Relative rates of single-copy DNA evolution in cranes

Abstract

Data from DNA-DNA hybridization studies provide a means by which to estimate variation in molecular evolutionary rates within and among taxonomic groups. Statistical analyses (ANOVA and F-ratio tests) of such data for the 14 species of cranes (Aves:Gruidae) suggest that rates of single-copy DNA evolution vary significantly between members of the two crane subfamilies, with crowned cranes (Balearicinae:Balearica) showing a relative acceleration of 1.3-1.6 times over the other 13 species (Gruinac). No available evidence suggests that this disparity correlates with variable age-at-first-breeding, though a more general generation-time effect may exist. The fossil record for Gruiformes provides two approximate points of calibration for the molecular clock in cranes, corresponding to the divergence of cranes and limpkins (Aramidae) and to the divergence of the two gruid subfamilies. Fossil time calibration indicates that the average genomic rate of DNA evolution in cranes is close to Sibley and Ahlquist's general estimate for birds with delayed breeding.