Contributions
to
Short
notes
and reviews
Carrying
metazoan
181-184
(2001)
Publishing bv,
70
The
Hague
Box 94766,
1090 GT
Zoology,
SPB Academic
(3)
forward in the 21st century
phylogenetics
Ronald+A. Jenner
Institute
Review
tion.
Ecosystem
The Netherlands. E-mail:
of and commentary
Evolu-
University of Amsterdam,
three
Living Phyla,
by
University Press, 2001,
x +
ISBN 0-19-850682-1
pp.,
Dynamics,
P.O.
[email protected]
Animal
on:
of the
Interrelationships
Claus Nielsen. Oxford
563
and
for Biodiversity
Amsterdam,
levels of Metazoa, Bilateria, and
ing organizational
Deuterostomia
forming the substrates of three
cessive Precambrian radiations.
(Pbk).
the ascend-
phylogenetic plateaus representing
suc-
Unsurprisingly, the
complete lack of resolution in the molecular phyinitial
My
browsing
Nielsen’s
produced
a
could
the book from
first read the last line of the last
phylogeny:
“The
18S rDNA
on
ible with the
evolutionary
is
sequences]
phylogeny proposed
surprise!
Anyone
even
phylogenetics
will
be
familiar
marginally
in
developments
recent
of
some
Certainly,
many
observation that
molecular
may
agree
with
“morphologists
upstarts,”
but in view
of Nielsen’s less
than enthusiastic
embrace of molecular
netic evidence in
previous publications
1997a, b) he
appears
phyloge-
However,
to
a
serve
glance
Nielsen’s molecular ‘tree’ offers immediate clari-
fication.
It resembles
grown with
the
a
three-layered
a
phylogenetic
massively
polyphyletic
decade
ago
notoriety
nation
of
grass
the
then most
phylogenetic
dition of IBS rDNA
which
recent
ignorance.
sequence
enjoyed
pictorial
a
some
incar-
Nielsen’s
data
of
advocated
defend
ren-
merely yields
this
phyla
Nielsen’s
of
such
even
as
the
molecular
fig. 57.1 nicely
some
phylogenetics
other issues
that have attracted
tention in the recent literature,
with
developmental
vided, but readers who
The
of six
candidly
chapter
new
original.
tive
phylogenetics
the extensive
himself
are
on
and the
con-
A short
section
is
biology
also
on
pro-
seriously interested in
are
best advised
primary literature
as
to
con-
Nielsen
recommends.
molecular
chapters
in this
phylogeny is just
new
Nielsen’s
one
edition of the 1995
layout of the first edition.
with
at-
the diffi-
as
The book has retained the overall
acquainted
briefly
molecular
phylogenetic estimates
different molecules.
molecular
support
widespread
such
culty of estimating divergence times,
evolutionary
to
Mollusca. Nielsen
very
congruence between
not
of several
morphologically best-
touches upon
on
my-
resolution for
of IBS data
shortcoming
monophyly
based
In
offers resolution where 18S data do
illustrates
or
of
offer.
(including
more
of the individual phyla. Nielsen’s
sult
over-
reminiscent
scheme
by Willmer(1990),
as
terrace
to
degree
can
provide it, namely for the monophyly
flict
(Nielsen,
particularly unlikely
candidate molecular convert.
(1997)
live with
to
phylogeneticists
prepared
are
defined
sur-
data sets.
Balter’s
learn
self)
the
resolution that 18S data
most
morpho-
any
others have reached
to say,
different conclusions about
phylogenetic
the
con-
below the
and molecular
morphological
with
major
rather
cladogram
the
animal
higher-level
aware
flicting phylogenetic signals lurking
face of
Imagine
tree. Needless
logical
inter-phylum relationships,
morphologi-
on
logeny-guarantees compatibility with
fact, where
sce-
fully compat-
cal evidence in this book...” (p. 519).
at
chapter
pictured in fig. 57.2 [a molecular cladogram
based
as a
have
scarcely
bigger surprise. Opening
molecular
nario
edition of Claus
new
Animal Evolution
the back I
on
of the
book,
For
it
attrac-
readers
is
a
not
compre-
182
R.A. Jenner
hensive
phyla,
of the
phylogenetic analysis
based upon
detailed
a
living animal
of their
study
is
parative morphology. Every phylum
in
separate chapter
a
of its
that offers
morphology and embryology
phyly of each phylum
character states
is
analysis
for the
in the book.
out
of
manual
computer-assisted
support
text
the results
reports
cladistic
of all
analysis
have
zoology ready
at
hand to
phyof
textbook
a
phyla
invertebrate
on
provide
pictorial
extra
definitive
Clearly,
by
cladistic
et
Zrzavy
ah, 2001)
et
ah, 2000;
differences in
of alternative
four
(Giribet
Peterson &
that
com-
How-
morpho-
computerah,
et
2000;
Eernisse, 2001;
published since last
were
of these trees agree,
parts
a
of informa-
metazoans.
Consider the
analyses
Sorensen
Although
extant
shortage
no
logical phylogenies.
assisted
quantity
vast
a
morphology of
there is
year!
phylogeny
of
of the
tree
is the result of
zoologist in total command of the
a
parative
phylogenetics
morphological
his
many
topology remain.
has chosen
Unfortunately, Nielsen
the relative merits of
the book, but the reader
throughout
to
tion
sets
illustrations
Adequate
is well-advised
a
clades in his
larger
56
simultaneously.
the
form
states
analyses presented
phylogenetic analyses of restricted
logcny, while chapter
analysed
through
the book Nielsen carries
Throughout
that make up the
phyla
character
the
penetrating analysis
ever,
relation-
intra-phylum
phylogenetic
mono-
and ancestral
reconstructed
or
of
ships. These plesiomorphic
the basis
descriptions
emphasizing
justified,
assumed
are
phylogenetic
considered
informative features. The
phylogenetically
a
lucid
duced
Metazoa?
com-
Metazoan
-
not to
discuss
numerical cladistic
published
studies. Instead, he offers several remarks that echo
more
than
a
whisper of despair
task that is still
before
the differences in
ses, and
499
p.
the
over
challenging
1) explain what
us:
causes
between different
topology
analy-
identify the best supported tree(s).
2)
read that in
we
On
phylogenetic
to
contrast
support for the dense morphological narrative. Apart
analyses of lower-level taxa, such
from the
perhaps also genera” where the data matrix “can
chapters
on
molecular
phylogeny (57) and
numerical cladistic
analyses (56) three other
chapters (9, 30, 32)
the
accompany
the
lids,
Four
latter
now
by the
3
1995
changed
now
chapter
its
are
were
now
on
‘Five
‘removed.’
(2, 56)
dis-
partly replaced
with
animal
early
The
enigmatic
origi-
taxa’
has
membership
within
while the
Mollusca,
newly
cycliophoran Symbion pandora is treated
incertae sedis.
Finally,
Nielsen has
globally
updated the information in the book, removed
streamlined
rors,
added several
new
the
text
in
various
illustrations. New
cal information and novel character
have
changed the topology
of the
places,
has written
by
a
of
a
interpretations
phylogeny
wonderful book that
of detail
despite
some-
Nielsen
the
treat-
possibly be made objective,” grim prospects await
those who wish to
and
definition of
acter
codings
subjective.”
doomed
hope
is
failure and
to
not.
shared
not
to
all
1992), and it does
jective analysis
marks of
of
and
testing.
ly, but these variables
between studies. A
may
Even
if
the
first edition.
the
has
Nielsen pro-
can
the
no
the
superior
are
is
(O’Hara,
The
an
ob-
key hall-
explicitness and the
Selection of taxa and char-
primary homology
can
be
even
may
extensive-
objectively compared
basis
for
an
objective judge-
merit of different
hypothesis
can
identify
analyses.
be nominated
summary of available
nevertheless
it
comparison of these variables
relative
single
I
characteristic
sciences
analyses, sometimes
then form
a
of historical events.
decisions of
differ between
is
principle prevent
objective science
possibility
acters,
in
is
time?
but
subjective,
or
historical
not
our
phylogenetic analysis
that this
recognize
objective
an
hypotheses
worthy of
The outcome of any
amongst
choice
coding of
personal, i.e.
that
cladistic
interpreter-dependent
essential
high degree of factual accuracy, and that amply
burning question remains:
believe
to
we
be
degree
to some
evaluation of alternative
on
great
Are
and
complete quagmire,” and “char-
a
will
taxa because “the
and choice
taxa
characters become
ment
amount
perform objective phylogenetic
analyses of higher-level
is characterized
a
justifies the frequent citation of
A
er-
and
morphologi-
what since the first edition. In conclusion,
ment
is
Acanthocephala
the Rotifera.
on
chapter.
separate
somewhat: Xenoturbella
placed
described
on
gnathostomu-
edition
dealing
chapter
merged with that
nal
as
theory
chapter
new
radiation. The old
now
a
first
chapters in the
the trochaea
cussing
is
receiving
chapters from the first edition
The two
shifting phylo-
of ctenophores and
genetic positions
new
“species, and
as
evidence,
those decisions that
as
we
are
Contributions
in
decisive
most
gies,
and
only
restrictive
taxa
of the
As
cladistic
A and
one
B,
not
conclude that
allowed
in
resides
true
a
objectivity
the
explicit-
strongly
of
56.1) while
(fig.
tree
and Nemertea
than 20
reduced
posterior
cladistic
sis-
are
we
diagnostic
included in
none
find that
we
have
been
less
no
proposed
sister group relation-
conflicting
None of these characters
Nielsen’s
analysis, and
new
con-
of the other studies included Nielsen’s
This
parenchymian apomorphy!
differences in character
clearly shows
selection
placements of platyhelminths.
that
contribute sub-
to the existence of conflicting
stantially
long cilia
examine other recently
analyses,
ships of platyhelminths.
For
phylogen-
an
effective
character congruence test of the alternatives, future
studies
so
that
must
no
potential
Of course,
to
select all
carefully
outcomes
before the
platyhelminths
can
most
pertinent characters
precluded
are
a
priori.
likely sister group(s)
be identified with confidence,
the other variables that differ between the studies
will
have to be scrutinized
Interestingly,
in
further
well.
provides
a
helpful
may
have
with
the
‘manual’
a reason-
analysis
per-
throughout this book, indicating that obvious
of characters
not
we
analyses show
logical inconsistencies between
are
platyhel-
apomorphy. Nielsen (p. 508)
writes that the “numerical
able accordance
of
and
the
the
construction
strongly
ties between the
hyposphere’
polyclad
In
of
set
a
Nielsen
ments,
apparently
but
also
close
that
the
to
“the
life
pilidium larva is definitely
my
the
You
italics).
a
any
nemerteans to other
linking
phylogenetic relevance
of
truly representative
permitting
Another
phyla,
the
search for
a
formative similarities
similari-
Gotte’s and the
nemer-
the
or
pilidium
nemertean
phylogenetically
interpreted
gastroneuron” (p. 305). This
stands in direct conflict with
the
defended in
most
recent
rated
by either
depending
cither
The
book.
three
or
upon
whether
manual,
This
analysis
a
at
position
base of the
this
for
demands either
or
a
time because
or
to
that is
architecture
of
from fossils
is
events
immediately
to metazoan
that took
on
at the
phylogenetic
recon-
place
and
development
habitually
in
the
molecular
while information
are
circumstances,
a
logical
congruence that
morphological
studies
more
excluded from cladistic
the Metazoa. Given such
different
phylog-
to
the basis of scattered
living animals,
Importantly, the
between
upon
imperfectly preserved
structure,
analyses of
phylo-
no
date (based
combined evidence) in-
rotifers
billion years ago
information
complex
a
reconsid-
protostomes.
struct diversification
a
consult
to
extremely challenging. We attempt
than half
sepa-
highly speculative theory
Morphological approaches
are
are
the
computer-generated
or
published
morphology, molecules,
dicates
and
body plan evolution. The latter option
preferable
genetic
chooses
one
phylogenies,
eration of an attractive but
seems
state-
phytogenies
of Rotifera
discrepancy
of Nielsen’s
about rotifer
must
five different ancestral nodes
Nielsen’s
revision
the
gastroneuron
common ancestor
phylogeny.
in
“neotenic descendants of the proto-
as
stomian ancestor,
ment
in-
example of internal inconsistency
tation.
on
might have
with other larval forms.
of
is based
it
original
multiple alternative hypotheses
phylogeny
evolved
Nielsen’s book is his conclusion that rotifers
be
a
(p. 288,
monophyletic Nemertea, thereby logically
for
larva
type” (p.
unique novelty that
a
the
involving
ancestral”
not
precluding
is
original
cycle
state-
that
only
not
have it both ways. Either
cannot
pilidium larva is
that these larval
contradictory
then concludes
pilidium larva “is
264),
assumes
respective monophyletic
interpretation
present.” However, the character ‘larva with
reduced
ancestral for the
are
phyla.
eny
hint that is
evaluating the confidence
in the parenchymian
formed
as
Nielsen’s discussion
minths and nemerteans
pilidium larvae, which
forms
apomor-
hyposphere’ (the
the band of
to
different characters
for
tean
within
analysis found one unambiguous
published
etic
we must
has
Platyhelminthes
‘larva with
versely
A.
taxon
analysis parameter: character
is reduced in size). When
are
proposed
of
example, consider the position
part of the larva
as
have
group
forming the cladc Parenchymia. Nielsen’s
ter taxa
phy:
For
testing these alternatives
in Nielsen’s
just
on
selection.
at
topolo-
data matrix.
platyhelminths
focusing
183
accordingly.
may
sister
a
analyses
concrete
a
2001
alternatives. Thus the
phylogenetic
ness
as
selection
taxon
test of available
of
C
or
study aimed
includes
-
determining conflicting
different analyses
either taxon B
a
(3)
future research
design
example,
When
70
Zoology,
to
attests
this difficult task. However,
to
at
the
we
expec-
do find
and molecular
tractability
this time it is
of
prac-
184
R.A. Jenner
tically
tween
impossible
thumb to
make
to
phylogenies,
just pick
and
the
reasoned choice be-
a
it is
newest
or
biggest analysis
the
many
“subjective”
feed into different cladistic
Nielsen
a
as
a
search
as
at least
we
of
trices (cither alone
paid
to
contemporary
studies
concerned
of the
with
data
morphological
only
the
in
ma-
phylogenetic
M.
minimal
(if any)
towards the detailed
accumulated
we
to
shift
accept pending
Nielsen’s
pensable
masterful
tool in such
further
synthesis
an
refute
can
fo-
or
us
provi-
study.
will
endeavor,
an
ships
of
indis-
and the book is
body plan
in the fas-
higher-level animal
evolution.
M,
position
Biol.
539-562.
49:
live
to
Sterner
with
molecular
and
of
Wheeler
W,
with
relationships
of 18S rDNA
RA. 2001.
of
cling
Nielsen
emphasis
WC.
on
the
Gnathostomulida, Cyclio-
Chaetognatha:
and
sequences
1997a.
Soc.
Nielsen
Bilaterian
a
combined
morphology. Syst.
C.
Animal
Fr.
tool.
The
Series
O’Hara
and
relation-
55.
Thomas
eds.
RH,
the
Association
Systematics
London, Chapman
1992.
RJ.
Telling
of
study
then
-
recy-
50: 730-742.
and
now.
243-253.
of the
phylogenetic position
RA,
Fortey
uncritical
Syst. Biol.
sets.
classification
122:
1997b. The
In:
and
phylogeny
data
morphological
C.
Bull.
the
&
Arthrorela-
Arthropod
Special
Volume
11-22.
Hall,
tree: narrative
evolutionary history.
representation
Biol.
Phil.
1:
135-
phylogeny
and
160.
KJ,
Eernisse
ancestry
and
18S
of
rDNA
Sorensen MV,
gene
the
Cycliophora
2001.
I)J.
Animal
bilaterians: inferences
Punch
2000. On
sequences.
P,
phylogeny
and
Evo.
Willerslev
E,
of the
from
Devel.
Hansen
Metazoa
Micrognathozoa.
Zool.
morphology
3:
170-205.
AJ,
in
Glesen
light
Anz.
of the
239;
297-
318.
Willmer
cinating problems
Pol/.
DL,
phora, Plathelminthes,
J.
be
required reading for anybody interested
and
phylogenetic system
1032-1034.
approach
of the
phylogenies. Only this will allow
we
Distel
276:
Triploblastic
tionships.
our
comparative study
conclude which trees
sionally
The
learn
Morphologists
Science
acoelomates and the
the
to
1997.
G,
2000.
Peterson
cus
animals.
atten-
robustness and reliabil-
have
Giribet
poda.
relative to those of other stud-
research
Balter
Jenner
ies. In order to achieve further progress in this field
of
P. 2000. Multicellular
re-
in combination with molecular
exploring
of their results
form
will have to take
cladistic
typically
sequence data) with
ity
not
century. This will
in
change
single
or
do
comparative study of al-
Recent
have been
depth analyses
tion
studies may appear to
enter the 21st
some
strategies.
Metazoa
Ax
upstarts.
phylogenetic hypotheses
center-stage
require
decisions that
“complete quagmire,” they
Gordian knot. Detailed
ternative
References
of the Metazoa. Springer-Verlag, Berlin.
(Jenner, 2001).
Although
phylogenetics
rule-of-
dangerous
a
Metazoan
-
mal
/rzavy
P. 1990. Invertebrate
evolution.
of
DP. 2001.
J, Hypsa V, Tietz
annelids.
Molecular
animals
with
and
2
Patterns in ani-
October
2001
Myzostomida
morphological support
anterior
170-198.
Received:
relationships.
Cambridge, Cambridge University Press.
sperm
flagella.
for
are
a
not
clade
Cladistics
17: