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- - posted in hierarchical competition models, multifractals, neutral models, spatially explicit models | Comments


Aggregation of objects is widespread phenomena in several sciences and of course in biology and ecology. Two cases I found and seem interesting to me are: the aggregation  in niche space: The clumping transition in niche competition, and the aggregation in neutral models: Clustering in neutral ecology.

This seems to depend only on the discreteness and finiteness of the objects and space. And in both cases the clumps have sizes distributed as power laws.
Furthermore when you have aggregation is possible that you will find multifractals, so is very possible that multifractals are widespread on ecological and biological phenomena.

All this introduction is because my article in Oikos is available as early view:

Multifractal growth in periphyton communities


And I added some new kind of measures to the multifractal estimation package oriented to estimate multifractals in spatial species distributions, they are not like the ones published by Borda-de-Agua in American Naturalist. They are simpler, I think: the first is the multifractal spectra of the most abundant specie, and the second is a little bit more complex, it requires two steps:
1) Assign the number 1 to the most abundant specie, the number two to the second most abundant and so on, so the result is a surface with higher numbers assigned to the most rare species.
2) Estimate the multifractal spectrum.

I did these to characterize species distribution in a neutral spatially explicit and a Tillman’s like model that I am analysing:



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