Sex‐Specific Trade‐Offs and Responses to Foliar Shade in the Gynodioecious Species Silene vulgaris (Caryophyllaceae)

Amy B Dykstra,Cynthia Weinig,Lynda F Delph,Marcus T Brock

doi:10.1086/597781

Amy B Dykstra, Cynthia Weinig + Show 2 more

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https://doi.org/10.1086/597781

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Abstract

Allocation trade‐offs are predicted to affect evolutionary dynamics, including the evolution of sexual dimorphism. In gynodioecious species, where populations have both females and hermaphrodites, selection may result in sexual dimorphism in individual traits or trait correlations because, in contrast to females, hermaphrodites acquire fitness through both male and female function. Using the gynodioecious species Silene vulgaris, we measured reproductive traits (ovule number, ovule size, anther size, and floral traits related to display) and a vegetative trait (internode length) among plants growing under full sun and foliar shade treatments. We tested for sex‐specific correlation structures as well as trait plasticity and the sensitivity of correlation structures to the light environment. Hermaphrodites exhibited a fixed trade‐off between anther size and ovule size, whereas females exhibited an ovule size–number trade‐off. For a few traits, we detected plasticity to light treatment and plasticity that di...

Highlights

In many species, the expression of diverse traits varies systematically across sexes
We evaluated whether sexual dimorphism exists in floral traits, floral trait integration, allocation trade-offs, and plastic responses in S. vulgaris under foliar shade and full sunlight regimes
Our study addressed the following questions: (1) Is there sexual dimorphism in the average expression of floral traits or in plasticity of floral or vegetative morphology to light treatments? (2) Do phenotypic correlations among floral traits related to display differ between hermaphrodites and females? (3) Do hermaphrodites exhibit fixed or environment-specific tradeoffs between allocation to male and female function? (4) Do females exhibit the classic life-history tradeoff between size and number for ovules either on average across environments or under light-limited conditions? (5) Do the sexes exhibit similar trade-offs between vegetative and reproductive traits? Taken together, the larger issue inherent to these specific questions is whether sexual dimorphism in environmental responses affects the expression of trade-offs

Summary

Introduction

The expression of diverse traits varies systematically across sexes. In gynodioecious plant species, where hermaphroditic and female individuals coexist within populations, hermaphrodites are expected to experience selection to increase male function (Charlesworth and Charlesworth 1978), and increases in allocation to male gametes might come at the cost of female gamete number or quality (Ashman 2003). Such tradeoffs could enhance sexual dimorphism by rendering hermaphrodites increasingly male.

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