Homework 3

Homework 3. Multivariate statistical approaches

As follow-up to Lab 3, please answer the questions below and turn in your answers during lab this week. You’ll need the paper I handed out in class (also posted under Homework on the course website). I am also including some of images we produced in class to assist you with the questions.

1. In a recent (2013) AJB article, Baker and Butterworth published an experiment testing the taxonomic circumscription of subspecific taxa within Coryphantha section Robustispina (Cactaceae). In one sentence, please try to summarize the overarching hypothesis these authors are testing.

2. Which biotic and abiotic factors do the authors think might be influencing genetic differentiation in Coryphantha section Robustispina?

3. On page 986 is a description of the morphological analysis conducted for this study. The authors ended up omitting some of the characters from their multivariate analyses. What are some reasons the authors give for omitting some of the characters?

4. Figure 2 and 3 show the first 3 axes of their principal components analysis. What do the numbers in these two plots represent?

5. Based on the PCA we generated in class, why might the authors have decided to use averages for populations rather than the individuals in the PCA?

6. Are the clusters in figures 2 and 3 (based on morphology) similar to those in figure 5 (based on microsatellite data (a.k.a., genetic fingerprints)? Briefly compare and contrast the graphs.