GENERIC AFFINITIES AMONG CROCODILIANS AS REVEALED BY DNA-FINGERPRINTING WITH A BKM-DERIVED PROBE

Genetic fingerprint profiles have been successfully used for establish ing biological relationships, in linkage analysis, and in studies of p opulation structure but have not so far been used for ascertaining phy logenetic relationships among related groups of species and genera. Th is is largely because these profiles are thought to evolve too rapidly to be informative over large time intervals. However, we show here th at among the Crocodilia, whose phylogeny is a debated issue, these pro files can provide phylogenetically useful information. By using the pr obe Bkm-2(8), DNA fingerprints with distinct bands distributed in the size range 0.5-23.0 kb were obtained for individuals of 18 species bel onging to seven of the eight genera of crocodilians. These genetic pro files showed individual-, species-, and restriction enzyme-specific pa tterns, In addition, striking differences were observed in the copy nu mber of Bkm-related sequences in genomes of different crocodilian spec ies. The qualitative data from DNA fingerprint profiles, and quantitat ive data on copy number variation in Bkm-related sequences, suggest th at these genera belong to two distinct groups, one of which includes A lligator, Paleosuchus, and Caiman; the other includes Crocodylus, Oste olaemus, Tomistoma, and Gavialis. A close relationship between Tomisto ma and Gavialis is also suggested by these results.