Paleogene Research Articles

Genome and pan-genome assembly of asparagus bean (Vigna unguiculata ssp. sesquipedialis) reveal the genetic basis of cold adaptation.

Asparagus bean (Vigna unguiculata ssp. sesquipedialis) is an important cowpea subspecies. We assembled the genomes of Ningjiang 3 (NJ, 550.31 Mb) and Dubai bean (DB, 564.12 Mb) for comparative genomics analysis. The whole-genome duplication events of DB and NJ occurred at 64.55 and 64.81 Mya, respectively, while the divergence between soybean and Vigna occurred in the Paleogene period. NJ genes underwent positive selection and amplification in response to temperature and abiotic stress. In species-specific gene families, NJ is mainly enriched in response to abiotic stress, while DB is primarily enriched in respiration and photosynthesis. We established the pan-genomes of four accessions (NJ, DB, IT97K-499-35 and Xiabao II) and identified 20,336 (70.5%) core genes present in all the accessions, 6,507 (55.56%) variable genes in two individuals, and 2,004 (6.95%) unique genes. The final pan genome is 616.35 Mb, and the core genome is 399.78 Mb. The variable genes are manifested mainly in stress response functions, ABC transporters, seed storage, and dormancy control. In the pan-genome sequence variation analysis, genes affected by presence/absence variants were enriched in biological processes associated with defense responses, immune system processes, signal transduction, and agronomic traits. The results of the present study provide genetic data that could facilitate efficient asparagus bean genetic improvement, especially in producing cold-adapted asparagus bean.

New cellular T-DNAs in naturally transgenic plants

Naturally transgenic plants represent the result of Agrobacterium-mediated gene transfer. T-DNA of soil bacteria Agrobacterium integrated into plants genome is called cellular T-DNA (cT-DNA) [1]. Today, more than 50 species of naturally transgenic plants, or natural GMO (nGMO) are known [2, 3]. The function of cT-DNA in plants remains unknown. It is assumed that the fixation of transgenes could give plants different selective advantages depending on which genes had been integrated into the plant [4]. In order to clarify this issue, it is necessary to study more naturally transgenic plants. Until recently, the list of nGM plants contained less than 2 dozen species, but a search through genomic and transriptomic sequencing data made it possible to more than double this list [2]. In this work, we used the same approach, looking for cT-DNA genes in whole genome sequencing data that have appeared in the NCBI WGS since 2021. We found 14 new species of naturally transgenic plants, among which the most extended cT-DNAs were found in Triadica sebifera, Lonicera japonica, and Lonicera maackii. The cT-DNAs in these species are organized as imperfect inverted repeats. In the genomes of the species Paulownia fortunei, Apocynum venetum, Elaeagnus angustifolia, Erythroxylum havanense, E. densum, E. daphnites, E. cataractarum, Ceriops decandra, Camellia oleifera, Silene uniflora, short cT-DNAs containing only opine synthesis genes were found. We also estimated the approximate age of the cT-DNAs. The first described examples date back to the Late Paleogene, and the process continues to the present. Thus, we can conclude that natural GMOs are a widespread phenomenon, many aspects of which remain unclear, requiring additional research on the topic.
 The article was made with support of the Ministry of Science and Higher Education of the Russian Federation in accordance with agreement No. 075-15-2022-322 dated 22.04.2022 on providing a grant in the form of subsidies from the federal budget of the Russian Federation. The grant was provided for state support for the creation and development of a world-class scientific center, Agrotechnologies for the Future.

Tectono-sedimentary evolution of the Paleogene Qikou Sag, Bohai Bay Basin, NE China

The Qikou Sag is a petroliferous tectonic unit within the Bohai Bay Basin, northeast China. The depositional system evolved temporally, spatially, and episodically in five rifting stages (stages 1–5) during the Paleogene and Neogene, with sedimentation responding to regional subsidence. This study focuses on the tectono-sedimentary evolution through stages 2–4, while the main oil-bearing sedimentary rocks were deposited in the Bohai Bay Basin. The depositional system exhibited retrogradation and then progradation during the rifting stage 2 (43–36.7 Ma), retrogradation in stage 3 (36.7–32.8 Ma), and upward coarsening and progradation in stage 4 (32.8–24.6 Ma). This vertical superposition corresponded to three episodic stages of rising and falling lake levels during the Paleogene, which were equivalent to a transgressive with regressive (stage 2), transgressive (stage 3), and then regressive (stage 4) cycle. The sediment fills coincided with the tectonism and the regional subsidence history of the Qikou Sag, which is composed of uplift areas and sub-sags. In this respect, the boundary fault activity around the sub-sags decreased from stages 2–4, leading to the migration of sub-sag depocenters from near faults to the center of sub-sags, which suggests that faults released control over the sedimentation. Secondly, tectonism and the total subsidence rate decreased from SQ1 to SQ7 (stages 2–3) and then accelerated at the end of stage 4 (SQ10 to SQ11). The tectonic subsidence rates decreased quicker than the total subsidence rate; this demonstrates that major rift faulting was the dominant geological process in the early Paleogene, whereas overall subsidence was dominant in the late Paleogene.

Geological structure and dynamic mechanism of the Termit rift basin in West African rift system

Based on seismic and drilling data in the study area, the geological structure and kinematic process of the Termit rift basin were studied using seismic profile interpretation and balanced restoration to find out the dynamic mechanism of the basin. (1) The geological structure of the Termit Basin is represented as a narrow rift basin, with development of series of structural styles in extensional, extensional strike-slip and compressional stress setting. On plane, it is narrow in the north and wide in the south, and transitions from graben to half-graben from north to south; it features a graben controlled by the boundary faults in the north and a fault-overlapped half-graben in the south. (2) Before the Cretaceous, a series of hidden faults developed in the West African rift system, which laid the foundation for the development location and distribution direction of the Termit Basin; during the Cretaceous to Paleogene periods, the basin experienced two phases of rifting in Early Cretaceous and Paleogene, which controlled the initial structure and current structural shape of the basin respectively; during the Neogene to Quaternary, the basin was subjected to weak transformation. (3) In the Precambrian, the Pan-African movement gave rise to a narrow and long weak zone within the African plate, which provided the pre-existing structural conditions for the formation of the Termit Basin. In the Early Cretaceous, affected by the South Atlantic rifting, the Pan African weak zone was reactivated, resulting in the first stage of rifting and the basic structural framework of the Termit Basin. In the Paleogene, affected by the subduction and convergence of the Neo-Tethys Ocean, the African-Arabian plate extended in near E-W trending, and the Termit Basin experienced the second stage of rifting. The oblique extension in this period caused intense structural differentiation, and the current structural pattern of alternate uplifts and depressions took shape gradually.

Petrogenesis and tectonic implications of Cenozoic mafic volcanic rocks in the Kahak area of central Urumieh–Dokhtar magmatic arc, Iran

• Mafic volcanic rocks in the Kahak area were erupted at ∼ 60–55 Ma and ∼ 21 Ma. • The Kahak basaltic rocks are divided into two groups of low and high Nb/Ta ratios. • The petrogenesis of the Kahak basaltic rocks involved slab dehydration and melting. • Slab rollback and mantle metasomatism occurred during the Paleocene–Eocene and Miocene . Cenozoic volcanic rocks are widely distributed in the Urumieh–Dokhtar magmatic arc (UDMA), Iran, but their petrogenesis and tectonic implications remain enigmatic. The volcanic rocks in the Kahak area of the central UDMA are mostly basalt and basaltic andesite. They show enrichment in light rare earth elements and large ion lithophile elements and depletion in the high-field-strength elements (Nb, Ta, and Ti), corroborating a subduction-related origin. U–Pb ages of zircon from these volcanic rocks demonstrate two episodes of magmatism during the Paleocene–Eocene (∼60–55 Ma) and Miocene (∼21.9–21.4 Ma). These rocks have 87 Sr/ 86 Sri values from 0.70485 to 0.70577, ɛ Nd (t) values from +2.0 to +5.0, and zircon Hf isotopes ε Hf (t) values from +8.3 to +10.2. These features with isotopic modeling support derivation from partial melting of an asthenospheric mantle wedge in an extensional intracontinental-arc basin. This mantle source was previously metasomatized by subducted slab components of the Neotethys Ocean. The mafic melts underwent fractional crystallization and minor crustal contamination during magma evolution. The Paleocene–Eocene basaltic rocks have subchondritic Nb/Ta ratios, indicating that the magma source was affected by fluids with low-Nb/Ta ratios, which were released during shallow metamorphism of a subducted slab. However, the Miocene basaltic rocks have unusual superchondritic Nb/Ta ratios, indicating slab melt involvement. Geochemical data and field relationship indicate that mafic volcanism in the Kahak area occurred in an extensional setting associated with the Paleogene shallowing of the northeastward-subducting Neotethyan oceanic lithosphere followed by Late Paleogene and Neogene slab rollback and eventual partial melting of a deeply subducted oceanic slab.

Basin-scale estimates of thermal stress and expelled petroleum from Mesozoic-Cenozoic potential source rocks, southern Gulf of Mexico

The Campeche and Yucatan salt basins remain two of the least explored areas of the Gulf of Mexico basin. This study uses a grid of 23,600 line-km pre-stack depth migrated (PSDM) 2D seismic reflection profiles, shipborne gravity data, and open-source geologic information to model the thermal stress of four potential source intervals (Oxfordian, Tithonian-centered, Cenomanian-Turonian, lower Miocene). We performed map-based, and 1D thermal modeling along two margin-perpendicular transects, each consisting of five pseudo-wells tied to the regional grid of seismic reflection data. Our modeling takes into account thermal stress variations related to the depth of base lithosphere, crustal type and thickness, paleo-water depth, Jurassic salt thickness, and the transient heat flow effects related to recent clastic sedimentation. We predict that deeply-buried, salt-related minibasins along the outer marginal trough are mature for petroleum expulsion with deeply-buried Mesozoic source rocks within the oil window from late Paleogene to early Neogene time. The ‘lag time’ required for vertical oil migration explains why oil maturation occurred during the late Paleogene to early Neogene but active oil seeps are observed today at the sea surface. We predict that oil is present in subsurface traps in the deepest part of the outer marginal trough and we calculate that the Oxfordian source interval has expelled a cumulative 20 million bbl of oil equivalent [BOE]/km2 and that the Tithonian-centered source interval has expelled 67 million bbl of oil equivalent [BOE]/km2.

Depositional record of confined turbidites in syn-subduction intraslope basin: insight from the Tufiti di Tusa Formation (Southern Apennines, Italy)

A detailed lithostratigraphy and facies analysis of a type section of the Tufiti di Tusa Formation, including deep-marine clastic successions with syn-orogenic volcanic detritus and deposited in the late Eocene - early Miocene basin system at the front of the growing Maghrebian - Southern Apennines orogen, is discussed in the paper. Based on facies analysis and composition, the study section was subdivided into the following units, from bottom to top: Unit I, mostly formed by contained-reflected beds (including a bed similar to the Contessa megabed of the Marnoso-arenacea Formation in the Northern Apennines), with the ratio of sandstone intervals to mudstone intervals (S/M) of 0.6 and with mostly-calciclastic sandstone to siltstone fraction; Unit II, recording a moderate decrease in contained-reflected beds and a moderate increase in slurry beds, with S/M ratio of 0.9, and with mostly-siliciclastic sandstone to siltstone fraction; Unit III, recording a further decrease in contained-reflected beds and an evident increase in slurry beds and very-thick beds with a basal massive very coarse to coarse-grained sandstone, with S/M ratio of 2.5, and with mostly-volcaniclastic sandstone to siltstone fraction.In accordance with the depositional models for the infill of confined turbidite basins, Units I and II are here interpreted as representing a flow ponding depositional phase, while Unit III as iconic of a flow stripping depositional phase. The compositional variation from Unit I to Unit II records cutoff of calciclastic supply from underplate sources, possibly tied to tectonic uplift of the external basin margin; while that from Unit II to Unit III records sudden availability of volcaniclastic sediment possible due to burial of morphological high(s) between the internal volcanic arc (source of the volcaniclastic sediment) and the depositional basin, and/or establishment of tectonically-controlled conduits cutting the above high(s). This study may improve the knowledge not only of infilling evolution of confined turbidite basins, but also of the depositional setting of the late Paleogene Southern Apennines subduction margin in the Central Mediterranean.

The Hoatzin

Joel Cracraft introduces the Hoatzin (Opisthocomus hoazin), an odd and enigmatic bird that defies classification.

Asthenospheric flow through the Izanagi-Pacific slab window and its influence on dynamic topography and intraplate volcanism in East Asia

The tectonics of East Asia are notoriously complex. Consisting of an intricate patchwork of microplates and accreted terranes, even the Cenozoic tectonic history of the region remains controversial, and many differing reconstructions have been proposed. While the exact kinematics remain poorly constrained, it is generally accepted that East Asia has been characterised by a long history of subduction and downwelling. However, numerous geological observations, at a first glance, appear to lie in stark contrast to this history. For example, seismically slow anomalies in the uppermost mantle are extensive in this region and coincide spatially with widespread intraplate volcanism since the latest Paleogene, which is seemingly at odds with the cold upper mantle and downwelling flow expected from a history of subduction. Here, we propose a solution to this paradox, in which hot asthenospheric material flows through the slab window opened by the subduction of the Izanagi-Pacific ridge during the early Cenozoic, passing from the Pacific domain into East Asia. To investigate this hypothesis, we compare several independent geological observations to the asthenospheric flow predicted by a suite of recently published global mantle circulation models. The timing and location of intraplate volcanism is compared with the predicted distribution of this hot material through time, while observations linked to uplift and erosion are compared to the changes in dynamic topography that it induces. These include the widespread late Eocene–Oligocene sedimentary hiatus in far eastern China and the regional erosion of the South China Block since the Miocene inferred from Apatite Fission Track Thermochronology studies. The westward influx of hot asthenospheric material is a robust feature in the models, being predicted regardless of the implemented Cenozoic tectonic reconstruction. However, we find that a small Philippine Sea Plate that overrides a marginal “vanished ocean” during the late Cenozoic provides an optimal fit to the geological observations considered. Flow of hot asthenospheric material through gaps in subduction has the potential to significantly affect the geodynamic and geologic history of backarc and hinterland regions, and might have been a recurring phenomenon throughout Earth’s history. However, further research will be required in order to establish this.

The significance of recent diversification in the Northern Hemisphere in shaping the modern global flora revealed from the herbaceous tribe of Rubieae (Rubiaceae)

The global herbaceous flora is probably shaped by both ancient and/or recent diversification, companied with the impacts from geographic differences between the Northern and Southern Hemispheres. Therefore, its biogeographic pattern with respect to temporal and spatial divergence is far from full understanding. Tribe Rubieae, the largest herbaceous tribe in the woody-dominant Rubiaceae, provides an excellent opportunity for studying the macroevolution of worldwide colonization. Here, we aim to reconstruct the evolutionary history of Rubieae with regard to climate fluctuation and geological history in the Cenozoic. A total of 204 samples of Rubieae representing all the distribution areas of the tribe were used to infer its phylogenetic and biogeographic histories based on two nrDNA and six cpDNA regions. The ancestral area of Rubieae was reconstructed using a time-calibrated phylogeny in RASP and diversification rates were inferred using Bayesian analysis of macroevolutionary mixtures (BAMM). Our results show Rubieae probably originated in European region during the middle Oligocene, with the two subtribes separating at 26.8 million years ago (Ma). All the genera in Rubieae formed separate clades between 24.79 and 6.23 Ma. The ancestral area of the subtribe Rubiinae was the Madrean-Tethyan plant belt and the North Atlantic land bridge (NALB) provided passage between North America and Europe for Rubiinae. The subtribe Galiinae clade originated in Europe/central Asia during the late Oligocene. Two diversification shifts were detected within Rubieae in the late Neogene. Most extant Rubieae species diverged recently during the Neogene within clades that generally were established during the late Paleogene. The tribe shows complex migration/dispersal patterns within the North Hemisphere combined with multiple recent dispersals into Southern Hemisphere. Our results highlighted the important role of recent biogeographic diversification in the Northern Hemisphere in shaping the modern global herbaceous flora during the latest and rapid worldwide expansion in the Neogene.

A New Genus of Spittlebugs (Hemiptera, Cercopidae) from the Eocene of Central Tibetan Plateau.

Simple SummaryThe superfamily Cercopoidea is commonly named as “spittlebugs”, as its nymphs excrete a spittle mass to protect themselves and hide from predators and parasites. Cosmoscartini (Cercopoidea: Cercopidae) is a large and brightly colored Old World tropical tribe, including 11 genera. A new genus Nangamostethos gen. nov. (type species: Nangamostethos tibetense sp. nov.) of Cosmoscartini is described from Niubao Formation, the late Eocene (ca. 39 million years ago) of central Tibetan Plateau (TP), China. Its placement is ensured by comparison with all the extant genera of the tribe Cosmoscartini. The new fossil represents one of the few fossil Cercopidae species described from Asia. It is likely that Nangamostethos was extinct from the TP due to the regional aridification and an overturn of plant taxa in the last 33 million years.The superfamily Cercopoidea is commonly named as “spittlebugs”, as its nymphs produce a spittle mass to protect themselves. Cosmoscartini (Cercopoidea: Cercopidae) is a large and brightly colored Old World tropical tribe, including 11 genera. A new genus Nangamostethos gen. nov. (type species: Nangamostethos tibetense sp. nov.) of Cosmoscartini is described from Niubao Formation, the late Eocene of central Tibetan Plateau (TP), China. Its placement is ensured by comparison with all the extant genera of the tribe Cosmoscartini. The new fossil represents one of few fossil Cercopidae species described from Asia. It is likely that Nangamostethos was extinct from the TP due to the regional aridification and an overturn of plant taxa in the late Paleogene.

Mapping the facies and geomorphology of igneous bodies by integrating multiple disciplines data: A case study of the BZ-A oilfield, Bohai Bay Basin, China

The BZ-A oilfield is one of the significant discoveries within the Huanghekou Sag, the southern Bohai Sea Basin, China, and the reservoirs of the BZ-A oilfield were deposited in the Paleogene period. Unfortunately, the spatial continuity of the Paleogene clastic reservoirs of the BZ-A oilfield was destroyed by the widely distributed igneous rocks. Characterizing those “isolated” clastic geobodies is the main task in the exploration and production phases. The exploration wells within the BZ-A oilfield demonstrate that the size of the clastic geobodies is one of the main factors that determine if a new drilled well is a commercial oil-producing well. The spatial distribution and the size of igneous rocks are other important factors affecting whether a drilled well is an oil-producing well. Thus, the analysis of 3D geomorphology of igneous rocks is among the most important tasks in well and development planning. We integrate 3D seismic data, well logs, and core data to characterize the Paleogene igneous bodies within the BZ-A oilfield. The analyzing procedure begins with determining the igneous rock types by analyzing the texture of cores and corresponding thin sections. Then, the volcanic/volcaniclastic facies are defined by integrating the well logs and igneous rock. Finally, the volcanic edifices are interpreted by integrating the seismic data, well logs, and core data. The analysis demonstrates that the volcanic edifice usually consists of five facies (volcanic conduit, effusive, explosive, extrusive, volcanic sedimentary, and subvolcanic facies). The overall shape of the edifice and the distribution of each facies are controlled by the volcanic eruption styles. In our study area, the seismic variance attribute can be used to locate the volcanic conduit facies, and the seismic root-mean-square amplitude can characterize the volcanic effusive facies.

Geochemical characteristics of crude oils and hydrocarbon accumulation in the Palogue Oilfield, Melut Basin, South Sudan

The Palogue Oilfield is the largest oilfield in the Melut Basin, an important petroliferous rift basin in Africa. Geochemical analyses, including gas chromatography and gas-mass chromatography were adopted to analyze the biomarker composition and geochemical characteristics of oils from the Palogue Oilfield and the neighboring Moleeta and Jamous lows. Oil-oil correlations were performed for the Palogue Oilfield and the Moleeta/Jamous lows, and the hydrocarbon accumulations of the Palogue Oilfield were studied based on the oil maturities, thermal evolution modelling of the Moleeta/Jamous lows and the petroleum system analysis of the Melut Basin. Geochemical analysis indicates that the oils of the Moleeta/Jamous lows are derived from terrestrial higher plants, with the low ratios (<1) of light n-alkanes to heavy n-alkanes (∑nC21-/∑nC22+) and the predominance of C29 regular sterane, but there still are some geochemical differences in distribution shape of n-alkanes, paleoenvironments and maturities in these two lows. The oils of the Palogue Oilfield have mixed-source features and their geochemical characteristics are more like those of the Jamous low, and a few oils are like the oils in the Moleeta low. The Jamous low has a larger area and higher thermal maturity than the Moleeta low, and the abundant oils generated by the Al Renk source rocks (upper part of early Cretaceous) in the Jamous low are the primary contributors to the formation of the giant Palogue Oilfield. The vitrinite reflectance equivalent (Rc) converted by the methyl phenanthrene ratio indicates that the oil maturities of the Palogue Oilfield range from 0.65% to 1.07%. Thermal evolution modelling of the Moleeta/Jamous lows indicates that the Jamous low generated and expelled hydrocarbons earlier than the Moleeta low. The maturity of Al Renk source rocks reached 0.65% at 70Ma (Late Cretaceous) and 1.07% at 38Ma (Eocene) in the Jamous low, and reached 0.65% at 59Ma (Paleocene) and 1.07% at present in the Moleeta low. Thus, the high-maturity oils (Ro> 1.07%) generated by the source rocks in the Jamous low since 38 Ma have not been discovered in the primary production layers of the Paleogene Samma and Yabus Formations in the higher part of the Palogue structure, a drape-anticline developing on a paleo-high between the Jamous and Moleeta lows. The maturity parameter of Ts/(Ts + Tm) shows that the oil maturities from late Cretaceous Formation in the well PS-7 and PS-8 are close to the oils in the Jamous Low and are significantly higher than the oils from the Paleogene Formation in the higher part of the Palogue structure. So, the Cretaceous Formation under the Paleogene pay zones and the Paleogene Formation in the lower part of the Palogue structure likely accumulated high-maturity oils from the Jamous low, which will enhance the exploration potential of the Palogue Oilfield. The petroleum system study indicates that the end of Oligocene (late Paleogene) is the critical moment for the Paleogene hydrocarbon accumulations in the Melut Basin. Whereas, the high-maturity oil accumulations (Ro> 1.07%) in Cretaceous formations in the Palogue Oilfield occurred after 38Ma (late Eocene), when the Al Renk source rocks in the Jamous low started to enter the high thermal evolution stage with the Ro> 1.07%.

Phylogeny, Divergence Time Estimation and Biogeography of the Genus Onnia (Basidiomycota, Hymenochaetaceae).

Species of Onnia are important tree pathogens and play a crucial role in forest ecosystems. The species diversity and distribution of Onnia have been studied, however, its evolutionary history is poorly understood. In this study, we reconstructed the phylogeny of Onnia using internal transcribed spacers (ITS) and large subunit (LSU) rDNA sequence data. Molecular clock analyses developed the divergence times of Onnia based on a dataset (ITS + LSU rDNA + rpb1 + rpb2 + tef1α). Reconstruct Ancestral State in Phylogenies (RASP) was used to reconstruct the historical biogeography for the genus Onnia with a Dispersal Extinction Cladogenesis (DEC) model. Here, we provide a robust phylogeny of Onnia, with a description of a new species, Onnia himalayana from Yunnan Province, China. Molecular clock analyses suggested that the common ancestor of Onnia and Porodaedalea emerged in the Paleogene period with full support and a mean stem age of 56.9 Mya (95% highest posterior density of 35.9–81.6 Mya), and most species occurred in the Neogene period. Biogeographic studies suggest that Asia, especially in the Hengduan-Himalayan region, is probably the ancestral area. Five dispersals and two vicariances indicate that species of Onnia were rapidly diversified. Speciation occurred in the Old World and New World due to geographic separation. This study is the first inference of the divergence times, biogeography, and speciation of the genus Onnia.

Diversity, Distribution, and Biogeography of Freshwater Fishes in Guangxi, China.

Simple SummaryThe Guangxi Zhuang Autonomous Region has one of the most abundant aquatic biodiversity in China, and it is a hotspot of global biodiversity research. In the present study, we explored the diversity, distribution, and biogeography of freshwater fishes in Guangxi. Our results showed that 380 species of freshwater fishes were recorded in Guangxi; the species diversity from northwest to southeast gradually decreased for most Sub−basins; the spatial turnover component was the main contributor to beta diversity; the freshwater fish system belonged to the South China division in the Southeast Asiatic subregion of the Oriental region.The Guangxi Zhuang Autonomous Region has the largest number of cavefish species in the world and is a global biodiversity hotspot. In this study, a species list of freshwater fishes in 12 Sub−basins of Guangxi was compiled systematically. Moreover, the species composition and distribution of the diversity were analyzed via the G-F index, taxonomic diversity index, and beta diversity index. Results showed that 380 species of freshwater fishes were recorded in this region, which belonged to 158 genera in 43 families and 17 orders in 2 phyla, in which 128 species of endemic fishes and 83 species of cavefish accounted for 33.68% and 21.84%, respectively. The species diversity from northwest to southeast gradually decreased for most Sub−basins. The G-F index has generally risen in recent years. The taxonomic diversity index showed that the freshwater fish taxonomic composition in Guangxi is uneven. The spatial turnover component was the main contributor to beta diversity. A cluster analysis showed that the 12 Sub−basins in the study area could be divided into four groups, and the phylogenetic relationships of freshwater fishes in Guangxi generally reflect the connections between water systems and geological history. The freshwater fish system in Guangxi, which belonged to the South China division in the Southeast Asiatic subregion of the Oriental region, originated in the early Tertiary period. The results will provide the information needed for freshwater fish resource protection in Guangxi and a reference for promoting the normalization of fish diversity conservation in the Pearl River Basin and other basins.

Climatic and tectonic drivers shaped the tropical distribution of coral reefs

Today, warm-water coral reefs are limited to tropical-to-subtropical latitudes. These diverse ecosystems extended further poleward in the geological past, but the mechanisms driving these past distributions remain uncertain. Here, we test the role of climate and palaeogeography in shaping the distribution of coral reefs over geological timescales. To do so, we combine habitat suitability modelling, Earth System modelling and the ~247-million-year geological record of scleractinian coral reefs. A broader latitudinal distribution of climatically suitable habitat persisted throughout much of the Mesozoic–early Paleogene due to an expanded tropical belt and more equable distribution of shallow marine substrate. The earliest Cretaceous might be an exception, with reduced shallow marine substrate during a ‘cold-snap’ interval. Climatically suitable habitat area became increasingly skewed towards the tropics from the late Paleogene, likely steepening the latitudinal biodiversity gradient of reef-associated taxa. This was driven by global cooling and increases in tropical shallow marine substrate resulting from the tectonic evolution of the Indo-Australian Archipelago. Although our results suggest global warming might permit long-term poleward range expansions, coral reef ecosystems are unlikely to keep pace with the rapid rate of anthropogenic climate change.

Paleo-exhumation histories of the Sakarya and the Istanbul Zones of the Western Pontides, the Almacık Block and its surroundings, NW Turkey

ABSTRACT The Almacık Block is a tectonic sliver formed during the activity of the North Anatolian Fault Zone (NAFZ). It includes two important tectonic zones of the Western Pontides (NW Anatolia): the İstanbul and the Sakarya Zones meet along a suture zone called the Intra-Pontide Suture Zone (IPSZ). The units within the İstanbul Zone are exposed in the eastern part of the Almacık Block, whereas the rocks of the Sakarya Zone are exposed in the west. In the presented study, some of the magmatic rocks have been analysed using the zircon U-Pb method: these rocks have previously been either incorrectly or not dated. The U-Pb results have shown that some of the granitic rocks in the İstanbul Zone, which intruded into the amphibolites of the Intra-Pontide Suture Zone, have a crystallization age of 559–556 Ma. A granitoid block in the Upper Cretaceous wild flysch formed over the units of the İstanbul Zone had an age of ~566 Ma. Two distinct granitoid bodies in the Sakarya Zone were dated at 404.5 ± 3.9 Ma (Early Devonian) and 161.8 ± 0.82 Ma (Late Jurassic) ages. The palaeo-exhumation evolutions of the zones were obtained using the zircon (U-Th)/He technique (ZrHe) to understand the differences in the geological evolution of the individual zones. ZrHe ages of the samples obtained from the İstanbul Zone indicate a pronounced Early Cretaceous palaeo-exhumation period. The Middle-Upper Jurassic Mudurnu Formation in the Sakarya Zone gave ZrHe ages close to its sedimentation age, which indicates that the major part of the unit was not buried too deep to open the ZrHe closure system. Unlike those the İstanbul Zone, the main ZrHe age peaks of the Sakarya Zone are ~202, 160, 98, 74, and 52 Ma. Finally, a sample of the metamorphic rocks that were assigned to the IPSZ yielded a peak age of ~63 Ma, which indicates that the final closure of the Intra-Pontide Ocean (IPO) took place during the Early Tertiary.

Estimated Divergence Times of Lecanicillium in the Family Cordycipitaceae Provide Insights Into the Attribution of Lecanicillium.

BackgroundThe genus Lecanicillium W.Gams & Zare is a recognized insect pathogen but members of the genus have been found parasitizing various hosts including arthropods, nematodes, plants, and fungi. The new classification system for fungi proposed to reject Lecanicillium and transfer some of the species to the genus Akanthomyces. However, the attribution problem of most species in the original genus Lecanicillium remains unsolved. The current study aimed to improve understanding of the pivotal internal phylogeny in Lecanicillium by estimating the divergence times of Lecanicillium to provide additional insights into the status of this genus within the family Cordycipitaceae.ResultsDating analyses support the supposition that the ancestor of Lecanicillium was in the Cretaceous period (84.36 Mya, 95% HPD: 72.12–94.74 Mya). After originating from a common ancestor, eight clades of Lecanicillium were derived and evolved independently in parallel with other genera of Cordycipitaceae. Based on the clear divergence age estimates, Lecanicillium clade 8 originated earlier as an independent group in the Cretaceous period (75.61 Mya, 95% HPD: 63.31–87.54 Mya), while Lecanicillium clades 1–7 originated later as an independent group in the boundary of the Cretaceous and Paleogene periods (64.66 Mya, 95% HPD: 52.75–76.74 Mya). Lecanicillium huhutii formed an independent branch in a polytomy together with a clade containing Lecanicillium tenuipes (BI posterior probabilities 1, ML bootstrap 100%).ConclusionThe pivotal internal phylogeny, origin, and evolutionary history of Lecanicillium in the family Cordycipitaceae were investigated. Phylogenetic and morphological analyses indicated that there are eight representative clades (four representative branches of evolutionary history), including clade 1 (members have a relatively uniform sporulation structure comprising globose heads with a higher number of conidia), clade 8 (including all members of Gamszarea), clades 2–5 (the differences of the divergence time estimations were smaller compared with other clades), and clade 6–7 (members are close to Gibellula, Hevansia, and Ascopolyporus). Based on the above findings, a novel spider-pathogenic fungus, Lecanicillium huhutii, is described. All other species in Lecanicillium clade 1 (Lecanicillium araneogemum, L. nodulosum, L. pissodis, and L. uredinophilum) should be transferred to the genus Akanthomyces. Furthermore, the monotypic genus Parengyodontium should be merged with the genus Gamszarea. More novel species need to be discovered to thoroughly resolve the attribution problem of Lecanicillium. Finally, no major lineages of Lecanicillium were correlated with the nearby Cretaceous-Tertiary extinction event, indicating that the diversity of Lecanicillium is more likely to be caused by long-term environmental adaptation and coevolution with insects rather than by dramatic extinction events.

Lateral Growth Mechanism of Proto‐Tibetan Plateau in the Late Paleogene: Implications From Detailed Crustal Structures of the Hoh Xil Basin

AbstractThe Hoh Xil Basin (HXB) was located in the foreland of the proto‐Tibetan Plateau and has obtained a high elevation and thick crust since the Late Oligocene. However, crust thickening cannot be explained by the limited amount of upper crustal shortening and requires a further mechanism. Based on a linear dense nodal array, we use the receiver function method to study the detailed crustal structure beneath the HXB. Our images reveal that the HXB crust has been thickened to &gt;70 km and is thicker than the protoplateau's crust. A series of north‐dipping interfaces imaged in the lower crust implies widespread imbrication structures. Considering the uplift history of the plateau, we propose that isostatic‐driven adjustments could equalize crustal thickness variations across the protoplateau margin in the Paleogene, and the HXB was elevated by extensive imbrications accommodated to a northward injection of the protoplateau lower crust in the Late Paleogene.

Long-term floristic and climatic stability of northern Indochina: Evidence from the Oligocene Ha Long flora, Vietnam

The antiquity of the tropical Asian flora is being revealed by recent detailed work on a number of Cenozoic plant megafossil sites, some of which have been radiometrically dated for the first time, but our knowledge of how the highly diverse modern biota came into being remains poor due to a sparsity of records. In this paper, we describe fossil plant assemblages from the Oligocene Dong Ho Formation of the Ha Long region, northern Vietnam. The Oligocene Ha Long megafossil flora has so far yielded 38 species, including conifers and angiosperms mainly belonging to Fagaceae, Lauraceae and Dipterocarpaceae, all with significant tropical Asian kinship. The Ha Long flora is similar to other Paleogene floras from southern China, especially those from the Pan Gulf of Tonkin region. The Ha Long floral composition is typical of a tropical-subtropical ecotone and the vegetation is reconstructed as a lowland tropical evergreen forest mixed with calcicole (limestone-loving) taxa. These taxa and the vegetation type they comprise still exist in this area. Palaeoclimate reconstruction made using both the Coexistence Approach and the Climate Leaf Analysis Multivariate Program indicate a mean annual temperature of ~20 °C, a coldest month mean temperature around 10 °C, and yearly precipitation averaging almost 2000 mm. These results suggest a warm and humid peripheral tropical environment. Floristic and climatic comparison within the Ha Long and other southern China palaeofloras reveals a long-term environmental, floristic and vegetational stability in this region since the Paleogene. This long-maintained plant diversity also provided a source for populating the East Asian flora and vegetation after the late Paleogene East Asian arid belt retreat.