Arbuscular mycorrhizal fungi reduce the construction of extrafloral nectaries in <Emphasis Type="Italic">Vicia faba</Emphasis> |
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Authors: | Robert A Laird John F Addicott |
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Institution: | (1) Department of Biological Sciences, University of Calgary, 2500 University Dr NW, T2N 1N4 Calgary, AB, Canada |
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Abstract: | Arbuscular mycorrhizal fungi (AMF) can alter the physiology and morphology of their host plant, and therefore may have indirect
effects on insect herbivores and pollinators. We conducted this study to test the hypothesis that AMF can also affect insects
involved in protection-for-food mutualisms. We examined the constitutive and inducible production of food rewards extrafloral
(EF) nectaries] in Vicia faba plants by manipulating the presence/absence of AMF and by simulating various levels of herbivory. Plants inoculated with
AMF produced significantly fewer EF nectaries than uninoculated plants, even after accounting for differences in plant growth.
In contrast to earlier studies, EF nectaries were not inducible: damaged plants produced significantly fewer EF nectaries
than undamaged plants. Moreover, the effects of mycorrhizal and damage status on EF nectary production were additive. The
reduction in EF nectaries in mycorrhizal plants potentially represents a mechanism for indirect effects of AMF on the protective
insects that exploit EF nectaries as a food source (e.g., ants). Reduced reward size should result in reduced protection by
ants, and could therefore be a previously unappreciated cost of the mycorrhizal symbiosis to host plants. However, the overall
effect of AMF will depend upon the extent to which the reduction of EF nectaries affects the number and activity of ants and
the extent to which AMF alter other aspects of host plant physiology. Our results emphasize the complexity of multitrophic
interactions, particularly those that span belowground and aboveground ecology. |
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Keywords: | Ant– plant interactions Cost of symbiosis Extrafloral nectar Indirect defence Trait-mediated indirect interactions (TMIIs) |
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