The paper on chilli archaeology that I described a couple of days ago included two recent references that caught my eye, both by Joshua J. Tewksbury at the University of Washington, Douglas J. Levey of the University of Florida, and various colleagues. They add to our understanding of why it is that chillis evolved to accumulate the chemical, capsaicin, that makes their fruits pungent.
Levey, D.J. et al. A field test of the directed deterrence hypothesis in two species of wild chili. Oecologia 2006, 150: 61-68.