Leaf silicification in grasses — A review

O'Reagain, P.J.; Mentis, M.T.

doi:10.1080/02566702.1989.9648158

Cited by 31 publications

(32 citation statements)

References 59 publications

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“…), suggesting that family‐specific defence traits, such as secondary metabolites (e.g. furanocoumaris for Apiaceae; Berenbaum, Zangerl & Nitao ), or silica content in grasses and sedges (O'Reagain & Mentis ; Vicari & Bazely ; Massey, Ennos & Hartley ; Massey & Hartley ) might drive conservatism of plant–herbivore interaction (Futuyma & Agrawal ). However, testing for family differences would require a larger species sampling than considered here.…”

Section: Discussionmentioning

confidence: 99%

Community‐level plant palatability increases with elevation as insect herbivore abundance declines

et al. 2016

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Summary1. Plants protect themselves against herbivore attacks through a myriad of physical structures and toxic secondary metabolites. Together with abiotic factors, herbivores are expected to modulate plant defence strategies within plant assemblages. Because the abundance of insect herbivore decreases in colder environments, the palatability of plants in communities at higher elevation should shift in response to both abiotic and biotic factors. 2. We inventoried grasshopper communities to document changes in herbivore abundance along elevation gradients and quantified associated shifts in plant palatability. We measured plant palatability by measuring the growth of Spodoptera littoralis generalist caterpillars fed with the leaves of 172 plant species. We related plant palatability to leaf traits and elevation at the species and community levels. 3. In congruence with the decrease in grasshopper abundance with elevation, we found that the mean palatability level of plant communities increases with elevation. In addition, plant palatability was negatively associated with the community-weighted mean of leaf dry matter content. At the species level, plants with high carbon-to-nitrogen ratio were less palatable, while we found no effect of species mean elevation on plant palatability. 4. Synthesis. Our results suggest that plant communities at higher elevation are composed of species that are generally more palatable for insect herbivores. Shift in plant palatability with elevation may thus be the outcome of a relaxation of the in situ herbivore pressure and changes in abiotic conditions.

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Section: Discussionmentioning

confidence: 99%

Community‐level plant palatability increases with elevation as insect herbivore abundance declines

et al. 2016

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“…As foliar nitrogen levels are often the principle limiting nutrient influencing the behaviour and performance of insect herbivores (Slansky & Scriber 1985), the reduction in nitrogen absorbed from grass due to silica‐based defences could have large impacts on both herbivore fitness and feeding preferences under field conditions, where inter‐ and intraspecific variation in grass foliar silica levels is high (O’Reagain & Mentis 1989; Massey et al . 2007).…”

Section: Discussionmentioning

confidence: 99%

“…Second, silica is known to decrease the efficiency with which herbivores can digest grass leaves (Massey & Hartley 2006). This could be for a number of reasons: silica may act as a physical barrier within leaves preventing access to nitrogen (O’Reagain & Mentis 1989; Vicari & Bazely 1993); there could be a reduction in the mastication of leaf material by the herbivore, not releasing as much nitrogen from plant tissues; or silica may be physically damaging the digestive tracts of herbivores thus reducing digestive efficiency.…”

Section: Introductionmentioning

confidence: 99%

Physical defences wear you down: progressive and irreversible impacts of silica on insect herbivores

Massey

Hartley

2008

Journal of Animal Ecology

335

307

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Summary 1.Silica in the leaves of grasses can act as a defence against both vertebrate and invertebrate herbivores. The mechanisms by which silica affects herbivore performance are not well characterized. Here we expose an insect herbivore Spodoptera exempta to high-silica diets and test two mechanisms by which silica has been proposed to act as a defence. First, that silica reduces the digestibility of leaves and second, that silica causes wear to insect mandibles, both of which could potentially impact on herbivore performance. 2. Silica reduced the efficiency with which S. exempta converted ingested food to body mass and the amount of nitrogen absorbed from their food, leading to reduced insect growth rates. The measure of how efficiently herbivores utilize digested food (ECD) was unaffected by silica. 3. These effects occurred even with short-term exposure to silica-rich diets, but they also increased markedly with the duration of exposure and affected late instars more than early instar larvae. This appears to be due to the progressive impacts of silica with longer exposure times and suggests that herbivores cannot adapt to silica defences, nor do they develop a tolerance for silica with age. 4. Exposure to silica-rich diets caused increased mandible wear in S. exempta . This effect was extremely rapid, occurring within a single instar, further reducing feeding efficiency and growth rates. These effects on insect growth and feeding efficiency are nonreversible, persisting after the herbivore has switched diets. Up to a third of this residual impact can be explained by the degree of mandible wear caused by previous silica-rich diets. 5. The impacts of silica on S. exempta larvae were progressive with exposure time and could not be compensated for, even by switching to a different diet. Thus, herbivores cannot easily adapt to physical defences such as silica, suggesting this defence will have major implications for herbivore fitness.

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“…Although coevolution between grasses and grazers has received a great deal of attention (Stebbins 1981;McNaughton 1984;Jernvall & Fortelius 2002;Prasad et al 2005), the ecological mechanisms by which grasses defend themselves against herbivores remain poorly understood (O'Reagain & Mentis 1989;Vicari & Bazely 1993). The silica content of grasses can be considerably higher than in many other plants and has been proposed as an antiherbivore defence strategy (McNaughton et al 1985;Gali-Muhtasib et al 1992;Vicari & Bazely 1993).…”

Section: Introductionmentioning

confidence: 99%

Experimental demonstration of the antiherbivore effects of silica in grasses: impacts on foliage digestibility and vole growth rates

2006

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The impact of plant-based factors on the population dynamics of mammalian herbivores has been the subject of much debate in ecology, but the role of antiherbivore defences in grasses has received relatively little attention. Silica has been proposed as the primary defence in grasses and is thought to lead to increased abrasiveness of foliage so deterring feeding, as well as reducing foliage digestibility and herbivore performance. However, at present there is little direct experimental evidence to support these ideas. In this study, we tested the effects of manipulating silica levels on the abrasiveness of grasses and on the feeding preference and growth performance of field voles, specialist grass-feeding herbivores. Elevated silica levels did increase the abrasiveness of grasses and deterred feeding by voles. We also demonstrated, for the first time, that silica reduced the growth rates of both juvenile and mature female voles by reducing the nitrogen they could absorb from the foliage. Furthermore, we found that vole feeding leads to increased levels of silica in leaves, suggesting a dynamic feedback between grasses and their herbivores. We propose that silica induction due to vole grazing reduces vole performance and hence could contribute to cyclic dynamics in vole populations.

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Leaf silicification in grasses — A review

Cited by 31 publications

References 59 publications

Community‐level plant palatability increases with elevation as insect herbivore abundance declines

Community‐level plant palatability increases with elevation as insect herbivore abundance declines

Physical defences wear you down: progressive and irreversible impacts of silica on insect herbivores

Experimental demonstration of the antiherbivore effects of silica in grasses: impacts on foliage digestibility and vole growth rates

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