Suppose you are sure, because of numerous characters, that species 1,2 and 3 are more closely related to one another than to species 4 (an outgroup)….

Suppose you are sure, because of numerous characters, that species 1,2 and 3 are more closely related to one another than to species 4 (an outgroup). We sequence a gene and find 10 nucleotide sites that differ among the four species.