Abstract
A long-standing mystery in genome evolution is why short tandem repeats vary so much in length and frequency. Here, we test the hypothesis that body temperature acts to influence the rate and nature of slippage-based mutations. Using the data from both 28 species where genome sequencing is advanced and 76 species from which marker loci have been published, we show that in mammals, maximum repeat number is inversely correlated with body temperature, with warmer-blooded species having shorter 'long' microsatellites. Our results support a model of microsatellite evolution in which maximum length is limited by a temperature-dependent stability threshold.