How the cricket lost its song - Part 2
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Featured scientist: Robin Tinghitella from the University of Denver
In Part 1 you determined that the Kauai flatwing mutation led to a decrease in parasitism rates for male crickets. Today, most of the male crickets on Kauai have evolved flat wings and can no longer produce songs that were previously used to attract female crickets. Without their songs, how do males attract females?
Background:
Without their song, how are flatwing crickets able to attract females? In some other animal species, like birds, males use an alternative to singing, called satellite behavior. Satellite males hang out near a singing male and attempt to mate with females who have been attracted by the song. This helps satellite males in two ways: they don't use energy to make a song, and they avoid attracting enemies like the fly. Perhaps the satellite behavior gives flatwing males the opportunity to mate with females who were attracted to the few singing males left on Kauai.
Robyn (left) with her advisor (right) counting the number of crickets entering a circle while the song was playing.
To test this idea, Robin set up a speaker playing cricket songs in the fields where the crickets live on Kauai, Oahu, and the Island of Hawaii. The speaker tricks male and female crickets into thinking there is a male cricket in the area making songs. Before the start of the experiment, Robin removed all the males found within a 2-meter circle around the speaker. She then broadcast cricket songs from the speaker for 20 minutes. She returned and counted the number of males in the 2-meter circle, measured the distance from male to the speaker, and noted whether each male was normal or flatwing. Robin expected that flatwing males would be more likely to use satellite behavior and, therefore, would be on average closer to the speaker than normal males.
A parasitoid fly sitting on top of it’s cricket host.
The male cricket on the left has a normal wing with all the calling structures. The male cricket on the right has the flatwing mutation and a wing without any of the calling structures. When we zoom in on the wing we see how flat it is.
Scientific Questions: How do flatwing males find mates without song? In what ways do their methods differ from those used by males that can produce song?
Scientific Data:
Find the hypothesis in the Research Background and copy/paste it below. A hypothesis is a proposed explanation for an observation, which can then be tested with experimentation or other types of studies.
Click on the graph tab, and explore the available variables. What data will you graph to explore the first hypothesis? Independent variable:
Dependent variable:Create your graph, and add Collection Data Type to your z-axis. Paste your graph below:
4. To find the mean of the data, add descriptive stats, select SEM, and paste it below:
5. Identify any changes, trends, or differences you see in your graph. Write one sentence describing what you see.
Interpret the Data:
6. Make a claim that answers the scientific question.
7. What evidence was used to write your claim? Reference specific parts of the tables or graph.
8. Explain your reasoning and why the evidence supports your claim. Connect the data back to what you learned about the flatwing mutation and satellite behavior
9. Did the data support Robin’s hypothesis? Use evidence to explain why or why not. If you feel the data were inconclusive, explain why.
Your next steps as a scientist:
10. Science is an ongoing process. What new question(s) should be investigated to build on Robin’s research? What future data should be collected to answer your question(s)?
These questions are a digital extension of the original Data Nuggets activity. The data manipulation and graphing tasks within are best completed here on DataClassroom.
10) Typically, scientists make use of statistical analysis to determine that any difference between groups is reflective of natural phenomena regardless of the population being surveyed. Go to the Graph Driven Tests located at the upper right corner of your screen to pick the appropriate test and list 2-3 reasons why it is most appropriate to test if the two types of crickets differ in their behavior.
11) What is your conclusion? How would you interpret the P - value obtained with this dataset? Paste results from the analysis here.
12) Another way to interpret how the average behavior of the flatwing and normal male crickets may differ is to visualize the distribution of the distance to speakers in both groups and view the position of the mean value in reference to the two distribution. Plot a histogram of the variables indicated in Q2, display the mean and standard deviation of the y variable in each treatment group as well as paste the corresponding values below the graph. Describe what you observe and if you can conclude the two groups are different based on this.
13) You may observe in the above case that the SEM (standard error of the mean) in the flatwing group is slightly higher than the normal group of crickets, even though the Standard deviation values have the opposite patterns in the two groups. Given what you know about the equation for SEM and what it signifies, explain why you might see this in this dataset specifically.
14) Robin tested normal males from two different islands - Oahu and Hawaii. If you wanted to test that the behavior of the normal males varied due to the habitat they were found in, how would you test it. Paste the appropriate graph, with mean and SEM / 95% CI values. Explain what you find and whether you expect to see any differences? You might have to exclude certain rows to be able to do this.
15) Would you use parametric or non parametric tests to check if the differences between the islands is significant or not? Name the corresponding test statistic appropriate for this comparison? Explain your reasoning. (Hint: Test for normality of distributions).
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This dataset and content is provided our by our friends at Data Nuggets.
Visit DataNuggets.org to see the original activity and additional materials