Is the rate of molecular evolution inversely related to body size?

Abstract

The wealth of molecular data generated over the past two decades has led to the documentation of highly disparate rates of molecular evolution among different taxa. Among the more intriguing studies is that of Martin and Palumbi (1993), who presented data (their Table 2) derived from a variety of vertebrate taxa purporting to show that the rate of molecular evolution is inversely correlated with body size (and its correlates: metabolic rate, generation time, etc.). Their hypothesis has been cited as a possible ex? planation for variation in rate of molecular evolution among different taxa (e.g., Hafner et al., 1994; Rand, 1994; Stewart and Baker, 1994). We argue, however, that no such re? lationship is evidenced from Martin and Palumbi's data and that the problem lies in the fact that their distance-based estimates for the rate of molecular evolution were un-