Genetic analysis of male reproductive success in relation to density in the zebrafish, Danio rerio

Spence Rowena, Jordan, Smith, Smith Carl

Description

We used behavioural and genetic data to investigate the effects of density on male reproductive success in the zebrafish, Danio rerio . Based on previous measurements of aggression and courtship behaviour by territorial males, we predicted that they would sire more offspring than non-territorial males. Results Microsatellite analysis of paternity showed that at low densities territorial males had higher reproductive success than non-territorial males. However, at high density territorial males were no more successful than non-territorials and the sex difference in the opportunity for sexual selection, based on the parameter I mates , was low. Conclusion Male zebrafish exhibit two distinct mating tactics; territoriality and active pursuit of females. Male reproductive success is density dependent and the opportunity for sexual selection appears to be weak in this species.

Informations

• Publié par: biomed
• Publié le: 01 janvier 2006
• Nombre de lectures: 15
• Langue: English

Extrait

Frontiers in Zoology

BioMedCentral

Open Access Research Genetic analysis of male reproductive success in relation to density in the zebrafish,Danio rerio 1 21 Rowena Spence*, William C Jordanand Carl Smith

1 2 Address: Departmentof Biology, University of Leicester, University Road, Leicester, UK andInstitute of Zoology, Zoological Society of London, Regent's Park, London, UK Email: Rowena Spence*  [e-mail]; William C Jordan  [e-mail]; Carl Smith  [e-mail] * Corresponding author

Published: 05 April 2006Received: 02 March 2006 Accepted: 05 April 2006 Frontiers in Zoology2006,3:5 doi:10.1186/1742-9994-3-5 This article is available from: http://www.frontiersinzoology.com/content/3/1/5 © 2006 Spence et al; licensee BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract Background:We used behavioural and genetic data to investigate the effects of density on male reproductive success in the zebrafish,Danio rerio. Based on previous measurements of aggression and courtship behaviour by territorial males, we predicted that they would sire more offspring than non-territorial males. Results:Microsatellite analysis of paternity showed that at low densities territorial males had higher reproductive success than non-territorial males. However, at high density territorial males were no more successful than non-territorials and the sex difference in the opportunity for sexual selection, based on the parameterI, was low. mates Conclusion:Male zebrafish exhibit two distinct mating tactics; territoriality and active pursuit of females. Male reproductive success is density dependent and the opportunity for sexual selection appears to be weak in this species.

Background The advent of genetic parentage analysis has had a sub stantial impact on our understanding of animal mating systems. Many socially monogamous species have proven to be genetically polygamous [1], while territorial or haremholding males have frequently been shown to be cuckolded [2]. Moreover, due to the operation of sperm competition [3] and cryptic female choice [4], mating suc cess is not equivalent to reproductive success. It is now recognised that genetic analyses are crucial for measuring parentage, and thereby in understanding mating system evolution and the strength of sexual selection [57].

The strength of sexual selection depends on the sex differ ence in the degree of variance in reproductive success for each sex; the greater the difference between the sexes, the

more opportunity there is for selection to operate [8]. In most species the variation in male mating success, as defined by mate number and offspring number, exceeds that of female mating success, as defined by clutch size and number of clutches. While females tend to produce similar numbers of offspring, variance in the number of offspring fathered among males can be high, with success ful males monopolising females and some males failing to reproduce. The sex difference in the opportunity for sexual selection can be quantified using the parameter I [8]; the difference in male and female variance in mates reproductive success as a function of the squared mean reproductive success for each sex:

I=II mates malesfemales

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