Many problems that involve a possible relationship between two or more variables can be thought of in terms of an association between distance matrices, often with one of the matrices relating to spatial distances. The following examples show the wide range of situations that can be approached in this way:
1. In Example 1.2, a matrix of distances between the continents based on the present-day earwig distribution (A) was compared with a matrix that reflects the present location of the continents (B) and with a matrix that reflects assumed positions of the continents before continental drift (C). A comparison of the level of association between A and B with the level of association between A and C showed that the latter association is stronger. This suggests that the present-day distribution of earwigs reflects evolution in Gondwanaland rather than evolution with the continents in their present positions.