GEOG 442
Biogeography
Biodiversity Measures: Alpha, Beta, and Gamma
Measuring Biodiversity
Biodiversity is an intuitively understandable concept, but it's a little slippery around the edges. One measure of biodiversity is species richness, but it can create inflated estimates of biodiversity when many of the species counted are rare and others normally almost completely dominate an area. It is so easy to apply, however, that it is commonly used, warts and all.Some attempts have been made to give species richness a greater depth by incorporating notions of geographical scale and of change across space. These are the focus of this lab.
Alpha diversity is the number of species found in a small and homogeneous area (say, less than 1,000 hectares or 2,500 acres). It is the same as species richness for a local community.
Beta diversity entails comparing one small and homogeneous community with another in the same general area. It is the number of species unique to each community in the pair of communities being compared.
Gamma diversity is kind of like alpha diversity, only at a larger geographical scale. It is the total species richness of all the patches or communities within a larger area, say, 1,000 hectares or 2,500 acres up to maybe 1,000,000 hectares or 2,500,000 acres.
Delta diversity is the change in diversity as you sample large landscapes along major climatic or other physical gradients.
Epsilon diversity is gamma diversity on steroids. It is the species richness of all the large landscapes in a really large region, say, in the 1,000,000 hectare to 100,000,000 hectare ballpark.
So, you can think of alpha, gamma, and epsilon diversity as sort of inventories, lists of species, or species counts. Beta and delta are more like estimates of the differences between communities rather than what's in communities.
In this lab, you'll get to practice estimating the three smaller of these
diversity measures, alpha, beta, and gamma. It presents species lists from
three imaginary quadrats in the Palos Verdes Peninsula, where our field trip
is situated.
Your Data
| Coastal Sage | Chaparral | Woodland |
|---|---|---|
| Artemisia californica | ||
| Artemisia douglasiana | ||
| Baccharis pilularis | ||
| Encelia californica | ||
| Eriogonum elongatum | ||
| Eriogonum fasciculatum | Eriogonum fasciculatum | |
| Salvia leucophylla | ||
| Salvia mellifera | Salvia mellifera | |
| Rhus integrifolia | Rhus integrifolia | |
| Lupinus longifolius | Lupinus longifolius | |
| Heteromeles arbutifolia | ||
| Prunus ilicifolia | ||
| Toxicodendron diversilobum | Toxicodendron diversilobum | |
| Salix exigua | ||
| Schinus molle |
Alpha Diversity
What is the alpha diversity (raw species richness counts) for your three quadrats (each 100 m x 100 m)?- __________ Coastal sage scrub quadrat
- __________ Chaparral quadrat
- __________ Woodland quadrat
Beta Diversity
What is the beta diversity between each of the following pairs of quadrat types (that is, how many of the species are completely unique to each quadrat, not shared with the other quadrat in the pair)?- __________ Coastal sage scrub versus chaparral
- __________ Chaparral versus woodland
- __________ Woodland versus coastal sage scrub
Gamma Diversity
What is the gamma diversity for the Palos Verdes area in which you did your fieldwork? That is, how many species did you find in all three quadrats (not double-counting those that occurred in more than one quadrat)?- __________ Gamma diversity