Establishment of F1 hybrid mortality in real time

Ashley Saulsberry,Robert M Brucker,Jeremy A Lynch,Seth R Bordenstein,Aaron Noll,Marisa Pinchas

doi:10.1186/s12862-017-0879-1

Abstract

BackgroundMeasuring the evolutionary rate of reproductive isolation is essential to understanding how new species form. Tempo calculations typically rely on fossil records, geological events, and molecular evolution analyses. The speed at which genetically-based hybrid mortality arises, or the “incompatibility clock”, is estimated to be millions of years in various diploid organisms and is poorly understood in general. Owing to these extended timeframes, seldom do biologists observe the evolution of hybrid mortality in real time.ResultsHere we report the very recent spread and fixation of complete asymmetric F1 hybrid mortality within eight years of laboratory maintenance in the insect model Nasonia. The asymmetric interspecific hybrid mortality evolved in an isogenic stock line of N. longicornis and occurs in crosses to N. vitripennis males. The resulting diploid hybrids exhibit complete failure in dorsal closure during embryogenesis.ConclusionThese results comprise a unique case whereby a strong asymmetrical isolation barrier evolved in real time. The spread of this reproductive isolation barrier notably occurred in a small laboratory stock subject to recurrent bottlenecks.

Highlights

Measuring the evolutionary rate of reproductive isolation is essential to understanding how new species form
Given the importance of determining the patterns that affect the tempo of speciation, renewed emphasis has been placed on understanding how fast reproductive isolation barriers evolve during the speciation process
Strain IV7R3-1b is derived from strain IV7, a Wolbachia infected strain that was collected in Utah and antibiotically cured of Wobachia in 2000 [16]

Summary

Introduction

Measuring the evolutionary rate of reproductive isolation is essential to understanding how new species form. The speed at which genetically-based hybrid mortality arises, or the “incompatibility clock”, is estimated to be millions of years in various diploid organisms and is poorly understood in general. Owing to these extended timeframes, seldom do biologists observe the evolution of hybrid mortality in real time. Complete F1 hybrid mortality has never been documented to evolve de novo, while there are a few cases of incomplete premating isolation [1,2,3,4] and a case of hybrid reproduction defects in experimentally evolved yeast [5]. Incomplete reproductive isolation and/or segregating variation for hybrid incompatibles can occur within various species, such as Arabidopsis [11] and Tribolium [12]. Intraspecific variation in hybrid incompatibilities indicates that there is segregating variation for hybrid incompatibility

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