Some materials for measuring diversity with candy
Here are some materials I have for using 'gummies' or other candy (or any object you like) as a means to teach sampling and diversity measurement. I’ve tried many iterations over the years, for any types of measurements and comparisons of species diversity. The main objective is to have students 'sample' candies to generate a site x species matrix. You can use this to ask dozens of questions in biodiversity, including calculating and comparing metrics, examining change through time/space, or whatever you like.
For generating a realistic set of patterns, you need to buy lots of species and get a reasonably shaped species abundance distribution (SAD) (a couple of very common species, several rare species). I usually try to get up to 30 or so species, so you can get some reasonable patterns emerging. The trick is to buy a variety of gummies so you can get lots of species (a couple common ones, many rare). I usually go for the vegan ones so that there are no issues, but you can of course, use anything that can be differentiated by size/shape/color. In the attached spreadsheet, I have the numbers I’ve used for awhile (sort of based on a reasonable SAD, but also fudged a bit to make sure enough rare species, etc.). You can just change the names to whatever you find. I put the gummies in a bag to represent a sample (this can of course be changed anyway you like) and then give each student multiple bags to represent multiple sampling sites (i.e., a metacommunity). I also have the entire class pool their samples for a 'regional' pool.
In this example exercise, we ‘pretend’ to study the effect of invasive raccoons in Europe on the gummie prey. But you can modify this to whatever your heart desires. Here, the main learning objective is to examine (i) the effect of sampling on diversity estimates and generating a species accumulation curve, (ii) quantifying impact of a driver (predators in this case) and how it is also scale-depenent. You can see the steps I have them go through in the text below (copied from our github readme).
Part II. Lab
- Each student will sample ALL organisms from each of 3 local sites (bags) in a metacommunity (samples will be given at the start of the exercise). Names of species given in ppt.
- Open up the Google Spreadsheet--https://docs.google.com/spreadsheets/d/1SGtdU61_3vX43Xtjaq579nEF1xuelRY3Dol2WGKFzUk/edit?usp=sharing
- Enter data for each 'control' sample in the appropriate place
- Calculate species richness for each local community (bag)
- Calculate species richness for each metacommunity (3 bags for each person)
- Calculate species richness for the entire region (sum of all 4 metacommunities [12 bags total])
- Draw species accumulation curve at 3 different spatial scales (1 local sample-->3 samples in a metacommunity-->entire region [all 4 metacommunities])
- Explore other summary variables (i.e., relative abundances, evenness, diversity) at each spatial scale
- Experimentally impose 'predation' of 50% of individuals by an introduced predator (e.g., raccoons invading Europe). IMPORTANT: Experimental predation must be random
- Repeat Step #3-7 but with 'impact' data (after predation)
- Compare species accumulation curves (from step #7) across scales
- Calculate log ratio effect sizes of species richness loss for each scale (local, metacommunity, region)