Subtropical Asia Research Articles

Pharmacognostic study and preliminary phytochemical investigation of Andrographis paniculata (Burm.f.) Wall. ex Nees

Andrographis paniculata (family –Acanthaceae) is an annual herbaceous plant with branches that grows up to a height of 50-150 cm in moist, shaded areas. Its stem is abruptly quadrangular, heavily branched, and has a delicate texture that is readily broken. It is found in Southeast Asia, tropical and subtropical Asia, and a few other nations like Vietnam, Cambodia, and the Caribbean islands, Indonesia, Laos, Malaysia, Myanmar, Sri Lanka and Thailand etc. It is widely used in different traditional medicinal systems or countries for medicinal purposes by the traditional practitioners, tribes or community as a folklore remedies. The present communication provides a detailed account of the pharmacognostic study carried out on various parts of the Andrographis paniculata. The study includes macroscopy, microscopy, powder microscopic studies, physicochemical tests, preliminary phytochemical screening, development of HPTLC (High Performance Thin Layer Chromatography) fingerprints profile and heavy metal tests. Physicochemical parameters were performed and found average values of three parts (root, stem and leaf) such as root loss on drying at 1050C 4.93% w/w, total ash value 10.16% w/w, acid insoluble ash value 0.21% w/w, alcohol soluble extractive value 13.98% w/w and water soluble extractive value 25.77%w/w. Stem loss on drying at 1050C 6.23% w/w, total ash value 6.88% w/w, acid insoluble ash value 0.25% w/w, alcohol soluble extractive value 18.46% w/w and water soluble extractive value 21.94%w/w and leaf loss on drying at 1050C was found 6.29% w/w, total ash value 7.30% w/w, acid insoluble ash value 0.13% w/w, alcohol soluble extractive value 21.93% w/w and water soluble extractive value 38.68%w/w. HPTLC (High Performance Thin Layer Chromatography) fingerprints profile of methanolic extract was done by using mobile phase toluene: ethyl acetate (7:3). Andrographolide and Ferullic acid standard markers were applied, major spots Rf values with colour were recorded before derivatization at 254nm. Rf values are 0.25 black, leaf, stem and root with Andrographolide standard marker, and 0.20 light black color of stem, and root with Ferullic acid standard marker. Andrographolide is higher present in leaf which was range from 1.51-162 than the stem range1.46-153 and root range 1.45-1.150, while Ferulic acid was higher present in stem range from 0.91-0.96 than root 0.76-0.82 but absent in leaf. Heavy metals i.e Pb, Cd, As, & Hg were tested and found under WHO limits Established parameters can be used as standards for quality control and identification of the plant in herbal compound formulations and also preparation of a monograph of the plant.

Fruit and seed morphometry and seed structure of the potentially invasive Calotropis procera (Aiton) W.T. Aiton (Apocynaceae)

Background: Calotropis procera is a plant native in the tropics and subtropics of Asia and Africa. In Mexico, its presence is now registered in Yucatán, Quintana Roo and Oaxaca.
 Questions and / or Hypotheses: Fruit and seed morphometry vary among places where it is native or exotic? Are seed structures well identified in Calotropis procera?
 Studied species: The exotic Calotropis procera has been already reported in several states in Mexico, however, information about its reproductive biology in Mexican populations is scarce. 
 Studied site and dates: Fruits were collected in Oaxaca, Mexico in September 2019.
 Methods: We obtained fruit and seed morphometric data and seed images with microscopy.
 Results: The fruits are green and ovoid. The average number of seeds per fruit is 364 ± 86 (SD). The seed is brown and flattened dorsoventrally. The length of the seeds is 8.37 ± 0.413 mm, the width is 5.01 ± 0.39 mm, and the weight is 10.5 ± 7.86 mg. The position of the hilum and the micropyle is reported and the occurrence of two types of trichomes on the testa. We suggest that the protrusion on the ventral surface of the seed is the raphe.
 Conclusions: From data obtained we concluded that fruit and seed characteristics are well conserved in this species. We confirmed the position of the hilum and micropyle and reported the presence of two types of trichomes in the testa. Location of the raphe is suggested, providing information that may be useful for future taxonomic studies.

Regime shift of the leading mode of winter surface wind speed in northwest China in 2003/04 and its possible link with Barents–Kara sea ice

AbstractUsing the ERA‐5 reanalysis datasets, NCEP/NCAR sea ice concentration (SIC) and observed winter surface wind speed (WSWS) in northwest China during 1979–2020, this study examined the regime shift of the leading mode of observed WSWS in northwest China and investigated its possible link with the winter Barents–Kara Sea (BKS) SIC. The leading mode of observed WSWS in northwest China showed negative anomalies in southern and northeastern Xinjiang, Gansu, western and northern Shaanxi Provinces, and positive anomalies in northwestern and middle Xinjiang, Qinghai and Ningxia Provinces. The signs of WSWS in the leading mode is generally opposite to their trends during 1979–2020. Leading principal component (PC1) of observed WSWS in northwest China underwent an obvious decreasing regime shift in 2003/04, as well as the winter BKS SIC. There are significant correlations between PC1 and BKS SIC on both interdecadal and interannual timescales. Decadal decrease of BKS SIC is accompanied with a positive phase of Scandinavia pattern (SP) with positive anomalies of 500‐hPa geopotential height over subtropical North Atlantic, Arctic‐Ural region and southern Asia, and negative anomalies over northern North Atlantic‐West Europe and Siberia regions. BKS SIC and SP significantly influenced the Northern China Wind Index (NCWI) at 200 hPa on interdecadal timescale, which was related to the PC1 on both interdecadal and interannual timescales after removing the signal of Arctic Oscillation. Meridional configuration of Siberian cyclonic anomaly and southern Asian anticyclonic anomaly associated with the winter BKS SIC could enhance the intensity of NCWI, which favoured the increase of observed WSWS in northwest China and thereby may contribute to the regime shift in 2003/04 of the leading mode. However, there were still some stations showing decreasing regime shift, which mainly located at the region of steeping terrain. These decreasing changes of WSWS may be related to circumfluence effect of terrain, urbanization and local microclimate, and these reasons still need further detailed study.

Paragonimiasis.

Paragonimiasis is a zoonotic disease caused by lung flukes of the genus Paragonimus. Humans usually become infected by eating freshwater crabs or crayfish containing encysted metacercariae of these worms. However, an alternative route of infection exists: ingestion of raw meat from a mammalian paratenic host. Adult worms normally occur in pairs in cysts in the lungs from which they void their eggs via air passages. The pulmonary form is typical in cases of human infection due to P. westermani, P. heterotremus, and a few other species. Worms may occupy other sites in the body, notably the brain, but lung flukes have made their presence felt in almost every organ. Ectopic paragonimiasis is particularly common when infection is due to members of the P. skrjabini complex. Human paragonimiasis occurs primarily in the tropics and subtropics of Asia, Africa, and the Americas, with different species being responsible in different areas (Table 6.1).

A new Ornithophila (Diptera: Hippoboscidae) species from Baikal State Nature Reserve (Russia)

The parasitic family Hippoboscidae is distributed around the world and currently includes more than 200 species. These insects are of high veterinary importance both as carriers of dangerous diseases and as transport for other groups of parasites. The genus Ornithophila is one of the smallest genera among Hippoboscidae. Currently, the genus Ornithophila includes only two species, namely Ornithophila gestroi and O. metallica. These species are full-winged, widely specialised parasites on birds that inhabit the tropics and subtropics of Asia, Africa, Europe, and Central Asia, including Russia and Kazakhstan. During the annual bird ringing in the Baikal State Nature Reserve (Russia), a new Ornithophila (Diptera: Hippoboscidae) species (Ornithophila baikalica sp. nov.) was collected and described. Ornithophila baikalica sp. nov. was found on Arundinax aedon, a bird that breeds in the south of Siberia and the Far East and migrates in winter to Southeast Asia, and sometimes to Egypt, Bhutan, Japan, and Malaysia. Ornithophila baikalica sp. nov. differs from the two other known species of the genus by reducing of tergites 3–5 of the female abdomen to the size of points and in the number of prescutellar setae, namely one long dark seta and several short light seta. Additionally, O. baikalica differs from O. metallica by the wing microtrichia, on which wings they are present, and by the smaller body size, body colour and wing length from O. gestroi. A new key for all three known Ornithophila species is composed.

COMPARATIVE ANALYSIS OF THE ANATOMICAL AND MORPHOLOGICAL FEATURES OF RHEUM TATARICUM L. PLANTS FROM DIFFERENT ECOPOPULATIONS

There are about 60 species of the genus Rheum L. (Polygonaceae) distributed mainly in temperate and subtropical Asia, with the largest number (38 species, including 19 endemics) recorded in China. All species of the genus are used as medicinal plants. According to modern pharmacology, the most important property of the rhubarb root is regulation of the stomach and intestine function, due to its laxa-tive effect; rhubarb also has antipyretic properties and antioxidant activity. The high content of dietary fibers provides protection against cardiovascular diseases, and vitamin K is valuable for the prevention of osteoporosis. However, the active ingredients and their mechanism of action have not been sufficiently studied.Rheum tataricum L., known for its high resistance to drought, salinity, and lack of nutrients is the least studied species of wild rhubarb. The whole plant, and especially the leaves, contains several toxic compounds, in particular anthraquinone glycosides and calcium oxalate crystals. Here we present the results of a comparative analysis of the anatomical and morphological structure of Rh. tataricum plants from ecopopulations growing in the Balkhash and Karatal districts of the Almaty region. We identified the differences due to the weather and climatic conditions of the ecopopulations. It is important to note that many idioblasts containing calcium oxalate were found in the rhizomes of Rh. tataricum, which prevent animals from eating plants and getting poisoned. The number of idioblasts in the central circle of the Rh. tataricum rhizome was smaller in the Balkhash district than in the Karatal district, while the idioblasts were larger in size in the former district. The medicinal and nutritional value of Rh. tataricum growing in a semi-desert environment indicates a high potential of the species in plant breeding, medicine, and as a food source.

No generality in biodiversity-productivity relationships along elevation in temperate and subtropical forest landscapes

An improved understanding of biodiversity-productivity relationships (BPRs) along environmental gradients is crucial for effective ecosystem management and biodiversity conservation. The stress-gradient hypothesis suggests that BPRs are stronger in stressful environments compared to more favorable conditions. However, there is limited knowledge regarding the variation of BPRs along elevational gradients and their generality across different landscapes. To study how BPRs change with elevation, we harnessed inventory data on 6,431 trees from 152 plots surveyed twice in eight to ten year intervals in mountain forests of temperate Europe and subtropical Asia. We quantified the relationship between aboveground productivity and different biodiversity measures, including taxonomic, functional, and phylogenetic diversity. To elucidate the processes underlying BPRs, we studied the variation of different functional traits along elevation across landscapes. We found no general pattern of BPRs across landscapes and elevations. Relationships were neutral for all biodiversity measures in temperate forests, and negative for taxonomic and functional diversity in subtropical forests. BPRs were largely congruent between taxonomic, functional and phylogenetic diversity. We found only weak support for the stress-gradient hypothesis, with BPRs turning from negative to positive (effect not significant) close to the tree line in subtropical forests. In temperate forests, however, elevation patterns were strongly modulated by species identity effects as influenced by specific traits. The effect of traits such as community-weighted mean of maximum plant height and wood density on productivity was congruent across landscapes. Our study highlights the context-dependence of BPRs across elevation gradients and landscapes. Species traits are key modulating factors of BPRs and should be considered more explicitly in studies of the functional role of biodiversity. Furthermore, our findings highlight that potential trade-offs between conserving biodiversity and fostering ecosystem productivity exist, which require more attention in policy and management.

Effects of global warming and Tibetan Plateau uplift on East Asian climate during the mid-Cretaceous

Sedimentary records indicate that subtropical and mid-latitude East Asia exhibited considerable drying and wetting, respectively, during the mid-Cretaceous, which is considered to be relevant to much higher atmospheric carbon dioxide (pCO2) concentrations and/or proto-Tibetan Plateau (proto-TP) uplift. In order to explore and compare their roles on the East Asian climate evolution, we conducted simulations of the mid-Cretaceous climate system with different atmospheric pCO2 levels and varying topographies. The results show that both factors had significant influences on the East Asian climate. As the increase in atmospheric pCO2 levels from ∼560–1120 ppmv to ∼1120–2240 ppmv, the precipitation increases considerably over mid-latitude East Asia, but only small changes in the subtropical portion of East Asia occur. Simultaneously, the effects of the proto-TP uplift are opposite to those of global warming trend during that period. Generally, it leads to a precipitation decrease over subtropical East Asia, but rather minor changes over mid-latitude East Asia. These changes are qualitatively consistent with the deduction based on the geological records, but the magnitudes of the modeled precipitation changes are relatively smaller. Therefore, we can conclude that the subtropical East Asian drying during the mid-Cretaceous can be partly explained by the proto-TP uplift, while the mid-latitude East Asian wetting was partly due to global warming. However, additional factor(s) also played a significant role in the East Asian climate evolution during the mid-Cretaceous.

The Summer Atmospheric Convection Variability over the Tropical Western North Pacific Independent of and Dependent on the Preceding Winter ENSO

Abstract It has been well known that the preceding winter ENSO affects the atmospheric convection over the tropical western North Pacific (WNP) in summer, which has important impacts on Asian climate. However, more than half of the interannual variance in tropical WNP convection cannot be explained by ENSO. This study separates the WNP convection into two components, namely, independent of and dependent on the preceding winter ENSO, and compares the anomalies associated with these two components. The linear regression results indicate that the independent convection suppression corresponds to significant cyclonic anomalies over East Asia in both the lower and upper troposphere, and correspondingly a southward displacement of upper-tropospheric East Asian westerly jet. By contrast, these circulation anomalies are weakened for the dependent convection suppression, which is more closely related to the lower-tropospheric cyclonic anomalies over the Indian Ocean. Accordingly, the independent and dependent components exert distinct impacts on rainfall and temperature in Asia. Specifically, the independent suppression corresponds to more significantly enhanced rainfall in subtropical East Asia compared with the dependent one. Moreover, there are colder surface air temperatures in the midlatitude East Asia for the independent suppression and warmer temperatures in South and Southeast Asia for the dependent suppression. Further analyses suggest that the circulation and climate anomalies for the independent component are mainly contributed by July and August, while those for the dependent component become weak from June to August. These results can be helpful for a better understanding of summer Asian climate variability and predictability.

The Variation of Compound Warm Dry Extremes Over Eastern China and the Associated East Asian Subtropical Jet in the Boreal Summer

AbstractThe compound warm dry extremes (CWDEs), which can lead to extreme impacts that are much larger than the sum of the impacts due to the occurrence of individual extremes alone, have frequently hit the land regions. In this study, the spatial‐temporal variations of the frequency, warm, and dry intensity of the CWDEs over eastern China and the associated East Asian subtropical jet variations have been investigated. The results show that the first two leading CWDE frequency modes over eastern China are characterized by an increase pattern and a dipole pattern. The increases in the CWDE frequency may be accompanied by both the strong warm and dry in the northern part of China. Whereas, these may be mainly related to the strong warmth in the southern part of China. The dominant increase pattern is associated with the weakened land‐branch East Asian subtropical jet, which is maintained by the negative phase of the interdecadal Pacific Oscillation, the warming over high‐latitudes of the Atlantic Ocean and the positive phase of the Arctic Oscillation. The dipole pattern is related to the southward shift of the ocean‐branch East Asian subtropical jet, which is sustained by the warming in central equatorial Pacific and Indian Oceans, as well as the negative phase of North Atlantic Oscillation and the Pacific‐Japan teleconnection. The relative contribution analysis has confirmed the importance of the jet variations to the CWDEs. These results would be helpful for understanding the drivers of the CWDEs.

First molecular detection of a novel Babesia species from Haemaphysalis hystricis in Taiwan

Newly recorded ticks and emerging tick-borne pathogens have recently been reported in subtropical and tropical East Asia. In this study, a total of 1,615 ticks (259 Haemaphysalis hystricis, 1334 Rhipicephalus microplus, 19 H. flava, and 3 R. haemaphysaloides) were collected by flagging from vegetation in Taiwan during 2019–2021. All 1,615 captured tick samples tested negative for SFTSV and Borrelia, but 12 of 356 tick samples tested positive for PCR amplification of a fragment of the 18S rRNA gene of Babesia spp., with an infection rate of 3.37 % (12/356) and a minimum infection rate of 0.74 % (12/1,615). Among the 12 detected Babesia spp., 11 were identified as Babesia bigemina in R. microplus, and the other one, detected in H. hystricis, was classified as an unnamed novel Babesia sp. Interestingly, the 18S rRNA sequence from the isolate detected in H. hystricis shared 98.79 % to 99.50 % identity with those of recent isolates from Japan, China and Nigeria. The exact origin of the Babesia species is not known, but the findings highlight the importance of international cooperation and the exchange of information on ticks and tick-borne pathogens. This represents a rare report of a Babesia sp. identified in H. hystricis, a tick species that has been proposed as a novel vector for some Babesia spp. This study supports H. hystricis as a possible vector of Babesia spp.

Enhancing subtropical monsoon grassland management: Investigating mowing and nutrient input effects on initiation of grazing lawns

Subtropical monsoon grasslands in Asia are commonly in a fire-dominated state with tall grasses (> 2 m) that provide poor-quality forage for mammalian herbivores. In contrast, small patches of grazing lawns with short, nutritious grasses are sparsely distributed within these subtropical monsoon grasslands. Despite the importance of grazing lawns in providing high-quality forage for mammalian herbivores, the process of formation and maintenance of grazing lawns has not been studied in the monsoon grasslands of subtropical Asia. We conducted a large-scale multi-year experiment in subtropical monsoon grasslands within a protected area in Nepal to examine whether mowing tall grasses at different frequencies and spatial scales, along with the application of chemical fertilisers (urea or single superphosphate), could change tall grasslands into grazing lawns. We found that nitrogen and phosphorus concentrations in grasses increased to levels exceeding the minimum maintenance requirements for ruminants in 3600 m2 plots that were mown four times and fertilised. The concentrations of nitrogen and phosphorus remained below the minimum maintenance level for ruminants in unfertilised and unmown plots and in small plots that were four-time mown and fertilised. The frequently mown plots exhibited a significant increase in the proportion of ground cover of lawn grass, from 1% to 3%, and a corresponding decrease in the proportion of ground cover of tall grasses, from 24% to 1%. These results supported our hypothesis that frequent mowing at a larger spatial scale with the addition of chemical fertilisers and grazing leads to the inception of grazing lawns that are favourable for wild herbivores. However, the persistence of the grazing lawns presents challenges due to the highly productive monsoon season and the functional extinction of large bulk grazers. To our knowledge, this is the first empirical study conducted in the subtropical monsoon grasslands of Asia to experimentally demonstrate the importance of active management for the initiation of grazing lawns. Our findings have important implications for the management of subtropical monsoon grasslands.

Typifications and a new synonym in the tribe Boehmerieae (Urticaceae)

This work discusses the nomenclature, synonymy and typification of two monotypic genera, Chamabainia and Neodistemon which belong to the tribe Boehmerieae and have a restricted range in tropical and subtropical Asia. Lectotypes are designated for names in both genera and their full synonymy is provided. Boehmeria meifenggensis is treated as a new synonym of Chamabainia cuspidata.

Prevalent atmospheric and oceanic signals of the unprecedented heatwaves over the Yangtze River Valley in July–August 2022

Unprecedented heatwaves attacked the Yangtze River valley (YRV) in July–August of 2022. The heatwave-favorable circulation pattern for the YRV is identified by using a self-organizing map. Result shows that the dominant daily circulation pattern driving heatwaves in the YRV is the East Asian anticyclonic pattern (EAAP), characterized by an anomalous deep anticyclone over the East Asian mid-latitudes. Remarkably, the unprecedented frequent occurrence of EAAP in 2022 contributes about 84.6% of the temperature anomalies in the 35 YRV hot days, which is the key dynamical factor for the heatwave in 2022. Physical mechanisms for the occurrence of EAAP are revealed on interannual and interdecadal time scales. On interannual time scale, the dipole sea surface temperature (SST) anomalies over the North Atlantic, characterized by warm and cold SST anomalies in the midlatitudes and subtropics, respectively, exert an important influence on the EAAP days. This dipole SST pattern is unprecedentedly strong in 2022. It facilitates the EAAP through the maintenance of the coupled British–Okhotsk Corridor pattern and the Silk Road pattern in the mid-latitudes. Additionally, the persistent cold SST anomalies in tropical Indian ocean and the central-eastern Pacific from the preceding spring to summer contribute to cooling of the tropical troposphere and induce easterly anomalies in the East Asian subtropics, thereby further promoting the occurrence of EAAP. On interdecadal time scale, the negative Pacific Decadal Oscillation may establish favorable circulation conditions for the occurrence of the EAAP through modulating the interdecadal Silk Road pattern. These findings improve our understanding of the physical mechanisms for driving extreme heatwaves in the YRV and have an implication for enhancing regional heatwave prediction.

The role of older adult-focused social vulnerability on the relationship between temperature and emergency department attendance in a subtropical Asian city

PurposeOlder adults exhibit a wide range of capabilities and vulnerabilities that affect their capacity to respond to heat. This study analysed the associations between hot temperatures and Accident & Emergency (A&E) attendance taking into account older adult-focused social vulnerability. MethodsDaily A&E attendance data of Young-old (65–74) and Old-old (75+) was obtained for Hong Kong 2010–2019 hot seasons and stratified into three Social Vulnerability Index (SVI) groups (Low, Moderate, High). Mean temperature (lag 0–2) was analysed on A&E attendance at each SVI using Generalized Additive Models and Distributed Lag Non-linear Models. ResultsHigh temperatures were associated with increased same-day (lag 0) relative risk (RR) of A&E attendance for Young-old and Old-old in High SVI districts, with RR being 1.024 (95 % CI: 1.011, 1.037) and 1.036 (95 % CI: 1.018, 1.053), respectively. The Old-old living in Moderate and Low SVI districts also demonstrated increased RR of 1.037 (95 % CI: 1.028, 1.047) and 1.022 (95 % CI: 1.009, 1.036), respectively. Fewer emergency visits were found on the subsequent day (lag 1) of hot temperatures. ConclusionsOlder adults, both young-old and old-old, living in districts with higher social vulnerability tended to have increased risk of A&E attendance associated with same-day high temperature. With climate change and rapidly aging population, cities should prepare to meet needs of more vulnerable older adults in extreme heat.

A new infrageneric classification of Gastrochilus (Orchidaceae: Epidendroideae) based on molecular and morphological data

Gastrochilus is an orchid genus containing 73 species of mainly epiphytic on trees or rocks in mountain forests of tropical and subtropical Asia. Previous phylogenetic analyses and morphological assessments have failed to produce a well-resolved phylogeny at the infrageneric level. In the present study, a new infrageneric classification of Gastrochilus is proposed based on thoroughly morphological and phylogenetic analyses based on 52 species. Our phylogenetic analysis divided the genus into six sections including three new sections, G. sect. Pseudodistichi, G. sect. Brachycaules and G. sect. Acinacifolii. We also reinstate G. suavis to the specific rank. Furthermore, two new species, G. armeniacus Jun Y. Zhang, B. Xu & Yue H. Cheng and G. minjiangensis Jun Y. Zhang, B. Xu & Yue H. Cheng, are described and illustrated. A key to six sections of the genus is presented.

Pharmacognostic Standardization and Physicochemical Evaluation of Premna barbata Wall. Ex Schauer leaves from Western Himalaya

Premna barbata Wall. ex Schauer; belongs to family Lamiaceae. It is a deciduous shrub or a tree. The plant is distributed in the forest area of the eastern and northern parts of India in tropical and subtropical Asia, Africa, Australia and the Pacific Island. It is found in the Shivalik tract and the lower Himalaya. The present work has been undertaken to establish the pharmacognostical parameter of P. barbata leaves. The leaf samples were subjected to organoleptic and microscopic analysis. Physico-chemical properties and fluorescence analysis of the sample under UV were studied as per World Health Organization norms. Hydroalcoholic extract was prepared and subjected to preliminary phytochemical screening and antioxidant activity. Morphological observations revealed that the leaves are simple, petiolate, opposite, reticulate venation, 5.0-5.2 cm long, ovate in shape, entire margin with acute apex. Microscopic analysis showed that the leaves are dorsiventral, uniseriate covering trichomes present on upper and lower epidermis. Vascular bundle existing was of open and bicollateral type and pith was composed of loosely packed, comparatively large round parenchyma cells etc. Parameters like ash and extractive values, moisture content and fluorescent characteristics of the leaf samples were determined and reported. The extract revealed the presence of carbohydrates, glycosides, alkaloids, flavonoids, steroids, triterpenoids, tannins and phenolic compounds. The standardization parameters studied in the present investigation will aid in the identification and will be helpful in maintaining the standard profile of Premna barbata.

Metagenomics of culture isolates and insect tissue illuminate the evolution of Wolbachia, Rickettsia and Bartonella symbionts in Ctenocephalides spp. fleas.

While fleas are often perceived simply as a biting nuisance and a cause of allergic dermatitis, they represent important disease vectors worldwide, especially for bacterial zoonoses such as plague (transmitted by rodent fleas) and some of the rickettsioses and bartonelloses. The cosmopolitan cat (Ctenocephalides felis) and dog (Ctenocephalides canis) fleas, as well as Ctenocephalides orientis (restricted to tropical and subtropical Asia), breed in human dwellings and are vectors of cat-scratch fever (caused by Bartonella spp.) and Rickettsia spp., including Rickettsia felis (agent of flea-borne spotted fever) and Rickettsia asembonensis , a suspected pathogen. These Rickettsia spp. are members of a phylogenetic clade known as the ‘transitional group’, which includes both human pathogens and arthropod-specific endosymbionts. The relatively depauperate flea microbiome can also contain other endosymbionts, including a diverse range of Wolbachia strains. Here, we present circularized genome assemblies for two C. orientis-derived pathogens ( Bartonella clarridgeiae and R. asembonensis ) from Malaysia, a novel Wolbachia strain (wCori), and the C. orientis mitochondrion; all were obtained by direct metagenomic sequencing of flea tissues. Moreover, we isolated two Wolbachia strains from Malaysian C. felis into tick cell culture and recovered circularized genome assemblies for both, one of which (wCfeF) is newly sequenced. We demonstrate that the three Wolbachia strains are representatives of different major clades (‘supergroups’), two of which appear to be flea-specific. These Wolbachia genomes exhibit unique combinations of features associated with reproductive parasitism or mutualism, including prophage WO, cytoplasmic incompatibility factors and the biotin operon of obligate intracellular microbes. The first circularized assembly for R. asembonensis includes a plasmid with a markedly different structure and gene content compared to the published plasmid; moreover, this novel plasmid was also detected in cat flea metagenomes from the USA. Analysis of loci under positive selection in the transitional group revealed genes involved in host–pathogen interactions that may facilitate host switching. Finally, the first B. clarridgeiae genome from Asia exhibited large-scale genome stability compared to isolates from other continents, except for SNPs in regions predicted to mediate interactions with the vertebrate host. These findings highlight the paucity of data on the genomic diversity of Ctenocephalides-associated bacteria and raise questions regarding how interactions between members of the flea microbiome might influence vector competence.

Land use and cover in subtropical East Asia and Southeast Asia from 1700 to 2018

Land-use/cover change (LUCC) has severely disturbed the terrestrial carbon balance in subtropical East Asia and Southeast Asia (SEASA). High-precision, long-term historical land cover (LC) data, and LC spatiotemporal patterns and transitions, exhibit high levels of uncertainty. This study constructed base and potential map containing 18 LC categories by integrating multisource high-resolution remote sensing datasets in 2014; then collected official reports, FAOSTAT, and long-term historical datasets, and used the correction coefficient method to obtain the area time series of forest, cropland, and urban at the provincial scale from 1700 to 2018; Finally, the fraction map of 18 LCs in SEASA at 1 km resolution during 1700–2018 was reconstructed based on a pixel level area calibration method, and the spatiotemporal patterns and transitions of LUCC were analyzed. Over the past 300 years, SEASA forest area decreased by 145.22 million ha, most rapidly from 1950 to 1980 (sevenfold that of the preceding 250 years). The loss of tropical forest, mainly in Indonesia, Myanmar, and Thailand, accounting for >80% of this decline. Subtropical forest areas increased significantly in China. Cropland and urban areas increased greatly, by 86.55 and 7.97 million ha, respectively, with the largest increases in China, Thailand, Myanmar, Japan, and Indonesia. Other natural land types closely related to human activity declined more, becoming cropland and urban areas, with greater variability. Conversion of forest to other LC types accounted for >70% of the total LC transition from 1700 to 2018. The main sources of cropland were forest (mainly in Thailand, central Myanmar, and southern Vietnam) and other nonforest natural land. Urban growth was mainly via encroachment on forest and other natural land. This study elucidates the spatiotemporal evolution of LUCC in SEASA from 1700 to 2018, and provides historical spatiotemporal data for large-scale bamboo forests, along with high-precision LUCC data for studying terrestrial ecosystem responses to climate change in the SEASA.

A gridded dataset of a leaf-age-dependent leaf area index seasonality product over tropical and subtropical evergreen broadleaved forests

Abstract. The quantification of large-scale leaf-age-dependent leaf area index has been lacking in tropical and subtropical evergreen broadleaved forests (TEFs), despite the recognized importance of leaf age in influencing leaf photosynthetic capacity in this biome. Here, we simplified the canopy leaves of TEFs into three age cohorts (i.e., young, mature, and old, with different photosynthesis capacities; i.e., Vc,max) and proposed a novel neighbor-based approach to develop the first gridded dataset of a monthly leaf-age-dependent leaf area index (LAI) product (referred to as Lad-LAI) at 0.25∘ spatial resolution over the continental scale during 2001–2018 from satellite observations of sun-induced chlorophyll fluorescence (SIF) that was reconstructed from MODIS and TROPOMI (the TROPOspheric Monitoring Instrument). The new Lad-LAI products show good performance in capturing the seasonality of three LAI cohorts, i.e., young (LAIyoung; the Pearson correlation coefficient of R=0.36), mature (LAImature; R=0.77), and old (LAIold; R=0.59) leaves at eight camera-based observation sites (four in South America, three in subtropical Asia, and one in the Democratic Republic of the Congo (DRC)) and can also represent their interannual dynamics, validated only at the Barro Colorado site, with R being equal to 0.54, 0.64, and 0.49 for LAIyoung, LAImature, and LAIold, respectively. Additionally, the abrupt drops in LAIold are mostly consistent with the seasonal litterfall peaks at 53 in situ measurements across the whole tropical region (R=0.82). The LAI seasonality of young and mature leaves also agrees well with the seasonal dynamics of the enhanced vegetation index (EVI; R=0.61), which is a proxy for photosynthetically effective leaves. Spatially, the gridded Lad-LAI data capture a dry-season green-up of canopy leaves across the wet Amazonian areas, where mean annual precipitation exceeds 2000 mm yr−1, consistent with previous satellite-based analyses. The spatial patterns clustered from the three LAI cohorts also coincide with those clustered from climatic variables over the whole TEF region. Herein, we provide the average seasonality of three LAI cohorts as the main dataset and their time series as a supplementary dataset. These Lad-LAI products are available at https://doi.org/10.6084/m9.figshare.21700955.v4 (Yang et al., 2022).