Central Indochina Research Articles

Taxonomic diversity of the Hipposideros larvatus species complex (Chiroptera: Hipposideridae) in mainland Asia

Hipposideros larvatus sensu lato constitutes a widespread species complex consisting of morphologically similar forms with a taxonomy that is in need of a revision. Here we present the results of a phylogenetic analysis of members of this species complex based on two mitochondrial (CytB and COI) and seven nuclear (ABHD11, ACOX2, COPS, RAG2, ROGDI2, SORBS2 and THY) genes, and a morphometric analysis. Morphological data, although showing certain diversity, does not allow an accurate delimitation of the taxonomic boundaries and occasionally contradict to genetic grouping. The molecular analyses based on mitochondrial data support the paraphyly of the H. larvatus species complex, with H. armiger recovered nested within. The nuclear data recovered all the lineages of H. larvatus sensu lato forming a monophyletic clade. Within it, apparently four different species-level clades could be revealed in Southeast Asia. One is distributed in northern Myanmar, southern China (including Hainan) and northern Vietnam, and also reaches into central Vietnam along the coast (Cham Islands). The valid name for this taxon must be H. poutensis Allen. The second clade is comprised by populations inhabiting the Malay Peninsula and the Sunda Islands, we identify this taxon as H. larvatus sensu stricto. The third taxon was identified only from southern Myanmar. The fourth taxon is distributed in southern and central Indochina. Its representatives were not related to any of the forms identified in Myanmar, and therefore, its previous identification with H. grandis sounds questionable. Since both the third and fourth taxa cannot now be unambiguously associated with a particular named form, we conventionally designate them as H. cf. grandis 1 and 2.

Aerosols over East and South Asia: Type Identification, Optical Properties, and Implications for Radiative Forcing

Identification of aerosol types has long been a difficult problem over East and South Asia due to various limitations. In this study, we use 2-dimensional (2-D) and multi-dimensional Mahalanobis distance (MD) clustering algorithms to identify aerosol characteristics based on the data from the Aerosol Robotic Network from March 1998 to February 2018 over the South and East Asian region (10°N~50°N, 70°E~135°E). The single scattering albedo (SSA), absorption Angstrom exponent (AAE), extinction Angstrom exponent (EAE), real index of refraction (RRI), and imaginary index of refraction (IRI) are utilized for classification of aerosols. Sub-regions with similar background conditions over East and South Asia are identified by hierarchical clustering algorithm to illustrate distinctive meteorological states in different areas. The East and South Asian aerosols are found to have distinct regional and seasonal features relating to the meteorological conditions, land cover, and industrial infrastructure. It is found that the proportions of dust aerosol are the highest in spring at the SACOL site and in summer at the sites near the Northern Indo-Gangetic Plain area. In spring, biomass-burning aerosols are dominant over the central Indo-China Peninsula area. The aerosol characteristics at coastal sites are also analyzed and compared with previous results. The 2-D clustering method is useful when limited aerosol parameters are available, but the results are highly dependent on the sets of parameters used for identification. Comparatively, the MD method, which considers multiple aerosol parameters, could provide more comprehensive classification of aerosol types. It is estimated that only about 50% of the data samples that are identifiable by the MD method could be classified by the 2-D methods, and a lot of undetermined data samples could be mis-classified by the 2-D methods. The aerosol radiative forcing (ARF) and the aerosol radiative forcing efficiency (ARFE) of various aerosol types at the top and the bottom of the atmosphere (TOA and BOA) are determined based on the MD aerosol classification. The dust aerosols are found to have the largest ARF at the TOA (−36 W/m2), followed by the urban/industrial aerosols and biomass-burning aerosols. The ARFE of biomass-burning aerosols at the BOA (−165 W/m2/AOD550nm) is the strongest among those of the other aerosol types. The comparison of the results by MD and 2-D methods shows that the differences in ARF and ARFE are generally within 10%. Our results indicate the importance of aerosol type classification in accurately attributing the radiative contributions of different aerosol components.

U - Pb geochronology and composition of zircon mineral from granodiorite in the G18 Gold mine, Quang Nam and its significance in regional tectonics

The Tam Ky - Phuoc Son suture zone (TPSZ) is located in central Indochina and is referred to as a amalgamation site between the Truong Son and Kon Tum terranes during the early Paleozoic. The amphibolite and ultramafic rocks within the region were considered as a part of the Tam Ky - Phuoc Son ophiolitic complex. In this study, the authors present results of the U - Pb dating and trace element composition of the zircon grains derived from a granodioritic sample collected in the G18 gold mine in Quang Nam province in order to clarify the timing of magma emplacement and tectonic setting. The U - Pb dating data indicates that the granodioritic rocks formed at 447,4±2,9 Ma while the U/Yb ratio is ̴1 (average: 1.32) and the Sc/Yb ratio is ̴ 1.04, high Hf content (Average Hf: 10937 ppm) and low Yb content (Average Yb: 308 ppm). These geochemical values are comparable with the zircon, which is formed in the continental magmatic arc. Combination with the pre - existing data allowed us to confirm the existence of two contrast magma members in the North Kontum massif: The Middle Cambrian island arc complex and the Middle Ordovician continental complex.

Migration Analysis of Sogatella furcifera (Hemiptera: Delphacidae) in the Northeastern Hunan Province in June.

The Sogatella furcifera (Horváth) is a notorious and destructive insect pest, targeting >4 million hectares of rice cultivated in the Hunan Province. To understand the immigration dynamics, we collected S. furcifera light trap catches from 2006 to 2012 at Niangxiang, Linxiang, and Hanshou. We conducted a migration analysis to estimate the immigration source for the northeastern Hunan Province in June. Moreover, we dissected the ovaries of S. furcifera to classify population characteristics. We found that the first appearance of S. furcifera occurred from late April to early May, with June as the primary time for migrations into the northeastern Hunan Province. The majority of June ovaries caught in light traps were Grade I and Grade II, whereas those collected in paddy fields were Grade III and Grade IV, suggesting that the majority of S. furcifera immigrated into the northeastern Hunan Province. Our analysis points toward the northern and central Indo China Peninsula, the southern Hunan Province, the Guangxi Zhuang Autonomous Region Province, the Guangdong Province, and the Hainan Province as possible immigration sources of S. furcifera in June for the northeastern Hunan Province. We propose terrain, loss of forward flow, and wind shear as causes for the difference observed in light trap catches between Ningxiang, Linxiang, and Hanshou monitoring stations in the June of 2009. Thus, our results suggest that monitoring and forecasting of S. furcifera should be done with particular emphasis in June.

Annual Fluctuations of Early Immigrant Populations ofSogatella furcifera(Hemiptera: Delphacidae) in Jiangxi Province, China

The white-backed planthopper, Sogatella furcifera (Horváth), is a destructive migratory pest in east and southeast Asia. Huge populations stemming from annual migrations by this insect have caused a series of devastating losses to rice production. There have been numerous early immigrations in five of the past 10 yr but few early immigrations in the others. The annual fluctuation in early immigration is evident, but the mechanism behind these annual fluctuations is unclear. This research aimed to determine the underlying causes for the annual fluctuations in early immigration. We used trajectory analysis to explore the source areas and investigated the meteorological conditions to determine the reason for the annual fluctuations. The results showed that 1) the source areas of S. furcifera are mainly located west of Guangdong and east of Guangxi; 2) the annual fluctuations of the immigrant population size is significantly correlated with the frequency of prevailing winds; and 3) early immigration is influenced by both winter and spring temperatures in the south central Indochina peninsula. These results indicated that an allopatric prediction and sustainable management of rice planthoppers would be difficult to implement within one country. International cooperation and information exchange about this pest between China and other countries in Southeast Asia should be implemented.

New data on recently described rodent species Paulina's Limestone Rat Saxatilomys paulinae Musser, Smith, Robinson & Lunde, 2005 (Mammalia: Rodentia).

BackgroundPaulina's Limestone Rat Saxatilomys paulinae Musser et al., 2005 was first discovered by Musser et al. (2005) based on specimens from the Khammouane Limestone National Biodiversity Conservation Area (NBCA) in Khammouane Province in central Lao People's Democratic Republic (PDR). This tower karst landscape is part of the Central Indochina Limestone massif, which extends eastward into north-central Vietnam in Quang Binh and Quang Tri Provinces.New informationIn April 2014, we conducted a rodent survey and collected four (4) whole specimens of Saxatilomys paulinae in Quang Binh province. This is the first record of Saxatilomys paulinae in Vietnam. External and craniodental characteristics of all specimens clearly exhibit the characters of Saxatilomys paulinae as described in Musser et al. (2005)​. The rats are of medium size (HB: 160.3 ± 2.03 mm, T: 192.3 ± 6.69 mm) with some specific morpological characteristics. The external and craniodental measurement of the specimens from Vietnam tend to be larger than those of specimens from Lao. However, this needs to be verified by more studies in future. The habitat of Saxatilomys paulinae in Vietnam is characterized by complicated terrain comprising low karst towers (around 400 m) with steep slopes covered under limestone humid evergreen forest. The forest has been affected by selected timber logging in the past, but still has a complex 4-layer structure. The population of Saxatilomys paulinae in Vietnam is threatened by rodent trapping/snaring and habitat disturbance. More status surveys should be conducted to assess the species distributional range and its population status for undertaking relevant conservation measures.

Revision of the genus Leopoldamys (Rodentia, Muridae) as inferred from morphological and molecular data, with a special emphasis on the species composition in continental Indochina.

A revision of the genus Leopoldamys is presented, and both the species composition and distribution in Indochina and Sundaic regions is reinvestigated. The phylogeny of the genus is recovered based on Cyt b, COI, and IRBP gene analyses. Five basal and 16 secondary monophyletic phylogenetic lineages were identified. A taxonomic reassessment of the continental and Sundaic populations is performed based on morphological verification of the genetically defined clades. Six clades were recovered in the phylogenetic analyses and correspond to morphologically defined species: L. revertens (distributed in lowlands of eastern and central Indochina), L. herberti (western and central Indochina, northward to northern Vietnam), L. edwardsi (China and northern Vietnam, northward of 21 degrees N), L. milleti (endemic of Dalat Plateau, southern Vietnam), L. sabanus (Borneo), and L. vociferans (lowlands of the Malacca Peninsula, northward to southwestern Thailand). The absence of proper L. sabanus in continental Indochina is revealed. The substitute name for the species known from the majority of Indochina under the name of L. sabanus should be L. revertens. The name L. neilli, which has been ascribed to populations from Thailand and Vietnam, is a junior synonym of L. herberti. Two related but rather divergent clades are found in Sumatra and the Malacca Peninsula. Based on their considerable genetic distances, these forms should be regarded as separate species from the L. sabanus type-bearing populations of Borneo, or as the members of L. sabanus polytypic superspecies. The substitute name for the lineage-bearing taxon from Malacca should be L. vociferans. The continental populations of Leopoldamys can be distinguished from each other by external and cranial characters and may be subdivided into four species. Two of these species (L. revertens and L. milleti) are well distinguished by external and cranial morphology, whereas the other two species (L. herberti and L. edwardsi) may be treated as sibling species that are difficult to distinguish based on morphological characters.

Diurnal variations of summer precipitation over the Asian monsoon region as revealed by TRMM satellite data

Climatological characteristics of diurnal variations in summer precipitation over the Asian monsoon region are comprehensively investigated based on the Tropical Rainfall Measuring Mission (TRMM) satellite data during 1998–2008. The topographic influence on the diurnal variations and phase propagations of maximum precipitation are identified according to spatiotemporal distributions of the amplitude and peak time of the diurnal precipitation. The amplitude and phase of diurnal precipitation show a distinct geographical pattern. Significant diurnal variations occur over most of continental and coastal areas including the Maritime Continent, with the relative amplitude exceeding 40%, indicating that the precipitation peak is 1.4 times the 24-h mean. Over the landside coasts such as southeastern China and Indochina Peninsula, the relative amplitude is even greater than 100%. Although the diurnal variations of summer precipitation over the continental areas are characterized by an afternoon peak (1500–1800 Local Solar Time (LST)), over the central Indochina Peninsula and central and southern Indian Peninsula the diurnal phase is delayed to after 2100 LST, suggesting the diurnal behaviors over these areas different from the general continental areas. The weak diurnal variations with relative amplitudes less than 40% exist mainly over oceanic areas in the western Pacific and most of Indian Ocean, with the rainfall peak mainly occurring from midnight to early morning (0000–0600 LST), indicating a typical oceanic regime characterized by an early morning peak. However, apparent exceptions occur over the South China Sea (SCS), Bay of Bengal (BOB), and eastern Arabian Sea, with the rainfall peak occurring in daytime (0900–1500 LST). Prominent meridional propagations of the diurnal phase exist in South Asia and East Asia. Along the eastern Indian Peninsula, there is not only the southward phase propagation with the peak occurring around 25°N but also the northward phase propagation with the peak beginning with the southernmost continent, and both reach the central Indian continent to finish. Along the same longitudes where southern China and Kalimantan are located, the diurnal phase of the former propagates from the oceanic area (northern SCS) toward the inland continent, while the phase of the latter propagates from the land area toward the outside sea, showing a landward or seaward coastal diurnal regime. A distinct zonal propagation of the diurnal phase is observed over the BOB oceanic area. The maximum precipitation zone originates from the land-sea boundary of the eastern coast of the Indian peninsula at around 0300 LST, and then propagates eastward with increasing time to reach the eastern coast of the BOB on 1800 LST, finally migrates into the Indochina continent on about 2100 LST.

Sea levels during late marine isotope stage 3 (or older?) reported from the Red River delta (northern Vietnam) and adjacent regions

A 60 m-long sediment core from the lower Red River delta in northern Vietnam contains three depositional sequences consisting mostly of regressive shallow-marine sediments bounded by unconformities. The youngest unit represents the modern Red River delta. The second unit, a facies succession comparable to the overlying deltaic succession, formed during an earlier sea-level highstand, as indicated by the marine isotope stage (MIS) 3 age obtained by radiocarbon dating. The third, undated unit might reflect earlier high sea levels of the middle to late Pleistocene. The MIS-3 ages, derived from shoreline-related sedimentary facies, are supported by records from adjacent mega-deltas and shelf sites with paleoshoreline facies. Proximal sites from the central Indochina craton show high sea levels during late MIS 3, whereas distal sites from the open continental shelf indicate much lower sea levels at the same time. Independent, globally relevant sea-level reconstructions suggest that both positions have been affected by later vertical movement. This discrepancy between sea-level records from central cratonic sites and the continental margin can be explained by a balanced response to locally differentiated sediment loading and compaction on the shelf, as is supported by published seismic data. However, if the complete set of radiocarbon dates is contaminated by younger material, then the second recorded sea-level highstand may be associated with MIS 5, as no marine deposits have yet been reported in any of the three Indochinese mega-deltas for this time interval.