2种杀菌制剂对微生物和大型无脊椎动物降解落叶的影响

水生真菌对于河流中的落叶降解这一重要的生态系统服务有着重要的作用。然而,杀真菌剂对于参与落叶降解的水生真菌和大型无脊椎动物的影响却鲜有了解。本实验将美国红枫（Acer rubrum）的叶片在河流中进行处理（处理组）以获得微生物（细菌与真菌）,或是在自来水下进行淋洗（未处理组）以模拟杀真菌剂可能带来的微生物生物量减少的情况。将处理组叶片分别置于绿钩虾属动物Hyalella azteca（端足类动物,在暴露开始时7日龄,是一种落叶分解物种）存在或不存在的环境中,在23 ℃条件下暴露于复合杀真菌剂QUILT（嘧菌酯和丙环唑）或是PRISTINE（啶酰菌胺和唑菌胺酯）培养14天。QUILT（~ 0.3 μg?L^-1, 1.8 μg?L^-1, 8 μg?L^-1）有加速端足类动物分解落叶的趋势（不显著）,却没有促进端足类动物本身生物量的同时增长,表明端足类动物对于落叶消费量的上升应该主要由于落叶营养成分的减少。PRISTINE（~ 33 μg?L^-1）显著地抑制了端足类动物的生长,降低其生物量（P<0.05）,在未处理组中也观察到类似结果。PRISTINE对于端足类动物生长显著的抑制作用以及随QUILT浓度升高而加快的落叶降解的趋势表明受到杀真菌剂影响的河流中落叶降解这一过程很可能被改变。在河流生态系统相关的条件下,如温度的变化和与杀虫剂混合后脉冲式的暴露,杀真菌剂对于落叶降解的影响需要进一步的研究。
精选自Adria A. Elskus, Kelly L. Smalling, Michelle L. Hladik, Kathryn M. Kuivila. Effects of 2 fungicide formulations on microbial and macroinvertebrate leaf decomposition under laboratory conditions. Environmental Toxicology and Chemistry: Volume 35, Issue 11, pages 2834–2844, November 2016. DOI: 10.1002/etc.3465
详情请见http://onlinelibrary.wiley.com/doi/10.1002/etc.3465/full
     

新烟碱类杀虫剂对非靶标生物毒性效应的研究进展

新烟碱类杀虫剂是目前全球市场占有率最高的一类杀虫剂,它们选择性作用于昆虫烟碱型乙酰胆碱受体,以往普遍认为其对非靶标生物毒性较低。然而,越来越多的证据表明,新烟碱类杀虫剂的暴露会对非靶标生物造成负面影响。本文综述了新烟碱类杀虫剂对水生生物、非靶标昆虫、鸟类和哺乳动物等多种非靶标生物的毒性,以及对人类健康的影响。新烟碱类杀虫剂对各类生物均具有急性致死毒性,但不同物种之间半数致死浓度(LC_(50))或半数致死剂量(LD_(50))差别较大,由低至高依次为昆虫(0.01～2.38 mg·L~(-1),3.7～81 ng·bee~(-1))、甲壳动物(0.59～37.75 mg·L~(-1))、鱼类(1.2～241 mg·L~(-1))、鸟类(15～>2 000 mg·kg~(-1))和哺乳动物(82～>5 000 mg·kg~(-1))。新烟碱类杀虫剂对非靶标生物的亚致死毒性表现在降低繁殖力和生长速度、降低活动性、影响神经系统、扰乱代谢平衡、损伤DNA等。总体上看,吡虫啉的毒性最高,呋虫胺和烯啶虫胺的毒性较低。啶虫脒、噻虫啉、噻虫嗪和噻虫胺的毒性大小顺序随物种不同而不同。对于水生生物和非靶标昆虫,噻虫啉和噻虫胺的毒性较高,而对于鸟类和哺乳动物,啶虫脒的毒性较高。最后针对现有研究的不足,提出了今后的研究方向,以期为该类杀虫剂的风险评估和合理施用提供科学依据。     

美国EPA高通量暴露建模工具适合化学物质分级

正2014年7月30日来自美国EPA科学协调与政策办公室(OSCP)的一个研究小组表示,美国EPA用于估计化学物质暴露的高通量工具适合用于对化学物质进行分级。该研究小组在参加《联邦杀虫剂、杀真菌剂和杀鼠剂法》(FIFRA)科学顾问小组的一次关于与用于估计化学品暴露的新高通量方法相关的科学问题的会议上,重点讨论了ExpoCast——一项旨在开发基于人类暴露潜力筛查化学物质的高通量工具的环保署计划。     

农药暴露的机制模型：蜜蜂毒理学的重要缺失

杀虫剂在最近的蜜蜂数量减少中所扮演的角色是有争议的，部分原因是实地研究常常无法检测到实验室研究所预测的效果。这种不一致性突出了蜜蜂毒理学研究领域的一个关键空白：对蜜蜂在它们的环境中杀虫剂暴露的模式和过程知之甚少。本文作者提出蜜蜂暴露杀虫剂的2个关键过程：1)工蜂采集花蜜的过程中收集农药；2)工蜂带回的农药在蜂巢中的再分配。工蜂收集农药的过程必须被理解为环境污染和蜜蜂觅食活动之间的时空交集。这意味着农药暴露是分配的，而不是离散的，觅食工蜂的一个子集可能会获得有害剂量的农药，而群体暴露将会显得安全。蜂箱中农药的分布是一个复杂的过程，主要是由群体成员之间食物转移的相互作用而产生，而这一过程中花粉和花蜜之间有重要的区别。因此应该优先将关于蜜蜂生物学的大量文献用于发展更严谨的蜂蜜农药暴露机制模型。与效应机制模型结合，暴露机制模型具有整合蜜蜂毒理学领域的潜力，以促进风险评估和基础研究。
精选自Sponsler, D. B. and Johnson, R. M. (2017), Mechanistic modeling of pesticide exposure: The missing keystone of honey bee toxicology. Environmental Toxicology and Chemistry, 36: 871–881. doi: 10.1002/etc.3661
详情请见http://onlinelibrary.wiley.com/doi/10.1002/etc.3661/full
     

77％氢氧化铜水分散粒剂对6种陆生生物的毒性及环境风险评估

氢氧化铜是一种利用铜离子杀死孢子细胞的杀菌剂,对柑橘树溃疡病具有良好的防治效果.本研究依据《化学农药环境安全评价试验准则》和《农药登记环境风险评估指南》,对6种模式陆生生物:日本鹌鹑(Cotumix japonica)、蜜蜂(Apis mellif-era L.)、家蚕(Bombyx mori)、赤眼蜂(Trichogramma dendrolimi)、七星瓢虫(Coccinella septempunctata)和蚯蚓(Eisenia foetida)进行急性毒性试验并对其进行环境风险评估.结果 表明,对鹌鹑急性经口半致死剂量(7 d-LD50)为225.9 mg a.i.-(kg bw)-1,对蜜蜂急性经口48 h-LD50为6.19 μg a.i.-蜂-1.在飘移场景下评估该农药对家蚕的风险,得到最外围一行桑树上的风险商(RQ):RQfr=3.083＞1,风险不可接受;该农药在农田内对寄生性天敌赤眼蜂的危害商(HQ):HQin =9.702＞5,风险不可接受.对土壤生物蚯蚓急性和慢性的RQ值分别为799.8和2666,RQ＞1,因此对土壤生物蚯蚓的风险不可接受.77％氢氧化铜水分散粒剂对蜜蜂急性经口和鸟类毒性为中毒.环境风险评估结果显示,上述3项环境风险不可接受,说明农药环境风险评估方法不能只停留在对某一类型模式生物的毒性分级上.基于目前发展趋势,更新评估手段,建立风险评估模型是大势所趋.所以,更需要对农药进行全面研究,以提高农药使用的安全性和合理性.     

7种农药对管氏肿腿蜂的毒性及初级风险评价

为评估农药对寄生类自然天敌昆虫的安全性,选择管氏肿腿蜂(Scleroderma guani Xiao et Wu)作为受试生物,采用管测药膜法测定了3种杀虫剂、2种除草剂、2种杀菌剂对其致死效应,并根据田间推荐剂量计算暴露量,采用风险商值HQ对杀虫剂进行风险评估。结果显示,与空白对照比较,3种杀虫剂均具明显毒性作用,其中丁硫克百威、吡虫啉和呋虫胺对管氏肿腿蜂的24 h半致死量(24 h-LR50)分别为5.11、2.92和0.06 g a.i.·ha-1,农田内风险商值分别为60.23、16.64和3 105。除草剂和杀菌剂在3倍最大田间推荐剂量作用下,24 h管氏肿腿蜂死亡率均小于50%。上述结果表明,在田间推荐用量下,3种杀虫剂对管氏肿腿蜂的初级风险评价为存在高风险,建议进一步开展高级阶段风险评估或者采取合理的风险管理措施来降低风险;除草剂和杀菌剂对管氏肿腿蜂的风险可接受。     

农药在土壤环境中的行为和归宿(一)

农药是指用来预防、消除或驱除有害昆虫、线虫、真菌、杂草及其它陆生或水生生物、植物和微生物的化学物质或其混合物。在习惯上,它常分为除莠剂、杀虫剂和杀菌剂三类。它们在农业上分别用于控制杂草、昆虫和植物病原菌。     

南极陆生线虫Plectus murrayi对铜的敏感性及其培养和毒性试验程序的开发

南极生态系统特定的环境质量指导值和修复目标是进行南极污染场地风险评估和修复的必需条件。南极土壤生物的生态毒理学测试是确定可靠的污染物效应阈值浓度的基础。本研究描述了针对生活在土壤颗粒间隙水中的南极特有的土壤线虫Plectus murrayi的最佳培养技术和水生毒性实验程序。毒性试验持续时间较长,用于揭示该物种的生理学和生活史特征。Plectus murrayi对水溶性铜的敏感性表现其卵孵化率的效应浓度（EC50）为139 μg/L。首次以卵的形式接触水溶性铜的孵化幼体不如在孵化的J2期初次接触铜的幼体敏感,这表明该卵具有潜在的保护作用。幼体对铜的敏感性随着暴露时间的延长而增加, 21天和28天的半数致死浓度（LC50s）分别为478 μg/L和117 μg/L。本研究描述了应用于南极土壤污染物对环境相关测试物种的风险评估新方法,并首次估算了南极陆生微型无脊椎动物对毒物的敏感性。     

国产防污漆中铜的海洋环境风险评估

为有效控制防污漆中杀生物活性物质给海洋环境带来的不利影响,亟需开展活性物质的环境风险评估研究,为筛选环境友好型活性物质提供依据。以25种国产防污漆中的铜为评估对象,采用防污漆活性物质环境风险评估的针对性方法,分步进行暴露评估、危害性评估和风险表征。暴露评估采用海洋防污剂预测环境浓度模型(MAMPEC)中的港口、码头和开阔海域等典型暴露场景;危害性评估基于铜对淡水和海水水生生物的慢性毒性数据,采用物种敏感度分布法和评估因子法;风险表征采用熵值法。结果表明,铜对全部水生生物和海水生物的预测无效应浓度分别为2.8和2.3μg·L~(-1),藻类对铜最为敏感。除1种配方外,其余24种防污漆配方中铜的风险熵均小于1,可判定铜为"相对低风险"类活性物质,使用上述防污漆时铜对生态环境造成的风险较小。铜在不同暴露场景中的环境风险分析表明其对水流交换较弱海域的码头造成的风险最大,其次是默认港口和码头,对于公海造成的风险最小。根据现有的评估结果,设计含铜型防污漆配方时,应使铜的释放速率不大于33.5μg·cm~(-2)·d~(-1),以避免对较封闭海域的生态环境造成不可忽视的风险。     

非致死剂量的四溴双酚A胁迫下蚯蚓的生长和抗氧化防御反应

以自然土壤为介质,考察赤子爱胜蚓(Eisenia fetida)的生长抑制率、蛋白质含量、超氧化物歧化酶(SOD)活性、谷胱甘肽转移酶(GST)活性等指标,进行了急性(14 d)、亚急性(28 d)暴露下四溴双酚A(tetrabromobisphenol A,TBBPA)非致死剂量胁迫对蚯蚓的生长和抗氧化防御效应研究。结果表明:在急性试验中TBBPA对蚯蚓的生长抑制均存在显著的剂量效应关系,而在亚急性暴露期,400 mg·kg~(-1)时显著抑制蚯蚓的生长(P<0.05);TBBPA对蚯蚓体内蛋白含量影响,在急性试验中各处理间差异不显著(P=0.712),进入亚急性期蛋白质含量在400 mg·kg~(-1)时被显著诱导(P=0.039,P<0.05);TBBPA对蚯蚓SOD酶活性的影响,在急性试验中50 mg·kg~(-1)时被显著诱导(P<0.01),在亚急性试验中400 mg·kg~(-1)时SOD酶活性显著升高(P<0.05);TBBPA对蚯蚓GST酶活性影响,在急性试验中400 mg·kg~(-1)时呈现显著诱导效应(P<0.05),在亚急性期各处理间差异不显著(P=0.428)。蚯蚓生长抑制率、蛋白质含量、体内各生化酶系对TBBPA暴露的时间效应和剂量效应的敏感性存在不同程度差异,应依据污染暴露指标的有效性和敏感性选择多时间段检测和多指标进行土壤安全评价诊断。     

Introduced Birds and the Fate of Hawaiian Rainforests

Abstract:  The Hawaiian Islands have lost nearly all their native seed dispersers, but have gained many frugivorous birds and fleshy-fruited plants through introductions. Introduced birds may not only aid invasions of exotic plants but also may be the sole dispersers of native plants. We assessed seed dispersal at the ecotone between native- and exotic-dominated forests and quantified bird diets, seed rain from defecated seeds, and plant distributions. Introduced birds were the primary dispersers of native seeds into exotic-dominated forests, which may have enabled six native understory plant species to become reestablished. Some native plant species are now as common in exotic forest understory as they are in native forest. Introduced birds also dispersed seeds of two exotic plants into native forest, but dispersal was localized or establishment minimal. Seed rain of bird-dispersed seeds was extensive in both forests, totaling 724 seeds of 9 native species and 2 exotics with over 85% of the seeds coming from native plants. Without suitable native dispersers, most common understory plants in Hawaiian rainforests now depend on introduced birds for dispersal, and these introduced species may actually facilitate perpetuation, and perhaps in some cases restoration, of native forests. We emphasize, however, that restoration of native forests by seed dispersal from introduced birds, as seen in this study, depends on the existence of native forests to provide a source of seeds and protection from the effects of ungulates. Our results further suggest that aggressive control of patches of non-native plants within otherwise native-dominated forests may be an important and effective conservation strategy.     

Whitebark pine (Pinus albicaulis) assisted migration potential: testing establishment north of the species range

The translocation of species into habitable locations outside of their current ranges, termed assisted migration, has been proposed as a means of saving vulnerable species from extinction as a result of climate change. We explore the use of this controversial technique using a threatened keystone species in western North America, whitebark pine (Pinus albicaulis), as a case study. Species distribution models predict that whitebark pine will be extirpated from most of its current range as temperatures rise over the next 70 years. However, the same models indicate that a large area within northwestern British Columbia, Canada, is climatically suitable for the species under current conditions and will remain so throughout the 21st century. To test the capacity of whitebark pine to establish relative to climatic and habitat features within its predicted climatic range, we planted seeds from seven populations in eight locations spanning from 600 km southeast to 800 km northwest of the northern boundary of the current species range. During the first three growing seasons, germination occurred in all locations. Nearly three times as many treated (induced maturation and broken dormancy) than untreated seeds germinated, and most treated seeds germinated a year earlier than the untreated seeds. Germination, survival, and growth were primarily influenced by seed mass, site climate conditions related to the duration of snow cover, and provenance temperature. Our experiment provides a preliminary test of models predicting the existence of climatically suitable whitebark pine habitat north of the current species ranges. More broadly, our techniques and results inform the development of scientific guidelines for assisting the migration of other species that are highly threatened by climate change. Applied case studies of this kind are critical for assessing the utility of species distribution models as conservation planning tools.     

The importance of seed dispersal in the Alexandria Coastal Dunefield, South Africa

The endozoochorous dispersal of seeds by mammals and birds between distinct vegetation communities was assessed to determine the importance of these processes in coastal dune field management. Isolated pockets of thicket vegetation (bush-pockets) within a large coastal dune field provided the opportunity to study vertebrate seed dispersal and its contribution to their origin and maintenance. Mammalian and avian faeces were collected for the quantification of seeds dispersed via endozoochory. Birds and mammals showed considerable overlap, dispersing intact seeds of 17 and 29 plant species, respectively, but mammals dispersed a greater diversity and size range than birds. Extrapolation of mammalian faecal data indicates an annual input of 23 million intact seeds to the dune field. Significantly more seeds are deposited by mammals and birds in the bush-pockets than on open sand, and birds deposited greater numbers of seeds nearer the seed source. Zoochory appears to be critical for the maintenance of the bush-pocket habitats through the dispersal of climax woody plant species into the dune field. Directional dispersal by birds and mammals to the bush-pockets is considered to be responsible for the maintenance and possible origin of these bush-pockets. The high number of exotic plant propagules dispersed by both avian and mammalian zoochory highlights the importance of management of the Alexandria Coastal Dunefield (ACD) beyond the reserve boundaries. In a dynamic system such as the ACD which is within a declared nature reserve, the continued existence of the bush-pockets may depend on the maintenance, beyond the reserve boundaries, of a reservoir of not only plant material but vertebrate dispersers as well.     

Weed-biocontrol insects reduce native-plant recruitment through second-order apparent competition

Small-mammal seed predation is an important force structuring native-plant communities that may also influence exotic-plant invasions. In the intermountain West, deer mice (Peromyscus maniculatus) are prominent predators of native-plant seeds, but they avoid consuming seeds of certain widespread invasives like spotted knapweed (Centaurea maculosa). These mice also consume the biological-control insects Urophora spp. introduced to control C. maculosa, and this food resource substantially increases deer mouse populations. Thus, mice may play an important role in the invasion and management of C. maculosa through food-web interactions. We examined deer mouse seed predation and its effects on seedling emergence and establishment of a dominant native grass, Pseudoroegneria spicata, and forb, Balsamorhiza sagittata, in C. maculosa-invaded grasslands that were treated with herbicide to suppress C. maculosa or left untreated as controls. Deer mice readily took seeds of both native plants but removed 2-20 times more of the larger B. sagittata seeds than the smaller P. spicata seeds. Seed predation reduced emergence and establishment of both species but had greater impacts on B. sagittata. The intensity of seed predation corresponded with annual and seasonal changes in deer mouse abundance, suggesting that abundance largely determined mouse impacts on native-plant seeds. Accordingly, herbicide treatments that reduced mouse abundance by suppressing C. maculosa and its associated biocontrol food subsidies to mice also reduced seed predation and decreased the impact of deer mice on B. sagittata establishment. These results provide evidence that Urophora biocontrol agents may exacerbate the negative effects of C. maculosa on native plants through a form of second-order apparent competition-a biocontrol indirect effect that has not been previously documented. Herbicide suppressed C. maculosa and Urophora, reducing mouse populations and moderating seed predation on native plants, but the herbicide's direct negative effects on native forb seedlings overwhelmed the indirect positive effect of reducing deer mouse seed predation. By manipulating this four-level food chain, we illustrate that host-specific biological control agents may impact nontarget plant species through food-web interactions, and herbicides may influence management outcomes through indirect trophic interactions in addition to their direct effects on plants.     

A Case Study in Applying the IUCN Regional Guidelines for National Red Lists and Justifications for their Modification

Abstract:  The World Conservation Union (IUCN) published guidelines to apply the criteria developed for global red lists at subglobal levels. So far only a few national red lists have been prepared according to these regional guidelines. We present a procedure based on the regional guidelines that was developed for the most recent red list of breeding birds in Switzerland. Special attention was given to step 2 of the IUCN regional guidelines, which consists of adapting categories according to an assessment of the extent to which extinction risk of the national population is affected by populations in neighboring countries. To avoid subjective assessments we formalized this "up- and downgrading" procedure by defining rules to answer the questions asked in the regional guidelines. Some modifications to the assessment procedure were introduced to account for the specific situation of applying it to birds as a very mobile group and Switzerland as a small country. The up- and downgrading procedure resulted in a change in category for 49 of the 195 bird species assessed. Overall, 9 species were upgraded, 21 species were downgraded by one category, and 19 species were downgraded by two categories. Formalizing step 2 allowed consistent application of the regional guidelines for all species and will make future revisions of the national red list and comparisons between different lists easier.     

Soil vs. canopy seed storage and plant species coexistence in species-rich Australian shrublands

The fire-prone shrublands of southwestern Australia are renowned for their high plant species diversity and prominence of canopy seed storage (serotiny). We compared species richness, abundance, and life history attributes for soil and canopy seed banks in relation to extant vegetation among four sites with different substrate conditions and high species turnover (50-80%) to identify whether this unusual community-level organization of seed storage might contribute to maintenance of high species richness. Soil seed bank (SSB) densities were low to moderate (233-1435 seeds/m2) compared with densities for other Mediterranean-type vegetation and were lowest for sites with highest canopy seed bank (CSB) species richness and lowest nutrient availability, but not richness or abundance of resprouters. Annuals were infrequent in the lowest nutrient sites, but there was no evidence that small SSB size was due to low seed inputs or a trade-off between seed production/storage and seed size in response to low nutrient availability. Sorensen's similarity between SSB and extant vegetation was 26-43% but increased to 54-57% when the CSB was included, representing levels higher than reported for most other ecosystems. Resprouting species were well represented in both the SSB and CSB, and there was no evidence for lower seed production in resprouters than in non-sprouters overall. The SSB and CSB held no species in common and were characterized by markedly different seed dispersal attributes, with winged or small seeds in the CSB and seeds dispersed by ants, birds, and wind (though none with wings) in the SSB. There was no evidence of spatial differentiation in the distribution of seeds of SSB species between vegetated and open microsites that might facilitate species coexistence, but most woody non-sprouters showed aggregation at scales of 1-2 m, implying limited seed dispersal. High similarity between overall seed bank (SSB + CSB) and extant species composition, high number of resprouting species, and seed dispersal processes before (SSB) and after fire (CSB) leading to differential spatial aggregation of post-fire recruits from the two seed bank types may buffer species composition against rapid change and provide a mechanism for maintaining species coexistence at the local scale.     

Biotic resistance via granivory: establishment by invasive, naturalized, and native asters reflects generalist preference

Escape from specialist natural enemies is frequently invoked to explain exotic plant invasions, but little attention has been paid to how generalist consumers in the recipient range may influence invasion. We examined how seed preferences of the widespread generalist granivore Peromyscus maniculatus related to recruitment of the strongly invasive exotic Centaurea stoebe and several weakly invasive exotics and natives by conducting laboratory feeding trials and seed addition experiments in the field. Laboratory feeding trials showed that P. maniculatus avoided consuming seeds of C. stoebe relative to the 12 other species tested, even when seeds of alternative species were 53-94% smaller than those of C. stoebe. Seed addition experiments conducted in and out of rodent exclosures revealed that weakly invasive exotics experienced relatively greater release from seed predation than C. stoebe, although this was not the case for natives. Seed mass explained 81% of the variation in recruitment associated with rodent exclusion for natives and weak invaders, with larger-seeded species benefiting most from protection from granivores. However, recruitment of C. stoebe was unaffected by rodent exclusion, even though the regression model predicted seeds of correspondingly large mass should experience substantial predation. These combined laboratory and field results suggest that generalist granivores can be an important biological filter in plant communities and that species-specific seed attributes that determine seed predation may help to explain variation in native plant recruitment and the success of exotic species invasions.     

Bat- and Bird-Generated Seed Rains at Isolated Trees in Pastures in a Tropical Rainforest

Abstract: Bats are abundant and effective seed dispersers inside the forest, but what happens when a forest is fragmented and transformed into pasture? The landscape at Los Tuxtlas, Mexico, originally rainforest, is greatly fragmented and covered with pastures. We analyzed the seed rains produced by frugivorous bats and birds under isolated trees in pastures in the fragmented landscape and the contribution of this process to vegetational recovery. We surveyed bats and obtained fecal samples under isolated trees in pastures. We also collected seed rain below the canopy of 10 isolated Ficus trees, separating nocturnally dispersed seeds from diurnally dispersed seeds. We caught 652 bats of 20 species; 83% of captures were frugivores. The most abundant species were Sturnira lilium (48%), Artibeus jamaicensis (18%), Carollia perspicillata (12%), and Dermanura tolteca (11%). Fecal samples contained seeds of 19 species in several families: Piperaceae (50%), Moraceae (25%), Solanaceae (12%), Cecropiaceae (10%), and others (3%). Sturnira lilium was the most important disperser bat in pastures. Seed rain was dominated by zoochorous species (89%). We found seed diversity between day and night seed captures to be comparable, but we found a significant interaction of disperser type (  bird or bat) with season. Seven plant species accounted for 79% of the seed rain: Piper auritum (23%), Ficus (  hemiepiphytic-strangler tree) spp. (17%), Cecropia obtusifolia (10%), P. amalago (10%), Ficus (  free-standing tree) spp. (8%), P. yzabalanum (6%), and Solanum rudepanum (5%). Bats and birds are important seed dispersers in pastures because they disperse seeds of pioneer and primary species (trees, shrubs, herbs, and epiphytes), connect forest fragments, and maintain plant diversity. Consequently, they might contribute to the recovery of woody vegetation in disturbed areas in tropical humid forests.     

Applying habitat and population-density models to land-cover time series to inform IUCN Red List assessments

The IUCN (International Union for Conservation of Nature) Red List categories and criteria are the most widely used framework for assessing the relative extinction risk of species. The criteria are based on quantitative thresholds relating to the size, trends, and structure of species’ distributions and populations. However, data on these parameters are sparse and uncertain for many species and unavailable for others, potentially leading to their misclassification or classification as data deficient. We devised an approach that combines data on land-cover change, species-specific habitat preferences, population abundance, and dispersal distance to estimate key parameters (extent of occurrence, maximum area of occupancy, population size and trend, and degree of fragmentation) and hence predict IUCN Red List categories for species. We applied our approach to nonpelagic birds and terrestrial mammals globally (∼15,000 species). The predicted categories were fairly consistent with published IUCN Red List assessments, but more optimistic overall. We predicted 4.2% of species (467 birds and 143 mammals) to be more threatened than currently assessed and 20.2% of data deficient species (10 birds and 114 mammals) to be at risk of extinction. Incorporating the habitat fragmentation subcriterion reduced these predictions 1.5–2.3% and 6.4–14.9% (depending on the quantitative definition of fragmentation) for threatened and data deficient species, respectively, highlighting the need for improved guidance for IUCN Red List assessors on the application of this aspect of the IUCN Red List criteria. Our approach complements traditional methods of estimating parameters for IUCN Red List assessments. Furthermore, it readily provides an early-warning system to identify species potentially warranting changes in their extinction-risk category based on periodic updates of land-cover information. Given our method relies on optimistic assumptions about species distribution and abundance, all species predicted to be more at risk than currently evaluated should be prioritized for reassessment.     

Effect of Edge Structure on the Flux of Species into Forest Interiors

Abstract: A key goal of conservation biology is to prevent the spread of exotic species. Previous work on exotic invasion has two limitations: (1) the lack of a spatially explicit approach and (2) a primary focus on the net effect of invasion by examining invasive species already present in the community. We address these limitations by focusing on the arrival of a potential invader into a community and use a spatially explicit approach to quantify the flow of seeds from the surrounding landscape into the interior of a forest. We hypothesize that the structure of forest-edge vegetation influences how the edge mediates seed flux. To test our hypothesis, we experimentally altered vegetation structure within 20 m of the edge to create two edge treatments: thinned and intact. We quantified the flux of seeds moving into the forest interior across the two treatments. We used seed traps randomly arrayed on transects from 5 to 50 m into the forest. More seeds crossed the thinned treatment than crossed the intact treatment to reach the forest interior. In addition, seeds that crossed the thinned treatment dispersed farther into the forest than those that crossed the intact treatment. These results were consistent throughout the period of maximum autumn dispersal, including periods before and after leaf drop. Our results show that the structure of vegetation on the edge interacts with the flux of wind-dispersed seed across the edge. We demonstrated that an edge with intact vegetation can function as a physical barrier to seed dispersal. Therefore, the structure of vegetation on edges can influence the function of edges as barriers to seed flux into the forest interior.