1. Hypotheses (motivate these in your introduction, discuss them in your discussion in the context of the results)
There are patterns of association between species presence and substrate type
There will be differences in the associations among species (why is this an important question – think about maintenance of diversity)
There are patterns of association between species presence and relief
There will be differences among species in these relationships.

2. General Methods Transects sampled: 60, 70, 80…150
Offshore and onshore sampling
2 samplers per transect
Point interval: .5 meters
Sampled species directly under point

3. Offshore
Onshore

4. Offshore
Onshore

6. Some notes For the written report
Each person will write their own paper
The paper will be based on the group data and your methods and results should cover the group project
Use the guidelines to help craft your paper

7. Some notes For the graphs
“Preference Index” is a standardized measure of the association from that expected by chance
For example if 40% of the substrate is boulder habitat then the expected abundance of leafy red algae on boulders is 40%. A positive deviation means more than expected, a negative deviation means less than expected
There are 3 categories of strength of association.
>.66 or <-.66 are considered Strong
.66> PI>.33, -.66< PI <-.33 are considered moderate
All other Deviations are considered weak

8. Preference Index
Observed number = the number of observations made for a species
Expected number = the expected number of observations for species given NO pattern of association
For example: if bedrock was 50% of all substrate then the expected percentage of observations on bedrock is 50% for all species
Assume that there were 120 observations of crustose coralline algae. Here the expected number on bedrock would be 50% x 120 observations = 60

9. Preference Index continued
Preference Index can be calculated as:
PI = (O-E)/(O+E)
Where O= observed and E = expected
PI scales between -1 (strong negative association) and 1 (strong positive association)
PI = 0 indicates no pattern of association (O=E)

10. Example: Crustose coralline algae
Substrate
Substrate Percent
Observed number (CCA)
Expected number PI
(O-E)/(O+E)
Association
Bedrock 50 60
none
Boulder 20 24
0.35
positive
Cobble 10
-0.41
negative
Sand 12 -1
strongly negative
Total
100%
120
Values >.66 or less than -.66 show strong associations
Values >.33 and <.66 or >-.66 and <-.33 show an association
Values <.33 and >-.33 show no important association

11. 2015
2015
2014
2014

13. Note dashed and dotted lines indicate levels of association: Strong, Moderate

15. Note dashed and dotted lines indicate levels of association: Strong, Moderate