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

Abstract

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.

Identifying crop plants with phytoliths (and starch grains) in Central and South America: A review and an update of the evidence

“…Massey and Hartley (2006) demonstrated that silica in grasses not only deterred feeding by field voles, but also inhibited the growth rates of the voles by decreasing nitrogen absorption from foliage. Ma et al (2006), working with rice, identified for the first time in a higher plant a silicon transporter gene, called Lsil, that controls silica uptake.…”

Silicon-based plant defences, tooth wear and voles

“…Plants respond to grazing intensity of the previous year by adjusting the Si content (by 0.6-1 percentage point; Wieczorek et al, 2015b) in their leaves (see also Massey et al, 2008;Reynolds et al, 2012), and voles are in turn negatively affected by increased phytolith levels (Massey and Hartley, 2006;Massey et al, 2008). But how plant phytoliths affect voles is still unclear.…”

“…It has been shown that grazing induces an increased concentration of silicon (Si) in leaves Massey et al, 2007a;McNaughton and Tarrants, 1983;McNaughton et al, 1985;Reynolds et al, 2012), which reduces palatability and digestibility (Gali-Muhtasib et al, 1992;Massey et al, 2007b), and in turn lowers body mass and growth rate of voles (Massey and Hartley, 2006;Massey et al, 2008). Very recently, Wieczorek et al (2015b) demonstrated in the first field-based study that (1) silicon concentrations in leaves are determined by the vole population density, and thus by the grazing intensity, of the previous year, and (2) overwintering success in voles is correlated with leaf silicon levels in autumn.…”

Applying Limestone or Basalt in Combination with Bio-Fertilizer to Sustain Rice Production on an Acid Sulfate Soil in Malaysia

“…High Al and/or Fe concentration in the water not only caused toxicity to rice, but also reduced the availability of P [33]. The low available P in the acid sulfate soil could be somewhat alleviated by the PSB, which were able increase soil pH to a level above 5 [8].…”