Facultative parthenogenesis in the Ryukyu drywood termite Neotermes koshunensis.

Kazuya Kobayashi,Yasushi Miyaguni

doi:10.1038/srep30712

Abstract

Parthenogenesis is a relatively rare reproductive mode in nature compared to sex. In social insects, the evolution of parthenogenesis has a notable impact on their life histories. Some termites with parthenogenetic ability produce numerous non-dispersing supplementary queens asexually, whereas other castes are produced via sexual reproduction. This asexual queen succession (AQS) system is adaptive because hundreds of the asexual queens improve the reproductive potential of the colony and maintain the genetic diversity within the colony. However, the evolutionary process of the AQS system remains unclear because parthenogenetic species without this system are unknown. Here, we report facultative parthenogenesis in the drywood termite Neotermes koshunensis. Although the eggs produced by females isolated from males hatched, the hatching rate of those eggs was lower than that of the eggs produced by females kept with males. These parthenogenetic offspring inherited only the maternal alleles and showed high homozygosity, which indicates that the mechanism of ploidy restoration is terminal fusion. A previous study showed that most colonies of this species have a single queen or orphan; thus, the AQS system has not evolved despite their parthenogenetic ability. Further investigations of N. koshunensis will reveal how parthenogenesis evolved and its role in the insect societies.

Highlights

Sexual reproduction is ubiquitous in nature despite its significant costs, which include the production of males and the dilution of an individual’s genetic contribution to the generation[1,2]
Our results revealed the parthenogenetic ability of N. koshunensis, which remains in the intermediate stage of transition from obligately sexual to sophisticated parthenogenesis
In the species of the genus Reticulitermes, colony-founding experiments showed that parthenogenetic eggs of the asexual queen succession (AQS) species hatched, as did the sexually produced eggs, but no larva were found from FF colonies of the non-AQS species[15,16]

Summary

Introduction

Sexual reproduction is ubiquitous in nature despite its significant costs, which include the production of males and the dilution of an individual’s genetic contribution to the generation[1,2]. Recent studies have revealed a loophole to this rule in some ant[3,4,5] and termite societies[6,7,8,9] These social insects conditionally use both sexual and asexual reproduction to obtain the advantages of both strategies: non-dispersing queens are produced asexually, whereas other castes (workers, soldiers and dispersing reproductives) are produced via normal sexual reproduction. This asexual queen succession (AQS) system allows queens to maximize their genetic contribution to the generation through the asexual reproduction of queens while maintaining the genetic diversity within a colony by the conditional use of sex for workers. We genotyped the offspring produced by FF pairs at seven newly developed microsatellite loci to confirm that they had inherited only the maternal alleles

Methods

Results

Conclusion