What do you think accounts for these differences? How might some of these differences be possible adaptations?

Codominace

Explanation:

Codominance simply refers to a situation whereby there is an equal genetic effect of two parents on their offspring. It is a situation whereby neither of the alleles (i.e. a variant or type of gene) of the two parents can dominate, mask or prevent the expression of the other. Consequently, this will result on the equal expression of the two alleles for trait of the two parents.

Using the human example, there is a codominance when there is the ABO blood group which permits both alleles A and B to be expressed. As a result, if alleles A is inherited by a child from his father and he inherited allele B from his mother, it will result in him having AB as his blood type.

Therefore, the pattern of dominance is the example given in the question is called "codominance."