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

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 Silerie vul^aris, we measured reproductive traits (ovule number, ovule size, anther size, and floral traits related to display) and a vegetative trait (intemode length) among plants growing under full sun and foliar shade treatments. We tested for sex-specific correlation structures as ' I well as trait plasticity and the sensitivity of correlation structures to the light environment. Hermaphrodites exhibited ' I a fixed trade-off between anther size and ovule size, whereas females exhibited an ovule siz^number trade-off, l-or a I few traits, we detected plasticity to light treatment and plasticity that differed significantly between sexes across light j, treatments. Fxposure ro foliar shade resulted in a sex-specific trade-off between vegetative and reproductive allegation; hermaphrodites exhibited a negative correlation (trade-off) between intemode elongation and ovule number, whereas females showed a marginally significant, positive correlation between these two traits. The tradeoffs observed in hermaphrodites are of particular evolutionary relevance, suggesting that hermaphrodites will evolve to Income increasingly male and populations increasingly sexually dimorphic.

Allocation to male vs female floral function varies by currency and responds differentially to density and moisture stress

“…Environmental sensitivity of floral nutrient allocation Both plant density and moisture are distributed coarsely over the landscape, and heterogeneity in these two environmental features may affect not only carbon pools but also the ability to take up N and P from the environment (Schlesinger et al, 1996;Wang et al, 2009). Allocation of biomass to floral organs is sensitive to competition and moisture (Carroll et al, 2001;Dykstra et al, 2009;Table 2;Lambrecht and Dawson, 2007). In the current study, both competition and drought reduced allocation of CNP in all organs at the level of the whole-plant reproductive budget.…”

Scale dependence of sex ratio in wild plant populations: implications for social selection

“…The environment – specifically light and moisture conditions – has been shown to affect sex expression and sex ratio in S. vulgaris (Dykstra et al. ) and Geranium maculatum (Van Etten and Chang ). Inbreeding also has been shown to significantly affect sex expression in S. vulgaris – the sex ratios of more inbred plants became increasingly female‐biased in a greenhouse crossing study (Glaettli and Goudet ).…”

“…The environmental and genetic factors that drive the observed patterns of spatial structure may alter predictions of any short-or long-term responses to social selection. The environmentspecifically light and moisture conditionshas been shown to affect sex expression and sex ratio in S. vulgaris (Dykstra et al 2009) and Geranium maculatum (Van Etten and Chang 2009). Inbreeding also has been shown to significantly affect sex expression in S. vulgaristhe sex ratios of more inbred plants became increasingly female-biased in a greenhouse crossing study .…”

“…; Dykstra et al. ; Van Etten and Chang ; Weiner and Freckleton ), and stand‐level characteristics can result in both competition and facilitation for pollinators, in addition to affecting the apparency of the stand to herbivores (Stevens et al. ; Kelly ; Aspi et al.…”

“…The spatial scale of interaction is likely to be a primary determinant of C ij 0 , especially in nonmotile organism such as plants, where fitness impacting interactions are determined by physical proximity or the movement of animal vectors. Plants compete for resources in the soil and to avoid shading (Bengtsson et al 1994;Dykstra et al 2009;Van Etten and Chang 2009;Weiner and Freckleton 2010), and stand-level characteristics can result in both competition and facilitation for pollinators, in addition to affecting the apparency of the stand to herbivores (Stevens et al 1995;Kelly 1996;Aspi et al 2003;Donohue 2004;Bartkowska and Johnston 2014). Considerable attention has been paid to the degree to which the fitness effects of population-and communitylevel phenotypes depend on the spatial scale of interactions (Barrett and Thomson 1982;House 1992;Aizen 1997;Stehlik et al 2008;Lin et al 2015).…”