AS9_CompMethods 23

Due: Fri. Dec 8, 2023 Assignment 9 Evolution PCB 4674 — Fall 2023 Comparative Methods Objectives First, to illustrate a principal method for testing adaptation in organisms. Second, to give you experience calculating phylogenetic independent contrasts, demonstrating the importance of phylogenetic history in reconstructing the past, even with regards to population genetic questions. Background Several studies have shown a relationship between numbers of matings by females in a species and the ability of males to produce sperm. One example regarding species of bats is presented in the textbook. The underlying model is that when a female has multiple copulations, the males that produce the most sperm have the greatest chance of fertilizing the eggs. The mating system sets up the conditions for sperm competition among the males, leading to selection for increased testes size. One set of researchers decided to test the model in a non-mammalian system. In the dragonfly genus Velociscimmer are various species that have different mating systems. In some, the females are very choosy and mate only once or twice. In other species, the females are either far more receptive or are smaller than males and less able to resist, and so have multiple copulations. The researchers hypothesized that as in bats and primates, species with multiple copulations will have selection for sperm competition, creating an evolutionary correlation between the two traits. The genus includes the species aerodyn, bugaboosi, cantdanz, darwini, erehwon, frikasee, gorjus , and huxleyi . Procedure Download the file AS9_Name_Answer.doc, into which you will type your answers. Attached is a phylogeny for the dragonfly genus Velociscimmer . The numbers to the right are the average number of copulations each female engages in and the average testes size for the males, in mg. A: “Tips” analysis First conduct an analysis using the traditional approach with just the raw data (species and measurements), not correcting for phylogenetic relatedness. Graph the data. You will need to conduct linear regression analyses for this assignment, so you can either graph neatly by hand and use a statistical program to conduct the analyses, use that program to both graph the data and run the regressions, or use the Excel spreadsheet we have created to run the analyses and do the graphing for you (“ AS9 Regression Tool.xlsx ” available on Canvas). The copulation number is the independent variable, testes size the dependent variable (because male testes are hypothesized to have evolved in response to female-mediated social systems). Draw a best-fit (regression) line (does not need to pass through the origin) and calculate the correlation (r 2 ) and P-value ( AS9 Regression Tool.xlsx does that automatically). Print out the graph. Q1 . What are the correlation and P-value? Q2. Does there appear to be a relationship between number of copulations and testes size in the raw data? Explain how you reach that conclusion. Do the data support the hypothesis? Why? B: Independent contrasts