Spring 2017 -Welcome!
Hi all. This is where you will be posting the overview of the section of the book you are responsible for. Others in the class will 'comment' on the post, which provides some guidance on what sorts of things to highlight in the in-class discussion. See our sister blog (Ecology of the Past, paleoecology.blogspot.com) for examples of how this works.
Deborah Boro and Dianna Krejsa
ReplyDeleteThese papers serve as an introduction to some key terms used in macroecology and to using mathematical modeling for ecology.
Paper 2: predict species in a given space
Paper 3: predict species given number of individuals present
Paper 4: predict number of species within genera in a given population
Several diversity indices presented:
1) Fisher’s Index for Diversity: log-series species
2) Index of Diversity (Williams)
Paper 2: Arrhenius 1920 SAR (species-area relationship)
Increase of species within an area can be expressed by mathematical approximation. This species-area relationship works on many levels, independent of size of the area or the disparate conditions of the habitats.
Question: Do you think this method of prediction would be as broadly applicable as the paper expects? What factors may dissolve this association?
Paper 3: Fisher, Corbet, Williams 1943 SAD (species-area distribution)
Methods to predict the number of species present based on the number of individuals present.
When sampling a population you will over sample common species and under sample rare species. Therefore you would want to design a model that predicts that there are more species than you actually found. This inflation for rare species is appropriate, however for the common species you may have actually detected all common species present and so the model will overestimate for common species. The Fisher’s Index of Diversity attempts to address this as well to correct for differences in sampling effort.
Question: Have you encountered Fisher’s Index in other places in the literature? Did you encounter any limitations with its use, or did the authors address them in any way?
Question: How would the sampling bias mentioned in the paper come about? How would a representative sample be taken correctly?
Paper 4: Williams 1947 S/G Rations (species-to-genus ratios)
Elton: In small communities, competition would be high and maintain a lower species-to-genus ratio.
Williams: Elton did not have a big enough sample size to make this comparison. And, in studies where sample size is adequate, he found the opposite to be true. If a particular genus is successful in a given environment, it is likely that other species with in the genera with similar genetic makeup should do well. Therefore you would have more species from fewer genera (a higher species-to-genus ratio).
Question: What do you think the rationale behind Williams’ findings is? What is the mechanism behind the higher species-to-genus ratio?
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