How to make a haploid male.

Laura Ross,Andy Gardner,Nicholas G Davies

doi:10.1002/evl3.107

Abstract

Haplodiploidy has evolved repeatedly among invertebrates, and appears to be associated with inbreeding. Evolutionary biologists have long debated the possible benefits for females in diplodiploid species to produce haploid sons–beginning their population's transition to haplodiploidy–and whether inbreeding promotes or inhibits this transition. However, little attention has been given to what makes a haploid individual male rather than female, and whether the mechanism of sex determination may modulate the costs and benefits of male haploidy. We remedy this by performing a theoretical analysis of the origin and invasion of male haploidy across the full range of sex‐determination mechanisms and sib‐mating rates. We find that male haploidy is facilitated by three different mechanisms of sex determination–all involving male heterogamety–and impeded by the others. We also find that inbreeding does not pose an obvious evolutionary barrier, on account of a previously neglected sex‐ratio effect whereby the production of haploid sons leads to an abundance of granddaughters that is advantageous in the context of inbreeding. We find empirical support for these predictions in a survey of sex determination and inbreeding across haplodiploids and their sister taxa.

Highlights

Evolutionary biologists have long debated the possible benefits for females in diplodiploid species to produce haploid sons–beginning their population’s transition to haplodiploidy–and whether inbreeding promotes or inhibits this transition
We find that inbreeding does not pose an obvious evolutionary barrier, on account of a previously neglected sex-ratio effect whereby the production of haploid sons leads to an abundance of granddaughters that is advantageous in the context of inbreeding
ONLY SOME sex determination (SD) MECHANISMS ALLOW THE RELIABLE PRODUCTION OF HAPLOID MALES Under what conditions are unfertilised, haploid eggs expected to develop as males rather than females (Fig. 2)? In the overwhelming majority of terrestrial arthropods, including all those that have given rise to haplodiploid clades (Fig. 1), an individual’s sex is determined by the genomic material it receives from its parent(s), and so we restrict our attention to such “genetic” sex-determination (GSD) mechanisms (Bull 1983; Bachtrog et al 2014; Beukeboom and Perrin 2014)

Summary

Introduction

Little attention has been given to what makes a haploid individual male rather than female, and whether the mechanism of sex determination may modulate the costs and benefits of male haploidy. Little attention has been given to what makes haploid individuals male rather than female in the first place, and how the mechanism of sex determination affects the costs and benefits of male haploidy.

Results

Conclusion