Biomedical Engineering Reference
In-Depth Information
phylogenetic inferences are strongly influenced by the
specific regional populations of rhesus and longtail
macaques that are studied due in part to the high level of
paraphyly in the fascicularis group of macaque species.
In a study of the mtDNA of species of the fascicularis
group of macaque species (
Smith et al., 2007
), most Indian
rhesus sequences formed a single homogeneous cluster of
haplotypes (comprising haplogroup Ind1) with little
geographical structure (i.e. little evidence of natural genetic
subdivision). Samples from Burma together with about 5%
of those from India formed a separate cluster that were
called haplogroup Burm1/Ind2 and exhibited far greater
diversity and/or structure than sequences assigned to Ind1.
It was argued that the Indian rhesus that belong to the Ind2
subcluster of Burm1/Ind2 reflect an incursion of rhesus
macaques from Burma during post-Pleistocene times, fol-
lowed by admixture with the indigenous Indian rhesus
population. The recent discovery that rhesus macaques
from Bangladesh are also monomorphic for the Ind2
mtDNA haplogroup (
Hasan et al., 2010
) strengthens the
argument for a dispersal into India from the east leading to
admixture with Indian rhesus macaques. The haplotypes of
Indian and Chinese rhesus macaques were all reciprocally
monophyletic and those from eastern and western China
formed separate clusters. While Indian rhesus sequences
alleged to represent different subspecies were intermingled
in the tree and are not consistent with subspecific difference
based on morphology, those from China reflect some, but
not all, aspects of subspecific taxonomy based on
morphological differences including the differentiation
between rhesus macaques in eastern China and western
China (
Smith et al., 2007; Li et al., 2011
).
In a parallel study of the STR genotypes of these same
populations of longtail macaques (
Kanthaswamy et al.,
2008a
), insular longtail populations were found to be far
more genetically heterogeneous and differentiated from
each other than both mainland longtail or rhesus pop-
ulations, probably reflecting the effects of both isolation of
longtail macaques on islands and hybridization between
rhesus and longtail macaques in Indochina. Indonesian
longtails appeared as outliers to all other populations.
Unlike the mtDNA study, the Philippine longtail macaques
were more similar to, not more distant from, mainland
populations than any other population. As for mtDNA,
these results concur with those of
Kawamoto et al. (2008)
indicating that Mauritian longtail macaques are genetically
homogeneous and lack significant population structure.
Further studies of STR loci provide evidence of ancient
introgression of rhesus macaques into longtail macaques in
Indochina (
Kanthaswamy et al., 2008a; Bonhomme et al.,
2009; Stevison and Kohn, 2009
). As reported by
Tosi et al.
(2002)
, based on Y-chromosome data Chinese rhesus
macaques and Indochinese longtail macaques more closely
resemble each other
conspecifics in India and insular Southeast Asia, respec-
tively (
Kanthaswamy et al., 2008a
). This suggests that the
relatively high level of diversity in Indochinese longtail
macaques results in part from inter-species hybridization
with rhesus macaques and does not necessarily reflect
a longer antiquity of longtail macaques (or its origin) on the
mainland than in insular Southeast Asia, which might have
important implications for the use of Indochinese longtail
macaques in biomedical research.
Most of these results were confirmed in a recent study of
approximately 800 rhesus SNPs shared with only one of
five different populations of longtail macaques (Mauritius,
Philippines, Malaysia, Sumatra, and Vietnam). In that study
approximately 75% of these 800 rhesus SNPs were shared
with the Indochinese (Vietnam) population (Trask et al.,
personal communication). In addition, longtail macaques
from Indochina exhibited far greater genetic heterogeneity
than any other longtail macaque population, exceeding that
of either Indian or Chinese rhesus macaques, and, as sug-
gested by the STR analysis, Chinese rhesus macaques more
closely resembled Indochinese longtail macaques than their
own conspecifics, Indian rhesus macaques. The sometimes
contrasting results among the mtDNA, STR, and SNP
analysis underscore that caution should be exercised when
drawing inferences about population structure or evolu-
tionary history based on a single locus, only a few loci, or
a larger number of loci that are unrepresentative of the
genome.
Far less is known about the genetic characteristics
within and among populations of pigtail macaques. As the
geographical origin of many pigtail macaques in captivity
is not known with certainty, species identity (whether
M. nemestrina or M. leonitis) is not even certain without
documentation of geographical region of origin. However,
the northern and southern pigtail macaques were once, but
no longer, regarded as con-specifics (
Groves, 2001
) and
exhibit reciprocally monophyletic distributions of mtDNA
(
Rosenblum et al., 1997
). Early reports suggest that pigtail
macaques exhibit the B and O blood group phenotypes
(
Moor-Jankowski and Wiener, 1971
).
Nair et al. (2000)
reported genotypes of pigtail macaques said to have orig-
inated in Indonesia and Malaysia, and therefore members
of species M. nemestrina, for 19 STR loci previously shown
to be polymorphic in baboons. Despite the expected influ-
ence of ascertainment bias, all 19 loci studied proved to be
relatively highly polymorphic in pigtail macaques with an
average gene diversity and allele number of 0.76 and 9.2,
respectively.
Other studies have shown that pigtail macaques from
Borneo and Sumatra, both of which are included among
those bred for biomedical research in the USA, are genet-
ically different from each other and that the latter, alleged
to be the predominant source of pigtail macaques bred in
the USA, are more closely related to their sister species,
than either
resembles their own
