Question

Calculate the value of the reproductive isolation index if (a) allof the matings within a population were successful, but noneof the matings between populations was successful; (b) salamanders are equally successful in mating with members of their own population and members of another population.

Short answer

1. All of the matings within a population were successful, and none of the matings between populations was successful, which indicates that populations are completely reproductively isolated. So the reproduction isolation index will be 2.0.
2. Salamanders are equally successful in mating within their population and with the members of other populations. So there is no reproductive isolation, and the reproductive isolation index is 0.

Step-by-step solution

Step 1: Reproductive isolation

Reproduction isolation involves the mechanisms that are critical for speciation and occur through behavioral and physiological means. It prevents the mating between organisms of different species and ensures the produced offspring are sterile. So it obstructs the gene flow between two species.

Explanation for the answer (a)

Allopatric speciation occurs due to the geographical isolation that prevents mating between members in different populations and stops gene flow between them. Dusky salamanders live in different mountain ranges, and all members are able to mate with each member of the population.

Still, there is no mating between two populations, so the reproductive isolation is completely successful, and the value of the reproductive isolation index will be 2 because the maximum value of the reproduction isolation index is 2.

Explanation for the answer (b)

The populations living in different mountain ranges are not isolated because members of one population are mating equally with the members of their population and with the members of other populations. So, the reproduction isolation index is minimum that is 0.