Research Article

# Count Your Eggs Before They Invade: Identifying and Quantifying Egg Clutches of Two Invasive Apple Snail Species (Pomacea)

• ckyle@uchicago.edu

Affiliation: Department of Ecology and Evolution, University of Chicago, Chicago, Illinois, United States of America

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• Affiliation: Department of Biology, Southwestern University, Georgetown, Texas, United States of America

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• Affiliation: Department of Mathematics and Computer Science, Southwestern University, Georgetown, Texas, United States of America

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• Affiliation: Department of Biology, Southwestern University, Georgetown, Texas, United States of America

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• Published: October 16, 2013
• DOI: 10.1371/journal.pone.0077736

### Correction to Table 3 and clarification of how to use the models

#### Posted by ckyle57 on 04 Apr 2014 at 17:36 GMT

I am Colin Kyle, the corresponding author on this PLOS ONE article ("Count Your Eggs Before They Invade: Identifying and Quantifying Egg Clutches of Two Invasive Apple Snail Species (Pomacea),"). A scientist recently contacted me about an error in Table 3 of this publication. Because this error is in the best fitting model for predicting the number of eggs per clutch (EPC) for non-native P. maculata, I would like to provide the correct value. Furthermore, I would like to clarify how to use our models to estimate EPC for those readers with their own egg clutches.

CORRECTION: The correct value for the intercept of the model predicting EPC using length*depth for non-native P. maculata in Table 3 is:

7.86×10-4

The value 7.86×10-3 is incorrect.

Each model in our article is a Generalized Linear Model with a Poisson distribution, which function just like normal linear regressions, except we take the natural log of the response variable (EPC in this case). The use of a natural log link function was not explicitly clear in our article. To predict the number of eggs per clutch using clutch length and depth, use the following equations:

ln(y)= a + b*x

or

y = e^(a + b*x)

where y is EPC, e is Euler's number, a and b represent the intercept and slope coefficients, respectively, from Table 3 and x is the explanatory variable. Table 3 contains the coefficients for different products of clutch dimensions to use as explanatory variables. However, in all apple snail populations we tested, the product of clutch length and depth best predicted EPC.

For example, the equation to predict EPC for non-native P. maculata is using clutch length and depth (in millimeters) is:

EPC = e^(6.75 + 0.000786*length*depth).

I apologize that this slipped by me during the review process. I have rechecked the remainder of the manuscript and found no other errors requiring correction. Please contact me at "ckyle@uchicago.edu" if you have any trouble using the models.

Sincerely,

Colin Kyle
Department of Ecology and Evolution
University of Chicago

No competing interests declared.

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