Hawkins, B.A., Diniz-Filho, J.A.F., Bini, L.M., Araújo, M.B., Field, R., Hortal, J., Kerr, J.T., Rahbek, C., Rodríguez, M.Á. & Sanders, N.J. (2007) Metabolic theory and diversity gradients: Where do we go from here? Ecology, 88, 1898–1902. doi:10.1890/06-2141.1
Metabolic Theory of Ecology (MTE) can be viewed as the core of a research program. The hypothesis of Allen et al. (2002), together with the model(s) developed to test it, is one facet of the program. Their model(s) can be tested and rejected, but this does not necessarily challenge the core. As pointed out by Hawkins et al. (2007), our evaluation was restricted to the predictions of Allen et al. (2002) and Brown et al. (2004) for richness gradients and cannot be generalized to MTE as a whole (also see Latimer 2007). Even so, we contend that the tests by Hawkins et al. (2007) are as valid as proponents’ tests and provide strong evidence against the model as a general explanation. Of course, it
is difficult to know whether the failure of the model’s predictions occurs at the postulate, hypothesis, or theory level. Incorporating additional variables (including spatial variation in average body size and abundance, as well including potential deviations from the energetic equivalence rule) might generate improved models that better fit the empirical data. Perhaps this could support the claim that MTE explains richness gradients, at least in part (see also Latimer 2007). But arguing that it might and showing to what extent it does are very different propositions.