## lords of the rings

**I**n the 19 Jan 2017 issue of Nature [that I received two weeks later], a paper by Tarnita et al discusses regular vegetation patterns like fairy patterns. While this would seem like an ideal setting for point process modelling, the article does not seem to get into that direction, debating instead between ecological models. Which combines vegetal self-organisation, with subterranean insect competition. Since the paper seems to derive validation of a model by simulation means without producing a single equation, I went and checked the supplementary material attached to this paper. What I gathered from this material is that the system of differential equations used to build this model seems to be extrapolated by seeking parameter values consistent with what is known” rather than estimated as in a statistical model. Given the extreme complexity of the resulting five page model, I am surprised at the low level of validation of the construct, with no visible proof of stationarity of the (stochastic) model thus constructed, and no model assessment in a statistical sense. Of course, a major disclaimer applies: (a) this area does not even border my domains of (relative) expertise and (b) I have not spent much time perusing over the published paper and the attached supplementary material. *(Note: This issue of Nature also contains a fascinating review paper by Nielsen et al. on a detailed scenario of human evolutionary history, based on the sequencing of genomes of extinct hominids.)*

February 9, 2017 at 8:41 am

I haven’t read the paper, but what you’re describing is pretty standard for mathematical ecology.

February 9, 2017 at 6:55 pm

Thanks Dan, long time no hear! But then how do they validate the use of this model?

February 10, 2017 at 2:00 am

It’s purely Bayesian :p Are their prior beliefs consistent with reality? (often by making verifiable predictions, but sometimes by saying “expert she believe this is correct”).