The ranges of the red-legged frog and the yellow-legged frog overlap in California. The red-legged frog (Rana aurora, left) breeding season lasts from January to March. The closely related yellow-legged frog (Rana boylii, right) breeds from late March through May. What type of reproductive isolating mechanism is mainly responsible for keeping these two species separate?

Temporal isolation.

Explanation:

The reproductive isolation may be defined as the mechanisms by which the two different species are ceased to reproduce. If the species overcome the reproductive isolation, the new species can be generated.

Two main types of reproductive isolation are pre reproductive isolation and post reproductive isolation. The temporal isolation is a type of pre reproductive that might occur due to the difference in the breeding season of the organisms.

Thus, the answer is temporal isolation.

The correct answer is - temporal isolation (pre)

Explanation:

Temporal isolation is the reproductive isolation mechanism for keeping two different species individuals to separate from one another and do not mate as they are active in the different breeding season or different times of the day.

In the given question, the red legged frog and yellow leg frogs have different breeding season so in these the reproductive isolation is of type of temporal isolation.

Thus, the correct answer is - temporal isolation.