Two species of tree frogs that live sympatrically in the northeastern United States differ in ploidy: Hyla chrysoscelis is diploid, and Hyla versicolor is tetraploid. The frogs are identical in appearance, but their mating calls, which females use to find mates, differ. Which difference most likely evolved first?

The correct answer is - polyploidy.

Explanation:

Speciation can be two types allopatric and sympatric speciation. Sympatric speciation is the process of speciation is developing the new species that diverged from the common ancestral species while the ancestral and developed species both can share the same place or geological area. The main cause of such speciation is due to the change in their genetic level more than environmental conditions.

In this case, the frog's species show differences in their ploidy level as well as their mating call but polyploidy is the most likely the difference that evolved first rather than females call for mating.

Thus, the correct answer is - polyploidy.

explanation:

the universal gravitation equation. since the gravitational force is directly proportional to the mass of both interacting objects, more massive objects will attract each other with a greater gravitational force. if the mass of one of the objects is doubled, then the force of gravity between them is doubled.