Summary of Tangled Nature discussion
The discussion centred around Christensen et al. and Schwämmle & Brigatti. One problem we identified was that there were no "methods" sections: you have to follow all through the papers to understand what exactly is being simulated. It would have been nice to know, for example, how exactly the linear regressions were done in Figure 2 of Schwämmle & Brigatti; as it is they seem to have been rather cavalierly drawn in, although the error bounds seem to indicate that a statistical method has been employed.
John was particularly happy to see that a non-asexual model was introduced in Christensen
et al., since so much theory gets done on asexuals. At the same time though it was unsatisfactory that the models are so limited, but there has to be a balance struck between sophistication and tractability. Finally we found Figure 1 of Schwämmle & Brigatti fascinating since it demonstrated some species reuniting after some time evolving separately; although it seems to me this would be considerably less likely to occur if the "strategies" were multiple-dimensional rather than one-dimensional.
Tangled Web papers
Readings provided by Martin Hely
These are papers about a model known as "tangled nature". Basically, they consider a large set of potential "species" where every pair of species has some randomly-determined interaction (mutualist, predator-prey, competition, or no interaction at all) AND there are mutations which can transform an individual of one of the species into one of another species. For appropriately chosen parameters, this model exhibits lengthy epochs where the makeup of the community is roughly constant, but with occasional periods of re-organization. In complex systems jargon, it exhibits punctuated equilibrium as an "emergent property".
Christensen et al. is the original presentation of the model. Laird, Lawson & Jensen give a run-down of the basic model and some of the variations that have arisen. Jensen 2004 pushes the model into the physics literature (as part of a memorial issue to Per Bak). Lipowski and Schwämmle & Brigatti are examples from physics journals of models related to tangled nature and I've included them more to stimulate discussion on the phenomenon of apparently rather substantial biological conclusions appearing in physics journals.
http://www.uq.edu.au/biohumanities/readings/christensenetal2002.pdfhttp://www.uq.edu.au/biohumanities/readings/jensen2004.pdfhttp://www.uq.edu.au/biohumanities/readings/lairdlawsonjensen.pdfhttp://www.uq.edu.au/biohumanities/readings/lipowski2005.pdfhttp://www.uq.edu.au/biohumanities/readings/schwaemmlebrigatti.pdf
