Son Truong Nguyen

Molecular phylogenetic analysis of nuclear genes suggests a Cenozoic over-water dispersal origin for the Cuban solenodon

The Cuban solenodon (Solenodon cubanus) is one of the most enigmatic mammals and is an extremely rare species with a distribution limited to a small part of the island of Cuba. Despite its rarity, in 2012 seven individuals of S. cubanus were captured and sampled successfully for DNA analysis, providing new insights into the evolutionary origin of this species and into the origins of the Caribbean fauna, which remain controversial. We conducted molecular phylogenetic analyses of five nuclear genes (Apob, Atp7a, Bdnf, Brca1 and Rag1; total, 4,602 bp) from 35 species of the mammalian order Eulipotyphla. Based on Bayesian relaxed molecular clock analyses, the family Solenodontidae diverged from other eulipotyphlan in the Paleocene, after the bolide impact on the Yucatan Peninsula, and S. cubanus diverged from the Hispaniolan solenodon (S. paradoxus) in the Early Pliocene. The strikingly recent divergence time estimates suggest that S. cubanus and its ancestral lineage originated via over-water dispersal rather than vicariance events, as had previously been hypothesised.

Phylogenetic position of Callosciurus erythraeus griseimanus from Vietnam in the genus Callosciurus

Callosciurus squirrels are widely distributed in Southeast Asia, eastern parts of South Asia, and southern parts of East Asia (Wilson and Reeder 2005). In this genus, there are 15 species; each species has many geographical forms (Corbet and Hill 1992; Wilson and Reeder 2005). Especially, at present, the Pallas’s squirrel (Callosciurus erythraeus) has 25 subspecies (atrodorsalis, bartoni, bhutanensis, bonhotei, castaneoventris, erythrogaster, flavimanus, gloveri, gordoni, griseimanus, harringtonii, hendeei, hyperythrus, intermedius, michianus, ningpoensis, pranis, rubeculus, shanicus, siamensis, sladeni, styani, thai, thaiwanensis, and zimmeensis) (Wilson and Reeder 2005). These many geographical forms clearly make sub-specific classification of C. erythraeus complicated (e.g., Lekagul and McNeely 1988). Of these subspecies, 18 (atrodorsalis, bonhotei, castaneoventris, flavimanus, gloveri, gordoni, griseimanus, hendeei, michianus, ningpoensis, pranis, rubeculus, shanicus, siamensis, styani, thai, thaiwanensis, and zimmeensis) were previously assigned to a distinct species, the bellybanded squirrel C. flavimanus (Ellerman and MorrisonScott 1951; Moore and Tate 1965). Corbet and Hill (1992), however, regarded C. flavimanus as a subspecies of C. erythraeus (i.e., C. erythraeus flavimanus) and assigned all C. flavimanus subspecies to C. erythraeus. At present, this taxonomic status is generally accepted (Wilson and Reeder 2005). Debates on subspecific classification of C. erythraeus have been based on morphological characteristics, such as skull shapes and pelage patterns, but not on any other systematic characteristics, such as molecular and cytogenetic data. To provide additional evidence for resolving the taxonomic and systematic status of C. erythraeus subspecies, we examined the phylogenetic position of C. erythraeus griseimanus among Callosciurus squirrel species by using mitochondrial (mt) cytochrome b gene sequences. Callosciurus erythraeus griseimanus is found in only the southeastern parts of the Indochina Peninsula. Judging from its restricted distribution pattern, this subspecies may be genetically distinct from other C. erythraeus subspecies and other Callosciurus species. We discuss here where we place this squirrel in the phylogeny of Callosciurus.

Phylogenetics of Petaurista in Light of Specimens Collected from Northern Vietnam

The southern part of China and northern part of Indochina Peninsula is one of the hot-spots of biodiversity (e.g., Cincotta et al. 2000; Cox and Moore 2005). In this area, there are many endemic mammalian species, such as giant panda Ailuropoda melanoleuca, saola Pseudoryx nghetinhensis, Tonkin snub-nosed monkey Rhinopithecus avunculus, Inornate squirrel Callosciurus inornatus, black-eared red-backed vole Eothenomys olitor, and Yunnan hare Lepus comus (e.g., Wilson and Reeder 2005). Meijaard and Groves (2006) also found high mammalian diversity in the east side of the Mekong River including this area. Therefore, this area would be very important for the speciation and diversity of mammals in Asia. Giant flying squirrels (genus Petaurista) are widely distributed throughout South and Southeast Asia and in southern China, Taiwan, and Japan (Corbet and Hill 1992; Wilson and Reeder 2005). At present, they are split into eight species: P. alborufus, P. elegans, P. leucogenys, P. magnificus, P. nobilis, P. petaurista, P. philippensis, and P. xanthotis (Wilson and Reeder 2005). In each species, many variations and synonyms are reported (e.g., Ellerman and Morrison-Scott 1951; Corbet and Hill 1992; Wilson and Reeder 2005). In the southern China and northern Indochina Peninsula, three giant flying squirrel species (P. alborufus, P. petaurista, and P. philippensis) are commonly found (Lekagul and McNeely 1988; Corbet and Hill 1992). Based on genetic variations and morphological characteristics, in southern China, Yu et al. (2006) recognized as distinct two additional species (P. hainana from Hainan Island and P. yunanensis from Yunnan), although these species had been classified as P. philippensis by Wilson and Reeder (2005). Thus, this area may also be a biodiversity hotspot for Petaurista species. Based on molecular data, Oshida et al. (2004a) proposed that Petaurista might have some geographical evolutionary units or groups. Southern China and the northern Indochina Peninsula may be the source of one geographical evolutionary unit of Petaurista. To explore this conjecture further, we examined the phylogenetic position of two Petaurista species collected from northern Vietnam, the Indian giant flying squirrel (P. philippensis) and the spotted giant flying squirrel (P. elegans). These two forms were phylogenetically compared with those from southern China and the island of Sumatra. Here, we discuss the phylogenetic relationships of P. philippensis and P. elegans.

Mitochondrial DNA Evidence Reveals Genetic Difference between Perny's Long-Nosed Squirrels in Taiwan and Asian Mainland

Abstract. Taiwan Island is thought to have formed around 6.0 million years ago, but, the formation of a ‘proto-Taiwan’ began around 9.0 million years ago. During the late Miocene, the proto-Taiwan is thought to have been a part of the Asian mainland. During the Pleistocene, Taiwan Island was again occasionally connected with the Asian mainland. Several mammal species migrated from the Asian mainland to Taiwan during Pleistocene glacial periods. Despite the connections between Taiwan and the Asian mainland, Taiwan has some endemic mammal species. Recent genetic evidence suggests that arboreal squirrels (Petaurista alborufus, P. philippensis, Belomys pearsonii, and Tamiops maritimus) adapted to Taiwans mountainous forests are endemic species. Since these squirrels may have similarly evolved from separate ancestral stock in Taiwan, we investigated the phylogenetic relationship of Pernys long-nosed squirrel (Dremomys pernyi) from Taiwan and the Asian mainland by using mitochondrial cytochrome b gene sequences. The Taiwanese form was distantly related to the mainland form, showing deep genetic difference (10.18–10.88%). Therefore, D. pernyi could include at least two distinct species, with the Taiwanese form being a species endemic to Taiwan.

A morphological analysis of the skull size and shape of Kerivoulinae (Chiroptera: Vespertilionidae) from Vietnam.

Southeast Asia is a region of high biodiversity, containing species of plants and animals that are yet to be discovered. In this region, bats of the subfamily Kerivoulinae are widespread and diverse with six species recorded in Vietnam. However, the taxonomy of the Kerivoulinae in Asia is complicated. In our study, we used diagnostic characters and multivariate analysis to determine morphological differences between the genera Kerivoula and Phoniscus. We showed that the two genera are distinguishable by the size of second upper incisors, the shape of skull, nasal sinus, canines, second upper and lower premolars. In addition, the two genera can be osteometrically separated by measurements of the braincase height, interorbital width and shape of anterior palatal emargination. Our data clearly revealed the morphological variations in the skull shape of Kerivoula hardwickii in Vietnam. This suggests a possible separation into three morphotypes, representing cryptic species supported by statistical differences with wide variation in skull shape, size and teeth. These results demonstrated Kerivoula hardwickii can be separated three subspecies, and the result will serve as the basis for the future assessment and classification of this group in Southeast Asia.

Mitochondrial DNA Evidence Suggests Challenge to the Conspecific Status of the Hairy-Footed Flying Squirrel Belomys pearsonii from Taiwan and Vietnam

Tatsuo Oshida1,*, Liang-Kong Lin2, Shih-Wei Chang3, Can Ngoc Dang4, Son Truong Nguyen4, Nghia Xuan Nguyen4, Dang Xuan Nguyen4, Hideki Endo5, Junpei Kimura6, Motoki Sasaki7, Akiko Hayashida8 and Ai Takano9 1 Laboratory of Wildlife Biology, Obihiro University of Agriculture and Veterinary Medicine, Obihiro 080-8555, Japan 2 Laboratory of Wildlife Ecology, Department of Life Science, Tunghai University, Taichung 407, Taiwan, R.O.C. 3 Division of Zoology, Taiwan Endemic Species Research Institute, Chichi 552, Taiwan, R.O.C. 4 Institute of Ecology and Biological Resources, Vietnam Academy of Sciences and Technology, Hanoi, Vietnam 5 The University Museum, The University of Tokyo, Tokyo 113-0033, Japan 6 College of Veterinary Medicine, Seoul National University, Seoul 151-742, Korea 7 Laboratory of Veterinary Anatomy, Obihiro University of Agriculture and Veterinary Medicine, Obihiro 080-8555, Japan 8 Nasu Animal Kingdom, Nasu 329-3223, Japan 9 Laboratory of Epidemiology, Department of Veterinary Medicine, Joint Faculty of Veterinary Medicine, Yamaguchi University, Yamaguchi 753-8515, Japan

Comparison of Jaw Muscle Morphology in Two Sympatic Callosciurine Squirrels (Callosciurus Erythraeus and Dremomys Rufigenis) in Vietnam

Laboratory of Anatomy, Department of Basic Veterinary Sciences, Obihiro University of Agriculture and Veterinary Medicine, Obihiro 080-8555, JapanIn this study, we focus on the jaw muscle morphol-ogy of two callosciurine squirrel species, Callosciuruserythraeus and Dremomys rufigenis. Callosciuruserythraeus (Callosciurini: Sciuridae: Callosciurinae) isan arboreal squirrel that inhabits Southeast Asia fromeastern India to the Malayan archipelago, Indochina,southern China, and Taiwan (Nowak 1999; Can et al.2008; Francis 2008; Smith and Xie 2008). D. rufigenis,another member of the tribe Callosciurini, is found sym-patrically with C. erythraeus throughout Southeast Asia(Nowak 1999; Can et al. 2008; Francis 2008; Smith andXie 2008). Koyabu et al. (2009) previously reported thatthe sympatric C. erythraeus and D. rufigenis displaynotable difference in craniodental mechanics. Both C.erythraeus and D. rufigenis are known to prefer fruitsand insects, as generally seen in other tree squirrels.However, C. erythraeus also feeds extensively on hardseeds and tough tree bark, which are rarely included inthe diet of D. rufigenis. For example, C. erythraeus isreported to frequently forage on the hard seeds ofPinus, Camellia, and Castanopsis tree (Chou et al.1985; Sonoda et al. 2001; Lu 2003; Men et al. 2007).Callosciurus erythraeus is also known to often strip toughbark to obtain sugar from sweet tree saps (Tamura andOhara 2005), whereas this dietary behavior seems to berare or not reported in D. rufigenis (Medway 1969;Nowak 1999; Smith and Xie 2008). Koyabu et al.(2009) demonstrated that C. erythraeus possesses agreater mechanical advantage of the masseter and tem-poralis muscles for chewing compared to D. rufigenis.Callosciurus erythraeus was also found to display greaterleverage of the masseter and temporalis for incision.Given these findings, it was suggested that C. erythraeusshould be capable of generating greater bite force for agiven muscle force at the cheek teeth and that the cranio-dental divergence between C. erythraeus and D. rufigenismay facilitate their trophic separation under sympatry.In their study, however, only the analysis of mechani-cal leverages was conducted, and comparisons of jawmuscle morphology were not incorporated. Althoughthe craniodental arrangements and mechanical advantageof the masticatory muscles are critical parameters thataffect the amount of force production, muscle mass isalso another essential contributor to the bite forces ananimal can generate (Raadsheer 1999). Since the biteforces an organism can generate should constrain therange of food items it can eat (Lucas 2004), variation inmasticatory muscle mass has undoubtedly been funda-mental for the dietary diversification of rodents. Giventhe great range of diet and phenomenal level of morpho-logical diversity found across rodents, studies on rodentmuscle mass variation should provide promising avenuesto study the ecomorphological patterns of mammals ingeneral. To date, reports on muscle mass are availablefor some muroids (e.g., Hiiemae and Houston 1971;Weijs and Dantuma 1975; Satoh 1997; Satoh and Iwaku2004) and New World squirrels (Ball and Roth 1995).Although Thorington and Darrow (1996) provideddetailed anatomical descriptions of jaw muscles for someOld World squirrel species, still very little is describedquantitatively for them. Here, to bridge the gaps in ourknowledge of Old World squirrel muscle morphology

Macroscopic and CT Examinations of the Mastication Mechanism in the Southern Tamandua

Abstract. The mastication system of the southern tamandua (Tamandua tetradactyla) was examined by means of gross anatomy and three dimensional image analysis. Three-dimensional computed tomography image analysis revealed that the mandibles medio-laterally rotated during the mastication. The temporal muscle dorso-medially pull the dorsal part of the mandubular bones, and the masseter muscle latero-rostrally operates the ventro-lateral part of the mandibles. The two muscles may contribute to the opening of the mandibles to enlarge the oral cavity and to house the contractile tongue. In contrast the medial and lateral pterygoid muscles may act as a closer of the mandible to medially pulling the ventro-medial part of the mandibles. The extraordinarily specialized mastication mechanism is functionally similar to that of the giant anteater. Although the muscles of the giant anteater show a more complicated structure in the temporal and masseter muscles than those of the southern tamandua, the weight distribution rate of mastication muscles is not so different between the two species. We suggest that the morphological design of the elongated skull and the derived feeding mastication are common in both species, and that the distribution pattern of the muscle weight has not drastically changed within the evolutionary history in Vermilingua and Myrmecophagidae.

Intraspecific phylogeny of the house shrews, Suncus murinus-S. montanus species complex, based on the mitochondrial cytochrome b gene

Abstract. A phylogenetic tree was reconstructed based on the mitochondrial cytochrome b gene nucleotide sequences of 169 individuals of house shrews (Suncus murinus and S. montanus) from 44 localities in East Asia, Southeast Asia, West Asia, and islands in the western Indian Ocean. Shrews from China (Zhejiang), Japan (Okinawa), Vietnam, and Indonesia (Java) formed a monophyletic group with less genetic variation. Therefore, the shrews of these regions appeared to have originated from one or a few localities. Contrary to this, shrews from Sri Lanka, Myanmar, and Pakistan consisted of several haplogroups. This finding suggests immigration movements to these areas. Fascinating findings were also obtained concerning the islands in the western Indian Ocean. First, shrews on Zanzibar Island (Tanzania) had almost the same haplotype as those in southwestern Iran. Therefore, the house shrew in Zanzibar may have immigrated from Iran (or vice versa). Second, shrews from Madagascar and Grande Comore Island shared the same haplotype, whereas the shrews on Réunion Island were clearly different from those of Madagascar and Comoros. Thus, there appears to have been several immigration routes to the islands of the western Indian Ocean.