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25 August 2020, Volume 42 Issue 04
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  • Articles
    Sharing earth with all life
    Hongwen Huang, Hang Sun, Zhekun Zhou
    2020, 42(04):  209-210.  doi:10.1016/j.pld.2020.08.002
    Abstract ( 93 )   HTML ( )   PDF (317KB) ( 31 )   Save
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    Maintaining biodiversity will define our long-term success
    Peter Raven, Mathis Wackernagel
    2020, 42(04):  211-220.  doi:10.1016/j.pld.2020.06.002
    Abstract ( 146 )   HTML ( )   PDF (3871KB) ( 29 )   Save
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    Human beings are not only a part of our planet's ecosystems, but also, they are massively overusing them. This makes ecosystem protection, including biodiversity preservation, vital for humanity's future. The speed and scale of the threat are unprecedented in human history. The long arch of evolution has been confronted with such a high level of human impact, that we are now facing the sixth mass extinction event, 66 million years after the last one. This threat heightens the imperative for bold human intervention. Our paper identifies three strategies for such an intervention. First, and possibly most challenging, human demand needs to be curbed so it fits within the bounds of what Earth's ecosystems can renew. Without meeting this quantitative goal, biodiversity preservation efforts will not be able to get scaled. Second, in the transition time, we must focus on those locations and areas where most biodiversity is concentrated. Such a focus on ‘hotspots' will help safeguard the largest portion of biodiversity with least effort. Third, to direct biodiversity preservation strategies, we need to much better document the existence and distribution of biodiversity around the globe. New information technologies could help with this critical effort. In conclusion, biodiversity preservation is no longer just a concern for specialized biologist but is becoming a societal necessity if humanity wants to have a stable future.
    Safeguarding our future by protecting biodiversity
    Richard T. Corlett
    2020, 42(04):  221-228.  doi:10.1016/j.pld.2020.04.002
    Abstract ( 835 )   HTML ( )   PDF (388KB) ( 469 )   Save
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    The Anthropocene is marked by twin crises: climate change and biodiversity loss. Climate change has tended to dominate the headlines, reflecting, in part, the greater complexity of the biodiversity crisis. Biodiversity itself is a difficult concept. Land plants dominate the global biomass and terrestrial arthropods probably dominate in terms of numbers of species, but most of the Tree of Life consists of single-celled eukaryotes, bacteria, and archaea. Wild plants provide a huge variety of products and services to people, ranging from those that are species-specific, such as food, medicine, and genetic resources, to many which are partly interchangeable, such as timber and forage for domestic animals, and others which depend on the whole community, but not on individual species, such as regulation of water supply and carbon sequestration. The use of information from remote sensing has encouraged a simplified view of the values of nature's contributions to people, but this does not match the way most people value nature. We can currently estimate the proportion of species threatened by human impacts only for a few well-assessed groups, for which it ranges from 14% (birds) to 63% (cycads). Less than 8% of land plants have been assessed, but it has been estimated that 30-44% are threatened, although there are still few (0.2%) well-documented extinctions. Priorities for improving protection of biodiversity include: improving the inventory, with surveys focused on geographical areas and taxonomic groups which are under-collected; expanding the protected area system and its representativeness; controlling overexploitation; managing invasive species; conserving threatened species ex situ; restoring degraded ecosystems; and controlling climate change. The Convention on Biological Diversity (CBD) COP15 and the United Nations Framework Convention on Climate Change (UNFCCC) COP26 meetings, both postponed to 2021, will provide an opportunity to address both crises, but success will require high ambition from all participants.
    Cenozoic topography, monsoons and biodiversity conservation within the Tibetan Region: An evolving story
    Robert A. Spicer, Alexander Farnsworth, Tao Su
    2020, 42(04):  229-254.  doi:10.1016/j.pld.2020.06.011
    Abstract ( 192 )   HTML ( )   PDF (25507KB) ( 56 )   Save
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    The biodiversity of the Himalaya, Hengduan Mountains and Tibet, here collectively termed the Tibetan Region, is exceptional in a global context. To contextualize and understand the origins of this biotic richness, and its conservation value, we examine recent fossil finds and review progress in understanding the orogeny of the Tibetan Region. We examine the deep-time origins of monsoons affecting Asia, climate variation over different timescales, and the establishment of environmental niche heterogeneity linked to topographic development. The origins of the modern biodiversity were established in the Eocene, concurrent with the formation of pronounced topographic relief across the Tibetan Region. High (>4 km) mountains to the north and south of what is now the Tibetan Plateau bounded a Paleogene central lowland (<2.5 km) hosting moist subtropical vegetation influenced by an intensifying monsoon. In mid Miocene times, before the Himalaya reached their current elevation, sediment infilling and compressional tectonics raised the floor of the central valley to above 3000 m, but central Tibet was still moist enough, and low enough, to host a warm temperate angiosperm-dominated woodland. After 15 Ma, global cooling, the further rise of central Tibet, and the rain shadow cast by the growing Himalaya, progressively led to more open, herb-rich vegetation as the modern high plateau formed with its cool, dry climate. In the moist monsoonal Hengduan Mountains, high and spatially extensive since the Eocene but subsequently deeply dissected by river incision, Neogene cooling depressed the tree line, compressed altitudinal zonation, and created strong environmental heterogeneity. This served as a cradle for the then newly-evolving alpine biota and favoured diversity within more thermophilic vegetation at lower elevations. This diversity has survived through a combination of minimal Quaternary glaciation, and complex relief-related environmental niche heterogeneity. The great antiquity and diversity of the Tibetan Region biota argues for its conservation, and the importance of that biota is demonstrated through our insights into its long temporal gestation provided by fossil archives and information written in surviving genomes. These data sources are worthy of conservation in their own right, but for the living biotic inventory we need to ask what it is we want to conserve. Is it 1) individual taxa for their intrinsic properties, 2) their services in functioning ecosystems, or 3) their capacity to generate future new biodiversity? If 2 or 3 are our goal then landscape conservation at scale is required, and not just seed banks or botanical/zoological gardens.
    The tropical-subtropical evergreen forest transition in East Asia: An exploration
    Peter Ashton, Hua Zhu
    2020, 42(04):  255-280.  doi:10.1016/j.pld.2020.04.001
    Abstract ( 223 )   HTML ( )   PDF (52918KB) ( 15 )   Save
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    The transition from tropical to subtropical (warm temperate) evergreen forests is more clearly apparent in East Asia, from Nepal to the western Pacific coast, than elsewhere in the tropics. We review the nature of this transition and hypothesize the physical, ultimatelyclimatic, factors that may maintain it, with a special focus on how the increasing instability and warming of climates will affect these forests. A primary climatic mediator of the transition is proposed, thereby offering a testable hypothesis for the climate-forest transition relationship. What is known of this transition is summarized in context of the primary climatic mediators of elevational zonation of forest formations in equatorial Asia to the tree line, in the Himalaya at the India-Indo-Burma northern tropical margin, and as both elevational and latitudinal zonation in southern China. Consequent secondary edaphic and other physical changes are described for the Himalaya, and hypothesized for southern China. The forest ecotones are seen to be primarily defined by tree floristic change, on which account changes in structure and physiognomy are determined. The montane tropical-subtropical transition in the Himalaya is narrow and observed to correlate with an as yet ill-defined frost line. A distinct tropical-subtropical transition forest is recognized in the southwest China mountains. There is a total change in canopy species at the Himalayan ecotone, but subcanopy tropical species persist along an elevational decline of c. 400 m. The latitudinal transition in South China is analogous, but here the tropical subcanopy component extends north over ten degrees latitude, albeit in decline. The tropical-subtropical transition is uniquely clear in East Asia because here alone a tropical wet summer-dry winter monsoon extends to 35° north latitude, encompassing the subtropical evergreen forest, whereas subtropical evergreen forests elsewhere exist under drier temperate summer climate regimes.
    Plant diversity in Yunnan: Current status and future directions
    Li-Shen Qian, Jia-Hui Chen, Tao Deng, Hang Sun
    2020, 42(04):  281-291.  doi:10.1016/j.pld.2020.07.006
    Abstract ( 224 )   HTML ( )   PDF (10790KB) ( 245 )   Save
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    Yunnan, located in southwestern China, harbors more than 19,000 higher plants, which represents the highest plant diversity in the country. However, plant diversity in Yunnan faces enormous threats today, including habitat destruction and fragmentation, environmental pollution, and over-exploitation of natural resources. Despite recent efforts to protect biodiversity, there are still thousands of threatened species, some of which have become extinct. We analyzed available data to gain a greater understanding of plant diversity and the status of plant conservation in Yunnan. We found that southern, southeastern, and northwestern Yunnan are hotspots of total species, endemic species, specimens, new species and threatened species, whereas southeastern Yunnan is a hotspot for plant species with extremely small populations. Moreover, we found that there are still conservation gaps and poorly protected areas in central, eastern, and northeastern Yunnan. We conclude that conservation of plant diversity in Yunnan requires modern field investigation, systematic research, the development of comprehensive databases, and government support. We recommend that conservationists pay more attention to building and improving functional protection systems and popularizing science.
    Contributions to the flora of Myanmar from 2000 to 2019
    Bin Yang, Min Deng, Ming-Xia Zhang, Aung Zaw Moe, Hong-Bo Ding, Mya Bhone Maw, Pyae Pyae Win, Richard T. Corlett, Yun-Hong Tan
    2020, 42(04):  292-301.  doi:10.1016/j.pld.2020.06.005
    Abstract ( 167 )   HTML ( )   PDF (31320KB) ( 32 )   Save
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    Myanmar is botanically rich and floristically diverse: one of the world's biodiversity hotspots. However, Myanmar is still very unevenly explored, and until a plant checklist was published in 2003, relatively little work was done on its flora. This checklist included 11,800 species of spermatophytes in 273 families. Since this checklist was published, the botanical exploration of Myanmar has accelerated and there have been many additional publications. We therefore surveyed the literature of taxonomic contributions to Myanmar's vascular flora over the last 20 years (2000-2019) and compiled a list of new and newly described taxa. Our list includes 13 genera, 193 species, 7 subspecies, 19 varieties, and 2 forms new to science; and 3 families, 34 genera, 347 species, 4 subspecies, 7 varieties, and 1 form newly recorded in Myanmar. Altogether, they represent 91 families and 320 genera. Most of the new discoveries belong to 15 families, with more than 25% (146 taxa) belonging to Orchidaceae. These new discoveries are unevenly distributed in the country, with about 41% of the newly discovered species described from Kachin State in northeast Myanmar. This reflects the incompleteness of our current knowledge of the flora of Myanmar and the urgent need for a greatly expanded effort. The completion of the flora of Myanmar requires more fieldwork from north to south, taxonomic studies on new and existing collections, and some mechanism that both coordinates the efforts of various international institutions and initiatives and encourages continued international cooperation. In addition, producing modern taxonomic treatments of the flora of Myanmar requires the participation of experts on all vascular plant families and genera. There is also an urgent need to attract young scientists to plant taxonomy, to work on inventories, identification, nomenclature, herbarium work, and comparative studies.
    Ethiopian vegetation types, climate and topography
    Mengesha Asefa, Min Cao, Yunyun He, Ewuketu Mekonnen, Xiaoyang Song, Jie Yang
    2020, 42(04):  302-311.  doi:10.1016/j.pld.2020.04.004
    Abstract ( 1814 )   HTML ( )   PDF (10759KB) ( 725 )   Save
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    Ethiopia is land of geographical contrasts with elevations that range from 125 m below sea level in the Danakil Depression to 4533 m above sea level in the Semien Mountains, a world heritage site. The diverse climate of various ecological regions of the country has driven the establishment of diverse vegetation, which range from Afroalpine vegetation in the mountains to the arid and semi-arid vegetation type in the lowlands. The formation of Ethiopian vegetation is highly connected to the climate and geological history of the country. Highland uplift and rift formation due to volcanic forces formed novel habitats with different topography and climatic conditions that have ultimately become drivers for vegetation diversification. Due to Ethiopia's connection with the temperate biome in the north and the Arabian Peninsula during the dry glacial period, the biotic assemblage of Ethiopian highlands consists of both Afrotropical and palearctic biota. In general, eight distinct vegetation types have been identified in Ethiopia, based mainly on elevation and climate gradients. These vegetation types host their own unique species, but also share several common species. Some of the vegetation types are identified as centers of endemism and have subsequently been identified globally as the East African Afromontane hotspot. Ethiopia is biologically rich, with more than 6500 vascular plant species. Of these species, 12% are endemic mainly due to geographical isolation and unique climatic conditions. However, researchers have yet to extensively investigate the ecology, phenology, as well as the evolutionary, genetics, and conservation status of Ethiopian vegetations at community and species level over space and time. This lack of research is a barrier to achieving the goal of zero global plant extinctions. Taxa extinction risk assessment has not been extensively carried out for majority of Ethiopian species. Detailed research is needed to explore how vegetation and species respond to rapidly growing environmental change. Currently, human-induced climate change and habitat fragmentation are severely threatening the country's biodiversity, and the consequences of these effects have not been studied at large. Furthermore, we still lack scientific evidence on how micro- and macro-ecological and evolutionary processes have been shaping vegetation structures in this climatically, topographically, and geologically diverse country. These gaps in our knowledge represent an opportunity for ecologists, geneticists, evolutionary biologists, conservation biologists, and other experts to investigate the biodiversity status and the complex ecological processes involved in structuring vegetation dynamics so as to help take effective conservation actions.
    Comparative population genetic analyses suggest hybrid origin of Rhododendron pubicostatum, an endangered plant species with extremely small populations endemic to Yunnan, China
    Xuemei Zhang, Hantao Qin, Weijia Xie, Yongpeng Ma, Weibang Sun
    2020, 42(04):  312-318.  doi:10.1016/j.pld.2020.06.012
    Abstract ( 166 )   HTML ( )   PDF (2531KB) ( 41 )   Save
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    Gene flow between sympatric congeneric plants is thought to be very common and may pose serious threats to endangered species. In the present study, we evaluate the genetic diversity and divergence of three sympatric Rhododendron species in Jiaozi Mountain using newly developed microsatellites through the Illumina MiSeq sequencing approach. Genetic diversity of all three Rhododendron species studied was moderate in comparison to genetic parameters previously reported from species of this genus. Interestingly, genetic structure analysis of the three species identified a possible hybrid origin of the threatened Rh. pubicostatum. This sympatry should be considered a unimodal hybrid zone, since Rh. pubicostatum is predominant here. Unimodal hybrid zones are uncommon in Rhododendron, despite the fact that hybridization frequently occurs in the genus. Issues pertaining to the conservation of Rh. pubicostatum resulting from admixture of genetic material from its parental species are discussed.