1. How are D. silvestris and D. heteroneura related to D. setosimentum? How do you know? (Note that in Table 2, D. setosimentum has the most inversions and D. heteroneura the fewest, the opposite of their positions in Table 1.)

Another possible extension of this investigation makes use of the data in Table 2. This table contains inversion data for 10 species of drosophilids, beginning with D. setosimentum. Five of the 10 species in Table 2 are represented in Table 1 as well, while five of the species are different.

A possible task is to draw an evolutionary tree for all 10 of the species in Table 2 using the methods developed for the previous data set. This tree then can be compared to the ages of the islands where the species live today.

In Table 2, the species D. heteroneura has the fewest inversions, whereas in the previous data set it had the most. Similarly, D. setosimentum had the fewest inversions in the first data set but has the most in the second. How can these results be reconciled?

Questions that can guide this extension of the elaboration phase include:

  1. Which groups of fly species have identical sets of inversions, and which flies have unique sets?

  2. What is a good way to express numerically the similarities and/or differences among these species based on the inversion data?

  3. Given the data available to you, which island was the most likely home for the ancestral species of these flies?

  4. What evidence do the tables contain to support the idea that new species tend to appear on younger islands?

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