Wasp Competition Ecology Spring 2016Monday

Your lab report

Your report for this lab will not be an IMRAD format.Just fill out this MS-Word document. I have provided this part of the lab as an MS-WORD document so that you may insert your answers and graphs (Prism and MS-Excel) directly into this document. Just fill out this MS-Word document. Please use a different font (I’ve used Arial here) so that I can readily distinguish your answers from the questions. Report all values using 3 decimal places.

[Like any good scientist, you will take advantage of the power of replicates and use mean values when making calculations and reporting values.]

1) A data table with the values for:

KM –

KN –

NM –

MN –

KN/NM –

KM/MN –

2a) A correctly drawn and labeled Lotka-Volterra graph of the values in 1 above.

Put Nasonia on the Y-axis and Melittobia on the X-axis.

2b) Report on the outcome of the interaction of Nasonia and Melittobia based upon your graph.

2c) Wherever the lines cross, an equilibrium between the two competing species has been reached. What are the values for Nasonia and Melittobia where the lines cross in your Lotka-Volterra graph (2A)?

For each answer of # 3, include either color, or well labeled graphs for each of the following questions in addition to text. Including the values you used for the variables is extremely helpful.

3) Use the ‘populationmodelling.xls’ spreadsheet that is linked to the data website. Let H1 = Melittobia and H2 = Nasonia. (Ignore the Predator column. It will have no effect if you do not copy it. Indeed, do not copy it.) Fill in the values for K,  and starting values of N from the data for each species. All values in MS-Excel should be to 3 decimal places (rounding up). (It is imperative that you use the correct values for N. Clearly, it will be an average value. Think about which column of data you should use. Check with me if you are unsure.)

Use a value of r = 0.261 for both species (This is the value empirically derived for Nasonia by Nagel and Pimentel (1964).

a. What are the values for NM = and NN = Put them in the spreadsheet.

b. What is your interpretation of the outcome of competition based on the MS-Excel graph?

c.Examine the population sizes for Nasonia and Melittobia where they appear to be in equilibrium in the MS-EXCEL graph (3a). Are these values similar to those you reported in 2c?

d. In nature, the population may fluctuate very closely around the equilibrium point. Examine your MS-Excel graph that you used for 3a above. Mark the point on the Lotka-Volterra in 2A where you think that equilibrium was lost. (Hint: You can find that value where you think it occurs on the graph while in MS-Excel. Just move the cursor to a point on the line and a box with the X & Y values will appear.)

e. Consider the nature of interaction of the two species based on the Lotka-Volterra graph in your answer to 2a. The value of what variable could be changed just a little (relative to its initial value) that could reverse the outcome of this interaction? (Think about the lab lecture. What is the one thing that I changed on the graphs on the board?)(Understanding the Lotka-Volterra graph is essential for answering this correctly.)

What value did you use?

Return the variable you changed back to its original value.

f. The life cycle of Melittobia can be nearly twice as long as that of Nasonia. What would its intrinsic rate of increase be relative to Nasonia?

Change the r value of Melittobia by that amount.

What is the new value of r =

Over 100 generations, what is your interpretation of the outcome of the competition?

Return all values back to the original starting values.

g. Using the growth models in Excel, demonstrate which species is the better competitor. (Explain what you did, and why.)

4) You will need to use Prism for this part of the assignment. For each question, clearly state:

i. What test you used (T-test or Mann-Whitneydo not bother to transform the data)

ii. The mean values from each comparison

iii. The P-values

iv. An answer to the question

Note: For any column of data you select, use all of the values, including zeros.

  1. In which species is intraspecific competition more important? Thimpk! For each species you will need to compare two columns of data.)

(T-test or Mann-Whitney?)

b In which species is interspecific competition more important?

Answer the following questions for your discussion:

1. Based on the graph of the Lotka-Volterra competition model, what is the predicted outcome of competition between the two species?

2. Do the results from the Excel population modeling support your conclusions from the Lotka-Volterra graph? Explain.

3. In this example, which is more important in determining the outcome of competition, initial population sizes or population growth rates?

4. “Gause’s Law” states that competitors that share exactly the same resources in the same way cannot coexist. This means that the species that most efficiently uses the contested resource will eventually eliminate the other at that location. Does Gause’s Law seem to apply to the interaction between Melittobia and Nasonia? Why or why not?

5. Based on the results of your experiment and data analysis, why don’t the two species use the same host in nature?

6. If these two species were to use the same host in nature, how might resource partitioning allow them to coexist? That is, could they partition the resources? If so, how?

7. The carrying capacities and competition coefficients are just estimates. What factors might affect the carrying capacities and competition coefficients for these two species?