1. Milkweed Analysis by Daphne Virlar
Hypothesis: As milkweeds become stressed, wing loading will increase.
Why does this matter? Plants can’t store high levels of ammonium in their cells, so excess of this nutrient is toxic to them.
WingLoad = seed mass / coma surface area

2. Methods Field: Transect parallel to milkweeds
Randomly selected distance to create perpendicular transect
Focal plant selected; random distance along secondary transect
Soil cores taken, along with randomly selected seed pods.
Seeds and soil analyzed later
Repeated ~20 times
In R:
A simple linear regression model was created, fitted, and evaluated.

3. Model Checks – Normality
Why do we check for normality?
We check normality so we can use the appropriate models for our data
Linear regressions already assume normality

4. Model Checks – Linearity and Collinearity
Why do we check for these?
We check to make sure our data points are all independent of one another.
Linear regressions already assume linearity

5. Model Checks – Homoskedasticity
What’s causing the odd shape?
Lack of independence between data points
Different values for wing loading had the same ammonium level in their soil

6. Model Checks – Independence
This data set has low independence.
How can this be fixed in the future?
By using materials that are more precise in their measurements, future teams can eliminate collinearity.

7. Results Parameter Estimate: 0.001 Upper Confidence Interval: 0.0008
Lower Confidence Interval: 0.002
R2 Value: 0.53
P-Value:
Variance is 53% accounted for, but is highly significant.

8. Discussion Hypothesis supported
As ammonium levels went up, so did wing loading
Why was wing loading chosen in the first place?
Wing loading is a proven proxy for dispersal

9. Conclusion Why should you care about Milkweeds and their dispersal?
Monarch butterflies
Habitat Fragmentation

10. Citations
Agrawal, A. A Phenotypic Plasticity in the Interactions and Evolution of Species. Science
Imbert, E., and O. Ronce Phenotypic plasticity for dispersal ability in the seed heteromorphic Crepis sancta (Asteraceae). Oikos 93:126–134.
Morse, D. H., and J. Schmitt Propagule size, dispersal ability, and seedling performance in Asclepias syriaca. Oecologia 67:372–379.
Zuur, A. F., and E. N. Ieno A protocol for conducting and presenting results of regression- type analyses. Methods in Ecology and Evolution 7:636–645.
Zuur, A. F., E. N. Ieno, and C. S. Elphick A protocol for data exploration to avoid common statistical problems. Methods in Ecology and Evolution 1:3–14.