Amino acid sequence versus morphological data and the interordinal relationships of mammals

To a large extent, the mutual affinities of the mammalian orders continueto puzzle systematists, even though comparative anatomy and amino acidsequencing offer a massive data base from which these relationships couldpotentially be adduced. In the present paper the consistency index--thenumber of character states less the number of characters in a data set,divided by the total number of changes in the character states on acladogram--was used to examine the relative resolving powers of recentlypublished morphological and molecular- sequence data. Consistency indiceswere calculated for previously published alpha crystallin A chain andmyoglobin amino acid-sequence cladograms and for four original aminoacid-sequence cladograms (alpha crystallin A, myoglobin, and alpha and betahemoglobin); these were found to be comparable to the consistency indicesof morphologically based cladograms. Qualitative comparisons between themorphologically based and molecularly based trees were also made; onlymoderate congruence between the two was observed. Moreover, there was ageneral lack of congruence between the cladograms specified by each of thefour proteins. Amino acid-sequence and morphological data agreed on theplacement of edentates as an early eutherian offshoot and on the groupingof hyracoids, proboscideans, and sirenians. Otherwise there was onlylimited congruence: morphology strongly supported the grouping oflagomorphs and rodents and the alliance of pholidotes and edentates, butsequence analyses did not. The placement of tubulidentates differed widelyamong proteins. Morphology indicated the close association of sirenianswith proboscideans; proteins suggested a pairing of sirenians withhyracoids. Sequence data did not identify many (morphologicallywell-diagnosed) orders as monophyletic (e.g., Lagomorpha).(ABSTRACTTRUNCATED AT 250 WORDS)