Polymorphic microsatellite markers demonstrate hybridization and interspecific gene flow between lumbricid earthworm species, Eisenia andrei and E. fetida.

Marta Jaskulak,Franck Vandenbulcke,Maxime Pauwels,Agnieszka Rorat,Barbara Plytycz,Paweł Grzmil,Karthikeyan Adhimoolam

doi:10.1371/journal.pone.0262493

Abstract

The lumbricid earthworms Eisenia andrei (Ea) and E. fetida (Ef) have been used as model organisms for studies on hybridization. Previously they have been identified by species specific sequences of the mitochondrial COI gene of maternal origin (‘a’ or ‘f’) and the nuclear 28S gene of maternal/paternal origin (‘A’ or ‘F’). In experimental crosses, these hermaphroditic species produce progeny of genotypes Ea (aAA), Ef (fFF) and hybrids (aAF and fFA) originating by self-fertilization or cross-fertilization. To facilitate studies on new aspects of the breeding biology and hybridization of earthworms, polymorphic microsatellite markers were developed based on 12 Ea and 12 Ef specimens and validated on DNA samples extracted from 24 genotyped specimens (aAA, fFF, aAF and fFA) from three laboratory-raised families and 10 of them were applied in the present study. The results indicate that microsatellite markers are valuable tools for tracking interspecific gene flow between these species.

Highlights

The uniformly reddish Eisenia andrei (Ea) and striped ‘tiger worms’ E. fetida (Ef) are widely used in toxicology, ecotoxicology, ecology, environmental studies [1, 2] and in biomedicine as a source of bioactive molecules [3, 4], all of which require accurate species identification
In response to the continuously growing need for new species-specific markers for studies on hybridization, the aim of the present work was to develop polymorphic microsatellite markers for E. fetida and E. andrei followed by their validation on DNA samples from three families of earthworms genotyped during previous experiments
Our results indicate that microsatellite markers are valuable tools for tracking interspecific gene flow

Summary

Introduction

The uniformly reddish Eisenia andrei (Ea) and striped ‘tiger worms’ E. fetida (Ef) are widely used in toxicology, ecotoxicology, ecology, environmental studies [1, 2] and in biomedicine as a source of bioactive molecules [3, 4], all of which require accurate species identification. The existence of hybrids was revealed by mixed patterns of electromorphs of esterase activity in laboratory mated specimens [5] and relicts of past hybridization between Ea and Ef were recognized in natural populations from Scandinavia [6].

Objectives

Methods

Results