DOI: 10.5061/dryad.bs449c6
title: Data from: Pulsed seaweed subsidies drive sequential shifts in the effects of lizard predators on island food webs

description: Most prominent theories of food-web dynamics imply the simultaneous action
 of bottom-up and top-down forces. However, transient bottom-up effects
 resulting from resource pulses can lead to sequential shifts in the
 strength of top-down predator effects. We used a large-scale field
 experiment (32 small islands sampled over 5 years) to probe how the
 frequency and magnitude of pulsed seaweed inputs drives temporal variation
 in the top-down effects of lizard predators. Short-term weakening of
 lizard effects on spiders and plants (the latter via a trophic cascade)
 were associated with lizard diet shifts, and were more pronounced with
 larger seaweed inputs. Long-term strengthening of lizard effects was
 associated with lizard numerical responses and plant fertilization.
 Increased pulse frequency reinforced the strengthening of lizard effects
 on spiders and plants. These results underscore the temporally variable
 nature of top-down effects and highlight the role of resource pulses in
 driving this variation.
description: Plant_RawData_CleanThese data were collected from buttonwood (Conocarpus erectus) plants located on small islands off the coast of Great Abaco, Bahamas. A detailed description of the experimental design and the study islands can be found in the paper and supplement. Column headings are as follows: eu = island identity; trip.date = date of sampling trip; sw.trt = seaweed treatment (several small = several small seaweed additions, several large = several large seaweed additions, single large = single large seaweed addition, control = no seaweed addition); liz.trt = brown anole (Anolis sagrei) lizard treatment (1 = lizards introduced, 0 = no-lizard control); block corresponds to groupings of 8 islands based on island size (blocks are named after local birds); plant = plant identity; percent damage = percent of leaf area damaged (from a sample of ~10 leaves); shoot.growth = shoot growth in the preceding sampling period (in mm, mean of ~4 stems); growth.s = shoot growth rate in the preceding sampling period (in mm per day, mean of ~4 stems); ellipsoid.volume = plant volume (in cubic meters, calculated by measuring height, length, and width, and assuming an ellipsoid shape) ; sandy.dam = plant damage resulting from Hurricane Sandy (proportion of ~4 marked, previously viable stems found dead after the storm); eu.ht.m = island height (meters above high water line at highest point).WebSpiders_RawData_CleanThese data were collected from on small islands off the coast of Great Abaco, Bahamas. A detailed description of the experimental design and the study islands can be found in the paper and supplement. Column headings are as follows: eu = island identity; trip.date = date of sampling trip (mmm-yy); sw.trt = seaweed treatment (several small = several small seaweed additions, several large = several large seaweed additions, single large = single large seaweed addition, control = no seaweed addition); liz.trt = brown anole (Anolis sagrei) lizard treatment (1 = lizards introduced, 0 = no-lizard control); block corresponds to groupings of 8 islands based on island size (blocks are named after local birds); number.spiders.dens = web spider density (in spiders per square meter).SalticidSpiders_RawData_CleanThese data were collected on small islands off the coast of Great Abaco, Bahamas. A detailed description of the experimental design and the study islands can be found in the paper and supplement. Column headings are as follows: eu = island identity; trip.date = date of sampling trip; sw.trt = seaweed treatment (several small = several small seaweed additions, several large = several large seaweed additions, single large = single large seaweed addition, control = no seaweed addition); liz.trt = brown anole (Anolis sagrei) lizard treatment (1 = lizards introduced, 0 = no-lizard control); block corresponds to groupings of 8 islands based on island size (blocks are named after local birds); salt.index = salticid density (number per bowl trap plus number per tap sample).Analyses_PlantVars_LizEffect_FinalThis file contains the R script used for the analyses of plant variables (leaf damage and shoot growth). Analyses were conducted using R version 3.4.3, lme4 version 1.1-15, and emmeans version 1.2.3.Analyses_WebSpider_LizEffect_FinalThis file contains the R script used for the analyses of web spider density. Analyses were conducted using R version 3.4.3, lme4 version 1.1-15, and emmeans version 1.2.3.Analyses_SalticidSpider_LizEffect_FinalThis file contains the R script used for the analyses of salticid spider abundance. Analyses were conducted using R version 3.4.3 and permute version 0.9-4.