Phylogeographic reconstruction of the marbled crayfish origin

Julian Gutekunst,Christopher E Skelton,Frank Lyko,Nathan J Dorn,Panagiotis Provataris,Olena Maiakovska,Hannes Horn,Stephan Wolf,Katharina Hanna

doi:10.1038/s42003-021-02609-w

Abstract

The marbled crayfish (Procambarus virginalis) is a triploid and parthenogenetic freshwater crayfish species that has colonized diverse habitats around the world. Previous studies suggested that the clonal marbled crayfish population descended as recently as 25 years ago from a single specimen of P. fallax, the sexually reproducing parent species. However, the genetic, phylogeographic, and mechanistic origins of the species have remained enigmatic. We have now constructed a new genome assembly for P. virginalis to support a detailed phylogeographic analysis of the diploid parent species, Procambarus fallax. Our results strongly suggest that both parental haplotypes of P. virginalis were inherited from the Everglades subpopulation of P. fallax. Comprehensive whole-genome sequencing also detected triploid specimens in the same subpopulation, which either represent evolutionarily important intermediate genotypes or independent parthenogenetic lineages arising among the sexual parent population. Our findings thus clarify the geographic origin of the marbled crayfish and identify potential mechanisms of parthenogenetic speciation.

Highlights

The marbled crayfish (Procambarus virginalis) is a triploid and parthenogenetic freshwater crayfish species that has colonized diverse habitats around the world
Sequencing of PCR amplicons from up to three markers and from 92 specimens showed that every analyzed P. fallax had at least one polymorphism (Fig. 1A) with the published P. virginalis reference sequence[8]
These findings strongly suggest that P. virginalis is not present within the native range of P. fallax

Summary

Introduction

The marbled crayfish (Procambarus virginalis) is a triploid and parthenogenetic freshwater crayfish species that has colonized diverse habitats around the world. Comparative genome sequencing of numerous specimens from diverse sources and locations confirmed that the global P. virginalis population is largely monoclonal with only very limited genetic differences between geographically separated populations[2,5,8]. This monoclonality can be reasonably explained by a recent founder event involving a single animal. While P. virginalis appears to have diverged from P. fallax as recently as 25 years ago[2,15], the genetic, phylogeographic, and mechanistic origin of the species has remained unresolved, resulting in the perception that marbled crayfish are enigmatic “mutants”. We have constructed a new genome assembly for P. virginalis to support a detailed phylogeographic analysis of 92 P. fallax from 23 locations across the native range and to identify the putative parent population(s) of P. virginalis

Methods

Results

Conclusion