GEOG/ES&P 330
California Ecosystems
Biodiversity Measures: Alpha, Beta, and Gamma
Measuring Biodiversity of Native Species
Biodiversity is an intuitively understandable concept, but it's a little fuzzy around the edges. One measure of biodiversity is species richness, but this 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 (very tiny area up to about 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. The greater the beta diversity between the pair of communities in comparison with the alpha diversity of each community, the greater the distinctiveness of the two communities.
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 six transects of shrub and subshrubs species in the Palos Verdes Peninsula, taken by three student teams on 23 February during the Spring 2013 section of GEOG 442. Each team took two 10 m transects in one patch of California sage scrub. One of the transects sampled plants at 1 m intervals along the named trail; the other sampled plants at 1 m intervals in the same area but at right angles to the first transect. The data below note only presence/absence data, whether a species was found in either transect in the three patches sampled.
To calculate alpha, beta, and gamma diversities for these three
patches, count each species in a patch if it occurs in either of the two
samples taken in that patch.
Your Native Species Data
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Fire Station Trail west of tank |
Crenshaw Extension south of tank |
Peacock Flats Trail west of tank |
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| Along Trail | Across Trail | Along Trail | Across Trail | Along Trail | Across Trail |
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Artemisia californica California sagebrush |
Artemisia californica California sagebrush |
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Artemisia californica California sagebrush |
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Atriplex lentiformis big saltbush |
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Atriplex lentiformis big saltbush |
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Encelia californica California encelia |
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Encelia californica California encelia |
Encelia californica California encelia |
Encelia californica California encelia |
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Eriogonum cinereum Ashy-leaf buckwheat |
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Eriogonum fasciculatum California buckwheat |
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Marah macrocarpus wild cucumber |
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Opuntia littoralis coastal prickly pear |
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Rhus integrifolia lemonadeberry |
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| GEOG 442 S/13 team: Latia Blair, Christine Chan, Carl Green, Anthony Maggio, Kevin Nguyendo, James Reyes, Sean Tabin, and McArthur Yang | GEOG 442 S/13 team: Simone Boudreau, José Guillén, Justin Hall, David Hughey, and Hasmik Zhamharyan | GEOG 442 S/13 team: Adonis Agkis, Joseph Amantea, Brian Ambrose, Jeffrey Billinghurst, Emily R. Feliciano, Richard Gieser, Michael Morgan, Jamie Ruiz, and Isis Troy | |||
Alpha Diversity
What is the alpha diversity (raw species richness counts) for your three pairs of contrasted two-sample transects? That is, how many species were noted, even in just one of the two samples, in each of the three patches?- __________ Fire Station Trail
- __________ Crenshaw Extension
- __________ Peacock Flats Trail
Beta Diversity
What is the beta diversity between each of the following pairs of patches? (that is, how many of the species are completely unique to each patch, not shared with the other patch -- only count the species found in only one of the two paired patches but not both -- again, a species counts for a patch if it is found in either or both transects taken in that patch but not if it occurs in even one of the transects taken in the other patch). Beta diversity is about contrasts and uniqueness.- __________ Fire Station Trail versus Crenshaw Extension
- __________ Fire Station Trail versus Peacock Flats Trail
- __________ Crenshaw Extension versus Peacock Flats Trail
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 pairs of transect samples (not double-counting those that occurred in more than one pair of transect samples)?- __________ Gamma diversity