After conducting ongoing observations near building 365 at Vancouver Island University, I have observed differences in leaf damage percentage between Gaultheria shallon (Salal) and Daphne laureola (Daphne). In this study, I plan to test the enemy release hypothesis by comparing insect herbivory on native and non-native plants at different ground levels and locations. Specifically, I will be conducting the study at three locations, which are described as follows:
In this study, I will be testing the hypothesis that when a non-native plant species is introduced to a new region, it may experience a decrease in regulation by herbivores and other natural enemies, leading to an increase in the distribution and abundance of the non-native species. Specifically, I predict that there will be a lower percentage of herbivory close to the highway compared to the middle ground, where plants are located near bird feeders and there is less disturbance. However, I also predict that the non-native species will be less abundant closer to the highway than at the lowest steep of the ground.
First I assessed the distribution of of Salal and Daphne by their morphologic traits and then counting the plant per species.
Date: April 22, 2023
Time: 1030
Conditions: Partly Clear and brief precipitation, 7.2 degrees Celsius, 64% humidity
Morphological Traits:
REPLICATE 1:
| Location 1: Near the Highway | Location 2: Middle Ground | Location 3: Lowest Ground | |
| Count of Daphne | 10 | 18 | 36 |
| Count of Salal | 7 | 15 | 28 |
| Species observed around the area | Squirrel | Birds/ Squirrel/ Students | Squirrel |
REPLICATE 2:
| Location 1: Near the Highway | Location 2: Middle Ground | Location 3: Lowest Ground | |
| Count of Daphne | 12 | 19 | 34 |
| Count of Salal | 7 | 13 | 26 |
| Species observed around the area | Squirrel | Birds/ Squirrel | Squirrel |
My goal was to assess the percentage of leaf damage in each plant to determine whether differences in ground level would affect herbivores or other natural enemies, which could influence the distribution of non-native and invasive species. Therefore, the next day, I went back to the study site and collected three leaves randomly from each location as a preliminary step for my project. To measure the amount of damage, I traced the original leaf onto graph paper and colored in the grids where herbivory damage was present.
Date: April 23, 2023
Time: 1230
Conditions: Cloudy and light rain 1.2 degrees Celsius, 74% humidity
| Location 1: Near Highway | ||||
| Replicates | DAPHNE | SALAL | ||
| Whole leaf: # of squares | Affected leaf: # of squares | Whole leaf: # of squares | Affected leaf: # of squares | |
| 1 | 18.00 | 0.50 | 95.00 | 4.00 |
| 2 | 33.00 | 0.125 | 120.00 | 9.00 |
| 3 | 22.00 | 0.75 | 60.00 | 5.00 |
| Location 1: Middle Ground | ||||
| Replicates | DAPHNE | SALAL | ||
| Whole leaf: # of squares | Affected leaf: # of squares | Whole leaf: # of squares | Affected leaf: # of squares | |
| 1 | 37.00 | 7.00 | 55.00 | 18.00 |
| 2 | 33.00 | 9.00 | 81.00 | 29.00 |
| 3 | 22 | 0.5 | 97.00 | 37.00 |
| Location 1: Low Ground | ||||
| Replicates | DAPHNE | SALAL | ||
| Whole leaf: # of squares | Affected leaf: # of squares | Whole leaf: # of squares | Affected leaf: # of squares | |
| 1 | 33 | 0.50 | 133.00 | 18.00 |
| 2 | 20 | 1.00 | 170.00 | 32.00 |
| 3 | 33 | 0.80 | 55.00 | 7.00 |
In this study, the dependent or response variable was the percentage of herbivory damage observed on the plants, Gaultheria shallon (native) and Daphne laureola (invasive). This response variable is categorical. Meanwhile, the independent variable (categorical) for testing the enemy release hypothesis in this experiment was to analyze the interaction between different plant origins (native vs. invasive) and observe the effects when introduced to the herbivore community and other natural enemies.
You have a good start here. You have a few different predictions here and be careful that doesn’t confuse you as you go on. You have your main hypothesis and prediction about herbivory damage and then you talk about populations levels with distance to the highway and the differences between invasive and native species populations in different areas.
I would suggest on focusing on one question and hypothesis and in this case it looks like herbivory is your main focus. I would give some thought to your experimental design such as what your sample unit is and how you will select it and how many replicates. Perhaps review the tutorial on experimental design and the activity in Module 3 may help you as well.