Summary
Despite growing evidence that niche shifts are more common in flowering plants than previously thought, little is known of whether such shifts are promoted by changes in photosynthetic ...pathways.
Here we combine the most complete phylogeny for epiphytic Malagasy Bulbophyllum orchids (c. 210 spp.) with climatic niche and carbon isotope ratios to infer the group’s spatial‐temporal history, and the role of strongly expressed crassulacean acid metabolism (CAM) in facilitating niche shifts and diversification.
We find that most extant species still retain niche (Central Highland) and photosynthesis (C3) states as present in the single mid‐Miocene (c. 12.70 million yr ago (Ma)) ancestor colonizing Madagascar. However, we also infer a major transition to CAM, linked to a late Miocene (c. 7.36 Ma) invasion of species from the sub‐humid highland first into the island’s humid eastern coastal, and then into the seasonally dry ‘Northwest Sambirano’ rainforests, yet without significant effect on diversification rates.
These findings indicate that CAM in tropical epiphytes may be selectively advantageous even in high rainfall habitats, rather than presenting a mere adaptation to dry environments or epiphytism per se. Overall, our study qualifies CAM as an evolutionary ‘gateway’ trait that considerably widened the spatial‐ecological amplitude of Madagascar’s most species‐rich orchid genus.
Whether wind pollination in trees can offset the negative genetic consequences of anthropogenic forest fragmentation is not clearly established. To answer this question, we examined the demographic ...genetics of Quercus bambusifolia over a 70-year recovery period in highly fragmented forests in Hong Kong. We sampled 1138 individuals from 37 locations, and genetically analysed the chronosequence through the classification of tree diameters from the same populations using 13 microsatellite markers. Our study reveals that severe fragmentation caused a significant genetic bottleneck with very few remaining but genetically diverse individuals. We observed an enhanced genetic diversity during demographic recovery. We found full-sibs within populations and half-sibs across the study range. This reflects a limited seed dispersal and extensive pollen flow. Despite reduced genetic structure both among and within populations, overall a strong persisting genetic differentiation (F'
= 0.240, P < 0.01) and significant small-scale spatial genetic structure (F
= 0.13, Sp = 0.024, P < 0.01) were observed. Existing bottlenecks and low effective population sizes within the temporal chronosequence suggest that the long-term effect of severe fragmentation cannot be entirely eliminated by wind pollination with demographic recovery in the absence of effective seed dispersal. Our results lead to recommendations for forest management.
The shark fin trade is a major driver of shark exploitation in fisheries all over the world, most of which are not managed on a species-specific basis. Species-specific trade information highlights ...taxa of particular concern and can be used to assess the efficacy of management measures and anticipate emerging threats. The species composition of the Hong Kong Special Administrative Region of China, one of the world's largestfin trading hubs, was partially assessed in 1999-2001. We randomly selected and genetically identified fin trimmings (n = 4800), produced during fin processing, from the retail market of Hong Kong in 2014-2015 to assess contemporary species composition of the fin trade. We used nonparametric species estimators to determine that at least 76 species of sharks, batoids, and chimaeras supplied the fin trade and a Bayesian model to determine their relative proportion in the market. The diversity of traded species suggests species substitution could mask depletion of vulnerable species; one-third of identified species are threatened with extinction. The Bayesian model suggested that 8 species each comprised >1% of the fin trimmings (34.1-64.2% for blue Prionace glauca, 0.2-1.2% for bull Carcharhinus leucas and shortfin mako Isurus oxyrinchus); thus, trade was skewed to a few globally distributed species. Several other coastal sharks, batoids, and chimaeras are in the trade but poorly managed. Fewer than 10 of the species we modeled have sustainably managed fisheries anywhere in their range, and the most common species in trade, the blue shark, was not among them. Our study and approach serve as a baseline to track changes in composition of species in the fin trade over time to better understand patterns of exploitation and assess the effects of emerging management actions for these animals. El mercado de aleta de tiburón es un importante conductor de la explotación de tiburones a nivel mundial, la mayoría de los cuales no están manejados a un nivel especifico de especie. La información específica de especies en el mercado resalta taxones de preocupación particular y puede usarse para avaluar la eficiencia de las medidas de manejo y anticipar las amenazas emergentes. La composición de especies en la Región Administrativa Especial de Hong Kong de la República Popular China, uno de los puntos más grandes de venta de aletas, fue evaluada parcialmente entre 1999 y 2001. Seleccionamos al azar e identificamos genéticamente pedazos de aletas (n = 4800) producidos durante el procesamiento de las aletas, en el mercado al menudeo de Hong Kong entre 2014 y 2015 para evaluar la composición contemporánea de especies dentro del mercado de aletas. Utilizamos estimadores no-paramétricos de especies para determinar que al menos 76 especies de tiburones, batoideosy quimeras suministraban al mercado de aletas y un modelo bayesiano para determinar su proporción relativa dentro del mercado. La diversidad de las especies en el mercado sugiere que la sustitución de especies podría enmascarar la disminución de las especies vulnerables; un tercio de las especies identificadas enfrentan riesgos severos de extinción. El modelo bayesiano sugirió que cada una de ocho especies constituyó >1% de los pedazos de aletas (34.1-64.2% para el tiburón azul Prionace glauca; 0.2-1.2% para el tiburón toro Carcharhinus leucas y el tiburón mako Isurus oxyrinchus); así, el mercado estuvo sesgado a unas cuantas especies con distribución mundial. Muchos otros tiburones costeros, batoideos y quimeras están en el mercado pero con un manejo muy pobre. Menos de diez de las especies que modelamos tienen pesquerías manejadas sustentablemente en cualquier parte de su extensión, incluyendo a la especie más común en el mercado, el tiburón azul. Nuestro estudio y nuestra estrategia sirven como una línea de base para rastrear los cambios en la composición de las especies dentro del mercado de aletas a través del tiempo para entender mejor los patrones de explotación y evaluar los efectos de las acciones de manejo emergentes para estos animales.
This paper presents the theoretical and experimental results on the phase noise spectrum and the rms frequency error of a fractional-N phase-locked loop (PLL) under frequency-modulated ...continuous-wave (FMCW) chirp generation. The phase noise spectrum under modulation is analytically calculated for a second-order charge pump PLL with a feedback divider ratio linearly changing over time. This is followed by an analysis of the steady-state rms frequency error of the output frequency after PLL settling is achieved during chirp generation. A fractional-N PLL with integrated frequency ramp generator is presented. Phase noise and jitter measurements on the PLL under modulation are performed at the output of the programmable feedback divider. The resulting low-frequency rms jitter is reduced by about 9dB with doubling the charge pump current, and reduced by about 6dB with halving the ramp slope. The rms frequency error under FMCW modulation is measured at the modulated voltage-controlled oscillator output. The dependence of the frequency error on the loop filter capacitance for various ramp slopes is given. A frequency error of 112kHz is achieved with a ramp slope of 1.28GHz/80<inline-formula> <tex-math notation="LaTeX">\mu \text{s} </tex-math></inline-formula> at a carrier frequency of 62GHz. The noise measurements are in good agreement with the developed phase noise model. A programmable loop filter capacitance is suggested to accommodate the static phase offset and the resulting noise performance to the ramp slope.
The design of wind turbine blades is a true multi-objective engineering task. The aerodynamic effectiveness of the turbine needs to be balanced with the system loads introduced by the rotor. Moreover ...the problem is not dependent on a single geometric property, but besides other parameters on a combination of aerofoil family and various blade functions. The aim of this paper is therefore to present a tool which can help designers to get a deeper insight into the complexity of the design space and to find a blade design which is likely to have a low cost of energy. For the research we use a Computational Blade Optimisation and Load Deflation Tool (CoBOLDT) to investigate the three extreme point designs obtained from a multi-objective optimisation of turbine thrust, annual energy production as well as mass for a horizontal axis wind turbine blade. The optimisation algorithm utilised is based on Multi-Objective Tabu Search which constitutes the core of CoBOLDT. The methodology is capable to parametrise the spanning aerofoils with two-dimensional Free Form Deformation and blade functions with two tangentially connected cubic splines. After geometry generation we use a panel code to create aerofoil polars and a stationary Blade Element Momentum code to evaluate turbine performance. Finally, the obtained loads are fed into a structural layout module to estimate the mass and stiffness of the current blade by means of a fully stressed design. For the presented test case we chose post optimisation analysis with parallel coordinates to reveal geometrical features of the extreme point designs and to select a compromise design from the Pareto set. The research revealed that a blade with a feasible laminate layout can be obtained, that can increase the energy capture and lower steady state systems loads. The reduced aerofoil camber and an increased L/D-ratio could be identified as the main drivers. This statement could not be made with other tools of the research community before.
•Multi-objective optimization of an industrial scale wind turbine blade.•Detailed structural layout using the classical laminate theory.•Reduction in camber lead to an enhanced L/D-ratio in the design range.•Compromise design has AoA distribution, which operates aerofoils at the local maximum L/D-ratio.•Increased relative profile thickness allowed for the reduction of blade mass.
Tropical forests are the main reservoirs for global biodiversity and climate control. As secondary forests are now more widespread than primary forests, understanding their functioning and role in ...the biosphere is increasingly important. This includes understanding how they achieve stability, how they accumulate species and build biodiversity and how they cycle nutrients and carbon. This study investigates how we can restore tropical secondary forests to resemble high biomass, highly biodiverse and stable ecosystems seen today only in primary, undisturbed forests. The study used historic aerial photographs and recent high-resolution satellite images from 1945 to 2014 to map forest patches with five age categories, from 14-years to over 70-years, in Hong Kong's degraded tropical landscape. A forest inventory comprising 28 quadrats provided a rare opportunity to relate patterns of species composition at different stages during the succession with topographic and soil characteristics. The topographic variables accounted for 15% of the variance in species abundance, and age of forest stands explained 29%. Species richness rapidly increased after the first 15 years, but was lower in old-growth, than in medium age forest. This is attributed to the inability of late-successional species to disperse into the young forests as the natural dispersal agents (birds, mammals) have been lost. Light-loving pioneers which are unable to tolerate the shade of older forests, cannot regenerate in their own shade, therefore species diversity declines after a few decades. For ecosystem restoration in tropical secondary forests, introduction of late-successional species is necessary to assist natural succession, given the absence of native fauna, seed dispersal agents, and the surrounding altered environment. We also show that remote sensing can play a pivotal role in understanding the recovery and functioning of secondary forest regeneration as its contribution to the biosphere is increasingly important.
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•Forest age classes determined through multi-temporal remote sensing.•Higher elevation forest is more diverse but less abundant.•Topography explained 15% of the variance in the species composition.•Species diversity is not increasing in the older forest patches.•Later successional species in the landscape are restricted to Feng Shui woods.
One third of chondrichthyan species (sharks, rays, and chimeras) are threatened with extinction, mainly due to unsustainable fishing. Large accessible international markets for meat and luxury ...products like dried fins can help drive overfishing by encouraging targeted capture or retention of high‐value export species. If this is common, then species in international trade could have heightened extinction risk. Here, we examined the species composition of the Hong Kong shark fin market from 2014 to 2018, finding that traded species disproportionately occur in threatened categories (70.9%) and all premium value species are threatened. A small number of cosmopolitan species dominate the trade, but noncosmopolitan coastal species are still traded at concerning levels given their limited distribution. These coastal species are not generally subject to retention prohibitions, fisheries management, or international trade regulations and without management many could become extinct. The conservation potential of international trade regulations alone for coastal chondrichthyans depends on the extent to which overfishing is driven by export markets; socioeconomic studies of coastal fishing communities are needed to make this determination. Nonetheless, adding international trade regulations for more coastal shark species that are in the fin trade could prompt broad engagement with overfishing in nations lacking effective management.
Overharvesting is one of the greatest threats to species survival. Farming overharvested species is a conservation strategy that can meet growing market demand and conserve wild populations of the ...target species. This strategy is compatible with the international community's desire to uphold the right of local communities to use biological resources to support their livelihoods. However, studies investigating whether farming can alleviate poaching pressure have focused almost exclusively on animals. To address the shortfall in plant‐focused studies, we compiled information on commercial cultivation of threatened plants to assess its conservation benefits. Because China's rising middle class has rapidly intensified demand for wildlife products, we searched the scientific literature published in Chinese (China National Knowledge Infrastructure and Baidu) and in English. We found 32 reports that contained data on 193 internationally or nationally threatened plant species that were under commercial cultivation. These reports showed that cultivations of 82% of the 193 species were sustained by collecting whole plants from the wild periodically or continuously. Although based on a small sample size, species that were maintained in cultivation only through artificial propagation or seeds collected in the wild were likely associated with a reported reduction in wild harvesting of whole plants. Even so, results of correlation analyses suggested that production system, scale, and when a species began being cultivated had little effect on conservation status of the species, either globally or in China. However, species brought into cultivation relatively recently and on a smaller scale were more likely to have undergone a reduction in collecting pressure. Farming of nonmedicinal plants was most problematic for species conservation because wild plants were laundered (i.e., sold as cultivated plants). For effective conservation, policy to guide cultivation operations based on the target species’ biological characteristics, cultural significance, market demand, and conservation status is needed.
Impactos en la Conservación del Cultivo Comercial de Plantas Sobreexplotadas y en Peligro de Extinción
Resumen
La sobreexplotación es una de las mayores amenazas para la supervivencia de una especie. El cultivo de especies sobreexplotadas es una estrategia de conservación que puede cumplir con la demanda creciente en el mercado y a la vez conservar especies silvestres de la especie diana. Esta estrategia es compatible con el deseo de la comunidad internacional de defender el derecho que tienen las comunidades locales a usar los recursos biológicos para mantener su sustento. Sin embargo, los estudios que indagan si el cultivo puede aliviar la presión de la colecta furtiva se han enfocado casi exclusivamente en animales. Para tratar con este déficit de estudios enfocados en plantas compilamos información sobre el cultivo comercial de plantas amenazadas para evaluar los beneficios de conservación del cultivo comercial. Ya que la creciente clase media china ha intensificado rápidamente la demanda de productos silvestres decidimos buscar en la literatura científica en chino (Infraestructura Nacional de Conocimiento de China y Baidu) y en inglés. Encontramos 32 reportes que contenían datos sobre 193 especies de plantas amenazadas nacional o internacionalmente que se encontraban en cultivos comerciales. Estos reportes mostraron que los cultivos del 82% de las 193 especies están sostenidos por la colecta de plantas completas en el campo de manera periódica o continua. Aunque nos basamos en un pequeño tamaño de muestra, las especies que se mantenían en cultivos sólo mediante la propagación artificial o mediante semillas recolectadas en campo tenían probabilidad de estar asociadas con una reducción reportada de la cosecha silvestre de plantas completas. Aún así, los resultados de los análisis de correlación sugieren que el sistema de producción, la escala, y cuándo se comenzó a cultivar a las especies tuvieron el menor efecto sobre el estado de conservación de la especie, fuera a escala mundial o en China. Sin embargo, las especies que se han introducido recientemente al cultivo y a menor escala tenían mayor probabilidad de haber sufrido una reducción en la presión de colecta. El cultivo de plantas no medicinales fue la más problemática para la conservación de especies ya que las plantas silvestres eran “lavadas” (es decir, vendidas como plantas cultivadas). Para una conservación efectiva se necesita de políticas que guíen las operaciones de cultivo con base en las características biológicas, la importancia cultural, la demanda en el mercado y el estado de conservación de la especie de interés.
摘要
过度采集是物种生存的两大威胁之一。对被野采过度的物种开展商业化养殖和种植被视为一种既能满足日益增长的市场需求, 又能对该物种野生种群起到保护的策略。该策略也符合国际社会维护当地社区利用生物资源维持生计的权利的愿望。然而, 调查商业化养殖和种植是否可以减轻偷猎偷采压力的研究几乎完全集中在动物物种。为了弥补缺乏以植物为研究对象的不足, 我们汇编了有关受威胁植物商业化种植的信息, 以评估其保护效益。由于中国崛起的中产阶级对野生动植物产品的需求迅速增加, 我们除了英文文献数据库外, 还搜索了中国文献数据库 (即中国知网和百度) 。在筛选了数百个搜索结果后, 我们选用了 32 份文献, 其中包含被国际自然保护联盟或物种所在国列为受威胁的 193 种植物物种的商业化种植信息。这些物种中有 82% 的商业种植有迹象表明靠不断地补充野外采集的整株植物来维持。尽管基于小样本量, 只依赖人工繁殖或仅通过收集种子来维持商业种植的物种更有其野外采集压力被减小的可能。即便如此, 相关性分析表明, 生产系统, 规模以及物种开始种植的时间对这些受威胁物种的濒危状况的改变几乎没有影响。然而, 最近 10 年内才开展商业种植且种植规范小的物种更有可能经历采集压力的降低。非药用植物的商业种植对于物种保护来说是最成问题的, 因为这类植物的商业种植容易造成野生植物假作栽培植物被出售。为了确保保育效果, 我们迫切需要根据目标物种的生物学特性, 文化意义, 市场需求和保护状况来指导商业种植方式的政策。
Article impact statement: Cultivation of overharvested plants may not benefit conservation; multiple stakeholders with different expertise are needed to ensure it does.
Trade‐driven overexploitation threatens many sharks. Twelve of the world's most vulnerable shark species have been listed on the Convention on International Trade in Endangered Species of Wild Fauna ...and Flora (CITES) to regulate internationally traded products such as meat and dried fins. CITES records indicate that Hong Kong was the world's top legal importer of dried fins from listed sharks in 2015 (N = 8 species at that time), but traded a relatively small volume, with a few partners, in a small number of shipments (16). In contrast two CITES Appendix II listed hammerheads were consistently the fourth and fifth most common species (out of >80) in processed fin trimmings (N = 9,200) collected randomly from the Hong Kong retail dried fin market from February 2014 to December 2016 and were found in 100% of sampling events and in 66% of sampled retail vendors. This difference, and the fact that exporting nations previously known to land these species were not among those to report trade to CITES, suggest that listed species were often imported without CITES documentation in 2015. There are a number of incentives for trade hubs to meet their obligations to this treaty, which they could achieve by scaling up monitoring capacity and increasing inspection efficiency.
Abstract
Threats to orchid survival continue to intensify, with > 50% of the orchids that have been assessed for the IUCN Global Red List falling in to one of the categories of threat. Despite the ...best efforts of the orchid conservation community, the capacity to develop solutions at the species-level will be outstripped by the sheer scale and pace of change. In response to these challenges, scientists and conservation practitioners must make difficult choices in prioritizing their work. Following the 6th International Orchid Conservation Congress, we call for greater overlap between science-driven research objectives and real conservation needs.
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