A single species of plant predicts territory occupancy in a population of Peruvian Plantcutters

Habitat selection assessments at multiple spatial scales provide a more complete understanding of the habitat requirements of a species, a matter that is especially useful for managing endangered wildlife. Studies of the diet and population distribution of threatened Peruvian Plantcutters (Phytotoma raimondii) suggest that the presence of Prosopis spp. trees, and the shrubs Grabowskia boerhaaviaefolia and Scutia spicata could explain the scattered distribution of their remnant subpopulations. However, our overall understanding of this remains unclear and incomplete because plantcutters are often absent in areas dominated by Prosopis spp., and other species of plants have largely been overlooked in distribution models. One way to address this issue is to also investigate spatial distribution patterns at finer scales within subpopulations. We modeled the probability of territory occupancy at one of their last strongholds, the Pómac Forest Historical Sanctuary in Peru. Our predictors were defined by biotic interactions using data collected in 2015 and 2016, and previous studies of their diet. We found that Peruvian Plantcutters consumed the leaves, fruits, and flowers of at least nine species of plants, but only G. boerhaaviaefolia shrubs, and the trees Prosopis spp. and Colicodendron scabridum were used more than expected based on availability. We did not observe consumption of S. spicata, but this plant was rare. Territory occupancy was positively influenced only by the availability of G. boerhaaviaefolia, a plant used by Peruvian Plantcutters both as a source of food and nest material. Our results suggest that, despite their diverse diet, Peruvian Plantcutters can be particularly dependent on the availability of G. boerhaaviaefolia. Accordingly, this may explain why both co-occur in most subpopulations. Lastly, although we found that Prosopis spp. did not explain territory occupancy, previous research shows that it does explain their distribution on a broader scale (across subpopulations). This inconsistency across spatial scales suggests a potential key role of Prosopis spp. in guaranteeing dispersal between and connectivity among subpopulations.     

Species-Habitat Relationships and Priority Areas for Marsh-Breeding Birds in Ontario

Populations of marsh-breeding birds have declined throughout the southern Laurentian Great Lakes basin. To advance conservation of these species, we used occupancy modeling, a regional prioritization scheme, and data from Birds Canada's Great Lakes Marsh Monitoring Program (2016–2018) to describe species-habitat relationships and identify priority habitat areas for 7 obligate marsh-breeding bird species in southern Ontario, Canada: American bittern (Botaurus lentiginosus), common gallinule (Gallinula galeata), least bittern (Ixobrychus exilis), marsh wren (Cistothorus palustris), pied-billed grebe (Podilymbus podiceps), sora (Porzana carolina), and Virginia rail (Rallus limicola). Given these species respond to land cover at widely varying spatial scales, we initially identified the most informative scale (buffer = 100 m, 200 m, 400 m, 800 m, 1,600 m, 3,200 m, or 6,400 m) for marsh, urban, agricultural, and forest cover to increase model performance. We also considered climate variables, whether sample sites were along a Great Lakes coastline or inland, and covariates influencing detection. Occupancy was best explained by land cover at a wide range of spatial scales depending on the species. All species except Virginia rail responded positively to marsh cover; American bittern and Virginia rail responded negatively to urban cover; least bittern, pied-billed grebe, and Virginia rail responded negatively and sora responded positively to agricultural cover; and American bittern, common gallinule, marsh wren, and pied-billed grebe responded negatively and Virginia rail responded positively to forest cover. Only American bittern responded negatively to mean May–June temperature; only pied-billed grebe responded positively to start of growing season; and only Virginia rail had higher occupancy at inland marshes compared to coastal. We combined predictions from the best model for each of 5 species with reasonably good model fit (we excluded sora and Virginia rail) to identify priority habitat areas for marsh-breeding birds. Expansion of wetland conservation work from existing priority areas based on waterfowl to also include these new additional priority areas based on marsh-breeding birds will be an important step towards conservation of all birds, and will help slow or maybe even reverse declining population trends. Some restoration activities outside but adjacent to priority areas will also be important for rebuilding marshes for these species across this intensively farmed and developed region. © 2020 The Wildlife Society.     

Reproductive strategies of animal-pollinated plants on high mountains: A review of studies from the “Third Pole”

Having hundreds of big mountains, the Qinghai–Tibetan Plateau and its southern boundary, the Hengduan Mountains Region, represent one of the world's biodiversity hotspots. In the so-called “Third Pole of the earth”, diverse effects of climate change and habitat heterogeneity could have driven the evolution of plant adaptive strategies. In this review, we collected and compiled recent sources of reproductive biology in animal-pollinated plants, stressing the questions that need further attention, including pollination system, pollen limitation, self-compatibility, and sexual system. We constructed plant–pollinator interaction networks based on the case studies from this region, showing that the majority of pollinators were bees, moths, butterflies, and flies were also important, and bats and birds were rare. As the unpredictable (cold, rainy or windy) weather affects pollinator activities, sexual reproduction seemed to be pollen limited, but available studies show that the exact pattern of pollen limitation is still under debate. Self-compatibility could be either a solution, or a result from pollen limitation. Moreover, plant sexual systems can be regarded as an integrated module that counters pollen limitation. As phylogenetic relationships were constructed, diverse genera experienced rapid radiation were revealed in these mountainous areas. Further studies of evolutionary transitions in reproductive systems of congeners will unveil potential factors shaping the general pattern of adaptive strategies in animal-pollinated plants. Further studies will be beneficial in using advanced new techniques, examining phenotypic selection under common gardens, and considering chemical ecology in interactions between plants and florivores, particularly in pollen fate.     

维生素A酸诱导HL-60细胞分化后银染核仁形成区的研究

用Ag-NOR、Brachet反应和作者改进的悬浮培养细胞Ag-aNOR的TEM技术等,综合地对RA诱导HL-60细胞分化后银染核仁形成区的变化进行了研究。实验结果表明,银染NOR的均值在给药组与对照组细胞中差异不显著。对间期细胞进行Ag-aNOR反应,结果??表明其数量在给药组比对照组明显减少,同时发现Brachet反应显示富含rRNA的核仁数与Ag-aNOR数改变极为一致,提示虽然活性的rRNA基因的数量在RA诱导分化的HL-60细胞中不变,但其转录明显受抑,使rRNA合成减少,进而在细胞水平出现了恶性表达的核仁变得少而小、甚至消失的分化表型。HL-60细胞的Ag-aNOR电镜观察更进一步证明了这一结论。     

高家镇旧石器遗址1998年出土的石制品

高家镇遗址是三峡地区一处重要的旧石器时代遗址。遗址埋藏于长江右岸第Ⅲ级基座阶地内。1995年和1998年经过两次发掘,揭露面积456m2,出土石制品2500余件,其中1998年在B区发掘出土石制品719件。石制品类型包括石器、石核、石片和断块等。古人类选取河卵石为原料运用锤击法剥片和加工石器;石器以大型为主,毛坯多为石核和完整石片,砍砸器是石器的主要类型;石器加工较简单,多数单向加工。石器工业具有中国南方旧石器时代主工业鲜明特点。地貌和地层对比,显示该遗址可能与冉家路口遗址同时,处于中更新世晚期。     

广西防城7种鹭类混群繁殖的空间生态位研究

2002年3~8月对广西防城万鹤山营巢的鹭类繁殖种群进行了调查研究,结果表明:万鹤山栖息有大白鹭(Egretta alba)、中白鹭(Egretta intermedia)、白鹭(Egretta garzetta)、黄嘴白鹭(Egretta eulophotes)、牛背鹭(Bubulcus ibis)、池鹭(Ardeda bacchus)、夜鹭(Nycticorax nycticorax)7种鹭类种群。除黄嘴白鹭为均匀分布之外,其他6种均为成群分布。鹭类在万鹤山上营巢繁殖具有明显的水平分布和垂直分布现象。对影响鹭类混群繁殖时空间分布的因素及各种群间的相互关系进行了探讨。     

Critical roles of interactions among switch I-preceding residues and between switch II and its neighboring alpha-helix in conformational dynamics of the GTP-bound Ras family small GTPases

GTP-bound forms of Ras family small GTPases exhibit dynamic equilibrium between two interconverting conformations, "inactive" state 1 and "active" state 2. A great variation exists in their state distribution; H-Ras mainly adopts state 2, whereas M-Ras predominantly adopts state 1. Our previous studies based on comparison of crystal structures representing state 1 and state 2 revealed the importance of the hydrogen-bonding interactions of two flexible effector-interacting regions, switch I and switch II, with the γ-phosphate of GTP in establishing state 2 conformation. However, failure to obtain both state structures from a single protein hampered further analysis of state transition mechanisms. Here, we succeed in solving two crystal structures corresponding to state 1 and state 2 from a single Ras polypeptide, M-RasD41E, carrying an H-Ras-type substitution in residue 41, immediately preceding switch I, in complex with guanosine 5'-(β,γ-imido)triphosphate. Comparison among the two structures and other state 1 and state 2 structures of H-Ras/M-Ras reveal two new structural features playing critical roles in state dynamics; interaction of residues 31/41 (H-Ras/M-Ras) with residues 29/39 and 30/40, which induces a conformational change of switch I favoring its interaction with the γ-phosphate, and the hydrogen-bonding interaction of switch II with its neighboring α-helix, α3-helix, which induces a conformational change of switch II favoring its interaction with the γ-phosphate. The importance of the latter interaction is proved by mutational analyses of the residues involved in hydrogen bonding. These results define the two novel functional regions playing critical roles during state transition.     

LMP1羧基端活化区3对鼻咽癌干细胞SP18迁移与侵袭的影响

为了观察潜伏性膜蛋白1(LMP1)羧基端活性区3(CTAR3)对鼻咽癌干细胞SP18迁移与侵袭的影响,本研究通过建立稳定表达LMP1及CTAR3突变型LMP1(LMP1△252-351)的SP18细胞系(即SP18-LMP1和SP18-LMP1△252-351),观察LMP1-CTAR3缺失突变后对SP18细胞增殖、迁移与侵袭的影响.采用基因芯片分析SP18-LMP1和SP18-LMP1△252-351间的差异表达基因,并验证基因的表达,用生物信息学分析差异表达基因间的相互关系.结果显示:a.SP-LMP1△252-351细胞生长速度较SP-LMP1细胞明显变缓,克隆形成和迁移与侵袭能力降低(n=3,P0.05);b.鉴定出LMP1羧基端CTAR3影响SP18细胞迁移与侵袭的18个基因(其中表达上调基因13个,下调基因5个),经荧光定量PCR验证与基因芯片检测结果基本一致.c.13个差异基因间相互联系,网络节点联系最多的基因是FN1、MMP14、THBS1、ITGA2、IL1B和IL6基因.结果提示,LMP1羧基端CTAR3可能通过调节FN1、MMP14、THBS1、ITGA2、IL1B和IL6基因的表达,发挥其促鼻咽癌干细胞SP18细胞迁移与侵袭的功能.     

Differential resilience of invertebrates to fire

Fires are natural to ecosystems in many parts of the world, yet few studies have examined multi‐taxa invertebrate responses to these fires. We sampled a wide range of invertebrate taxa and feeding guilds at sites 3 months, 1 year and 3 years after fire, and in unburned control sites at the same time. A range of invertebrate sampling techniques was used on Table Mountain, in the Cape Floristic Region biodiversity hotspot, an area prone to natural and human‐induced fires. Sampling time differences strongly affected the composition of the whole assemblage, with fire having a major additional influence. Assemblages showed differential resilience to fire, especially in terms of species richness and abundance. One year after fire, the burned sites had the most compositional differences for the surface‐active species compared to control sites, while after 3 years, these sites were similar. Aerial assemblages were very different 3 years after burning, especially the pollination guild. Furthermore, these 3‐year‐old burned sites had the most unique species, suggesting that burning and longer‐term recovery is important for overall diversity. Some components of the invertebrate assemblage were remarkably resilient to fire (particularly ants), while others were far more conservative (pollinators). Nevertheless, fire allows new species to enter the ecosystem and can thus be used to promote local biodiversity if used appropriately. Ants alone should not be used to represent the whole invertebrate assemblage as they do not represent the more fire‐prone groups. A cross‐section of functional guilds is recommended in invertebrate recovery/fire management conservation programmes. These results have general significance in that a variety of feeding guilds need to be sampled when monitoring invertebrate responses to fire.     

自然保护区可持续发展环境指标与生态旅游评价指标初探——以北京松山自然保护区为例

生态旅游已成为当今旅游业的热点,而自然保护区则是开展生态旅游的重要依托。如何处理保护与开发的关系,是保护区开展生态旅游面临的一个重要的问题。松山国家级自然保护区在北京的生态环境及其旅游中处于举足轻重的位置,在保护区内积极开展具有特色的生态旅游,并在此基础上提出了生态旅游评价指标体系,为自然保护区的保护与开发,可持续发展,提供必要的、科学的决策依据;为松山自然保护区的可持续发展和管理,提供了新思路和途径。