THE FLORIDA MANATEE: CYTOCHROME B DNA SEQUENCE

The Florida manatee (Trichechus manatus latirostris ) is a large, plant-eating aquatic mammal inhabiting coastal areas, lagoons, and certain rivers of Florida. It is a subspecies of the West Indian manatee, found from the southern United States to the northeast coast of Brazil. The manatee's endangered status, in large measure from high mortality and habitat loss associated with human activity, has focused a great deal of interest on its biology and medical management. To date, virtually nothing is known at the DNA level about this species' phylogeny or population genetics. Since the early 1960s the reconstruction of phylogenies has depended upon the examination of the similarities among proteins as analyzed by sequencing, isoenzyme analysis, and immunological comparisons. For example, both protein sequencing of alpha -crystallin A chains and allozyme analyses of 24 presumptive gene loci have been examined in manatees. Such comparisons were first proposed by Zuckerkandl and Pauling to be used as a molecular clock to date the divergence of extant species. Likewise, population biologists have used these rechniques, as well as newer methods including DNA-DNA hybridization, ribosomal DNA sequencing, and restriction enzyme digestion of nuclear and organellar DNA, but have found them lacking in precision, because they estimate sequence difference instead of measuring it directly.