Chemical defenses against herbivores and fungi limit establishment of fungal farms on salt marsh angiosperms

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• 作者：R. Drew Sieg ; Kevin Wolfe ; Drew Willey ; Vicky Ortiz-Santiago ; Julia Kubanek
• 关键词：Antifungal ; Antiherbivore ; Chemical defense ; Herbivore ; Pathogen ; Spartina
• 刊名：Journal of Experimental Marine Biology and Ecology
• 出版年：2013
• 出版时间：August, 2013
• 年：2013
• 卷：446
• 期：Complete
• 页码：122-130
• 全文大小：477 K

文摘

Within coastal salt marshes of eastern North America, the snail m>Littoraria irroratam> facilitates fungal growth on live plant tissues to gain access to a palatable and nutritious fungal food source. This snail-fungal mutualism increases exposure of the foundation species m>Spartina alternifloram> to infection, whereas fungal farming on other local marsh plants is rarely observed. We sought to identify traits from five salt marsh angiosperm species, such as chemical defenses against snails or fungi, which restrict m>L. irroratam> habitat choice, feeding patterns, and ability to establish fungal farms. In the field and in mesocosm experiments, m>L. irroratam> densities were significantly higher on m>S. alternifloram> than on other available plants, indicating that m>S. alternifloram> is a favored habitat for m>L. irroratam>. Highly avoided plants were rich in chemical defenses that rendered these plants unpalatable to m>L. irroratam> in feeding trials, whereas m>S. alternifloram> extracts deterred m>L. irroratam> feeding only slightly. Removal of plant structure did not alter m>L. irroratam> preferences indicating a negligible role of tissue toughness as a defense. All plants in our study produced compounds that inhibited growth of fungi typically farmed by m>L. irroratam>, although m>S. alternifloram> antifungal compounds were weaker than those of other plant species, consistent with the observation of fungi only on wounded m>S. alternifloram> tissues. We propose that the weak chemical defenses produced by m>S. alternifloram> make it a preferred plant for fungal farming, whereas less abundant species that invest in potent chemical defenses against grazers and fungi are not as frequently colonized, consumed, or subjected to fungal farming by m>L. irroratam>. The inability of m>S. alternifloram> to adequately deter herbivores and pathogens may lead to increasing losses in plant biomass and reduce the ecosystem services provided by this foundational species.