Mitochondrial 16S rRNA Sequence Diversityof Hominoids
R. Noda, C. G. Kim, O. Takenaka, R. E. Ferrell, T. Tanoue, I. Hayasaka,
S. Ueda, T. Ishida, and N. Saitou

We determined nucleotide sequences of the 16S rRNA gene of mitochondrial DNA(mtDNA) (about 1.6 kb) for 35 chimpanzee, 13 bonobo, 10 gorilla, 16 orangutan, and23 gibbon individuals. We compared those data with published sequences and estimated nucleotide diversity for each species. All the ape species showed higher
diversity than human. We also constructed phylogenetic trees and networks. The
two orangutan subspecies were clearly separated from each other, and Sumatranorangutans showed much higher nucleotide diversity than Bornean orangutans.
Some gibbon species did not form monophyletic clusters, and variation within species was not much different from that among species in the subgenus Hylobates.

From the Laboratory of Evolutionary Genetics, National Institute of Genetics, Mishima, 411–8540 Japan( Noda, Kim, and Saitou), Primate Research Institute,
Kyoto University, Inuyama, Japan ( Takenaka), Department of Human Genetics, University of Pittsburgh,
Pittsburgh, Pennsylvania ( Ferrell), SanwaKagaku Kenkyusho Kumamoto Primate Park ( Tanoue and Hayasaka), and Department of Biological Science, Universityof Tokyo ( Ueda and Ishida). This study was partially
supported by grants-in-aid for scientific studies from
the Ministry of Education, Culture, Sport, Science, andTechnology, Japan and by the Cooperation Research
Program of Primate Research Institute, Kyoto University (to N.S.). We thank Aoshima Akiko, Suzuki Mayumi,
and Kondo Masayo for their experimental assistance.
We also thank Suzuki Mayumi for assistance in submitting sequence data to DDBJ via SAKURA. We thank the
Ueno Zoo of Tokyo for providing us two gorilla samples. This study was planned by N. Saitou. DNA samples of 3 orangutan and all gibbons were provided by
O. Takenaka; those of 14 chimpanzee, 7 gorilla, 8 orangutan, and all bonobo were provided by R. E. Ferrell; 2chimpanzee, 1 gorilla, and 1 orangutan were provided
by S. Ueda; 4 orangutan were provided by T. Ishida; andthose of 19 chimpanzee individuals were provided by
T. Tanoue and I. Hayasaka. Sequences of gibbons,orangutan, gorilla, and bonobo were determined by R.
Noda, while C. G. Kim determined those of all chimpanzees. Sequence analyses were conducted by R.
Noda and N. Saitou, and the manuscript was written by
N. Saitou and R. Noda. Address correspondence to N.
Saitou at the address above or e-mail: nsaitou@genes.
nig.ac.jp. This paper was delivered at a symposium entitled ‘‘Primate Evolutionary Genetics’’ sponsored by
the American Genetic Association at Town and Country
Resort and Convention Center, San Diego, CA, USA,May 19–20, 2001.
 2001 The American Genetic Association 92:490–496

490

Superfamily Hominoidea of Primates is divided into two families, Hominidae thatconsists of human, chimpanzee, gorilla,
and orangutan, and Hylobatidae containing gibbons and siamang (Gloves 1997).
The phylogenetic relationship of Hominidae species is now established (e.g., Chen
and Li 2001; Horai et al. 1995, Ruvolo 1997;
Saitou 1991; Sibley and Ahlquist 1987). In
this respect, nucleotide sequences of various regions of mitochondrial DNA(mtDNA) have been frequently used for
elucidating the phylogenetic relationshipof hominoids (e.g., Arnason et al. 1996;
Brown et al. 1982; Hixson and Brown 1986;
Horai et al. 1992, 1995; Hayashi et al. 1995;
Roos and Geissmann 2001; Ruvolo et al.
1994; Xu and Arnason 1996).
It is important to estimate genetic diversity of apes not only from the natural history viewpoint, but also for comparison
with human. In recent years mtDNA sequence data have been used to examine
the genetic diversity of apes following thegreat wave of human mtDNA diversity
studies (e.g., Gagneux et al. 1999; Garnerand Ryder 1996; Goldberg and Ruvolo
1997; Morin et al. 1994; Muir et al. 2000;
Ruvolo et al. 1994; Saltonstall et al. 1998;
Warren et al. 2001; Wise et al. 1997; Zhi etal. 1996). However, even those alreadypublished mtDNA sequence data seem to
be insufficient for estimating the genetic
diversity of apes, in particular, orangutans
and gibbons. As for gibbons, the phylogenetic relationship of species in the family
Hylobatidae is not yet clarified.
We collected ape genomic DNA to study

the intraspecific variation of ape species
as a part of the ape genome project Silver( http://sayer.lab.nig.ac.jp/⬃silver/). As theinitial step, we examined mtDNA 16S rRNA
diversity of chimpanzee, bonobo, gorilla,orangutan, and eight gibbon species. We
particularly focused on the diversity ofthe two orangutan subspecies and on thephylogenetic relationship of the gibbon
species.

Materials and Methods
Genomic DNA samples for 35 chimpanzee(Pan troglodytes), 14 bonobo (Pan paniscus), 10 gorilla (Gorilla gorilla), 16 orangutan (Pongo pygmaeus), and 23 gibbon (genus Hylobates) individuals were used (seeTable 1). Polymerase chain reaction (PCR)
was carried out using specific primers
based on primate mitochondrial sequences: SN-MtSd, 5⬘-CACACCGCCCGTCACYCYCYTCAA-3⬘, and SN-MtSr, 5⬘-ACCGGGCTCTGCCATCTTAACSN-3⬘ for PCR. This region
includes part of the 12S rRNA, valinetransfer RNA, and most of the 16S rRNA
gene. Each PCR mixture contained 160 mM
each of dATP, dTTP, dCTP, and dGTP, 150mM MgCl2, reaction buffer containing no
Mg2⫹ ion, 1 mM of each primer, and 2 units
Taq polymerase ( TOYOBO and NIPPON
GENE). About 200 ng of genomic DNA wasused as template. The PCR program consisted of 20–45 cycles of 1-min denaturation at 94⬚C followed by 1-min primer annealing at 65⬚C or 68⬚C, and a 2-min
extension at 72⬚C (PE GeneAmp PCR system 2400 and 9700). Immediately preced-

Table 1. Ape DNA samples used in this study
Species individual ID

Accession numbers

Chimpanzee
chimp#1–#35

AB062513–AB062547

Bonobobonobo#1–#5
bonobo#6–#13

AB050147–AB050151
AB065137–AB065144

Gorillagorilla#1–#4
gorilla#5–#10

AB050152–AB050155
AB064490–AB064495

Orangutanorang#1–#16

AB050156–AB050172

H. agilis (subgenus Hylobates)
H. agilis#1–#3

AB050172–AB050174

H. lar (subgenus Hylobates)
H. lar#1–#3

AB050175–AB050177

H. muelleri (subgenus Hylobates)
H. muelleri#1–#2

AB050178–AB050179

H. klossii (subgenus Hylobates)
H. klossii#1–#3

AB050180–AB050182

H. pileatus (subgenus Hylobates)
H. pileatus#1–#3

AB050183–AB050185

H. moloch (subgenus Hylobates)
H. moloch#1–#2

AB050186–AB050187

H. syndactylus (subgenus Symphalangus)
H. syndactylus#1–#5

AB050188–AB050192

H. concolor (subgenus Nomascus)
H. concolor#1

AB050193

ing and following these 20–45 cycles, a 9min hot-start step at 94⬚C and a 60-min
extension step at 72⬚C were included.
PCR products were confirmed by 1.5%

Figure 1. Phylogenetic networks of the mtDNA 16SrRNA gene region for (A) chimpanzee, (B) bonobo, and(C) gorilla. Numbers designate individuals of Table 2.
D and X designate sequences determined by Horai etal. (1995) and Xu and Arnason (1996), respectively.
Edge lengths are proportional to the number of nucleotide differences. Arrows indicate the edges in whichroots are probably located.

agarose gel electrophoresis and were purified using Micro Spin Columns (Pharmacia Biotech). The purified PCR products were sequenced by the dideoxy
chain-termination method using fluorescent ddNTPs, sequenase enzyme, andbuffer from the ThermoSequenase kit (PEBiosystems). Samples were electropho-

resed in the automated sequencer ABI
PRISM 377 (PE Biosystems). Both the PCRprimers were used for sequencing. In addition, two other primers were used: SNMtSi1, 5⬘-CAATTAAGAAAGCGTTCAAGCTC3⬘, and SN-MtSi2, 5⬘-TGCTAGAGGTGATGT
TTTTGG-3⬘.
CLUSTAL W version 1.6 ( Thompson etal. 1994) was used for multiple alignment
and phylogenetic tree construction. Phylogenetic trees were constructed using theneighbor-joining method (Saitou and Nei
1987). Phylogenetic networks ( Bandelt
1994; Saitou and Yamamoto 1997) werealso constructed. MEGA2 ( Kumar et al.
2000) was used for computation of nucleotide diversity and UPGMA tree construction. Nucleotide sites containing missing
data and gaps were excluded from constructing trees and networks.

Results
Because there were considerable nucleotide differences among hominoid mtDNA
16S rRNA sequences, we divided hominoids into three groups: African apes,
orangutan, and gibbons.
African Apes
We determined mtDNA sequences for 35
chimpanzee, 13 bonobo, and 10 gorilla.
The following sequence data retrieved
from the DDBJ/EMBL/GenBank International Sequence Database were also used
for comparison: two chimpanzee sequences ( D38113 and X93335), one bonobo sequence ( D38116), and two gorilla se-

Figure 2. Phylogenetic tree of the mtDNA 16S rRNA gene region for chimpanzee, bonobo, and gorilla. The tree
was rooted by using the midpoint rooting method.

Noda et al • Hominoid mtDNA 16S rRNA Diversity 491

Table 2A. Variant sites of chimpanzee

cies identification is not clear for all thechimpanzees used in this study, but mostof them seem to be Pan troglodytes verus
according to their mtDNA control region
sequences (Shinoda K, personal communication). Therefore it is possible that thesmall cluster with four chimpanzees may
correspond to another subspecies, probably Pan troglodytes troglodytes.
We also constructed a phylogenetic tree
for human, chimpanzee, bonobo, and gorilla ( Figure 2). Two human sequencesthat showed the greatest divergence outof the 53 complete mitochondrial genomes ( Ingman et al. 2001) were includedin this tree. The tree was rooted by using
the midpoint rooting method. The phylogenetic relationship of the four species iscompatible with that based on the complete mtDNA sequences ( Horai et al.

Chimps 13, 16, 18, 19, 20, 22, 25, and 29 were identicalwith this sequence.
b
Chimps 6, 7, 10, 12, and 21 were identical with thissequence.
c
Chimp 5 was identical with this sequence.
dChimp 17 was identical with this sequence.
e
Chimps 23, 27, and 30 were identical with this sequence.
fChimps 24 and 28 were identical with this sequence.
g
Chimps 33 and 34 were identical with this sequence.

aquences ( D38114 and X93347). Nucleotide
sequences with accession numbers starting with D were determined by Horai et al.
(1995), while those with accession numbers starting with X were determined by
Xu and Arnason (1996). Those sequence
data were multiply aligned for each species, and variant nucleotide sites are presented in Table 2A, B, and C for chimpanzee, bonobo, and gorilla, respectively.
Phylogenetic networks for each species
were constructed based on the multiplyaligned sequence data ( Figure 1). Fourchimpanzee individuals (nos. 2, 4, 5, and9) were clearly separated from the remaining individuals. Arrows indicate the position of the roots based on the phylogenetic tree of four hominid species shown in
Figure 2. Networks for chimpanzee ( Figure1A) and for gorilla ( Figure 1C) happened
to be unrooted trees, for all the nucleotide
sites were compatible with each other.
One rectangle in the bonobo network ( Figure 1B) denotes the existence of incompatible nucleotide configurations; the configuration at site 1788 is incompatible withthose at sites 225, 687, and 1368. Subspe-

492 The Journal of Heredity 2001:92(6)Table 2C. Variant sites of gorilla

Table 2B. Variant sites of bonobo

1995). Phylogenetic relationships of the
haplotypes belonging to the same species
were more or less compatible with thephylogenetic networks shown in Figure 1.
The nucleotide diversity within species
was calculated using the Jukes–Cantor correction, and the result is shown in Table 3.
The nucleotide diversities of chimpanzee,
bonobo, and gorilla (0.0027 ⫾ 0.0007,
0.0033 ⫾ 0.0008, and 0.0024 ⫾ 0.0007, respectively) were greater than that for human (0.0016 ⫾ 0.0004), in which sequence
data of the 53 complete mitochondrial genomes ( Ingman et al. 2001) were used. It
should be noted that individuals sampledfrom the global scale were used for human.
Orangutan
We determined mtDNA sequences for 16
orangutans. Orangutan sequence data retrieved from the DDBJ/EMBL/GenBank International Sequence Database were also

Table 3. Nucleotide diversity (␲) in 14 hominoid species
SpeciesNo. of sequencesa ␲ ⫾ S.E.b

Homo sapien
Pan troglodytes
Pan paniscus
Gorilla gorilla
Pongo pygmaeus pygmaeus
Pongo pygmaeus abelii
Hylobates lar
Hylobates agilis
Hylobates muelleri
Hylobates klossii
Hylobates pileatus
Hylobates moloch
Hylobates syndactylus

53 (53)37 (2)
14 (1)
12 (2)
9 (1)
9 (1)
4 (1)
3 (0)
2 (0)
3 (0)
3 (0)
2 (0)
6 (0)

0.0016 ⫾ 0.0004
0.0027 ⫾ 0.0007
0.0033 ⫾ 0.0008
0.0024 ⫾ 0.0007
0.0034 ⫾ 0.0008
0.0066 ⫾ 0.0013
0.0028 ⫾ 0.0011
0.0319 ⫾ 0.0037
0.0065 ⫾ 0.0020
0.0347 ⫾ 0.0041
0.0405 ⫾ 0.0042
0.0203 ⫾ 0.0035
0.0058 ⫾ 0.0014

No. of sites ( bp)c
1669
1546
1676
1704
1574
1667
1530
1661
1541
1537
1423
1601
1715

a

The numbers in parentheses show the sequences retrieved from the DDBJ/EMBL/GenBank database.

bStandard error (S.E.) was calculated by the bootstrap method of MEGA2.

c

Number of nucleotide sites compared.

Table 4A. Variant sites of the Bornean orangutan

used for comparison: D38115 determinedby Horai et al. (1995) for a Bornean orangutan (P. p. pygmaeus) and X97707 determined by Xu and Arnason (1996) for a
Sumatran orangutan (Pongo p. abelii). Sequences for ora#001, ora#002, ora#003,
ora#004, ora#006, ora#007, ora#014, andora#015 determined in the present study
were closely related with the Bornean
orangutan sequence, while those for
Table 4B. Variant sites of the Sumatran orangutan

ora#005, ora#008, ora#009, ora#010,
ora#011, ora#012, ora#013, and ora#016
were similar to the Sumatran orangutan.
These sequence features were compatible
with the source of the individuals.
The nucleotide difference between
these two groups is substantial. There are
54 nucleotide differences in the 1.7 kb region that contains the complete 16S rRNA
gene. We therefore concluded that those

Figure 3. Phylogenetic networks of the mtDNA 16SrRNA gene region for (A) Sumatran orangutan and (B)Bornean orangutan. Numbers designate individuals ofTable 4. D and X designate sequences determined by
Horai et al. (1995) and Xu and Arnason (1996), respectively. Edge lengths are proportional to the number ofnucleotide differences. Arrows indicate the edges inwhich roots are probably located.

two sequence groups belong to two subspecies of orangutan. These two groups ofsequences were multiply aligned, as
shown in Table 4. Phylogenetic networks
for each subspecies were constructedbased on the multiply aligned sequence
data ( Figure 3). Both networks turned out
to be unrooted trees because of no reticulation. We also constructed a phylogenetic tree for the two orangutan subspecies ( Figure 4). As expected, individuals
belonging to the two subspecies formed
clear monophyletic groups, separated bya branch with 100% bootstrap probability.
Nucleotide diversities within subspecies
are 0.0034 ⫾ 0.0008 and 0.0066 ⫾ 0.0013
for Bornean and Sumatran orangutans, respectively (see Table 3). Therefore Sumatran orangutan was shown to have about
two times higher mtDNA diversity than
Bornean orangutan. It is interesting tonote that nucleotide diversities for those
two subspecies are greater than those for
African great apes and for human, even if
we treated the two subspecies separately.
Gibbons
We determined the mtDNA 16S rRNA sequences for 22 individuals of gibbons. Because the number of individuals examined
was small for most of the species (see Table 1), we present variant sites only for

Noda et al • Hominoid mtDNA 16S rRNA Diversity 493

Table 5. Variant sites of siamang (Hylobates
syndactylus)
Sequence

Site position
11111
11122346688911257
1289905075612369082
1234783951978447868069703

Consensus
H. syndactylus#1
H. syndactylus#2
H. syndactylus#3
H. syndactylus#4
H. syndactylus#5

Figure 4. Phylogenetic tree of the mtDNA 16S rRNA gene region for Sumatran and Bornean orangutan. The tree
was rooted by using the midpoint rooting.

siamangs ( Table 5). Figure 5 shows thephylogenetic network for those five siamang sequences. We observed one pair ofincompatible configurations: one for site1199 and the other for sites 191 and 668.
This is why there is one rectangle.
Figure 6 shows the phylogenetic tree ofthe 22 gibbon sequences and a Hylobates
lar sequence determined by Xu and Arnason (1996; DDBJ/EMBL/GenBank accession number X99256). The root was determined by the outgroup sequences( human, chimpanzee, bonobo, gorilla, andorangutan). We covered three subgeneraof gibbons in this study (see Table 1), andthe subgenus Symphalangus made a clear
monophyletic cluster. Subgenus Hylobates
also formed a monophyletic group, except
for one individual (no. 3) of H. pileatus.
This H. pileatus individual was very close
to a H. concolor individual (see Figure 6).
Because H. concolor belongs to the subgenus Nomascus (Gloves 1997), this clustering was unexpected. This kind of species intermingling was also observed
within the subgenus Hylobates. H. agilis individual no. 1 clustered with H. klossi no.
2, while H. agilis no. 3 clustered with two
H. muelleri individuals. H. klossi also
showed nonmonophyly.
We therefore estimated net nucleotide
substitutions or evolutionary distance between species by subtracting within-species variation ( Nei 1987). UPGMA wasused for reconstructing the species phylogeny. This is because the branch lengthsof a species tree should be proportional
to evolutionary time. Figure 7A shows a
UPGMA tree for eight gibbon species. Because one individual of H. pileatus clustered with a H. concolor individual in thephylogenetic tree of mtDNA genes (see494 The Journal of Heredity 2001:92(6)Figure 6), we also constructed a UPGMA
tree after eliminating this H. pileatus individual (tree in Figure 7B). Only the position of H. pileatus differs between the twotrees.

Discussion
Higher Nucleotide Diversity of Apes
Than Human
All the ape species used in the present
study, except for H. concolor in which only
one individual sample was available,
showed higher nucleotide diversity thanfor human. Although a limited number ofindividuals were used in the present
study, this finding is consistent with thatof previous studies for mtDNA (e.g., Gagneux et al. 1999; Goldberg and Ruvolo
1997; Wise et al. 1997). This tendency toward higher nucleotide diversity in apes
than human was also observed for nuclear
DNA ( Kaessmann et al. 1999; Kitano et al.
2000; Sumiyama et al. 2000). This is indirect support for the recent expansion
model on modern humans. We compared
the same set of 53 human individuals forthe whole D-loop region of mtDNA ofabout 1.1 kb using Ingman et al.’s (2001)
data. Nucleotide diversity for the control
region was estimated to be 0.0158 ⫾0.0017, which is 10 times higher than that
(0.0016 ⫾ 0.0004) for the 16S rRNA region.
Because the same set of individuals wasused for these two computations, thesource of the difference comes from thatof the evolutionary rate. If we assume thatthe same relationship holds for ape
mtDNA sequence evolution, mtDNA D-loop
diversity values for our sample are expected to be about 10 times those shownin Table 3.

GTTATAATTCCCTAAATACTAATTA****..GC....CG.G..TCG....
GTTA......TT....C........
***...GC.........GT....C.
TA...C..CT.T..G......GC.G*.ATC.....TT....C....G...

Relationship of Bornean and SumatranOrangutan
The two orangutan subspecies (Pongo pygmaeus pygmaeus and P. p. abelii) differ cytogenetically by a pericentric inversion inchromosome 2, a specific inversion inchromosome Y, and Sumatran Y carries adistally located nuclear organizing region
that is absent in Bornean orangutan, butthey interbreed in captivity and produce
fertile offspring ( Xu and Arnason 1996).
Genetic differences between and within
Bornean and Sumatran orangutans havebeen studied by various authors. Zhi et al.
(1996) examined mtDNA restriction fragment length polymorphisms (RFLPs), partial sequences of the 16S rRNA gene, andnuclear minisatellite polymorphism. Bornean orangutan (and P. p. pygmaeus) clearly separated from Sumatran orangutan (P.
p. abelii) in the mtDNA gene genealogy.
This dichotomous pattern was also observed by Warren et al. (2000), who used
mtDNA control region sequences. We also
observed two distinct lineages in orangutan ( Figure 4). However, Muir et al. (2000)
presented a somewhat different pictureusing NADH dehydrogenase subunit 3 andcytochrome b gene sequences. Bornean

Figure 5. Phylogenetic networks of the mtDNA 16SrRNA gene region for H. syndactylus (siamang). Edge
lengths are proportional to the number of nucleotide
differences. Arrows indicate the edges in which roots
are probably located.

(2000); nucleotide diversity (0.0066 ⫾0.0013) for Sumatran orangutan was about
twice as high as that (0.0034 ⫾ 0.0008) for
Bornean orangutan. Zhi et al. (1996) estimated nucleotide diversity based on their
mtDNA RFLP data, and Sumatran orangutan showed more than five times higher
diversity (0.0175) than Bornean orangutan(0.0033). However, their mtDNA 16S rRNA
sequence data seem to show higher variation for Bornean orangutan than Sumatran orangutan. A slightly higher heterozygosity was observed for Bornean
orangutan from DNA fingerprint data ( Zhi
et al. 1996).

Figure 6. Phylogenetic tree of the mtDNA 16S rRNA gene region for gibbons.

haplotypes formed a compact cluster,while Sumatran haplotypes showed muchlarger heterogeneity, and the root of theorangutan gene tree is within the Sumatran group ( Figure 4 of Muir et al. 2000).
Because sampled individuals differ fromstudy to study, in the future it may be necessary to study more individuals as wellas nuclear sequence data to clarify the relationship between Bornean and Sumatranorangutans.

The same problem applies to withinsubspecies sequence variation. Warren etal. (2001) studied many Bornean orangutan individuals and found a considerable
amount of mtDNA variation in Bornean
orangutan. On the other hand, Muir et al.
(2000) found much greater genetic variation among Sumatran orangutan than Bornean orangutan. Our present results areintermediate between the results of Warren et al. (2000) and those of Muir et al.

Figure 7. Phylogenetic tree of the eight gibbon species. UPGMA was used. (A) When all three H. pileatus individuals were included. (B) When H. pileatus no. 3 which was closely related to H. concolor was eliminated fromthe comparison.

Phylogenetic Relationship of Gibbon
Species
Hayashi et al. (1995) used a single individual for six gibbon species and estimatedthe phylogenetic tree of those gibbon species. The five species of subgenus Hylobates (H. lar, H. klossii, H. agilis, H. moloch,and H. pileatus) formed a clear monophyletic cluster in their tree. We also observed a clear clustering of the Hylobates
species subgenus, except for one individual of H. pileatus ( Figure 6). However, therelationship within this subgenus is unclear. H. lar and H. klossii formed a monophyletic group with 100 bootstrap probability in Hayashi et al. (1995). Two
individuals of H. klossii clustered with H.
lar in our results, but one H. klossii individual clustered with two H. agilis individuals ( Figure 6). There are several competing hypotheses on the phylogenetic
relationship of species within subgenus
Hylobates (Geissmann 1995). Because
these gibbon species are closely related,hybridization is possible, and this may be
the source of incongruent phylogenetic relationships, depending on the individuals
used from the same species. Anotherproblem is species identification. It is not
so easy to identify gibbon species (Geissmann 1995).
It is known that a mating of siamang andcommon gibbon produced a viable offspring (Myers and Shafer 1979). Therefore
there is a possibility of introgression, evenbetween subgenera. However, a close similarity between one individual of H. pileatus and H. concolor is problematic, for thegeographic distributions of H. concolorand H. pileatus does not overlap (Geissmann 1995). Further study will be necessary on this matter.
The phylogenetic relationship of thesubgenera of Hylobatidae is also not yet
established. H. concolor of Nomascus was
located as basal in Hayashi et al. (1995),

Noda et al • Hominoid mtDNA 16S rRNA Diversity 495

and H. gabriellae and H. leucogenys, bothbelonging to subgenus Nomascus, werealso basal in Roos and Geissmann (2001).
However, our gene tree for gibbons ( Figure 6) showed that H. syndactylus, belonging to subgenus Symphalangus, was basal.
Because of the shorter branch lengths for
the H. syndactylus lineage, H. concolor became basal in the species tree estimatedby using UPGMA ( Figure 7). More sequence data from nuclear DNA as well as
mtDNA are necessary to clarify this higher
order phylogenetic relationship of gibbons.

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Corresponding Editor: Oliver A. Ryder

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