High male fertility in males of a subdioecious shrub in hand-pollinated crosses.

Hui Wang,Michinari Matsushita,Nobuhiro Tomaru,Michiko Nakagawa

doi:10.1093/aobpla/plw067

Abstract

Female reproductive success in females versus hermaphrodites has been well documented. However, documenting a potential advantage in male fertility of male versus hermaphrodite individuals in subdioecious species is also essential for understanding the evolutionary pathway toward dioecy from hermaphroditism via gynodioecy. Siring success in terms of fruit set, fruit mass, number of seeds and mean seed mass was compared by hand-pollinated crosses in the subdioecious shrub Eurya japonica The pollen was from male and hermaphrodite individuals, and the pollen recipients were females and hermaphrodites. Seed quality was also evaluated in terms of seed germination rate, seed germination day and seedling survival. Overall, pollen from males sired more fruits of larger size and more seeds than did pollen from hermaphrodites. The male advantage was observed when pollen recipients were females, whereas no effect was found in hermaphrodite recipients. Pollen from males also produced better quality seeds with higher germination rate and sooner germination day. Although these results could also be explained by a higher pollen load for crosses with male pollen donors, we took care to saturate the stigma regardless of the pollen donor. Therefore, these results suggest that male individuals of E. japonica have advantages in male fertility in terms of both quantity and quality. Our previous studies indicated that females exhibit higher female reproductive success compared with hermaphrodites. Thus, both the female and male functions of hermaphrodites are outperformed by females and males, respectively, raising the possibility that the subdioecious E. japonica at this study site is entering the transitional phase to dioecy along the gynodioecy-dioecy pathway.

Highlights

Plants have diverse and complex sexual expression, and mixtures of individuals bearing various combinations of female, male and hermaphrodite flowers are sometimes observed within a single population
The sex of both pollen donor and pollen recipient and the interaction between the two had significant effects on fruit set in E. japonica (Table 2)
Fruit set was significantly greater when flowers were hand-pollinated with pollen from male individuals than with that from hermaphrodite individuals, whereas no significant difference was found in hermaphrodite recipients in post hoc comparisons (Fig. 1A)

Summary

Introduction

Plants have diverse and complex sexual expression, and mixtures of individuals bearing various combinations of female, male and hermaphrodite flowers are sometimes observed within a single population. The gynodioecy–dioecy pathway is considered one of the most important evolutionary routes from hermaphroditism to dioecy via gynodioecy. In this pathway, female individuals (male-steriles) invade a hermaphrodite population, hermaphrodites are VC The Authors 2016.

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Conclusion