4.7.3 Molecular Taxonomy Above the Species Level
169
orang-utan (Pongo pygmaeus) and the seven species of gibbons (Hylobates sp.). In order to clarify
the family relationships between man and the
various anthropoids, various sets of molecular
data have been applied, in particular DNA
sequences from the 'Y]-globin pseudogenes, fimmunoglobulin pseudogenes, various noncoding DNA regions and mtDNAs, ATm values,
restriction data, amino acid sequences, and
immunological and electrophoretic data. All the
molecular family trees first separate the gibbons
and the orang-utan from the evolutionary line.
The branching scheme between man, chimpanzee
and gorilla, however, remains controversial; the
difference in time between the splitting off of the
two anthropoids is apparently so short that the
molecular data do not allow a statistically certain
conclusion to be drawn about the sequence of
events. The majority of authors assume a closer
relationship between man and the chimpanzee,
with the branch point between them given as 4-6
million years ago, depending upon which data are
used; the dwarf chimpanzee arose later. This
conclusion has now been accepted by the palaeontologists, who initially proposed a much
greater phylogenetic age for man [54, 140,
143, 160, 180,354,417,438]. Man and the chimpanzee together present a particularly instructive
example of the fact that the rate of evolution of
complex phenotypic characters is not strongly
correlated with the substitution rate for DNA,
and that the evolution of complex features cannot
simply be explained by gradual, randomly distributed changes in DNA sequences. It only became
possible to solve the puzzle of the taxonomic
position of the giant panda or bamboo bear (Ailuropoda melanoleuca) with the use of molecular
data; this had not been possible with morphological and palaeontological data alone. Does the
giant panda belong to the family of bears (Ursidae) or the racoons (Procyonidae), or should it be
assigned to a unique family (Ailuropodidae)?
What exactly is its relationship to the lesser panda
(Ailurus fulgens)? DNA hybridization data, electrophoretically determined D values, and the
immunological distance of the albumins and
transferrins clearly placed the giant panda close
to the brown bears and the lesser panda with the
raccoons. However, it is not yet decided whether
the giant panda should be classified as a separate
family or as a subfamily of the Ursidae [302].
From the sequences of a-crystallin and a- and ~globin, it was concluded that the Procyonidae is a
sibling group of the Mustelidae (martens) and
should not, as has often been attempted, be
placed close to the Ursidae and Canidae (canines) [197]. The phylogenetic origin of the South
African aardvark Orycteropus afer was previously
a complete puzzle; however, a family tree constructed from data on the lens protein a-crystallin
indicated as close relatives the manatee (Sirenia),
hyrax (Hyracoidae) and elephant (Proboscoidae)
[195]. From the immunological data on albumin
for 34 of the 37 existing cat species (Felidae), a
family tree may be constructed that coincides
with the karyotype data and the fossil record:
about 12 million years ago the small South American species, such as the ocelot, first separated;
8-10 million years ago the relatives of the
domestic cat separated; 4-6 million years ago the
cheetah, serval and puma diverged; and the lines
to the lynx and the Panthera species of the lion
and tiger separated only about 2 million years ago
[76]. Restriction analysis of the mtDNA of the
seven species of the Equidae points to there having been a common ancestor about 3.9 million
years ago [130].
Immunological investigations on various egg
and serum proteins have shown that the southern
and central American curassow (Cracidae) are
not more closely related to the chicken (Galliformes) than to the duck (Anseriformes) and should
not be placed in the Galliformes family; these
methods have also indicated that the penguin,
whose evolution was hitherto a complete mystery,
is apparently quite closely related to the grebes
(Gaviiformes and Podicipediformes), the petrel
(Procellariiformes), and the bawler (Ciconiiformes) [333]. The urodelan family Plethodontidae,
with 23 genera and more than 200 species, is
widely distributed in the New World; only two
species from this group, Hydromantes italicus and
H. genei are found in southern Europe. Enzyme
electrophoresis and the immunological distances
of the serum albumins show that these two species migrated from North America in the Oligocene and further developed in isolation [425].
Immunological albumin comparisons carried out
on numerous species of the tree frog (Hylidae)
have assisted in the clarification of a whole series
of phylogenetic-taxonomic questions. In this way,
it was shown that the morphological similarity of
Hyla regilla to other species of the Hyla genus is
a case of convergence, that Anotheca spinosa
belongs to the Hylinae rather than to the pouched
frogs (Amphignathodontinae), and finally that
the branch frog Phyllomedusa is not more closely
related to Hyla than to Bufo and should, therefore, not be counted amongst the Hylidae but
placed in its own family [266]. The approximately
169
orang-utan (Pongo pygmaeus) and the seven species of gibbons (Hylobates sp.). In order to clarify
the family relationships between man and the
various anthropoids, various sets of molecular
data have been applied, in particular DNA
sequences from the 'Y]-globin pseudogenes, fimmunoglobulin pseudogenes, various noncoding DNA regions and mtDNAs, ATm values,
restriction data, amino acid sequences, and
immunological and electrophoretic data. All the
molecular family trees first separate the gibbons
and the orang-utan from the evolutionary line.
The branching scheme between man, chimpanzee
and gorilla, however, remains controversial; the
difference in time between the splitting off of the
two anthropoids is apparently so short that the
molecular data do not allow a statistically certain
conclusion to be drawn about the sequence of
events. The majority of authors assume a closer
relationship between man and the chimpanzee,
with the branch point between them given as 4-6
million years ago, depending upon which data are
used; the dwarf chimpanzee arose later. This
conclusion has now been accepted by the palaeontologists, who initially proposed a much
greater phylogenetic age for man [54, 140,
143, 160, 180,354,417,438]. Man and the chimpanzee together present a particularly instructive
example of the fact that the rate of evolution of
complex phenotypic characters is not strongly
correlated with the substitution rate for DNA,
and that the evolution of complex features cannot
simply be explained by gradual, randomly distributed changes in DNA sequences. It only became
possible to solve the puzzle of the taxonomic
position of the giant panda or bamboo bear (Ailuropoda melanoleuca) with the use of molecular
data; this had not been possible with morphological and palaeontological data alone. Does the
giant panda belong to the family of bears (Ursidae) or the racoons (Procyonidae), or should it be
assigned to a unique family (Ailuropodidae)?
What exactly is its relationship to the lesser panda
(Ailurus fulgens)? DNA hybridization data, electrophoretically determined D values, and the
immunological distance of the albumins and
transferrins clearly placed the giant panda close
to the brown bears and the lesser panda with the
raccoons. However, it is not yet decided whether
the giant panda should be classified as a separate
family or as a subfamily of the Ursidae [302].
From the sequences of a-crystallin and a- and ~globin, it was concluded that the Procyonidae is a
sibling group of the Mustelidae (martens) and
should not, as has often been attempted, be
placed close to the Ursidae and Canidae (canines) [197]. The phylogenetic origin of the South
African aardvark Orycteropus afer was previously
a complete puzzle; however, a family tree constructed from data on the lens protein a-crystallin
indicated as close relatives the manatee (Sirenia),
hyrax (Hyracoidae) and elephant (Proboscoidae)
[195]. From the immunological data on albumin
for 34 of the 37 existing cat species (Felidae), a
family tree may be constructed that coincides
with the karyotype data and the fossil record:
about 12 million years ago the small South American species, such as the ocelot, first separated;
8-10 million years ago the relatives of the
domestic cat separated; 4-6 million years ago the
cheetah, serval and puma diverged; and the lines
to the lynx and the Panthera species of the lion
and tiger separated only about 2 million years ago
[76]. Restriction analysis of the mtDNA of the
seven species of the Equidae points to there having been a common ancestor about 3.9 million
years ago [130].
Immunological investigations on various egg
and serum proteins have shown that the southern
and central American curassow (Cracidae) are
not more closely related to the chicken (Galliformes) than to the duck (Anseriformes) and should
not be placed in the Galliformes family; these
methods have also indicated that the penguin,
whose evolution was hitherto a complete mystery,
is apparently quite closely related to the grebes
(Gaviiformes and Podicipediformes), the petrel
(Procellariiformes), and the bawler (Ciconiiformes) [333]. The urodelan family Plethodontidae,
with 23 genera and more than 200 species, is
widely distributed in the New World; only two
species from this group, Hydromantes italicus and
H. genei are found in southern Europe. Enzyme
electrophoresis and the immunological distances
of the serum albumins show that these two species migrated from North America in the Oligocene and further developed in isolation [425].
Immunological albumin comparisons carried out
on numerous species of the tree frog (Hylidae)
have assisted in the clarification of a whole series
of phylogenetic-taxonomic questions. In this way,
it was shown that the morphological similarity of
Hyla regilla to other species of the Hyla genus is
a case of convergence, that Anotheca spinosa
belongs to the Hylinae rather than to the pouched
frogs (Amphignathodontinae), and finally that
the branch frog Phyllomedusa is not more closely
related to Hyla than to Bufo and should, therefore, not be counted amongst the Hylidae but
placed in its own family [266]. The approximately