Homework 3 

Work in groups if possible.

You can use whatever software you like, but I suspect that it is best to stick to spreadsheet software alone. There will probably be a fair bit of data manipulation before the data are in proper shape to use.

Find a community data matrix (2 bonus points if they are your own data, otherwise you can use one from the Demo.xls file). Remember, this kind of data matrix must have species abundances as the entries. For part 2, the samples must also have at least one environmental variable associated with them.

If you use your own data, please supply a copy of the data matrix.

For this analysis, relativize the species composition.

1. Calculate the Euclidean distance between two samples that seem very similar to each other (based on a casual inspection), and between two samples that seem very dissimilar to each other.

2. Choose an environmental variable.

a. What is the mean and standard deviation of this variable?

b. Choose two species. What are their weighted means and standard deviations for this variable? How do you interpret these biologically? How do they compare to the results of 2a, and why?