GEOG 442
Biogeography
Biodiversity Measures: Alpha, Beta, and Gamma
Measuring Biodiversity
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 (say, 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
three transects of shrub and subshrubs species in the Palos Verdes Peninsula,
taken by three student teams during the Fall 2011 section of GEOG 442.
Your Data
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Fire Station Trail west of tank |
Crenshaw Extension north of tank |
Scarps off Burma Road southwest of tank |
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Artemisia californica sagebrush |
Artemisia californica sagebrush |
Artemisia californica sagebrush |
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Atriplex lentiformis big saltbush |
Atriplex lentiformis big saltbush |
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Rhus integrifolia lemonadeberry |
Rhus integrifolia lemonadeberry |
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Baccharis salicifolia mulefat |
Baccharis salicifolia mulefat |
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Eriogonum parvifolium coast buckwheat |
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Eriogonum fasciculatum California buckwheat |
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Salvia leucophylla purple sage |
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Isocoma menziesii coast goldenbush |
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Opuntia littoralis coastal prickly pear |
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GEOG 442 F/11 team: Paula Ducoing, Mystyn Mills, Thoai Nguyen, Jess Trautt, Saul Villicana |
GEOG 442 F/11 team: Joseph Diminutto, Kenny Pomeroy, Maribel Ramos, Anthony Sandoval, Katherine Settlemyer |
GEOG 442 F/11 team: Gabriel Brambila, Katherine Jena, Jesse Mantia, David Marks, Evan Morey, Bobbi Valencia |
Alpha Diversity
What is the alpha diversity (raw species richness counts) for your three pairs of transects (each 10 m long)?- __________ Fire Station Trail
- __________ Crenshaw Extension
- __________ Scarps off Burma Road
Beta Diversity
What is the beta diversity between each of the following pairs of paired transect types (that is, how many of the species are completely unique to each transect pair, not shared with the other transect pair -- only count the species found in only one of the two but not both)?- __________ Fire Station Trail versus Crenshaw Extension
- __________ Fire Station Trail versus scarps off Burma Road
- __________ Crenshaw Extension versus scarps off Burma Road
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 transects (not double-counting those that occurred in more than one transect pair)?- __________ Gamma diversity