astigmata, Acaridae). Exp Appl Acarol. 2003;29(1-2):109–114. doi: 10.1023/a:1024260719013. [DOI] [PubMed] [Google Scholar]
- Zahavi A. Mate selection-a selection for a handicap. J Theor Biol. 1975 Sep;53(1):205–214. doi: 10.1016/0022-5193(75)90111-3. [DOI] [PubMed] [Google Scholar]