No difference in plasticity between different ploidy levels in the Mediterranean herb Mercurialis annua

Julia Sánchez Vilas, John R. Pannell

Open Access

https://doi.org/10.1038/s41598-017-07877-3

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Abstract

Increased phenotypic plasticity for a number of plant traits has been suggested as a possible reason for the success and spread of polyploids. One such trait is a plant’s sex allocation (or gender), which influences its reproductive success directly as a function of the potentially heterogeneous mating prospects in the population. However, it is unknown how polyploidy per se might affect plasticity in a plant’s sex allocation. Although there have been numerous comparisons between diploid and (usually) tetraploid taxa, we know very little about how elevated ploidy above the diploid level might affect plasticity. Here, we ask whether different ploidy levels > 2x express different plasticity in the ruderal plant Mercurialis annua. We grew tetraploid and hexaploid hermaphrodites under different levels of nutrient availability and compared their reaction norms for growth (above-ground biomass, SLA) and reproductive traits (reproductive effort, phenotypic gender). Overall, we found that an increase in ploidy level from 4x to 6x in M. annua is associated with an increase in the relative biomass allocated to seeds, measured as female reproductive effort. However, our study provides no support for the idea that increasing ploidy level increases the ability to express different phenotypes in response to changes in the environment.

Highlights

Polyploidy is common in angiosperms, in which most lineages reflect one or more whole genome duplication events[1, 2]
The extent to which polyploidy might play a role in increasing phenotypic plasticity in sex allocation in poorly known, yet such knowledge would contribute to an understanding of the basis of associations between ploidy and gender[51]
We found no evidence of significant differences in plasticity between tetraploid and hexaploid individuals of M. annua

Summary

Introduction

Polyploidy is common in angiosperms, in which most lineages reflect one or more whole genome duplication events[1, 2]. Plant vigour and biochemical flexibility may allow polyploids to enjoy broader ecological tolerance and occupy a wider range of environments[10, 19,20,21,22], helping to explain their evolutionary success[23, 24] In other words, their putative broader ecological tolerance may be due to their greater ability to express different phenotypes in response to changes in the environment, i.e., phenotypic plasticity[10]. The extent to which polyploidy might play a role in increasing phenotypic plasticity in sex allocation in poorly known, yet such knowledge would contribute to an understanding of the basis of associations between ploidy and gender (e.g., gender dimorphism appears to be more common among polyploid than diploid lineages)[51]

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