Pioneering aquarium experiments showed that laboratory-reared, mature female Trinidadian guppy fish (Poecilia reticulata) could copy the mate-choice of other females.
Each experiment consisted of an observation period, when a “focal female” could observe two males, each in a separate chamber at each end of her aquarium. One of the males could court another female (the “model female”), who was adjacent to the male but separated by glass.
In a following preference test, the model female was removed, and the focal female was allowed to choose between the two males. The time that the focal female spent within the preference zones adjacent to the male chambers indicated her mate preference.
In 17 out of 20 trials of this experiment (Experiment 1), the focal females preferred to associate with the male that they had previously observed interacting with the model female.
This provided evidence that newly acquired social cues could potentially influence mate selection.
However, four alternative hypotheses could also potentially explain these results. Four other sets of experiments, similar to Experiment 1 but with some modifications, were designed to test these hypotheses.
Match the four experimental designs (1 to 4) with the four hypotheses (A to D) that were tested in these experiments.
Hypothesis
Description
A Schooling Hypothesis
Females prefer the side where they have seen the larger number of fish
B No-Interaction Hypothesis
Females prefer the side where they have seen a male and a female together but without sexual interaction between the pair
C Male-Activity Hypothesis
Females prefer a male that was more active in the recent past
D Female Sexual Priming Hypothesis
Females who have seen a female-male encounter might choose males that behave as though they have just been involved in an interaction with a female
Design
Description
1
After the observation period, both the females were removed and a “naive” female, never exposed to males, was introduced and allowed to choose between the same two males in the end chambers
2
Females were placed in the two end chambers of the test aquarium instead of males
3
Two tests, similar to Experiment 1, were carried out simultaneously in two test aquaria invisible to one another. The males from the two aquaria were exchanged immediately before the focal female was allowed to choose between them
4
One-way mirrors were placed between the test aquarium and each of the end chambers. Lighting was such that the two males saw their own images but the model and the focal females saw through the mirrors as though they were clear glass
Q21.A. Which experimental design tests the Schooling Hypothesis (females prefer the side where they have seen the larger number of fish)?
Q21.B. Which experimental design tests the No-Interaction Hypothesis (females prefer the side where they have seen a male and a female together but without sexual interaction)?
Q21.C. Which experimental design tests the Male-Activity Hypothesis (females prefer a male that was more active in the recent past)?
Q21.D. Which experimental design tests the Female Sexual Priming Hypothesis (females who have seen a female-male encounter might choose males that behave as though they have just been involved in an interaction with a female)?
Question reproduced from IBO 2023, Theoretical Paper 1, licensed under CC BY-NC-SA 4.0 - attributed to the International Biology Olympiad. Open the full exam PDF