POLYGYNANDRY IN THE DUSKY PIPEFISH SYNGNATHUS FLORIDAE REVEALED BY MICROSATELLITE DNA MARKERS.

Adam G Jones,John C Avise

doi:10.1111/j.1558-5646.1997.tb01484.x

Adam G Jones, John C Avise

Open Access

https://doi.org/10.1111/j.1558-5646.1997.tb01484.x

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Abstract

In the dusky pipefish Syngnathus floridae, like other species in the family Syngnathidae, 'pregnant' males provide all post-zygotic care. Male pregnancy has interesting implications for sexual selection theory and the evolution of mating systems. Here, we employ microsatellite markers to describe the genetic mating system of S. floridae, compare the outcome with a previous report of genetic polyandry for the Gulf pipefish S. scovelli, and consider possible associations between the mating system and degree of sexual dimorphism in these species. Twenty-two pregnant male dusky pipefish from one locale in the northern Gulf of Mexico were analyzed genetically, together with subsamples of 42 embryos from each male's brood pouch. Adult females also were assayed. The genotypes observed in these samples document that cuckoldry by males did not occur; males often receive eggs from multiple females during the course of a pregnancy (six males had one mate each, 13 had two mates, and three had three mates); embryos from different females are segregated spatially within a male's brood pouch; and a female's clutch of eggs often is divided among more than one male. Thus, the genetic mating system of the dusky pipefish is best described as polygynandrous. The genetic results for S. floridae and S. scovelli are consistent with a simple model of sexual selection which predicts that for sex role-reversed organisms, species with greater degrees of sexual dimorphism are more highly polyandrous.

Highlights

Male pregnancy, otherwise rare in the biological world, is ubiquitous in fishes of the family Syngnathidae and has interesting evolutionary implications
Male investment varies among syngnathid species, as do apparent mating behaviors and degrees of sexual dimorphism (Vincent et al 1992)
The study of sex role-reversed organisms promises to enhance our understanding of sexual selection as an evolutionary process (Williams 1975), but highly polymorphic molecular markers seldom have been applied to investigate the genetic mating systems of species with reversed sex roles

Summary

Introduction

Otherwise rare in the biological world, is ubiquitous in fishes of the family Syngnathidae and has interesting evolutionary implications. Males may have a luxury of being choosy (Rosenqvist 1990; Berglund and Rosenqvist 1993) This sex-role reversal provides opportunities to test theories of sexual selection from a unique perspective (Williams 1975). Field studies often ignore extra-pair paternity and use the social mating system as a correlate to sexual dimorphism (Webster 1992; Winquist and Lemon 1994). The study of sex role-reversed organisms promises to enhance our understanding of sexual selection as an evolutionary process (Williams 1975), but highly polymorphic molecular markers seldom have been applied to investigate the genetic mating systems of species with reversed sex roles (but see Oring et al 1992). An important step in addressing the predicted relationship between polyandry and sexual dimorphism would be to describe the genetic mating systems of additional sex role-reversed taxa. The discovery of microsatellite markers (Tautz and Renz 1984; Tautz 1989) has opened new possibilities for the genetic assessment of parentage and mating systems in nature (e.g., Brockmann et al 1994; Craighead et al 1995; Kellogg et al 1995; Primmer et al 1995; Colbourne et al 1996)

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