Sexual differences in response to simulated herbivory in the gynodioecious herb Geranium sylvaticum

Varga, Sandra, Kytöviita, Minna-Maarit and Siikamäki, Pirkko (2009) Sexual differences in response to simulated herbivory in the gynodioecious herb Geranium sylvaticum. Plant Ecology, 202 (2). pp. 325-336. ISSN 1385-0237

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Several factors have been proposed to explain female maintenance in gynodioecious popu- lations. In this study, we propose and test a novel hypothesis: greater tolerance to herbivory through more beneficial interactions with plant fungal mutu- alists might also help to explain female maintenance. Herbivory limits the amount of carbon and nutrients available for the plants and has been shown to affect mycorrhizal colonization. We hypothesized that sim- ulated herbivory would decrease reproductive output, mycorrhizal colonization intensity, and the phospho- rus content relatively more in hermaphrodites, so females would achieve higher advantage over hermaphrodites when under herbivory pressure. We tested it in the field using the gynodioecious plant Geranium sylvaticum. We found that simulated herbivory had a negative effect on the reproductive output in both sexes and that there was a similar reduction in fruit set, seed set, and total seed number in both sexes. Defoliation did not affect any fungal parameter measured, but decreased phosphorus con- tent relatively more in females. The plants had a sex- specific relationship with mycorrhizae, but this was not related to herbivory. Thus, we conclude that females do not gain any specific advantage under defoliation from its symbionts at short-term even though it seems that the plants have sex-specific relationship with their mycorrhizal symbionts.

Keywords:Arbuscular mycorrhizae, Geraniaceae, Defoliation, Gynodioecy, Reproductive output, Sexual dimorphism
Subjects:C Biological Sciences > C180 Ecology
C Biological Sciences > C220 Mycology
C Biological Sciences > C200 Botany
Divisions:College of Science > School of Life Sciences
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ID Code:17270
Deposited On:25 Apr 2015 19:00

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