Consequences of the interaction between nutrients and plant secondary metabolites on herbivore selectivity: benefits or detriments for plants?

Abstract

Concentrations of nutrients and plant secondary metabolites (PSM) vary temporally and spatially, creating a multidimensional feeding environment. Interactions between nutrients and PSM are poorly understood because research has relied largely on studying the isolated effects of nutrients or PSM on foraging behavior. Nevertheless, their interactions can influence food selection and the dynamics of plant communities. Our objective was to explore how interactions between nutrients and PSM influence food selection. For 7 d, three groups of lambs received intraruminal infusions of three different doses of a PSM (0=Control; low and high) and 2 h later they were offered two foods that contained either low (high in energy) or high (high in protein) protein/energy ratios. The foods were offered 7 d before (baseline) and 7 d after PSM infusions. We conducted five trials each with a different PSM‐ terpenoids, cyanogenic glycosides, sodium nitrate, quebracho tannin, and lithium chloride. Lambs consistently preferred the food high in energy to the food high in protein, but toxins modified the degree to which this preference was manifest. Terpenoids, nitrate, and lithium chloride depressed intake of the food high in energy. Cyanogenic glycosides had the opposite effect, and at higher doses they depressed intake of the food high in protein. Tannins enhanced intake of the food high in energy at lower doses and they depressed its ingestion at higher doses. Thus, PSM selectively depressed or enhanced intake depending on the macronutrient composition of the foods. These results imply that the probability of a plant being eaten will depend not only on its chemical defenses but also on the quantity and quality of nutrients in the plant and its neighbors, and that the ability of herbivores to learn associations between nutrients and PSM may have a substantial impact on the way herbivores regulate ecosystem processes.

Host Species Affects Herbivory, Pollination, and Reproduction in Experiments With Parasitic Castilleja

“…Both nutrient and defensive compound uptake are likely to influence herbivore preference nonlinearly (Slansky and Wheeler 1992, Behmer et al 2002, Villalba et al 2002. Host species did not affect herbivory on Indian paintbrush in this study, despite strong effects of alkaloid uptake on Indian paintbrush herbivory at the same site in the previous year (Adler 2000).…”

Preference by sheep for endophyte-infected tall fescue grown adjacent to or at a distance from alfalfa

“…However, temporal changes in preference -even when in the aforementioned range -are indicative of the impact of nutrients and toxins on food selection by herbivores (Villalba et al, 2002b). This is relevant in situations, like in this study, when differences in the nutrient profile of food alternatives were small or when the concentration of ergovaline in the forage was below toxic levels (Lyman et al, 2008;Bernard et al, 2013).…”

Effect of supplementation with barley and calcium hydroxide on intake of Mediterranean shrubs by goats

“…Adaptation and supplemental nutrients allowed the animals to better cope with secondary compounds and to feed more readily on Mediterranean shrubs. Without supplemental nutrients, secondary compounds have considerable negative effects on the intake of shrubs, although the mechanisms are not well known (Villalba et al, 2002c). Generally, in our study, goats fed with secondary compound-rich shrubs benefited from eating barley, which suggests that energy from supplements is likely to influence the intake and preference for shrubs in goats browsing on Mediterranean bush-lands.…”