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Wall J.D.,University of California at San Francisco | Kim S.K.,University of California at San Francisco | Luca F.,University of Chicago | Carbone L.,Oregon Health And Science University | And 3 more authors.

We sequenced reduced representation libraries by means of Illumina technology to generate over 1.5 Mb of orthologous sequence from a representative of each of the four extant gibbon genera (Nomascus, Hylobates, Symphalangus, and Hoolock). We used these data to assess the evolutionary relationships between the genera by evaluating the likelihoods of all possible bifurcating trees involving the four taxa. Our analyses provide weak support for a tree with Nomascus and Hylobates as sister taxa and with Hoolock and Symphalangus as sister taxa, though bootstrap resampling suggests that other phylogenetic scenarios are also possible. This uncertainty is due to short internal branch lengths and extensive incomplete lineage sorting across taxa. The true phylogenetic relationships among gibbon genera will likely require a more extensive whole-genome sequence analysis. © 2013 Wall et al. Source

Zihlman A.L.,University of California at Santa Cruz | Mootnick A.R.,Gibbon Conservation Center | Underwood C.E.,University of California at Santa Cruz
International Journal of Primatology

Compared with the great apes, the small-bodied hylobatids were treated historically as a relatively uniform group with 2 genera, Hylobates and the larger-bodied Symphalangus. Four genera are now recognized, each with a different chromosome number: Hoolock (hoolock) (38), Hylobates (44), Nomascus (crested gibbon) (52), and Symphalangus (siamang) (50). Previous morphological studies based on relative bone lengths, e. g., intermembral indices; molar tooth sizes; and body masses did not distinguish the 4 genera from each other. We applied quantitative anatomical methods to test the hypothesis that each genus can be differentiated from the others using the relative distribution of body mass to the forelimbs and hind limbs. Based on dissections of 13 hylobatids from captive facilities, our findings demonstrate that each of the 4 genera has a distinct pattern of body mass distribution. For example, the adult Hoolock has limb proportions of nearly equal mass, a pattern that differentiates it from species in the genus Hylobates, e. g., H. lar (lar gibbon), H. moloch (Javan gibbon), H. pileatus (pileated gibbon), Nomascus, and Symphalangus. Hylobates is distinct in having heavy hind limbs. Although Symphalangus has been treated as a scaled up version of Hylobates, its forelimb exceeds its hind limb mass, an unusual primate pattern otherwise found only in orangutans. This research provides new information on whole body anatomy and adds to the genetic, ecological, and behavioral evidence for clarifying the taxonomy of the hylobatids. The research also underscores the important contribution of studies on rare species in captivity. © 2011 The Author(s). Source

Mootnick A.R.,Gibbon Conservation Center | Cunningham C.,University of Abertay Dundee | Baker E.,Marshall University
American Journal of Primatology

Although there have been few studies of self-scratching in primates, some have reported distinct differences in whether hands or feet are used, and these variations seem to reflect the evolutionary history of the Order. Monkeys and prosimians use both hands and feet to self-scratch while African great apes use hands almost exclusively. Gibbons represent an evolutionary divergence between monkeys and great apes and incidental observations at the Gibbon Conservation Center pointed to a difference in self-scratching among the four extant gibbon genera (Hoolock, Nomascus, Symphalangus, and Hylobates). To validate and further explore these preliminary observations, we collected systematic data on self-scratching from 32 gibbons, including nine species and all four genera. To supplement gibbon data, we also collected self-scratching information from 18 great apes (four species), five prosimians (two species), 26 New World Monkeys (nine species) and 20 Old World Monkeys (seven species). All monkeys and some prosimians used both hands and feet to self-scratch, whereas one prosimian species used only feet. All African great apes used hands exclusively (orangutans were an exception displaying occasional foot-use). This appears to represent a fundamental difference between monkeys and great apes in limb use. Interestingly, there was a clear difference in self-scratching between the four gibbon genera. Hylobates and Symphalangus self-scratched only with hands (like all African great apes), while Hoolock and Nomascus self-scratched with both hands and feet (like monkeys and prosimians). This difference in gibbon behavior may reflect the evolutionary history of gibbons as Hoolock and Nomascus are thought to have evolved before both Hylobates and Symphalangus. What evolutionary pressures led to this divergent pattern is currently opaque; however, this shift in limb preference may result from niche separation across the order facilitating differences in the behavioral repertoire associated with hind and forelimbs. © 2012 Wiley Periodicals, Inc.. Source

Kim S.K.,University of California at San Francisco | Carbone L.,Childrens Hospital Oakland Research Institute | Carbone L.,Oregon Health And Science University | Becquet C.,University of California at San Francisco | And 4 more authors.
Molecular Biology and Evolution

Gibbons are small, arboreal, highly endangered apes that are understudied compared with other hominoids. At present, there are four recognized genera and approximately 17 species, all likely to have diverged from each other within the last 5-6 My. Although the gibbon phylogeny has been investigated using various approaches (i.e., vocalization, morphology, mitochondrial DNA, karyotype, etc.), the precise taxonomic relationships are still highly debated. Here, we present the first survey of nuclear sequence variation within and between gibbon species with the goal of estimating basic population genetic parameters. We gathered ∼60 kb of sequence data from a panel of 19 gibbons representing nine species and all four genera. We observe high levels of nucleotide diversity within species, indicative of large historical population sizes. In addition, we find low levels of genetic differentiation between species within a genus comparable to what has been estimated for human populations. This is likely due to ongoing or episodic gene flow between species, and we estimate a migration rate between Nomascus leucogenys and N. gabriellae of roughly one migrant every two generations. Together, our findings suggest that gibbons have had a complex demographic history involving hybridization or mixing between diverged populations. © 2011 The Author Published by Oxford University Press on behalf of the Society for Molecular Biology and Evolution. All rights reserved. Source

Mootnick A.R.,Gibbon Conservation Center | Fan P.,Dali University
American Journal of Primatology

Crested gibbons (Nomascus) are in the rarest genus of the family Hylobatidae, with the Hainan gibbon (Nomascus hainanus) being the rarest primate in the world. In the past, the number of species in this genus has been at the center of much controversy, in part, because their color changes during immaturity as well as other factors, such as physical similarities in genitalia, creating difficulties in accurately determining the sex of individuals. Furthermore, owing to their rarity, illusiveness, and the rough terrain that comprises their native habitat, Nomascus is one of the least studied Hylobatidae. This article represents the most comprehensive dissemination of visual characteristics of the genus Nomascus to assist in the accurate identification of captive and wild crested gibbons. Through differences in pelage color, skeletal anatomy, dentition, vocalizations, behavior, distribution, and genetic studies, we are able to determine more accurately whether or not a subspecies should be elevated to species level. From the current data, there are six species and one subspecies in the genus Nomascus. However, reports of a recently identified light-cheeked gibbon (Nomascus sp.) in northeast Cambodia, Central Vietnam, and South Lao PDR, will add additional taxa to this genus. © 2010 Wiley-Liss, Inc. Source

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