5. Green swordtails are sexually dimorphic: males have a long, swordlike project

Question

5. Green swordtails are sexually dimorphic: males have a long, swordlike projection from their tails, and females have rounded tails.

An experimenter decides to perform a female choice experiment. He isolates unmated females with a choice of two mails, each from one of four groups of males.

1) Unmodified control males

2) A second group of males with tails cut off, and re-glued.

3) Males with shortened tails.

4) Males with lengthened tails.

Imagine the researcher got the following data.

Chosen by female # vs group, for each trial. Trials were replicated 20 times

            Trial                        Who the Female Chose

Group 1 vs. Group 2     Group 1- 10     Group 2- 10    

Group 1 vs. Group 3     Group 1- 18      Group 3- 2

Group 1 vs. Group 4     Group 1- 6       Group 4- 14

Group 2 vs. Group 3     Group 2- 16      Group 3- 4

Group 2 vs. Group 4     Group 2- 6        Group 4- 14

Group 3 vs. Group 4     Group 3- 0        Group 4- 20

What might this data indicate, in terms of sexual selection?

Why might this be the case?

Go online and research. List three studies of sexual selection, the organism, and their conclusions.

Explanation / Answer

1)

This data might indicate in terms of sexual selection that the amount of mating that occurs between the different groups. Here, the female chose mostly Males with lengthened tails followed (Group 4) by A second group of males with tails cut off, and re-glued (group 2). This is because, they have long tails and more attractive to the females.

2)

The cause may be due to the fact that it may be easier for the females to see the males with the long tails. And/or it could be easier for them to recognize them as the same species or it is easier for them to mate with each other.

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