Better theory of species range limits

I'm reading "Geographic range limits: achieving synthesis" by Kevin Gaston (2009). Gaston paints a rather grim picture of our understanding of species range limits, and identifies a few areas that need exploration.

First, Gaston says that empirical studies lag substantially behind theoretical developments. We need empirical analyses of species ranges!

Second, he emphasizes the connections between genetics, physiology, and population dynamics, and the fact that many different factors can limit a species range at the same time. To address this, Gaston suggests that we need "studies that document variation in all of the parameters [immigration, birth, death, and emigration]" (and to identify organisms that would be suited to this work - challenging!).

He ends with this sentence: "[I]t has often proven frustratingly difficult to explain what determines the limits of a particular species at a given place and time." What a dim ending to an important article on such an important topic (with implications for biological invasions, habitat loss, climate change, emerging diseases, and food security)!

I think that combining some of the theoretical concepts around range boundaries with empirical data from a range of species could provide some great information about what is going on and hopefully shine some light on the determinants.

Gaston, K.J. 2009. Geographic range limits: achieving synthesis. Proceedings of the Royal Society B 276:1395-1406.