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Read the following paper (abbreviated hereafter as MF2015):

Maddison, W. P., and R. G. FitzJohn. 2015. The unsolved challenge to phylogenetic correlation tests for categorical characters. Systematic Biology 64(1):127–136.

Please briefly answer the following questions:

  1. What is pseudoreplication (as the term is used in this paper)?

  2. Describe the simulation experiment used to claim that Pagel’s (1994) test of character correlation is susceptible to pseudoreplication.

  3. MF2015 say that their paper is not simply another reminder that correlation does not imply causation, and that they have a more forceful message. What is that more forceful message?

  4. What are the four scenarios described as litmus tests?

  5. Which of the four scenarios should (according to MF2015) comparative methods identify as evidence of significant evolutionary correlation? Why?