Biomedical Engineering Reference
In-Depth Information
many small nearby islands, including the three southern-
most Nicobar Islands (
Fooden, 1995
).
In Indochina, male rhesus macaques have interbred with
female longtail macaques. Their male offspring exhibit the
Y-chromosome but not the mitochondrial DNA haplotypes
typical of rhesus macaques (
Tosi et al., 2002
) for an
unknown, but significant, length of time after the diver-
gence of these two species from each other. This admixture
resulted in the introgression of rhesus macaque genes into
the mainland longtail macaque genome (
Tosi et al., 2002;
Kanthaswamy et al, 2008a; Stevison and Kohn, 2008, 2009;
Bonhomme et al., 2009
). Because few Indochinese rhesus
macaques have been extensively studied, the extent of
longtail macaque genes into rhesus macaques is uncertain.
In contrast to this instance of introgressive hybridiza-
tion, portions of the geographical range of longtail
macaques in insular Southeast Asia have been isolated by
marine barriers from other portions for extended periods of
time during the Pleistocene as well as post-glacially
(
Heany, 1986; Abegg and Thierry, 2002; Woodruff, 2003
),
fostering the potential for genetic subdivision. Notwith-
standing evidence for inter-species hybridization and
differential levels of isolation that must have led to different
levels of genetic similarity and difference among pop-
ulations of longtail macaques, little consideration is given
to the country or geographical region of origin of longtail
macaques chosen as animal models for the study of specific
human diseases, and only recently have the relative levels
of genetic differentiation among regional populations of
rhesus macaques and longtail macaques been systemati-
cally studied (
Smith et al., 2006, 2007; Kanthaswamy et al.,
2008a; Satkoski et al., 2008a; Bonhomme et al., 2009
).
of M. fascicularis throughout the Pleistocene also affected
the distribution of southern pigtailed macaques.
The northern pigtail macaques (M. leonina) inhabit
peninsular Thailand, Burma, and Indochina as well as
Bangladesh, India, and Southern China. The ranges of the
two different species of pigtail macaques are separated at
the Khlong Marai Fault on the Thai-Malay peninsula that
experienced a marine transgression after about 180 000 ybp
(
Rosenblum et al., 1997
). Thus, the two species have been
separated from each other approximately as long, and are
probably as genetically different from each other, as Indian
and Chinese rhesus macaques whose divergence
Hernandez
et al. (2007)
date to approximately 160 000 ybp. Interest-
ingly, this same biogeographical barrier differentiates
longtail macaques with the rhesus and Insular Southeast
Asian longtail forms of the Y-chromosome that suggests
introgression of the rhesus Y-chromosome into Indochinese
longtail macaques through inter-species hybridization (
Tosi
et al., 2002
). Thus, the same, or temporally related and
contiguous, event(s) that resulted in the divergence between
these two species of pigtail macaques might also have been
responsible for divergence of the Indian and Chinese rhesus
macaques and the introgression of Chinese, but not Indian
rhesus macaque, genes
into longtail macaques
in
Indochina.
As for longtail macaques, the eastern boundary of
southern pigtail macaques is discretely separated from that
of the Sulawesi macaques to their southeast by Wallace's
Line (
Evans et al., 1999
). Given the broad and disjoint
geographical distribution of members of the silenus group
of macaque species, southern pigtail macaques are likely to
exhibit at least as great genetic differentiation among
regional populations as longtail macaques. However, if the
ancestry of most pigtail macaques bred domestically in the
USA can be traced to southern Sumatra, as alleged, genetic
subdivision among regional populations of this species bred
in captivity in the USA should not be nearly as great
a concern as it is for rhesus and longtail macaques, captive
populations of which have very diverse origins.
Pigtail Macaques
Pigtail macaques (M. nemestrina) are more distant from
both rhesus and longtail macaques than the latter two
species are from each other. Though no longer extant in
Java, the oldest fossil evidence of the species pre-dates the
earliest evidence of M. fascicularis in Java (
Aimi, 1981
)
and the species, partly due to the disjunct geographical
distribution of the silenus group of macaque species, is
believed to have diversified prior to the diversification of
longtail macaques (
Karanth, 2003
). The species is believed
to naturally hybridize, albeit not widely, with its close
macaque relative, M. leonina, the northern pigtail macaque
(
Groves, 2001
), and likely shares a relatively large
proportion of its genome with rhesus and longtail macaques
due to the descent of these species from a nemestrina-like
ancestor. Because the natural habitat of the southern pigtail
macaque includes much of the range of M. fascicularis
(Indonesia (except Java), Malaysia, and Thailand), the
same geographical barriers that influenced the distribution
Bonnet Macaques
The geographical range of the bonnet macaque (M. radi-
ata), limited to the southern half of the Indian subcontinent,
is much more restricted than that of the three macaque
species discussed above, but includes a broad array of
microclimates, including evergreen and wet deciduous
forests up to elevations of 2000 meters. The northern range
of the species is constrained by that of M. mulatta, although
mixed-species groups and presumed inter-species admix-
ture have been reported near the boundary between the two
species. To their south, bonnet macaques range interspersed
with liontail macaques (M. silenus) with which they are not
reported to hybridize (note that the bonnet macaque and the
