Explain4 marksStandard
The table shows the number of base differences in a mitochondrial gene sequenced from four species of bird belonging to the genus Avifuga.
| Species pair | Number of base differences |
|---|---|
| A. rubra and A. caerulea | 8 |
| A. rubra and A. viridis | 42 |
| A. caerulea and A. viridis | 44 |
| A. rubra and A. flava | 65 |
| A. caerulea and A. flava | 67 |
| A. viridis and A. flava | 58 |
Explain how these data can be used to infer evolutionary relationships among the four species. Suggest how speciation may have occurred, with reference to allopatric and sympatric mechanisms.