Supplement 1. A text file and detailed instructions for implementing the statistical test using mixed model regressions in R.

File List Shipley.dat with the following variables: 1. site: a numeric code giving the site from which the observations comes. 2. tree: a numeric code giving the tree from which the observation comes. 3. Lat: the latitude of the site. 4. year: the year in which the observation was taken. 5. Date: the Julian date when the bud burst occurs. 6. DD: the number of degree days when bud burst occurs. 7. Growth: the increase in diameter growth of the tree. 8. Survival: the probabil;ity of survival until the next year (used only for the simulation). 9. Live: a binary value (1 = tree lived the following winter, 0 = tree died the following winter). Help files/documentation: Shipley.pdf Description The data file is "Shipley.dat" and is a text file that can be imported into R. The documentation file "Shipley.pdf" contains a step-by-step explanation of how to use the nlme and lme4 packages in R to fit mixed-effect models and use the output to implement the inferential test for path models that is described in the <em>Ecology</em> paper.