Ecological Archives E096-192-A4

María C. Rodríguez-Rodríguez, Pedro Jordano, and Alfredo Valido. 2015. Hotspots of damage by anatgonists shape the spatial structure of plant–pollinator interactions. Ecology 96:2181–2191. http://dx.doi.org/10.1890/14-2467.1

Appendix D. Description of the methodology used to estimate the proportion of viable seeds consumed per fruit by predispersal seed predators, plus a table containing the estimated interaction strengths per animal guild.

Methods

Estimation of the proportion of viable seeds consumed per fruit by predispersal seed predators

We defined the proportion of viable seeds consumed by seed predators (P_sc) in the infested fruits as P_sc = (S_i – S_r) / S_i, where S_i is the initial number of viable seeds produced by the fruit, and S_r the number of remaining viable seeds after larvae predation.

The estimation of P_sc was done in three steps. First, we separated the infested fruits in the respective plant (total n = 185 fruits from 71 plants) from the uninfested ones, and counted the number of remaining viable seeds within the infested fruits (S_r). Second, we predicted the initial number of viable seeds present in the fruit before predation (S_i) by linear regression. For this, we used data only from uninfested fruits produced by those plants that interacted with seed predators, instead of data from all studied plants. This procedure avoided bias in the estimation of S_i caused by mother plant effects. Concretely, we fit a zero-inflated model with the number of viable seeds per uninfested fruit as response variable, and fruit width as explanatory variable (negative binomial family, log link function). After model fitting, we predicted S_i for the infested fruits substituting their respective values of fruit width into the regression equation. Third, we estimated P_sc using the above-mentioned formula after obtaining S_i and S_rvalues.

Results

Table D1. Estimates of the interaction strengths between Isoplexis canariensis and its animal mutualists and antagonists, accompanied by the proportion of plants that interacted with each functional group, or any of their animal guilds. See Appendix A for the taxonomic composition of animal guilds.

Notes: Data included in the table are means ± SD. Frequency indicates the proportion of plant censuses (mutualists) or surveys (antagonists) in which the plant-animal interaction was observed. Intensity represents the proportion of flowers probed by mutualists per plant visit, or the proportion of reproductive units (flowers/inflorescences/fruits) damaged by antagonists per plant survey; see Methods in the article. Coefficient of variation (%) is calculated for the product of frequency and intensity. Sample sizes indicate the number of plants in which the interaction frequency (n_freq) and intensity (n_int) was estimated for the respective animal functional group or guild. a Due to logistic constraints, the data set contained missing values (n = 16 out of 714 values, 15 plants) in the interaction strengths of mutualists (legitimate bird pollinators n = 4, facultative bird pollinators n = 2, legitimate lizard pollinators n = 4) and antagonists (predispersal seed predators n = 6). These values were estimated by multiple imputation using Bayesian regression models (Gaussian family; mi package in R, Su et al. 2011). The sample size n_pl indicates the number of plants (out of 119) that had contact with the corresponding animal functional group or guild.

Literature cited

Su, Y. S., A. Gelman, J. Hill, and M. Yajima. 2011. Multiple imputation with diagnostics (mi) in R: opening windows into the black box. Journal of Statistical Software 45:1–31.

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