Search

To understand the acoustic and physical properties of piston core samples collected from the Sunda continental shelf and analyze their distribution patterns, the samples were analyzed in laboratory, from which three provinces were divided in sound speed, sound speed ratio, porosity, wet bulk density, and maximum shear strength. Province I had lower sound speed and sound speed ratio (<1.04), high porosity, and low wet bulk density. Province II had higher sound speed and sound speed ratio (>1.04), low porosity, and high wet bulk density. Province III had the lowest sound speed and sound speed ratio (0.99), highest porosity (81%), and lowest wet bulk density (1.34 g/cm3). The distribution pattern indicates that sediment movement, sediment source, topography, and hydrodynamic conditions influenced the distribution of acoustic and physical properties. Furthermore, we investigated the relationship of the maximum shear strength to the porosity and wet bulk density, and found that the maximum shear strength was proportional to both the porosity and wet bulk density. This finding has significant implications for ocean engineering applications. [ABSTRACT FROM AUTHOR]

Incised valleys are commonly investigated based on outcrop, modern setting and seismic data, which are often limited by data availability, especially for broad (ca >100 km wide) shelf settings. Consequently, few have described complete depositional systems of the incised valleys, especially those linked to their corresponding modern rivers in a source‐to‐sink framework to determine comprehensive controlling factors. This study documents Late Quaternary incised valleys and their characteristics in the Balingian – Central Luconia shelf based on regionally‐extensive three‐dimensional seismic data, two‐dimensional high‐resolution seismic data and boreholes. The three‐dimensional seismic data show that the main Tatau incised valley and tributary Suai incised valley fed the Tatau–Suai shelf‐edge delta. The Tatau incised valley is interpreted as the main incised valley based on its broader width, thicker infill, two‐tier stratigraphic architecture and its larger drainage basin area compared to the tributary Suai incised valley. The Tatau incised valley shifted its direction towards an active tectonic lineament (West Baram Line) and bypassed sediments to the deep‐water via a series of upper slope channels. The Tatau incised valley system comprises the following elements: (i) an upstream segment characterized by rivers dissecting an uplifted hinterland comprising Neogene sedimentary rocks, humid‐tropical vegetation, monsoonal climate, extremely high river discharge and sediment supply; (ii) a midstream segment comprising an emergent, vegetated (tropical rainforest to mangroves) and relatively narrow (ca 150 to 200 km wide) shelf, which was characterized by basinward‐increasing, tectonically‐driven accommodation space, valley incision and deposition; (iii) a downstream segment with increasing tidal‐influence where the Tatau and its tributary valley merged; and (iv) a short (15 to 20 km), narrow (10 to 15 km), tectonically‐controlled shelf‐edge delta and channelized upper slope. This study demonstrates the value of documenting an incised valley system in the context of its broader source‐to‐sink setting, which may provide a useful analogue for ancient incised valleys in comparable geological settings. [ABSTRACT FROM AUTHOR]

The Sunda Shelf plays a key role in the sedimentation of the southern South China Sea (SCS). However, the impact of past climate changes on sediment transfer to the Sunda Shelf and the southern SCS is still unresolved. Here, we present new data on grain size, clay mineralogy, and Sr‐Nd isotopes of three marine cores, river sediments, and surface sediments of the Sunda Shelf. The results indicate that clay fractions of the central Sunda Shelf and the Gulf of Thailand derived mainly from the Mekong River and the rivers of northern Thailand since the last deglaciation. Significant changes in sediment sources are observed at 7.5 cal ka BP. From 13.3 to 7.5 cal ka BP, sediments in the Gulf of Thailand mainly originated from the rivers of northern Thailand, with contributions from the Mekong River increasing after 7.5 cal ka BP. An opposite shift is observed in the central Sunda Shelf. Such variations in the spatial distribution result from a combination of sea level and East Asian monsoon effects. After 7.5 cal ka BP, less Mekong River sediments were transported southeastwards into the southern SCS, and more sediments were gradually trapped within the delta and transported in a southwesterly direction into the Gulf of Thailand due to intense East Asian winter monsoon, which forced a strong southwestward coastal current. Our results demonstrate the important impact of East Asian winter monsoon strengthening and sea level rise in the mid‐Holocene, which can change sediment sources and transport processes on the Sunda Shelf. Plain Language Summary: Sea level and monsoon are two important factors controlling sediment transfer in the tropical and subtropical continental marginal seas. However, the impact of past sea level and monsoon changes on mineralogical composition and sediment transfer to the Sunda Shelf (the largest low‐latitude continental shelf) and the southern South China Sea (SCS) is unclear. This study provides new data on grain size, clay mineralogy, and Sr‐Nd isotopes of sediment from marine cores, river sediments, and surface sediments of the Sunda Shelf to constrain sediment sources and climatic control on sediments deposited on the Sunda Shelf since the last deglaciation. We find that the Mekong River and the rivers of northern Thailand are two major sediment sources to the Sunda Shelf. An opposite shift of sediment sources at 7.5 cal ka BP is observed between the Gulf of Thailand and the central Sunda Shelf, which results from the transfer of the Mekong River sediments between the southern SCS and the Sunda Shelf caused by sea‐level rise and East Asian winter monsoon strengthening in the mid‐Holocene. Our results highlight that sea level and East Asian winter monsoons can significantly change sediment sources and transport processes on the Asian low‐latitude continental shelf. Key Points: Clay minerals and Sr‐Nd isotopes identified sediment sources to the Sunda Shelf since the last deglaciation as Mekong and Thailand riversEstimation of the Mekong and Thailand river inputs to the sedimentation of the Sunda Shelf and the southern South China SeaSea‐level rise and East Asian winter monsoon strengthening drove major sediment‐source changes on the Sunda Shelf at 7.5 ka BP [ABSTRACT FROM AUTHOR]

The islands of Southeast Asia comprise one of the most geologically and biogeographically complex areas in the world and are a centre of exceptional floristic diversity, harbouring 45,000 species of flowering plants. Cyrtandra, with over 800 species of herbs and shrubs, is the largest genus in the family Gesneriaceae and is one of the most emblematic and species-rich genera of the Malesian rainforest understorey. The high number of species and tendency to narrow endemism make Cyrtandra an ideal genus for examining biogeographic patterns. We sampled 128 Cyrtandra taxa from key localities across Southeast Asia to evaluate the geo-temporal patterns and evolutionary dynamics of this clade. One nuclear and four chloroplast regions were used for phylogenetic reconstruction, molecular dating, and ancestral range estimation. Results from the dating analysis suggest that the great diversity of Cyrtandra seen in the Malesian region results from a recent radiation, with most speciation taking place in the last five million years. Borneo was recovered as the most likely ancestral range of the genus, with the current distribution of species resulting from a west to east migration across Malesia that corresponds with island emergence and mountain building. Lastly, our investigation into the biogeographic history of the genus indicates high levels of floristic exchange between the islands on the Sunda shelf and the important role of the Philippines as a stepping stone to Wallacea and New Guinea. These patterns underlie much of the plant diversity in the region and form an emerging paradigm in Southeast Asian plant biogeography.

Foraminiferal geochemistry applies geochemical elements embedded in foraminiferal calcites through bioaccumulation to interpret and reconstruct past oceanic climate histories. Due to its extensive variability and abundance, foraminifera is the easiest to retrieve and the best indicator of marine productivity and ocean temporal changes. In this review, we discuss the development of foraminiferal geochemistry studies in Southeast Asia, analyzing its current status and potential areas to be developed, namely, the Sunda Shelf. The Sunda Shelf is one of the world’s largest low-latitude shelves, bordered by marginal seas and sensitive to sea-level changes. The shelf response towards changes in ocean salinity affected the isotopic signals in foraminiferal calcites, which can indicate sea-level changes ideally. The Sunda Shelf has the potential to be developed as a study area for eustatic sea-level changes as it is located far from major glaciation centers; hence through this review, we aim to highlight the potential of exploring the application of geochemical elements in foraminifera as an indicator for sea-level changes. To date, literature on foraminiferal geochemistry in this region is very limited, thus inhibiting progress in such studies. A comprehensive summary of past studies in this region is provided to give a general overview of the direction of foraminiferal geochemistry studies and serve as guidelines for future research. [ABSTRACT FROM AUTHOR]

Phenacostethus sikat, new species, is described from coastal drainages of Kalimantan Selatan, the southeastern province of Indonesian Borneo, that flow into the Java Sea and the Straits of Makassar. This discovery and description brings the number of valid species of priapiumfishes, the atheriniform subfamily Phallostethinae, to 24 and extends the known distribution of the phallostethines to drainages on the eastern margin of the modern Sunda Shelf. Phenacostethus sikat differs from congeners in features of the priapium, the complex bilaterally asymmetric, subcephalic copulatory organ of males, and is readily distinguished by a unique, brush-shaped seminal papilla in males, as opposed to a simpler, ruffled seminal papilla in Phe. smithi, its inferred sister species based on morphology, and a smooth seminal papilla in males of Phe. posthon and Phe. trewavasae. Males of Phe. sikat and Phe. smithi are either sinistral or dextral, the hooked toxactinium arises on the right or left side of the head and curves strongly under the head towards the aproctal side of the body. Males of Phe. posthon and Phe. trewavasae are exclusively dextral or sinistral, respectively. Males of Phe. sikat have an ossified inner pulvinular bone which is cartilaginous or absent in Phe. smithi. Males of Phe. sikat and Phe. smithi have a curved and pointed or blunt second ctenactinium as opposed to a highly reduced second ctenactinium in males of Phe. posthon and Phe. trewavasae. Females of the new species lack rudimentary pelvic fins which are present in adult females of Phe. smithi, Phe. posthon, and Phallostethus. The new species is also diagnosed by a colour pattern with few or no melanophores along the horizontal septum anterior to the anal-fin origin. The mtCOI sequences of Phe. sikat differ from those of congeners by 13.85-24.23%, with an average of 21.54%, an extraordinarily high level of divergence comparable to that of other diminutive fishes. Like congeners, Phe. sikat is a miniature species. The largest specimen known is an adult female just 15.3 mm SL. [ABSTRACT FROM AUTHOR]

To mark A.R. Wallace's 200th birthday, we review the direct and indirect contributions he made to our understanding of the Indo‐Australian Archipelago's biogeography. He is widely known for his field research (1854–1862) and his 1863 boundary line separating the Oriental and Australasian faunal realms (between Bali and Lombok, Borneo and Sulawesi, and the Philippines and the Moluccas). Notably, though, he never accepted Huxley's 'Wallace Line' proposal (1868), whose northern part runs between the main Philippine islands and the Palawan Group to the west. Furthermore, in 1910, which was 3 years prior to his demise, he transferred Sulawesi's fauna to the Oriental realm. In 1924, Merrill introduced the 'Wallacea' transition zone. Although the label is today widely used to denote a sub‐region within the Indo‐Australian Archipelago between Wallace's 1863 line and Lydekker's 1896 line (first presented by Darlington in 1957), the western boundary was originally based on Huxley's line, and thus included the Philippine islands minus the Palawan group. Most biogeographers appear to be unaware of Merrill and his intention. Finally, recent attempts to define the faunal break have not led to a consensus view, despite the huge increase in primary data plus the application of modern analytical techniques. This reflects the complexities and diversity of the region's faunal distribution patterns, plus the differences in the ways that researchers choose to process their data. [ABSTRACT FROM AUTHOR]

Understanding sediment provenance in continental shelf basins is essential for reconstructing paleoenvironmental changes, enhancing insights into sedimentary dynamics, and elucidating their contributions to the global carbon cycle. To decipher sediment provenances and enhance comprehension of the sediment dispersal patterns and the factors governing geochemical compositions on the Sunda Shelf, we conducted an exhaustive analysis of trace elemental concentrations and the isotopic ratios of strontium (87Sr/86Sr) and neodymium (εNd) in the silicate fractions of 35 surface sediment samples. These samples were collected from the western Sunda Shelf and its proximate major river end-members, namely, the Mekong, Rajang, Pahang, and Kelantan Rivers. Through the application of various statistical methodologies, including classical cluster analysis, Principal Component Analysis (PCA), the La-Sc-Th discrimination diagram, and an array of elemental ratios, we identified three distinct geochemical provinces on the Sunda Shelf. Each province is defined by unique geochemical signatures indicative of varied sediment sources or provenances. This distinction was primarily attributed to pronounced sediment heterogeneity, reflecting lithologic variances from the diverse river end-members. In pursuit of a holistic understanding of sediment provenance in the region, Sr Nd isotopic data was also integrated from prior studies encompassing the eastern Sunda Shelf and the southern South China Sea. By utilizing the Sr Nd mixing model, complemented with Monte-Carlo simulations, we estimated the sediment contributions from surrounding river end-members to the southern South China Sea basin. According to the model, the Mekong River emerges as the principal sedimentary source of the Sunda continental shelf and the southern South China Sea, attributed to its substantial sediment outputs. Additionally, the model has identified significant contributions from the Rajang, Pahang, and Kelantan rivers, particularly in offshore regions near their estuaries. Further, this study revealed the previously underappreciated influence of South China's rivers, namely the Red and Pearl Rivers, on the eastern Sunda Shelf and deeper southern South China Sea region beyond the continental shelf. This study not only delineates the dominant sediment sources influencing the Sunda Shelf and the South China Sea but also underscores the importance of considering a broad spectrum of river end-members to understand sedimentary dynamics in an active marine environment. • Mekong River is the primary but not sole sediment source for the Sunda Shelf. • Geochemical signatures enable sediment provenance studies. • Sr Nd models quantify diverse river sediment inputs. • Red and Pearl rivers are important sources of the southern South China Sea. [ABSTRACT FROM AUTHOR]

• DOC crucial in coastal biogeochemical cycles, but its behavior varies based on sources. • Bulk DOC stable isotope ratio (δ 13C DOC) faces limitations in complex coastal waters. • Issues like narrow separation and reservoir effects in δ 13C DOC addressed by deuterium (δ 2H n). • The result shows δ 2H n and δ 13C DOC agree well in quantifying the terrigenous DOC fraction. • The δ 2H n proves comparable effectivity in quantifying tDOC, offering an alternative in settings where δ 13C DOC is inadequate. Dissolved organic carbon (DOC) is a key component of coastal biogeochemical cycles, but its composition and reactivity depend on the relative contribution of autochthonous aquatic versus allochthonous terrigenous DOC (tDOC). In complex coastal waters, tDOC is commonly quantified using the bulk DOC stable carbon isotope ratio (δ 13C DOC). However, several limitations can hamper the use of δ 13C DOC in marine ecosystems, such as (1) the narrow and often overlapping separation of the autochthonous and allochthonous endmembers, and (2) mineralization of tDOC to dissolved inorganic carbon creates a reservoir effect such that autochthonous DOC can acquire a terrigenous-like δ 13C DOC. The stable isotope ratio of non-exchangeable hydrogen in the DOC (δ 2H n) has emerged as a new tool that can potentially overcome these limitations: (1) δ 2H n has a large separation between aquatic and terrigenous endmembers (>50‰) and (2) it is not subject to reservoir effects caused by tDOC mineralization. Here, we evaluate the potential of δ 2H n obtained from solid phase-extracted dissolved organic matter (SPE-DOM), by comparing it to δ 13C DOC and chromophoric DOM (CDOM) optical properties. We collected samples at a site in Southeast Asia's Sunda Shelf that experiences substantial seasonal variation in tDOC input, driven primarily by the monsoon-induced physical advection of peatland-derived tDOC. Over a 1-year monthly time series, the terrigenous fraction of DOC (f terr) determined using δ 2H n of SPE-DOM and δ 13C DOC of bulk DOC was well correlated (r2 = 0.42), and there was no significant difference in f terr between the two isotope systems. In fact, δ 2H n displayed slightly stronger correlations with salinity and CDOM optical properties compared to δ 13C DOC. Our results indicate that δ 2H n of SPE-DOM is effective for quantifying tDOC across coastal gradients, potentially offering greater sensitivity than δ 13C DOC , and is a viable alternative in settings where δ 13C DOC is inadequate. [ABSTRACT FROM AUTHOR]

Although Borneo has received more attention from biologists than most other islands in the Malay Archipelago, many questions regarding the systematic relationships of Bornean mammals remain. Using next-generation sequencing technology, we obtained mitochondrial DNA sequences from the holotype of Suncus ater, the only known specimen of this shrew. Several shrews collected recently in Sarawak are closely aligned, both morphologically and mitochondrially, with the holotype of S. ater. Phylogenetic analyses of mitochondrial sequences indicate that the S. ater holotype and new Sarawak specimens do not belong to the genus Suncus, but instead are most closely related to Palawanosorex muscorum. Until now Palawanosorex has been known only from the neighboring Philippine island of Palawan. Additional sequences from nuclear ultra-conserved elements from the new Sarawak specimens strongly support a sister relationship to P. muscorum. We therefore transfer ater to Palawanosorex. The new specimens demonstrate that P. ater is more widespread in northern Borneo than previously recorded. Continued sampling of Bornean mammal diversity and reexamination of type material are critical in understanding the evolutionary history of the biologically rich Malay Archipelago. [ABSTRACT FROM AUTHOR]

Long‐term organic carbon (OC) burial on continental shelves has been widely recognized for regulating atmospheric CO2 (pCO2) and the global climate. However, quantitatively assessing shelf OC burial's role and process in prominent climate transitions is challenging. Using 367 drilling sites, we evaluated the impact of OC burial on the Sunda Shelf, the world's largest tropical shelf, on the middle Miocene carbon perturbation and climate change. Comparing the Miocene Climatic Optimum (MCO) and the Middle Miocene Climate Transition (MMCT) results demonstrated that OC was buried faster during the MMCT with an increment of 0.07–0.14 × 103 GtC/Myr. This would cause an additional 34.77–69.16 ppm pCO2 sequestration, contributing at least one‐sixth of the global pCO2 reduction. We found OC burial regulated the long‐standing Monterey carbon isotope excursion via negative and positive feedbacks during the MCO and MMCT, respectively. Expanded terrestrial carbon reservoirs and enhanced burial efficiency were key steps in the latter positive feedback. Plain Language Summary: The organic carbon (OC) formed by the photosynthesis of marine and terrestrial organisms consumes atmospheric CO2 (pCO2). Its long‐term burial in marine environments, especially on continental shelves, could influence the global carbon cycle and induce climate change. However, precisely assessing how much OC has been buried on shelves and quantifying how it affected climate change in the geological past is challenging. This is mainly due to the difficulty of obtaining complete spatial‐temporal records buried deeply on shelves and the complexity of climate feedbacks involving OC burial. To fill this gap to a certain extent, we calculated the middle Miocene OC burial of the Sunda Shelf, the world's largest tropical shelf, using 367 drilling sites and evaluated its impact on the profound carbon perturbation and climate transition of this period. We found that more OC was buried during the greenhouse period, but a faster burial rate occurred after polar cooling. The accelerated OC burial on the Sunda Shelf would cause an additional 34.77–69.16 ppm pCO2 sequestration, accounting for at least one‐sixth of the global pCO2 reduction of the middle Miocene. Efficient OC burial on the shelf was promoted by drainage system progradation and vegetation expansion arose along with sea level drop. Key Points: Organic carbon (OC) burial on the Sunda Shelf is essential to the global carbon cycle during the middle MioceneThe OC burial rate of the Middle Miocene Climate Transition (MMCT) was faster than that of the Miocene Climatic OptimumExpanded terrestrial carbon reservoirs and enhanced organic matter burial efficiency promoted the MMCT [ABSTRACT FROM AUTHOR]

Abstract Impending anthropogenic climate change will severely impact coastal organisms at unprecedented speed. Knowledge on organisms’ evolutionary responses to past sea‐level fluctuations and estimation of their evolutionary potential is therefore indispensable in efforts to mitigate the effects of future climate change. We sampled tens of thousands of genomic markers of ~300 individuals in two of the four extant horseshoe crab species across the complex archipelagic Singapore Straits. Carcinoscorpius rotundicauda Latreille, a less mobile mangrove species, has finer population structure and lower genetic diversity compared with the dispersive deep‐sea Tachypleus gigas Müller. Even though the source populations of both species during the last glacial maximum exhibited comparable effective population sizes, the less dispersive C. rotundicauda seems to lose genetic diversity much more quickly because of population fragmentation. Contra previous studies’ results, we predict that the more commonly sighted C. rotundicauda faces a more uncertain conservation plight, with a continuing loss in evolutionary potential and higher vulnerability to future climate change. Our study provides important genomic baseline data for the redirection of conservation measures in the face of climate change and can be used as a blueprint for assessment and mitigation of the adverse effects of impending sea‐level rise in other systems.

Aim: Although the underlying biotic and abiotic factors of phylogeographic patterns is an important topic in biogeography, they remain largely unexplored in marine fishes. We empirically investigated the effects of several biological traits on phylogeographic patterns of selected marine fishes. We predict that overall similarity in these traits correlates with similarity in phylogeographic patterns among species, and that genetic diversity and demographic stability are associated with these traits, as well as the local (paleo)environment. Location: Five localities in the South China Sea (SCS). Taxon: Thirteen species of coastal marine fishes. Methods: Phylogeographic Concordance Factors (PCFs) based on mitochondrial DNA sequences were tested for correlation with similarity based on distribution range, depth of occurrence, habitat preference, salinity tolerance and fecundity among the subset of the focal species. The relationship between phylogeographic patterns and these traits was also qualitatively examined. Bayesian model averaging was used to test the association between these traits and the genetic diversity estimates. Results: Pairwise PCFs of five species across all localities were correlated with pairwise biological similarity, with depth and distribution ranges contributing most to the biological similarity. Nucleotide diversity of Indo‐west Pacific species tended to be greater than that of circumtropical species. Populations showing signs of demographic expansions were concentrated in three localities. A novel concordant population break across six focal species and other marine organisms coincided with the dispersal barrier previously suggested by biophysical dispersal modelling. Main conclusions: Abiotic factors were dominant in controlling phylogeographic patterns, with possible contributions from biotic factors. Depth and distribution ranges, or other eco‐physiological traits underlying these, might have influenced the phylogeographic patterns of several species, presumably coupled with historical vicariance. The geography of local populations relative to the shallow continental shelf may explain the heterogeneous demography. Historical vicariance and contemporary ocean currents have contributed to the concordant population break. [ABSTRACT FROM AUTHOR]

This paper documents a database of fossil foraminiferal occurrences from a core sample (2 m) retrieved from offshore southeastern Peninsular Malaysia, in 1993, with additional data on their modern distribution from published source. Five sub-samples were analysed for foraminiferal studies (0.1 m, 0.4 m, 0.6 m, 1.2 m, and 2.0 m), alongside with their diversity indices values. In addition, we also present the lithological description of the core sediment, together with the radiocarbon age of our sample. These data are potentially be reused in other paleoceanography related research, such as reconstructing paleo environments, and for future research on the Late-Quaternary/Holocene sedimentary and sea-level history of Sunda Shelf.

Relative sea-level (RSL) records from far-field regions distal from ice sheets remain poorly understood, particularly in the early Holocene. Here, we extended the Holocene RSL data from Singapore by producing early Holocene sea-level index points (SLIPs) and limiting dates from a new ~40 m sediment core. We merged new and published RSL data to construct a standardized Singapore RSL database consisting of 88 SLIPs and limiting data. In the early Holocene, RSL rose rapidly from −21.0 to −0.7 m from ~9500 to 7000 cal. yrs. BP. Thereafter, the rate of RSL rise decelerated, reaching a mid-Holocene highstand of 4.0 ± 4.5 m at 5100 cal. yrs. BP, before falling to its present level. There is no evidence of any inflections in RSL when the full uncertainty of SLIPs is considered. When combined with other standardized data from the Malay-Thai Peninsula, our results also show substantial misfits between regional RSL reconstructions and glacial isostatic adjustment (GIA) model predictions in the rate of early Holocene RSL rise, the timing of the mid-Holocene highstand and the nature of late-Holocene RSL fall towards the present. It is presently unknown whether these misfits are caused by regional processes, such as subsidence of the continental shelf, or inaccurate parameters used in the GIA model. [ABSTRACT FROM AUTHOR]

Clay minerals preserved in marine sediments carry important information about sediment transport processes from sources to sinks. To reveal the dynamic transport processes of clay minerals and related controlling factors in the southern South China Sea, spatiotemporal variations of clay mineral assemblages from previous studies (Cores MD05-2893, CG2, SO18287-3, MD01-2393, SO18383-3, and MD97-2150) are integrated to assess their controlling factors over the past 30 ka. Based on the smectite/(illite + chlorite) ratio in six cores, we found that the clay mineral variations on the continental slope off Sunda Shelf (Cores MD05-2893, CG2, and SO18287-3) have been controlled by the sea-level changes during the last glacial sea-level lowstand and by the East Asian monsoon during the Holocene sea-level highstand periods. Meanwhile, the clay mineral variations on the continental slope off the Mekong River (Cores MD01-2393, SO18383-3, and MD97-2150) have been driven by the chemical weathering in the Mekong River basin that associates with the East Asian summer monsoon evolution. Accordingly, we conclude that the glacial-interglacial variation of clay minerals in an integrated picture of the southern South China Sea region since the Last Glacial Maximum has been mainly controlled by sea-level change and East Asian monsoon evolution. However, these controlling factors play independent roles in different parts of the southern South China Sea, which appears more heterogeneous than generally expected. [ABSTRACT FROM AUTHOR]

Impending anthropogenic climate change will severely impact coastal organisms at unprecedented speed. Knowledge on organisms' evolutionary responses to past sea‐level fluctuations and estimation of their evolutionary potential is therefore indispensable in efforts to mitigate the effects of future climate change. We sampled tens of thousands of genomic markers of ~300 individuals in two of the four extant horseshoe crab species across the complex archipelagic Singapore Straits. Carcinoscorpius rotundicauda Latreille, a less mobile mangrove species, has finer population structure and lower genetic diversity compared with the dispersive deep‐sea Tachypleus gigas Müller. Even though the source populations of both species during the last glacial maximum exhibited comparable effective population sizes, the less dispersive C. rotundicauda seems to lose genetic diversity much more quickly because of population fragmentation. Contra previous studies' results, we predict that the more commonly sighted C. rotundicauda faces a more uncertain conservation plight, with a continuing loss in evolutionary potential and higher vulnerability to future climate change. Our study provides important genomic baseline data for the redirection of conservation measures in the face of climate change and can be used as a blueprint for assessment and mitigation of the adverse effects of impending sea‐level rise in other systems. [ABSTRACT FROM AUTHOR]

Understanding the exact origin of sedimentary organic matter (OM) was crucial for assessing carbon cycle processes and environmental contamination in continental margin. However, such studies are less performed on shelves far away from the mainland. Here, the abundance and composition of lipid biomarkers were determined in surface sediments from 58 sites at the eastern Sunda Shelf, South China Sea, to identify the sedimentary OM sources and characterize the spatial variation of OM input from specific sources. The results indicated that the sedimentary OM were derived mainly from algae, bacteria, seagrass, terrestrial plants, mangroves, petroleum, and rock erosion products, and the relative significance of these sources varied between different sites. Algal OM input, as indicated by the abundances of short-chain n -alkanes, cholest-2-ene, dinosterol, brassicasterol, and C 30 1,15 alkyl diol, was relatively high at five sites (ZW 47, 51, 55, 82, and 86). Conversely, long-chain n -alkane and long-chain n -alkanol proxies suggested terrestrial plant input was most predominant at three other sites (ZW68, 103, and 106), and high abundances of taraxerol and β-amyrin in these sites imply the dominance of mangrove vegetation in the terrestrial OM. UCM (unresolved complex mixture) and αβ-hopanes indicated a relatively high input of petroleum-derived OM at another five sites (ZW3, 8, 25, 51, and 97). The analysis of abundance variations in the biomarkers suggested a substantial spatial heterogeneity in terrestrial plant OM input and a much lower heterogeneity in algal OM input, probably resulting from great variation in riverine transport intensity and relatively homogeneous water environment across the studied region. Correlation analysis indicated that both algal and terrestrial plant OM significantly contributed to the OM buried in the sediments. These results can form a basis for understanding the carbon cycle processes in Sunda Shelf. The finding of petroleum contamination in several sites can benefit for environmental protection and management of the shelf. • Sedimentary OM source and spatial variation in OM input were studied in eastern Sunda Shelf. • Both algae and terrestrial plants contributed significantly to the sediment OM. • Mangroves may be the dominant component of terrestrial OM in some sites. • Input of petroleum-derived OM was prominent at a few sites of the shelf. • Input of terrestrial plant OM had a much greater spatial heterogeneity than algal OM. [ABSTRACT FROM AUTHOR]

High-resolution records of grain size, major and trace elements, and Sr-Nd isotopes of Core K17 from the western Sunda Shelf were investigated to evaluate the response of weathering and terrigenous input to climatic changes and human activities over the past 7400 years. Sr-Nd isotopic results indicate that the Kelantan River is the main source of sedimentary material in the study core since the mid-Holocene. Chemical weathering levels are represented by the chemical index of alteration (CIA), αAlNa, and K2O/Al2O3 ratios; and geochemical and grain size proxies (including TiO2/CaO, Rb/Sr ratios, and grain size end-member) were used to establish variations of terrigenous input into the study core since 7400 cal yr BP. Based on these records, the evolution of weathering and terrigenous input processes in the western Sunda Shelf can be divided into four stages. During stage 1 (7400–3700 cal yr BP), increasing precipitation and decreasing temperature jointly balanced the relatively stable weathering and terrigenous sediment supply. Dramatically decreasing weathering rates were consistent with less rainfall and lower temperatures during stage 2 (3700–2600 cal yr BP). Heavy rainfall played a more important role than low temperature in controlling weathering and erosion, leading to increasing terrigenous input in stage 3 (2700–1600 cal yr BP). Because of the decoupling between weathering, erosion, and climate in the late Holocene (stage 4, since 1600 cal yr BP), increasing agriculture and related human activities likely dominated weathering and erosion relative to climate changes. Furthermore, the initial time at which human activity overwhelmed natural processes in the southern South China Sea (SCS) is similar to that in the northern SCS. Our results highlight that human activities during the past 1600 years have gradually overwhelmed natural climatic controls on weathering and erosion processes in the western Sunda Shelf.

Due to its position between the highly distinct Oriental and Australasian biogeographical realms, much effort has been spent demarcating associated separations and transitions in the faunal assemblages of the Indo‐Australian Archipelago. Initially, sharp boundary lines were proposed, with the earliest dating from the mid‐1800s. Notably, the one published by Alfred R. Wallace in 1863, based upon land‐mammal and land‐bird distributions, has since achieved iconic status and today its significance is recognized well beyond the confines of the biogeography community. Over the next four decades many such divides were engraved onto plates and inked onto charts of SE Asia using additional information, different organisms or other criteria. However, it became apparent that, as Wallace had noted, all such lines were to some degree permeable, and by the 1880s transition zones were being put forward instead; the label 'Wallacea' was introduced in 1924. Interestingly, the last decade has seen new divides and sub‐regions being proposed, some departing markedly from earlier offerings. Although currently there is general agreement regarding much of the terminology associated with both the lines and the areas, the record of publication indicates that this consensus has emerged obliquely, and in some cases is weakly founded. This review does not present new data nor new analyses; rather it summarizes the development of ideas and reflects upon attendant issues that have emerged. After reviewing the key proposals, recommendations are presented that should in future alleviate perceived difficulties or inadequacies. Reference to specific divides must be true to their original definitions; there are many instances where the secondary literature has portrayed them incorrectly and with some this has rippled through into later publications. Moreover, Wallace's 1863 line is not the one that he finally settled upon (in 1910); its path around Sulawesi was transferred from the west to the east of the Island. Ideally, Huxley's divide (1868) should carry his name rather than Wallace's; the latter never accepted the proposition. Lydekker's Line (1896) ought to be labelled the Heilprin–Lydekker Line in recognition of Angelo Heilprin's 1887 contribution. Concerning transition zones, ideally Wallacea should correspond to its original 1924 description, which incorporated the Philippine islands bar the Palawan group. Notably, though, a smaller form (introduced by Darlington in 1957, used frequently from 1998 onwards) in which all of the Philippine islands are excluded is entrenched within the recent literature, but this is often without evident justification. It should also be recognized that the 'reduced' (=southern) Wallacea area was effectively defined by Heilprin in 1887, but was then labelled the 'Austro‐Malaysian Transition Zone'. Finally, the application in recent years of modern analytical techniques has not led to a consensus view on where the lines/areas should run/be placed; with such a large, diverse set of organisms, each with differing histories, this is perhaps not surprising. [ABSTRACT FROM AUTHOR]

This paper documents a database of fossil foraminiferal occurrences from a core sample (2 m) retrieved from offshore southeastern Peninsular Malaysia, in 1993, with additional data on their modern distribution from published source. Five sub-samples were analysed for foraminiferal studies (0.1 m, 0.4 m, 0.6 m, 1.2 m, and 2.0 m), alongside with their diversity indices values. In addition, we also present the lithological description of the core sediment, together with the radiocarbon age of our sample. These data are potentially be reused in other paleoceanography related research, such as reconstructing paleo environments, and for future research on the Late-Quaternary/Holocene sedimentary and sea-level history of Sunda Shelf. [ABSTRACT FROM AUTHOR]

Shifts in phytoplankton phenology were observed in the Strait of Malacca (SM) and Sunda Shelf (SS), which were speculated to be potentially related to global warming and climate anomaly events. Such interactions between phytoplankton structure and physico-chemical factors were less known in narrow straits. Therefore, the spatial distribution pattern and diversity of surface phytoplankton assemblage, local hydrology, and nutrient regimes were investigated over the SM and SS (South China Sea, SCS) during 2017 and 2018 pre-monsoon season (spring). Diatoms, dinoflagellates, and cyanobacteria were representatives of microphytoplankton in the survey area. Total phytoplankton abundance peaked near Singapore Strait (SGS) and diminished toward SS. From the lower ratio of diatoms to dinoflagellates (

Historical and contemporary processes shaping striking variation in terrestrial biodiversity along elevational gradients have received much attention from evolutionary biologists, often by way of comparisons to latitudinal environmental gradients. Here we synthetically review what is known of the diversity and origin of upland endemic geckos across the Malesian region (south-east Asia and Melanesia). Approximately 20% of the regional gecko fauna is endemic to mountains, but only around 8% have distributions centred on what we consider true montane habitats over 1000 metres above sea level. A majority of upland lineages lack close relatives in surrounding lowlands (although there are many exceptions) and some are highly phylogenetically divergent (e.g., estimated divergence from all other gecko taxa dating to the mid-Miocene or earlier). In several cases upland radiations are allied to other taxa centred on small islands or in disturbed lowland habitats, but absent or exceptionally rare in most lowland rainforest areas. A number of other upland lineages may have originated on smaller islands that are now merged into larger landmasses such as Sumatra and New Guinea. Based on often deep phylogenetic divergences, low community diversity and disjunct distributions across uplands and islands, we suggest that at least some upland lineages are more limited by biotic interactions than they are by climate. As global climates continue to warm in coming decades, such taxa may be particularly affected by upslope shifts of competitors and predators from lower elevations. [ABSTRACT FROM AUTHOR]

Catastrophic events, such as volcanic eruptions, can have profound impacts on the demographic histories of resident taxa. Due to its presumed effect on biodiversity, the Pleistocene eruption of super‐volcano Toba has received abundant attention. We test the effects of the Toba eruption on the diversification, genetic diversity, and demography of three co‐distributed species of parachuting frogs (Genus Rhacophorus) on Sumatra. We generate target‐capture data (~950 loci and ~440,000 bp) for three species of parachuting frogs and use these data paired with previously generated double digest restriction‐site associated DNA (ddRADseq) data to estimate population structure and genetic diversity, to test for population size changes using demographic modelling, and to estimate the temporal clustering of size change events using a full‐likelihood Bayesian method. We find that populations around Toba exhibit reduced genetic diversity compared with southern populations, and that northern populations exhibit a shift in effective population size around the time of the eruption (~80 kya). However, we infer a stronger signal of expansion in southern populations around ~400 kya, and at least two of the northern populations may have also expanded at this time. Taken together, these findings suggest that the Toba eruption precipitated population declines in northern populations, but that the demographic history of these three species was also strongly impacted by mid‐Pleistocene forest expansion during glacial periods. We propose local rather than regional effects of the Toba eruption, and emphasize the dynamic nature of diversification on the Sunda Shelf. [ABSTRACT FROM AUTHOR]

Phytoplankton play important roles in marine ecosystems and have major impacts on the global biogeochemical cycles, yet the knowledge of the processes for oceanic environments controlling the phytoplankton dynamics still needs to be improved, particularly in the coastal ecosystems. Monitoring diversity of phytoplankton communities, including micro/nano- and pico-forms, as well as their dynamics in relation to environmental factors, is thus of critical significance. Here, we conducted two cruises in the southern Sunda Shelf during spring and fall 2016 to investigate the community structure and dynamics of phytoplankton assemblages in relation to environmental factors combining microscopy and flow cytometry. Micro/nanophytoplankton communities changed from Trichodesmium spp. and diatoms co-dominance in spring to communities dominated by Trichodesmium spp. in fall. Diatoms were a highly diverse group, with 78 species, followed by dinoflagellates (35 species). Differences in average abundance of micro/nanophytoplankton between spring and fall might be attributed to the shift in dominance of Trichodesmium spp. and diatoms. Picophytoplankton characterized by a great abundance of picocyanobacteria were dominated by Synechococcus. The dynamics of picophytoplankton during spring and fall might be associated with the differences in dominant Synechococcus strains. Environmental variables had significant influence on the dynamics of phytoplankton communities, especially nitrate and silicate. Silicate was a major driver responsible for the variations of micro/nanophytoplankton. Low silicate potentially limited the diatom growth during fall, leading to the overwhelming dominance of Trichodesmium spp. Picophytoplankton showed positive correlations with nitrate and silicate, suggesting that these nutrients collectively controlled variations in picophytoplankton communities during spring and fall. [ABSTRACT FROM AUTHOR]

Pollen analysis has been conducted on a 90 cm gravity core taken from the Karimata Strait to reveal pollen facies in marine sediment and Late Holocene environmental changes in the central Sunda Shelf region. The core site is at 32 m water depth and located about 170 km northwest of Bangka Island. Indonesia. Ten samples were collected at 10 cm intervals through the core. The total number of pollen grains counted in the samples varies between very low (<50 grains) to abundant (>200 grains). High frequencies (50 - 70%) of mangrove pollen are found at 90 to 40 cm indicating that pollen facies in offshore marine sediment may be comparable with those in mangrove forest floor sediment. The core site has been in a neritic environment since its early deposition ca. 1.800 yr B.P. (~150 A.D.) when mangroves vastly grew on the tidal flats of the surrounding islands and they persisted to ca. 700 yr B.P. (~1,250 A.D.). In the middle of this period, a catastrophic event speculatively due to the 535 A.D. Krakatau eruption might have responsible for the decrease of mangroves and the disappearance of benthic foraminifers. The deposition of silicious materials (tephra) due to tins eruption might have provided an opportunity for benthic foraminifers to increase their population subsequently. From ca. 700 yr B.P. (~ 1.250 A.D.) mangroves declined, as indicated by lower frequencies of pollen grain in samples from 30 cm deep upward. It occurred simultaneously with the deposition of coarser sediment and the increase of benthic foraminifer abundance. Interplay of anthropogenic activities, strengthening ENSO cycle, and lowering erosion base level might have been responsible for these environmental changes. [ABSTRACT FROM AUTHOR]

Drastic paleogeography changes in the Indonesian archipelago over the Plio‐Pleistocene, either in response to sea level oscillations or vertical land motion, enabled the periodic emergence of the Sunda shelf. When emerged, this wide continental platform in the heart of the Maritime Continent may have modified regional and global climate systems. We investigate the effect of the exposure of the Sunda shelf on climate dynamics using a set of numerical simulations with (i) atmosphere‐land surface and (ii) fully coupled general circulation models. We first explore the impact of convection schemes on the rainfall regime simulated over the Maritime Continent and show how they could explain the discrepancies among previous studies. We further depict a robust and common mechanism that prevails. We show that diurnal heating of the surface of the continental platform enhances low‐level convergence and local convection, and fosters local precipitations. This effect, to a second order, is modulated by the radiative effect and increased turbulent heat flux driven by vegetated surface properties such as albedo or roughness. Increasing precipitations over the exposed platform also impacts freshwater export into seawater, making salinity of the Indian Ocean and Indonesian Throughflow highly dependent on the routing scheme over the exposed shelf. Key Points: An emerged Sunda shelf induces increased advection and precipitation over the Maritime Continent at seasonal scaleSeasonal response is not dependent on convection parameterization in the modelThe magnitude of regional climate impact of an emerged shelf only partly depends on the vegetation cover prescribed [ABSTRACT FROM AUTHOR]

Abstract Siliciclastic grain size, clay mineralogy, and major element geochemistry of Core MD05–2893 from the lower continental slope off the Sunda Shelf in the southern South China Sea were investigated to assess the response of terrigenous sediment input to sea-level and climatic changes since the last deglaciation. The chronology is based on foraminiferal AMS 14C dates and oxygen isotope records combined with carbonate stratigraphy. In this study, we reconstruct variations in terrigenous sediment input using clay/silt, TiO 2 /CaO, SiO 2 /Al 2 O 3 , Al 2 O 3 /K 2 O, and smectite/(illite + chlorite) proxies. Clay/silt, TiO 2 /CaO, and SiO 2 /Al 2 O 3 ratios are clearly correlated to sea-level change, showing high values during the early phase of deglacial sea-level rise (17.2–14.5 cal ka BP, Stage I) and rapidly decreasing values during the meltwater pulse 1A and further sea-level rise (14.5–11.1 cal ka BP, Stage II). Meanwhile, variations in Al 2 O 3 /K 2 O and smectite/(illite + chlorite) correspond well to monsoon rainfall variability during the late phase of deglacial sea-level rise and Holocene sea-level highstand (11.1–1.5 cal ka BP, Stage III). Based on these records, we recognize three stages of evolution of terrigenous sediment input to the southern South China Sea continental slope. Dominance of terrigenous sediment input occurred during Stage I, when most part of the Sunda Shelf was still exposed and drained by several rivers. The stepwise elevated sea level by meltwater pulse 1A and subsequent rising sea-level after 14.5 cal ka BP could have led to a drop in terrigenous sediment input to this area due to regression of the paleo-Sunda river systems (Stage II). Thereafter during last phase of sea-level rise and sea-level highstand with the evolution of the modern coast, sediments have a clear fingerprint of chemical weathering induced by a strengthening of the East Asian summer monsoon (Stage III). Our findings highlight that the variability of terrigenous sediment input to the lower continental slope in the southern South China Sea was first in the late Pleistocene mainly driven by sea-level change and later in the Holocene by a strengthened East Asian summer monsoon. Highlights • Multiple sources have contributed terrigenous sediments to the southern South China Sea. • Higher terrigenous sediment input to the South China Sea occurred during the sea-level lowstand. • Terrigenous input has been controlled by sea-level change and East Asian monsoon evolution. [ABSTRACT FROM AUTHOR]

The goals of this study were to reconstruct the phylogeny of Prunus subgenus Laurocerasus section Mesopygeum and to provide a preliminary assessment of its spatio‐temporal diversification in the Malesian region. We inferred the phylogeny using nuclear ITS and ETS and plastid psbA‐trnH, rps16, rpl16, and trnC‐petN sequences. Our analyses support the monophyly of sect. Mesopygeum. Within sect. Mesopygeum, we identified four main subclades: (i) Prunus lancilimba from continental Asia; (ii) Prunus ruthii from Malay Peninsula; (iii) a subclade comprising species from areas centered on the Sunda shelf and also a few species from continental Asia and Wallacea; and (iv) a subclade composed of species from areas of the Sahul shelf, with a small number of taxa also from areas of the Sunda shelf, continental Asia, and the Philippines. We estimated that sect. Mesopygeum originated in continental Asia at c. 44.71 Mya (95% HPD: 31.66–46.90). Nine dispersals between major geographic areas were inferred. From continental Asia, three and two dispersals were inferred to the Sunda shelf and the Sahul shelf in the mid‐Oligocene, respectively. Two dispersals were inferred from the Sahul shelf region to the Sunda shelf in late Oligecene and early Miocene, respectively. There were also two dispersals inferred from the Sunda shelf region, one to the Philippines and one to Wallacea, in the middle and late Miocene, respectively. The diversification in sect. Mesopygeum was likely driven by active geologic events and orogenies in the Neogene in the Malesian region. [ABSTRACT FROM AUTHOR]

Abstract: Aim: The genetics of organisms currently isolated in refugia has received little attention compared to post‐glacial expansions. We study the population history and connectivity of a rat endemic to montane habitat in Borneo to better understand the history and potential of populations in interglacial mountain refugia. Location: Sabah, Borneo, Malaysia. Methods: We performed a field survey of the summit rat (Rattus baluensis) on two mountains, Mt. Kinabalu and Mt. Tambuyukon, its entire known distribution. We sequenced mitogenomes and 27 introns (19 of which were polymorphic) in 49 individuals from both populations. We analysed their current genetic structure and diversity, and inferred their demographic history with approximate Bayesian computation. Results: Summit rats were tightly associated with mountain mossy forest and scrubland above 2,000 m, facilitating the prediction of their past and future distributions. The genetic analysis supports a Holocene fragmentation of a larger population into smaller ones that are now isolated in interglacial refugia on mountaintops. These findings are consistent with climatic reconstructions and the retreat of upland forest to higher elevations after the Last Glacial Maximum (LGM), ~21 kya. Main conclusions: The two isolated populations of summit rats formed through the upland shift of their habitat after the LGM. The current trend of global warming will likely lead to diminishing suitable upland habitat and result in the extinction of the population on Mt. Tambuyukon. The population on Mt. Kinabalu, the higher peak, could persist at higher elevations, highlighting the singular value of high tropical mountains as reservoirs of biodiversity during past and ongoing climate change. [ABSTRACT FROM AUTHOR]

We describe a new species of squirrel (Sciuridae, Callosciurus) from Hon Khoai Island, located off the coast of southern Vietnam (centered at ca. 8°26′08″N, 104°49′58″E) and discuss its phylogenetic position in the genus Callosciurus. Compared to other Callosciurus occurring on the Indochina Peninsula, the new species (Callosciurus honkhoaiensis) is strikingly small, especially head and body length, body mass, and hind foot length. Unlike other species of Callosciurus, the hairs at the tip of the tail are white with a black base, and the venter and feet are whitish cream. The new species at present is known only from the type locality, Hon Khoai Island. Phylogenetically, the new species is closely related to C. caniceps, suggesting that it evolved from C. caniceps or an ancestor in common with C. caniceps, possibly during the Pliocene. Genetic distances between the 2 species calculated from comparison of mitochondrial cytochrome b sequences are 10.1–10.3%. During both glaciations and interglaciations of the Pleistocene, the new species may have been isolated from other Callosciurus populations by rivers and sea, respectively. [ABSTRACT FROM AUTHOR]

Geological and climatological processes can drive the synchronous diversification of co-distributed species. The islands of Sumatra and Java have experienced complex geological and climatological histories, including extensive sea-level changes and the formation of valleys between northern, central, and southern components of the Barisan Mountain Range, which may have promoted diversification of their resident species. We investigate diversification on these islands using 13 species of the parachuting frog genus Rhacophorus . We use both mitochondrial and nuclear sequence data, along with genome-wide SNPs to estimate phylogenetic structure and divergence times, and to test for synchronous diversification. We find support for synchronous divergence among sister-species pairs from Sumatra and Java ∼9 Ma, as well as of populations of four co-distributed taxa on Sumatra ∼5.6 Ma. We found that sister species diverged in allopatry on Sumatra and conclude that divergence on Sumatra and Java was affected by sea-level fluctuations that promoted isolation in allopatry. [ABSTRACT FROM AUTHOR]

With 70 named species and multiple morphologically cryptic lineages, the genus Hipposideros is a diverse and taxonomically contentious group of insectivorous bats in the Old World tropics. Half of the named species and most of the cryptic diversity in Hipposideros are concentrated in the bicolor species group. Here we resolve the taxonomic status of Hipposideros bicolor (Temminck, 1834), the species group's namesake. Two morphologically cryptic but acoustically and genetically distinct lineages of H. bicolor co-occur in peninsular Malaysia and Thailand. Pending taxonomic revision, these lineages were named according to the average frequency of maximum energy of echolocation calls of populations in central peninsular Malaysia, H. bicolor-131 and H. bicolor-142. To determine the taxonomic status of the two lineages we measured cranial characters from all available type specimens in the H. bicolor species group, and collected morphometric, acoustic and mitochondrial DNA sequence data for H. bicolor-131, H. bicolor-142, and closely related lineages, from multiple localities on the Malay peninsula and Borneo. Consistent with prior studies, acoustic and genetic analyses strongly support species status for H. bicolor-131 and H. bicolor-142. We find subtle but significant differences in cranial characters, including a longer skull and longer upper and lower tooth rows in H. bicolor-131 relative to H. bicolor-142. Most importantly, inclusion of cranial measurements for type specimens in the H. bicolor species group indicates that H. bicolor-131 should retain the species name, while H. bicolor-142 is distinct from all previously named species. We therefore provide a complete description for this new species of bat from Southeast Asia, Hipposideros kunzi sp. nov. [ABSTRACT FROM AUTHOR]

Abstract: Aim: To test whether or not fungal communities associated with the widespread seagrass, Syringodium isoetifolium can be differentiated on either side of Wallace's line, a boundary line separating Asian and Australasian fauna. Additionally, we examine whether host multilocus genotype predicts fungal community composition. Location: A total of 77 samples were collected from 14 sampling sites spanning the Indonesian archipelago. Methods: We sequenced the fungal ITS1 gene using Illumia MiSeq technology and used a clustering‐free Divisive Amplicon Denoising Algorithm to infer ribosomal sequence variants. Data were analysed via non‐metric multidimensional scaling, Mantel tests and permutational multivariate analysis of variance. Binary and quantitative null models were used to determine whether results significantly deviated from random. Host genotype was determined by genotyping at 18 microsatellite loci and standard genetic analysis was performed in the R package APE. Results: Significant differences in fungal community composition were detected on either side of Wallace's line (p = <.001 R2 = .040). A significant distance decay of similarity pattern was observed between ribosomal sequence variants and geographical distance (p = .001 R2 = .227) and several fungal ribosomal sequence variants were significantly associated with sampling sites found either east or west of Wallace's line. Main conclusions: Fungi are generally considered to have excellent dispersal potentials and marine fungi have the potential to disperse far and wide in an environment that has no obvious barriers to dispersal. Despite this assumed excellent dispersal potential, we show that fungal communities on either side of Wallace's line are significantly different from one another. We speculate that limited dispersal and differences in habitat type are responsible for the observed pattern. Work examining biogeographical patterns in marine fungi is still in its infancy and further research is required to fully understand marine fungal biogeography. [ABSTRACT FROM AUTHOR]

Abstract: Aim: This study seeks to understand the geological and climatological processes that have promoted biodiversity on the Sunda Shelf in Southeast Asia. Using the parachuting frog genus Rhacophorus, we estimate divergence times and quantify the respective contributions of between and within‐island diversification to species richness and endemism. Location: East and Southeast Asia, the Sunda Shelf. Methods: We generated a concatenated mitochondrial and nuclear DNA sequence alignment for 40 species of Rhacophorus. We estimated phylogenetic relationships and divergence times, constructed lineage‐through‐time (LTT) plots and reconstructed ancestral ranges. Results: We found that Rhacophorus originated 33.0 Ma (95% HPD 27.0–38.0 Ma), and that the diversification rate slowed towards the present. Dispersal was important in early Rhacophorus evolution, but subsequent in situ diversification produced most species diversity on Sumatra and Borneo. Clades that diversified via in situ processes contained higher proportions of endemic species. Main conclusions: Species diversification on the Sunda Shelf is ancient and has occurred slowly. Both dispersal and in situ diversification have promoted Sundaland species accumulation, but within‐island phylogenesis has produced a greater proportion of endemic species on Sumatra and Borneo. Species richness and endemism are most influenced by the size of an island, rather than connectivity. [ABSTRACT FROM AUTHOR]

Abstract: Aim: The genus Xylocarpus contains two mangrove species, X. granatum and X. moluccensis, and a rare non‐mangrove, X. rumphii. The two mangrove species are ideal models to study the biogeography of coastal plants with a unique dispersal ability, that is via buoyant propagules. We constructed the phylogeny of Xylocarpus and its relatives and determined the population structures of the two mangrove species. We aimed to elucidate the roles of continental drift and long‐distance dispersal (LDD) in shaping the present‐day distribution of Xylocarpus and to determine the factors affecting the patterns of population differentiation. Location: The Indo‐West Pacific (IWP) region. Methods: Thirty populations of X. granatum, 15 of X. moluccensis and four of X. rumphii were sampled across the IWP region. Five chloroplast DNA intergenic spacers were sequenced for Xylocarpus and outgroup species to determine divergence times. The genetic diversity, divergence and structure of the two mangrove species were further analysed using five nuclear and two chloroplast DNA loci. Migrations between oceanic regions were estimated. Results: The genus Xylocarpus diverged from its sister genus Carapa approximately 19.4 Ma. The populations of X. granatum differentiated into three groups, with genetic breaks present across the Malay Peninsula and Wallacea, whereas X. moluccensis populations differentiated into two groups, with a genetic break present only across the Malay Peninsula. Migration was also observed between populations of the Southeast Asian and Australasian regions in X. moluccensis but not in X. granatum. Main conclusion: Since Xylocarpus originated after the breakup of Gondwana and subsequent plate motions, its current distribution range should have been facilitated by present‐day LDD instead of past continental drift. Despite the capacity of LDD, the presence of differing population structures across land barriers (the Sunda and Sahul Shelves) and ocean currents indicated differential limitations in the dispersal capabilities of X. granatum and X. moluccensis. [ABSTRACT FROM AUTHOR]

We studied the phylogeny, population structure, and demographic history of Scolopsis taenioptera in the western Pacific Ocean. Using the 80 samples collected from four locations, we obtained the nucleotide sequences of mitochondrial cytochrome c oxidase subunit I and cytochrome b genes. We identified two distinct lineages showing a clear phylogeographic break that was possibly due to the Pleistocene sea-level change. One lineage was distributed in Iloilo (Philippines) and the other in Terengganu (Malaysia), Rayong (Thailand), and Ha Long Bay (Vietnam). The Terengganu and Rayong populations showed clear signs of demographic expansion; the Iloilo and Ha Long Bay populations were relatively stable or spatially expanded as geographically subdivided populations. [ABSTRACT FROM AUTHOR]