Drosophila pseudoobscura and D. persimilis are now considered separate species,

Question

Drosophila pseudoobscura and D. persimilis are now considered separate species, but originally they were classified as Race A and Race B of a single species. They are morphologically indistinguishable from each other, except for a small difference in the genetialia of the males. When crossed in the laboratory, abundant adult F1 progeny of both sexes are produced. Outline the program of observations and experiments that you would undertake to test the claim that the two forms are different species.

Please answer this question COMPLETELY and I will be sure to "thumbs up" your answer! Thank you!

Explanation / Answer

Drosophila pseudoobscura and D. persimilis are two different species, which may cross or mate and produces offspring and these offspring are sterile. So through mechanism of reproduction isolation or hybridization mechanism, these species are able to maintain the integrity of a species.

The complete reproductive isolation has made, D. pseudoobscura and D. persimilis as separate species. D. pseudoobscura is sexually active in the afternoons, whereas D. persimilis is active in the mornings.

The courtship song elements of these species are different with respect to interpulse interval and intrapulse frequency and this is due to the two inversion which are responsible for the difference in between these two species.

The structure of the genital arch and the hypandrium in D. pseudoobscura and D. persimilis are similar, but difference can be seen in the dimensions and the proportions of the penis. In D. pseudoobscura, it is long and cylindrical whereas in D. persimilis, it is short and broader. The mean index is 8.61±0.31 and it is 6.48±0.51.

With whole genome sequence assemblies, it has found that the difference in the genome sequence is low in pericentromeric and peritelomeric regions. It has helped to observe the patterns of sequence divergence among these two genomes, for chromosomes XL, XR, 2, 3 and 4. The first three chromosomes showed only a fixed or nearly fixed single inversion between the two species and can found variable arrangement on chromosome 3 and chromosome 4 is having similar alignment in both and low level of differentiation found on chromosome 5 along its entire length. These results confirmed that the two species genome are having considerable difference.

We can distinguish these species by observing the banding sequence of salivary chromosomes, the salivary chromosomes of these two species differ by an inversion in the second chromosome and also shows difference in the left limb of the X.

One more method is by determining the frequencies of allozymes at certain diagnostic loci (Est-5, lap, Adh, Me-1, Me-2, Hk-2, Hk-3 and Pt-D).

With the above mentioned observations and experiments we can easily conclude that the D. pseudoobscura and D. persimilis belongs to different species.

Related Questions

Navigate

• Browse (All)
• Browse D
• Subjects

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.