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Gender-specific floral and physiological traits: implications for the maintenance of females in gynodioecious Lobelia siphilitica

Caruso, CM, H Maherali, RB Jackson
Journal Volume/Pages: 
135: 524-531

A common gender dimorphism in angiosperms is gynodioecy, in which hermaphrodites and females co-occur. Females are at an inherent disadvantage because they can transmit their genes only through ovule production. One mechanism by which females can compensate for the loss of male function is by producing more seeds than hermaphrodites. As such, females should (1) increase resource uptake to support higher seed production and (2) allocate resources saved by the loss of male function to seed production. To test this hypothesis, we measured physiological and floral traits of gynodioecious Lobelia siphilitica, controlling for both environmental and genetic variation through a comparison of greenhouse-grown siblings. Pre-reproductive females had 14% higher area-based (A; Z = 2.14; P = 0.04) and 32% higher mass-based (Z = 1.96; P = 0.05) photosynthetic rate than hermaphrodites, suggesting that they have increased carbon acquisition by altering photosynthetic physiology. Female L. siphilitica produced flowers with 4-8% smaller corollas than hermaphrodites (all P

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