pollination experiment (corrected)

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pollination experiment (corrected)

Mariano Devoto
Hi everyone.
(apologies for sending this again; this time data is properly available).

I am trying to assess the effect of five pollination treatments on a
plant's fruit set. The data set is not too good (few samples and unbalanced
-we lost many field samples to vandalism-, quite a few zeros). I counted
the n of flowers that received each treatment and the number of fruits at
the end of the experiment. I am using a binomial model, but the results
look awkward.
I'll be grateful for any advice on how to reliably test the significance of
the treatments and do multiple pairwise comparisons.
Thanks in advance for your help!

Here is the code to load the data and perform the analysis.

#loading data and curating data
require(RCurl); require(lme4); require(multcomp)
my.file <- getURL("
sistrep <- read.csv(textConnection(my.file), head=T)
nofruits <- sistrep$flowers-sistrep$fruits

#plot the data
prop <- sistrep$fruits/sistrep$flowers
boxplot(prop ~ treatment, data=sistrep, las=1, ylab="Fruit set (n fruits/n
flowers)", boxwex=0.6)

#model and pairwise comparisons
M0 <- glm(cbind(fruits, nofruits) ~ 1, data = sistrep, family = "binomial")
M1 <- glm(cbind(fruits, nofruits) ~ treatment, data = sistrep, family =

summary(glht(M1, mcp(treatment = "Tukey", interaction_average=F)))

Dr. Mariano Devoto

Profesor Adjunto - Cátedra de Botánica General, Facultad de Agronomía de la
Investigador Adjunto del CONICET

Av. San Martín 4453 - C1417DSE - C. A. de Buenos Aires - Argentina
+5411 5287-0069

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