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Linesville, PA, United States

Steets J.A.,Oklahoma State University | Ashman T.-L.,University of Pittsburgh | Ashman T.-L.,Pymatuning Laboratory of Ecology
International Journal of Plant Sciences | Year: 2010

Maternal effects of herbivory for fitness-related traits of offspring, especially those traits that are expressed later in a plant's life, have rarely been studied. To better understand how herbivory to the maternal plant influences traits of its progeny and whether this depends on the mating system that produced the seed or the growth environment of the seedling, we examined maternal effects of herbivory in Impatiens capensis. Impatiens capensis is well suited to this study because it exhibits a mixed mating system by producing obligately selfing cleistogamous flowers and facultatively outcrossing chasmogamous flowers on a single plant. In a natural I. capensis population, we manipulated maternal herbivory and collected seeds from cleistogamous and chasmogamous flowers and assessed their fitness in the presence or absence of intraspecific competitors in the greenhouse. We found that maternal herbivory had positive effects for many offspring traits but the magnitude of the maternal effect depended on the offspring competitive context. In addition, for offspring biomass and total flower production, the expression of maternal effects varied with seed source (i.e., chasmogamous or cleistogamous flower). Our results demonstrate that maternal herbivory has consequences for the next generation that persist throughout the offspring life cycle, indicating that there may be important demographic consequences of maternal effects. © 2010 by The University of Chicago. All rights reserved.

Bishop E.J.,University of Pittsburgh | Bishop E.J.,Pymatuning Laboratory of Ecology | Spigler R.B.,University of Pittsburgh | Spigler R.B.,Pymatuning Laboratory of Ecology | And 2 more authors.
Botany | Year: 2010

Sex-allocation plasticity is thought to play an important role in the evolution of separate sexes in plants. Accordingly, much attention has been paid to environmentally induced variation in fruit and seed production in sexually dimorphic species, but we know little about whether this variation arises as a direct response to environmental variation or is instead an indirect consequence of changes in plant size. In this study, we characterize sex-allocation plasticity across a resource gradient for several reproductive traits in hermaphrodites of gyno(sub)dioecious Fragaria virginiana Duch. We find significant plasticity, on average, for flower number, proportion fruit set, ovule number, proportion seed set, and runner number in response to resource variation. Plasticity of most traits examined tended to be at least partially independent of variation in plant size, suggesting that it is not simply an indirect consequence of plant allometry. Moreover, we find genetic variation for plasticity of key reproductive traits. Comparisons of relative plasticities among traits reveal that F. virginiana hermaphrodites are more likely to adjust female investment via changes in fruit and seed set than ovule number, and most likely to adjust male investment via flower number rather than anther number or pollen per anther, although there is genotypic variation for plasticity in pollen per anther. Evidence of within-population variation can logically be extended to suggest that variation in hermaphrodite sex-expression seen among natural populations of F. virginiana may be due, at least in part, to sex-allocation plasticity.

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