Lab #1
Dispersion patterns of Plantago major and P. lanceolata
This exercise gives you the opportunity to evaluate the population dispersion
patterns of two locally common herbs in relation to environmental heterogeneity, and
their modes of growth and reproduction. The species of interest are Plantago major
(Common Plantain, below left) and P. lanceolata (Narrowleaf Plantain, below right).
Both P. major and P. lanceolata are considered invasive weeds that benefit, like many
invasive species, from habitat disturbance. P. major is believed to have originated in
Europe, and P. lanceolata from Eurasia, but dates of spread to the United States are
unknown. Both species are “naturalized” and are widespread in this country.
You will be visiting Myrick Farm, home of the Brandywine Valley Association,
the oldest conservation and environmental education organization in the country. The
purpose of the lab will be to determine 1) the dispersion patterns, and 2) the relationship
of reproductive effort to plant size for both species.
1) Dispersion Patterns
Establish a 12m x 12m plot in a transitional area containing both species, such
that half of the plot (6m x 12m) has more grass cover (is less frequently mowed) and half
has less grass cover (is mowed approximately weekly throughout the growing season).
Place rebar posts at the corners of the 144-m2 plot and connect them with string (to help
make sure the plot is square, the diagonal between opposite posts should be 17 m (recall
Pythagorus). Mark the border string at 1-m intervals. Now cut additional string to
produce columns and rows through the plot to produce 1-m2 subplots. Count the number
of plants of each species in each subplot, and estimate the amount of vegetation cover in
the 1-m2 subplot on a scale of 0-10. Continue until you have entered data for all 144
subplots in Table 1 below.
To help interpret the dispersion patterns, dig up several plants to determine if they
are connected by underground roots. Does root size provide any evidence of clonal
behavior or about probability of a plant being mature? Likewise, open up one of the seed
pods for each species, and look at the number of seeds per pod using a hand lens. Is seed
dispersal likely to have contributed to the dispersion patterns observed?
2) Relationship of total above-ground mass to Inflorescence Mass and Seed Number
Collect 30 individuals of each species in individually marked plastic bags for later
measurements of total above-ground weight (TW), inflorescence weight (IW) and
number of seeds (SN). Individual plants should be from a location not recently mowed
(so that portions of the plant haven’t been mowed), and should differ as widely as
possible in total size. In particular, attempt to include about 10 very small individuals, to
determine whether the onset of reproduction as a function of size differs between species.
The plant weights will be recorded using the analytical or top-loading balance in the prep
room between SSN379 and SSN381, sometime between the field trip and the following
“data analysis” lab (below). Each student will be assigned a subset of the plants. Enter
the data in Table 2.
Second Week: Data Analysis
Morisita’s Index of Aggregation
We will use Excel to analyze and display the data. Compute Morisita’s Index of
Aggregation (Id) for each species and plot size, using each of the spatial scales (1m x 1m,
2m x 2m, 3m x 3m, 4m x 4m) (we will share the computation chores). Once the data are
complete, create a data file in Excel, with 3 variables and 4 cases. In the first column
enter the name Scale in the first cell, with the numbers 1m2, 4m2, 9m2 and 16m2 in the
cells beneath. In the second column enter the name PMAJOR, with the Morisita’s Index
calculations for P. major corresponding to the four scales in the cells below. In the third
column, enter the name PLANCE, and enter the calculations for P. lanceolata.
Highlight the entire spreadsheet, including labels. Then pull down under Insert to
Chart, and specify a Line Plot. You want a plot with straight lines connecting the points
(middle left option). Customize the graph with appropriate axis titles and colors, and
save it for inclusion in your write-up.
Graphical Display of Spatial Pattern
You will create separate 4 surface contour plots, showing the dispersion of a)
Plantago major seedlings, b) Plantago major adults, c) P. lanceolata seedlings, and d) P.
lanceolata adults using Excel. For each graph, enter the data in the same form as the
datasheet, including the column and row headings. Now click on the Chart Wizard, and
specify Surface under Chart Type. Further select the colored 2-D graph (lower left
option). Save all 4 graphs for your write-up.
Effects of Vegetation Cover on Population Density
Open Excel, and place the following titles at the top of the first 5 columns:
VegCov, Pmseedl, Pmadult, Plseedl, and Pladult. In the two cells under VegCov type
in Mowed and Un-Mowed. Then enter the total number of plants for each species/age
class in the remaining cells.
Now highlight all cells (including titles), pull down under Insert to Graph and
select a multiple column chart. Examine the resulting graph for accuracy, and add axis
titles (under Layout/Axis Titles). Save for your write-up.
Effects of Ramet Size on Reproductive Effort
Analysis of the question regarding effects of ramet size on reproductive effort
requires a separate spreadsheet in your Excel workbook. You will need to add the data as
shown in Table 2. Now highlight just the P. major data (including the titles), specify XY
(Scatterplot), and choose the upper left option without lines.
You should see a scatterplot relating inflorescence weight (on the Y-axis) to total
weight (on the X-axxis) of just Plantago major. Click on the chart to edit it. Click on
Design, and then Select Data. In Select Data Source window, click Edit, and change the
name of the series to P. major. Now, before closing the Select Data Source window,
click on Add, and then add the IW vs. TW data for P. lanceolata as series 2 (changing
the name of the series to P. lanceolata).
If you’ve been successful, the scatterplot should now show the relationship of
inflorescence weight to total above-ground weight for both species. Finally, to clean up
the plot, make sure it is highlighted, then click on Layout, and then Axis Titles. Add a
title for both the Y-axis (e.g., Inflorescence Weight (g)) X-axis (e.g., Total Weight (g)).
Write-up
Answer the following questions, inserting graphs to accompany each answer.
1. Which species shows greater aggregation? At what spatial scale is aggregation most
pronounced for each species/age class? Is the “intensity” of aggregation (Id) at smaller
spatial scales greater for seedlings vs. adults, perhaps suggesting self thinning or densitydependent mortality? What factors might promote aggregation? (e.g., are the species
clonal? Do they require resource patches, and if so, what is the nature of these patches?
Are they responding to or being excluded by the patchiness of competitors for space or
some other resource?) Include the graph of Morisita’s Index, and the graphs of the 4
spatial patterns as part of your answer.
2. How is population density of seedlings vs. adults of each species affected by
surrounding vegetation? Are both species successful in producing seedlings, and do
these seedlings appear to survive in the two habitats studied? Include the multiple
column chart of abundances in mowed vs. un-mowed vegetation as part of your answer.
3. For a plant of a particular total above-ground weight, do both species allocate the
same amount of mass to reproduction? Is the threshold, below which there appears to be
no reproduction, the same in both species? Explain, and include the graph of IW vs. TW
as part of your answer.
4. A study by van der Toorn and Pons (1988) examined the response of both species to
light availability in “gaps” with little surrounding vegetation vs. closed vegetation. Based
on the paper (on e-Reserve under Fairchild (BIO470/570, pw=BIO470)), answer the
following questions.
a. How does plant morphology of each species favor success in the two habitats
you studied? Why might one species be more impacted than the other by dense
vegetation?
b. How did the biomass index and leaf length:width ratio of individual surviving
plants (S) of each species (measured by leaf length x width x number) differ in the
two habitats studied (Table 4)? Explain in terms of the likely survival of the two
species in dense vegetation.
Table 1. Density and dispersion patterns of Plantago major and P. lanceolata, in relation
to vegetation cover.
P. major (Seedlings/Adults)
1
2
3
4
5
6
7
8
9
10
11
12
5
6
7
8
9
10
11
12
5
6
7
8
9
10
11
12
12
11
10
9
8
7
6
5
4
3
2
1
P. lanceolata (Seedlings/Adults)
1
2
3
4
12
11
10
9
8
7
6
5
4
3
2
1
Vegetation Cover (scale 0-10)
1
12
11
10
9
8
7
6
5
4
3
2
1
2
3
4
Table 2. Relationship between Total Weight (TW), and Inflorescence Weight (IW)
P. major
Total Weight (g)
Inflor Weight (g)
P. lanceolata
Total Weight (g)
Inflor Weight (g)