Scientists recently published a paper about an endangered population of Scarlet Bass (species A) in Lake Erie. The authors also published its entire mitochondrial DNA sequence on Genbank, an online system where scientists submit genomic data. Another group of scientists later published an article using molecular data to estimate gene flow among populations of the very abundant Grey Bass species (species B) in Lake Erie, and published mitochondrial data on Genbank as well. After you read the papers you realize that the ranges for species A and a few isolated populations of species B overlap; you look at the sequence data published online from both studies, and you realize they are very similar and differ only by a few nucleotide differences. 8. Do you think these are closely related species, or variants of the same species

They are variants

Explanation:  

The biological concept of species states that members of the same species can reproduce they have a genetic reservoir in common: many genetic variants.

Genetic variability is the measure of a species organism´s tendency to differentiate. In genetic variability, individuals of the same species are not identical. They are recognizable as members of the same species, but they differ in shape, function, and behavior. There exist variations among individuals of the same species.

Genetic variability originates from mutations, recombinations, and karyotype alterations. It allows or makes possible evolution.

Groups A and B can be considered variations of the same species. They not only overlap but also share most of the genetic sequences with only a few nucleotide differences.

These variations might be the previous step for sympatric speciation.  

i believe it would cause an increase of percipitation, though i could be wrong. so i would say b is the answer.