DOI: 10.5061/dryad.j0zpc86mf
title: Silicon-based anti-herbivore defense in tropical tree seedlings

description: Silicon-based defenses effectively deter insect herbivores in many
 cultivated and wild grass species. Furthermore, in some of these species,
 silicon (Si) uptake and defense can be induced by herbivory. Tropical
 trees also take up Si and leaf Si concentrations vary greatly across and
 within species. As herbivory is a major driver of seedling mortality and
 niche differentiation of tropical tree species, understanding
 anti-herbivore defenses is pivotal. Yet, whether silicon is a constitutive
 and inducible herbivory defense in tropical forest tree species remains
 unknown. We grew seedlings of eight tropical tree species in a full
 factorial experiment, including two levels of plant-available soil Si
 concentrations (-Si/+Si) and a simulated herbivory treatment (-H/+H). The
 simulated herbivory treatment was a combination of clipping and
 application of methyl jasmonate. We then carried out multiple-choice
 feeding trials, separately for each tree species, in which leaves of each
 treatment combination were offered to a generalist caterpillar (Spodoptera
 frugiperda). Leaf damage was assessed. Three species showed a significant
 decrease in leaf damage under high compared to low Si conditions (by up to
 72%), consistent with our expectation of Si-based defenses acting in
 tropical tree species. In one species, leaf damage was increased by
 increasing soil Si and in the remaining four species, no effect of soil Si
 on leaf damage was observed. Opposite to our expectation of Si uptake and
 defense being inducible by herbivory damage, simulated herbivory increased
 leaf damage in two species. Furthermore, simulated herbivory reduced Si
 concentrations in one species. Our results showed that tropical tree
 seedlings can be better defended when growing in Si-rich compared to
 Si-poor soils, and that the effects of Si on plant defense vary strongly
 across species. Furthermore, Si-based defenses may not be inducible in
 tropical tree species. Overall, constitutive Si-based defense should be
 considered part of the vast array of anti-herbivore defenses of tropical
 tree species. Our finding that Si-based defenses are highly
 species-specific combined with the fact that herbivory is a major driver
 of mortality in tropical tree seedling, suggests that variation in soil Si
 concentrations may have pervasive consequences for regeneration and
 performance across tropical tree species.
description: # Title of Dataset: Silicon-based herbivory defence in tropical tree
 seedlings Results (leaf damage) of multiple-choice feeding trials. We grew
 seedlings of eight tropical tree species in a full factorial experiment,
 including two levels of plant-available soil silicon (Si) concentrations
 (-Si/+Si) and a simulated herbivory treatment (-H/+H). The simulated
 herbivory treatment was a combination of clipping and application of
 methyl jasmonate. We then carried out multiple-choice feeding trials,
 separately for each tree species, in which leaves of each treatment
 combination were offered to a generalist caterpillar species. ##
 Description of the Data and file structure Each row contains data for one
 seedling. Columns are the following: ind\_id: id of seedling (overall)
 nb\_trial: id of feeding trial species: species code Si: "+" =
 Individual grew in Si-rich soil; "-" = Individual grew in
 Si-poor soil treatment: "H" = Individual received simulated
 herbivory treatment; "C" = Individual did not receive simulated
 herbivory treatment individual: id of seedling (within species) date: date
 trial was carried out area\_left: area (in cm¹) left after the trial
 (YYYYMMDD) damage\_percent: (1-(area\_left/2))100, each leaf disk was 2cm²
 Si\_content: Leaf Silicon concentration (mg/g) of the individual (for one
 individual data could not be obtained and is therefore denoted
 "NA")