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Lecture 12. September 22, 2008. 1. The problems of moving water A. Gr ünbaum et al. 2007. PowerPoint Presentation
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Lecture 12. September 22, 2008. 1. The problems of moving water A. Gr ünbaum et al. 2007. 2. Other problems with moving water. What were the goals of the Gr ü nbaum et al. paper?. Arctic charr. Experimental Design. 1. cross males and females 2. obtain 13,000 eggs

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Lecture 12. September 22, 2008. 1. The problems of moving water A. Gr ünbaum et al. 2007.


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Lecture 12. September 22, 2008.

1. The problems of moving water

A. Grünbaum et al. 2007.

2. Other problems with moving water

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Experimental Design

1. cross males and females

2. obtain 13,000 eggs

3. divide eggs into 8 lots

4. choose those that hatch at a close time

5. raise at 4 different water speeds: fast, medium, slow, still,

2 replicates per treatment

6. pull out 4 fish of each of the 8 canals (4 treatments * 2 replicates)

once every 2 days for 100 days

7. measure a bunch of traits

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Traits Measured

head length (HL)

head height (HH)

yolk sac height (YSH)

dorsal fin base (DFB)

body height (BH)

anal fin base (AFB)

caudal peduncle height (CPH)

caudal fin height (CFH)

standard length (SL)

total length (TL)

body length (BL) = SL-HL

caudal fin length (CFL) = TL-SL

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1. Could they accurately measure their traits?

Yes. Measurement error was

very low (<1%).

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2. Did animals differ between the two replicates?

i.e. Did slow canal 1 differ from slow canal 2, etc.?

There were differences between

treatments, but not between

the replicates within treatments.

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Three statistics to understand:

mean

standard deviation

coefficient of variation = standard deviation / mean

Important Point!

The standard deviation goes up with the mean. If they had just looked

at the standard deviation, they would have concluded that the variability

of the traits went up with time.

The coefficient of variation allows you to look at the variability independent

of the mean.

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Does trait variability vary with time and water speed?

medium plasticity?

low plasticity?

medium plasticity?

high plasticity?

medium plasticity?

high plasticity?

medium plasticity?

high?

low plasticity?

low plasticity?

What do these graphs tell us?

Do you agree with the idea that there are two critical periods for development?

Do they define plasticity?

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Analysis of Shape

What does this table tell us about shape differences in charr?

What data went into this analysis?

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What are the major “take home” messages from this paper?

On a scale of 1-10 (10 being best), what would you rate this

paper?

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Other Challenges Faced by Moving Water

1. Fertilization - Water speed is infinitely faster than sperm velocity. Water speed

most likely effects sperm traits. Some folks hypothesize that high stream speeds

leads to many, small, short-lived sperm (as opposed to still water).

2. Foraging - Different types of food resources in fast versus still water.

3. Olfaction - Water speed moves chemical cues in a directional fashion.

4. Sound - Streams are nosier than lakes/ponds.

5. Avoiding predators ????

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Review Questions

1. Explain the goals/objectives of Grunbaum et al. What was the experimental

design? What data did they collect? How did their data relate to their primary

objectives/questions? What were the null hypotheses (even if they didn’t state

them)?

2. Explain figure 2. What data does this show? What is your interpretation?

3. Explain figure 3. What data does this show? What was the interpretation of

the authors? Did you find this interpretation convincing? What is the

definition of phenotypic plasticity? How would you measure it?

4. Look at table 4. How do the authors interpret PC1, PC2, and PC3? Which

one is more important in explaining overall variation in the measured traits?

Explain what figure 4 C,D, and E show.

5. Explain table 2 and how one calculates measurement error? Was the

measurement error high or low in this study?

6. Graduate students: This paper violates one of my major rules on data

reporting. They rarely report the sample sizes for the means and standard errors

nor do they report the degrees of freedom in the denominator for many of their

tests. Why is this a problem? How big of a problem is this?

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Review Questions Cont’d.

7. What do the authors claim is the major result of this paper? Do you believe

it? Do you believe that juvenile Arctic charr get bigger in faster moving water?

8. What is the evidence for the idea that different traits have different critical

windows of time for development? Does this paper provide good evidence

for the authors claims?

9. In general, list several ways that living in moving water differs from living

in still water. What are the implications for reproduction, foraging, sensory

biology, etc.?