Strong population structure despite evidence of recent migration in a selfing hermaphroditic vertebrate, the mangrove killifish (Kryptolebias marmoratus)

ANDREY TATARENKOV,BRUCE J. TURNER,MARK MACKIEWICZ,HONG GAO,JOHN C. AVISE,D. SCOTT TAYLOR

doi:10.1111/j.1365-294x.2007.03349.x

Abstract

We employ a battery of 33 polymorphic microsatellite loci to describe geographical population structure of the mangrove killifish (Kryptolebias marmoratus), the only vertebrate species known to have a mixed-mating system of selfing and outcrossing. Significant population genetic structure was detected at spatial scales ranging from tens to hundreds of kilometres in Florida, Belize, and the Bahamas. The wealth of genotypic information, coupled with the highly inbred nature of most killifish lineages due to predominant selfing, also permitted treatments of individual fish as units of analysis. Genetic clustering algorithms, neighbour-joining trees, factorial correspondence, and related methods all earmarked particular killifish specimens as products of recent outcross events that could often be provisionally linked to specific migration events. Although mutation is the ultimate source of genetic diversity in K. marmoratus, our data indicate that interlocality dispersal and outcross-mediated genetic recombination (and probably genetic drift also) play key proximate roles in the local 'clonal' dynamics of this species.

Highlights

Hermaphroditism occurs in about 6% of animal species distributed across more than 20 phyla (Jarne 1995; Jarne & Auld 2006)
The six TC91 individuals distinguished by instruct formed a well-supported NJ cluster that included MI6
With the exception of one individual in each case, specimens from SL, LK, CC, LM, and mixture of local (MI) formed clusters corresponding to their respective localities

Summary

Introduction

Hermaphroditism occurs in about 6% of animal species distributed across more than 20 phyla (Jarne 1995; Jarne & Auld 2006). Fewer than 20% of the 142 hermaphroditic species studied to date have self-fertilization rates greater than 0.8, and most of these are pulmonate mollusks. We address the population genetic features of self-fertilization in the mangrove killifish, Kryptolebias (formerly Rivulus) marmoratus, the only vertebrate species known to self-fertilize routinely and the only known vertebrate that shows androdioecy (the presence of males as well as hermaphrodites). In K. marmoratus, each hermaphrodite normally fertilizes itself, with syngamy occurring inside an internal ‘ovotestis’ (Harrington 1963; Sakakura et al 2006). Most populations contain hermaphrodites almost exclusively, but males are common (10–25% frequency) at some sites in Belize (Turner et al 2006). Factors that mediate male frequencies in nature are not understood

Methods

Results

Conclusion