Paper 37 - Wright 1983

Paper 37 -  Wright 1983

Wright, D.H. 1983. Species-energy theory: an extension of species-area theory. Oikos 41:496-506. 

Blog author: Angel Sumpter

Blurb author: David Currie:

●     professor at the University of Ottawa where he teaches in the Biology Department

●      BSc McGill University (1976) and PhD McGill University (1983)

●     The three goals of Dr, Currie’s research are:

○     To  identify broad-scale patterns in the distribution, abundance and diversity of life;

○     To  determine which environmental variables exert the strongest control on those patterns

○     To determine how human activities influence them. Recent research focuses on influences of climate, habitat conversion and pesticide use on these properties of natural systems.

Paper author: David Wright 

●     Department of Ecology and Evolutionary Biology at the University of Arizona.

●     Researcher at the US Fish and Wildlife Service. His research interests are in ecology, entomology, and agronomy.

Paper Summary

1. Main Question
1. Background: Throughout history, ecologist have wondered how to predict how many species will occur in a community. Previous work has shown that the energy supply supporting a community is limited by the capacity of the community in order to contain the species. A modified version of the Preston, MacArthur and Wilson model was used to replace the area parameter with available energy.  This was done by modifying the models of species number and showing how energy supply can limit species number. The idea of this was to explore the implications of the theory resulting from this replacement. This concept was used to  predict species occurrence and abundance on an island.  While conducting the study, the author kept under consideration the relevance of a broad set of observations relating energy supply and species diversity and abundance, and attempted to provide a unified basis for understanding these patterns. 
2. Main question: Does species energy theory do a better job of explaining/predicting a species abundance compared to the regular species area theory?  
2. Methods
1. Testing done to provide results in comparison to predictions of the theory was measured by using total available energy on an island accessible to a specific group of species in relation to the population of species on the island. General equation data was gather based on two groups; species of angiosperms and of land and freshwater/land birds that were available at the time over the islands. Few islands were excluded for various reasons some being due to lack of exploration or high latitude. The Angiosperms used actual evapotranspiration (AET) to measure available energy while land and freshwater birds used total net primary production (TNPP). Results represents that islands at high latitudes had “low per-unit-area rates of AET and NPP (Wright, 1983)” which produce lower species numbers than lands with equal total AET and NPP, but higher per-unit-area rates. Application of the theory illustrates that available energy can explain species variation in comparison to islands of varying terrains. 
3. Results
1. The diversity of trophic levels: Prediction that lower trophic levels should be more diverse.
2. Metabolic requirements and diversity: Species with greater metabolic requirements should in general be less diverse, abundant, and frequent compared to species with lower requirements.
3. Rarity and patchy distribution: Rare species are more prone to extinction and occur less frequently than more abundant species on larger islands.
4. Seasonal variation in diversity: Seasonal trends in diversity mirror seasonal trends in energy availability.
5. Latitudinal diversity gradients: A rough correlation shows that area of low latitude habitats is also much greater than that of high latitude habitats.
4. Conclusions
1. The species -energy theory lacks universal applicability.
2. Many of the predictions found by using the species-energy theory can also be found by identifying what takes less energy in an environment and deciding that the non energetic factor will typically have increased abundance.
5. Questions/ Comments:
1. I feel like the equations are pretty self explanatory and this makes understanding the math and the graphs easier.
2. Obviously you can see where there are some flaws in the Species-energy theory, but the author set out a goal to make a more simple/general model than the species area model and I think that he did a good job as to heading in the right direction, but he has a lot more work to do.