有机肥中4类典型兽药抗生素的多残留测定

建立了固相萃取-超高效液相色谱-串联质谱（SPE—UPLC—MS／MS）法同时测定有机肥中7种磺胺类、4种氟喹诺酮类、4种四环素类和3种大环内酯类抗生素残留的方法。采用乙腈和磷酸盐缓冲液（pH=3）的混合液作为有机肥样品的提取溶液,用强阴离子交换柱（SAX）-亲水亲脂平衡萃取柱（HLB）串联进行提取液的富集和纯化。以甲醇-φ=0．1％的甲酸溶液作为流动相,进行液相质谱分析。18种抗生素在5—500μg·kg-1的浓度范围内线性关系良好,决定系数（r2）1〉0．99。以3倍信噪比估算磺胺类、氟喹诺酮类、四环素类和大环内酯类的检测限分别为0．37～4．65、0．43—2．42、0．94～2．78和0．83～4．20μg·kg-1,这4类抗生素50和500μg·kg。2个添加水平的样品平均加标回收率分别为71．6％～94．3％、72．3％～86．7％、71．0％～102．2％和70．7％～93．3％,相对标准偏差在2．1％～11．4％之间。采用所建方法对南京地区市售8种有机肥中18种抗生素含量的测定结果显示,除磺胺类外,其他抗生素均有不同程度的检出。     

长江三角洲地区典型废水中抗生素的初步分析

采用高效液相色谱-串联质谱方法,对城市生活污水、养猪场和甲鱼养殖场废水进行抗生素污染检测.污水处理厂污水中检出磺胺二甲嘧啶、磺胺甲氧嘧啶和磺胺甲恶唑3种磺胺类抗生素,浓度都低于5 μg·l-1.养猪场废水中检出磺胺甲恶唑、磺胺对甲氧嘧啶、磺胺嘧啶、磺胺二甲嘧啶和磺胺氯哒嗪5种磺胺类抗生素(＜5μg·l-1),四环素类的四环素、土霉素和强力霉素(30.05-100.75μg·l-1).甲鱼养殖场废水检出氯霉素、甲砜霉素和氟甲砜霉素3种氯霉素抗生素,浓度低于检测下限0.1μg·l-1.结果表明,在3种典型废水中,养猪场废水检出抗生素的种类最多,浓度也最高;磺胺类在3种废水中检出频率最高,尤其是磺胺甲恶唑、磺胺二甲嘧啶和磺胺甲氧嘧啶.说明城市生活污水、畜禽养殖场废水和水产养殖废水都是水环境潜在的抗生素污染源.     

配套养殖体系中部分抗生素的污染特征

采用超声提取-固相萃取-高效液相色谱串联质谱技术分析配套养殖体系粪便、水体和沉积物中4种磺胺类(SAs)、2种四环素类(TCs)、2种大环内酯(MLs)和2种喹诺酮类(QLs)抗生素的含量和分布特征.研究结果显示,在水体中共检出8种抗生素,浓度在ND—382 ng·L-1,2种四环素类抗生素未被检出,且水体中抗生素的浓度呈现旱季高于雨季;沉积物中共检出7种抗生素,其浓度分别在ND—3400μg·kg-1范围内,磺胺嘧啶(SDZ)、磺胺甲噁唑(SMX)和罗红霉素(RTM)未被检出;在猪粪和鸭粪中均检出甲氧苄啶(TMP)、诺氟沙星(NFX)、脱水红霉素(ETM-H2O)和罗红霉素(RTM),同时猪粪中还检出2种四环素类,鸭粪中检出磺胺二甲嘧啶(SMZ)和环丙沙星(CFX),其中鸭粪中甲氧苄啶的最高浓度达到6.11 mg·kg-1.研究结果表明,不同介质中抗生素的含量存在一定差异,其中磺胺类抗生素在水体中浓度最高,喹诺酮类和四环素类在沉积物中的浓度最高;粪便中抗生素的种类与施药的种类密切相关,并且可能会加剧抗生素对水体环境的污染.     

猪场废水中24种抗生素同时检测方法优化

采用优化固相萃取-液相色谱-串联质谱同步检测养猪废水中24种抗生素的.水样用1 mol·L~(-1)盐酸调节p H值至3.5—4.0,流经Oasis HLB固相萃取柱富集后再用甲醇和乙酸乙酯(V∶V=1∶1)进行洗脱.以Agilent eclipse plus C_(18)色谱柱为分离柱,以0.1%甲酸水溶液和乙腈为流动相进行梯度洗脱,采用电喷雾正离子源,多反应监测模式检测.24种抗生素的检出限(S/N=3)在0.03—3.00μg·L~(-1)之间.进一步以不同养猪场废水进行实际样品测定,四环素类、大环内酯类、β-内酰胺类、喹诺酮类、磺胺类等5大类抗生素均有检出,土霉素、替米考星和磺胺甲嘧啶等3种抗生素为主要污染抗生素,最高浓度可达147.10、107.83、100.20μg·L~(-1),磺胺甲噻二唑及去甲基金霉素均未检出.本研究建立了快速准确的同步分析5大类24种抗生素的分析方法.     

渭河西安段磺胺类抗生素的分布特征及生态风险评价

采用HPLC-MS/MS对渭河西安段(咸阳至西安)表层水体中的磺胺类抗生素污染物进行检测分析,丰水期共检出包括磺胺嘧啶、磺胺二甲嘧啶、磺胺甲唑、磺胺间甲氧嘧啶、磺胺吡啶、磺胺喹喔啉、磺胺氯哒嗪和磺胺增效剂甲氧苄啶8种药物残留,检出率50%—100%,检出浓度nd—178.44 ng·L~(-1);平水期检测到除磺胺氯哒嗪外7种,检出率25%—100%,检出浓度nd—114.46 ng·L~(-1).与国内其他河流相比,渭河西安段检出的磺胺类抗生素种类较多,浓度处于中等水平.磺胺类抗生素的浓度分布呈现:平水期,上游中游下游;丰水期,中游下游上游的特点;平水期和丰水期共同检出的磺胺类抗生素比较,平水期检出总浓度高于丰水期.源分析初步表明,生活污水、工业和医疗废水、禽畜和水产养殖是渭河西安段磺胺类抗生素浓度水平较高的主要原因.此外,渭河西安段表层水体中磺胺类抗生素浓度与COD、NH_3-N、TN、TP等其他同步水污染指标无明显相关关系.风险商值RQs分析表明除磺胺甲唑(RQs≥1)对相应物种存在高风险,其他抗生素的风险较低(RQs0.1).     

高效液相色谱-荧光检测法同时测定畜禽粪便中4种磺胺类药物残留

建立了高效液相色谱-荧光检测法测定畜禽粪便中4种磺胺药物(磺胺甲基嘧啶(SM1)、磺胺氯哒嗪(SCP)、磺胺邻二甲氧嘧啶(SDM’)、磺胺喹噁啉(SQ))的方法.样品用25 mL甲醇提取3次,合并提取液,浓缩干燥,用0.1 mol.L-1的HCL溶解残渣,经荧光胺衍生化后,用反相C18柱为分离柱,以乙腈∶0.5%乙酸=40∶60(V/V)为流动相进行洗脱,20 min内分离4种药物.在0.05—5.00μg.mL-1范围内,4种磺胺类药物的峰面积与质量浓度的线性关系良好(R2≥0.999),SM1、SCP、SDM’、SQ的定量限(LOQ)分别为2.3、6.3、4.3和9.6μg.kg-1;添加水平为50、100、1000μg.kg-1时,SM1、SCP、SDM’、SQ的回收率分别为74.91%—81.82%、78.45%—91.43%和86.10%—92.88%,RSD小于8.82%.     

长江南京段表层水体中12种磺胺类抗生素的污染水平及风险评价

为评价长江南京段表层水体磺胺类抗生素的污染水平、生态风险及健康风险,利用高效液相色谱-串联质谱测定了长江南京段水体中14个采样点的12种磺胺类化合物.结果显示,长江南京段表层水体中共检出了8种磺胺类化合物,总浓度范围为13.2—21.0 ng·L~(-1),中值为16.4 ng·L~(-1),平均值为16.2 ng·L~(-1),8种检出抗生素中最高的为磺胺甲唑,浓度范围为6.76—8.98 ng·L~(-1),其次是为磺胺嘧啶,浓度范围为2.52—6.59 ng·L~(-1).其中磺胺甲噻二唑、磺胺间甲氧嘧啶、磺胺甲氧哒嗪及磺胺噻唑在所有采样点均未检出.总体来说,长江南京段水体中的磺胺类抗生素浓度与国内及国外其他水体包括河流湖泊相比处于相对较低的水平.对4种磺胺类抗生素的生态风险评价结果表明,所有的4种抗生素RQs均小于0.01.采用简单叠加模型计算的磺胺类抗生素的联合毒性风险熵范围为0.0029—0.0039,表明长江南京段磺胺类抗生素对于水生生物风险不显著.对4种磺胺类抗生素的人体健康风险评价结果表明,每种化合物对于每个年龄段的RQs均小于1,表明长江南京段表层水体中的磺胺类抗生素对人体健康无风险.     

水中磺胺对甲氧嘧啶抗生素的平面波导免疫传感器检测

为满足对水中磺胺类抗生素磺胺对甲氧嘧啶(SMD)快速灵敏检测的需求,本研究基于间接竞争免疫反应原理,结合本课题组自主研发的平面波导免疫传感器,建立了快速检测水环境中的磺胺对甲氧嘧啶(SMD)抗生素的方法.研究结果表明,当抗体浓度优化为1.50μg·mL~(-1)、溶液pH值为中性时,磺胺对甲氧嘧啶(SMD)的检测限可至5.24 ng·L~(-1),定量检测区间为0.03—1.37μg·L~(-1),满足水中SMD抗生素的检测需求;四环素、林可霉素及双酚A三类典型污染物对SMD的检测无明显干扰,本方法具有良好的特异性和选择性,检测周期(包括检测及再生)仅20 min.传感芯片再生性研究表明,检测的核心单元免疫芯片可再生后重复使用,其检测性能在运行100个工作周期后无明显衰减.利用本方法对两种实际水样进行加标回收测试,回收率分别在86.3%—93.2%、86.7%—90.5%之间,相对标准偏差均小于10%.结果表明本方法可用于实际水中SMD的快速检测,同时为其它磺胺类抗生素快速灵敏检测方法的建立提供了参考.     

水中微量磺胺甲恶唑的现场快速前处理方法

本文制备了磺胺甲恶唑分子印迹聚合物,通过静态吸附实验及红外光谱等手段研究其性能,并以该聚合物为核心材料自制液体样品快速前处理装置,建立且优化出一种水溶液中微量磺胺甲恶唑的简单、经济的现场批量前处理方法.通过加标回收实验验证了该方法的可行性,并进行了实际样品的现场前处理与测定.结果表明,所制备的印迹聚合物(MIP)具有良好的亲和性和特异选择性;在0.50—1000.00μg·L-1范围内,所建立方法的水样加标回收率为72.0%—100.3%,相对标准偏差为2.2%—5.1%(n=6),方法的检测限为0.01μg·L-1.本实验所采集的5种实际样品(红湖水样、水上乐园水样、鱼塘水样、牛尿和猪尿)中均检出磺胺甲恶唑,其浓度分别为0.76、1.23、1.94、202.0、435.3μg·L-1.     

三种磺胺类药物对罗非鱼肝脏组织中谷胱甘肽转移酶（GST）和丙二醛（MDA）的影响

研究磺胺嘧啶（sulfadianzine,SDZ）、磺胺二甲基嘧啶（sulfadimidine,SM2）和磺胺甲基异恶唑（sulfamethoxazole,SMZ）三种典型磺胺类抗生素对罗非鱼（Oreochromis niloticus）肝脏谷胱甘肽转移酶（GST）活性和丙二醛（MDA）含量的响应。采用饲料暴露的给药方式,用磺胺药物浓度为4和40g·kg-1的人工配合饲料喂养试验罗非鱼,对照组投喂不含磺胺药物的空白饲料。暴露时间为7d,每天2次投喂饲料,饲料的日投喂量按鱼体重的3%计,分别在24、72和168h采集肝脏样品待测。结果表明各浓度组GST和MDA分别在暴露后72和24h受到最大程度的诱导,其中GST活性比空白组提高了6.72倍,MDA含量比空白组提高了24.75倍。在4g·kg-1的药物浓度下SM2对GST和MDA有最强诱导,在40g·kg-1的药物浓度下三种药物对罗非鱼GST和MDA诱导效应大小顺序为SDZ〉SMZ〉SM2。GST和MDA在磺胺药物诱导下的响应敏感,适合作为磺胺类药物暴露的生物标记物。     

Achieving Open Access to Conservation Science

Conservation science is a crisis discipline in which the results of scientific enquiry must be made available quickly to those implementing management. We assessed the extent to which scientific research published since the year 2000 in 20 conservation science journals is publicly available. Of the 19,207 papers published, 1,667 (8.68%) are freely downloadable from an official repository. Moreover, only 938 papers (4.88%) meet the standard definition of open access in which material can be freely reused providing attribution to the authors is given. This compares poorly with a comparable set of 20 evolutionary biology journals, where 31.93% of papers are freely downloadable and 7.49% are open access. Seventeen of the 20 conservation journals offer an open access option, but fewer than 5% of the papers are available through open access. The cost of accessing the full body of conservation science runs into tens of thousands of dollars per year for institutional subscribers, and many conservation practitioners cannot access pay‐per‐view science through their workplace. However, important initiatives such as Research4Life are making science available to organizations in developing countries. We urge authors of conservation science to pay for open access on a per‐article basis or to choose publication in open access journals, taking care to ensure the license allows reuse for any purpose providing attribution is given. Currently, it would cost $51 million to make all conservation science published since 2000 freely available by paying the open access fees currently levied to authors. Publishers of conservation journals might consider more cost effective models for open access and conservation‐oriented organizations running journals could consider a broader range of options for open access to nonmembers such as sponsorship of open access via membership fees. Obtención de Acceso Abierto a la Ciencia de la Conservación     

Some polyphagous Homoptera gain protection from their natural enemies by feeding on the toxic plantsSpartium junceum andErythrina corallodendrum (Leguminosae)

Summary Interactions were studied among alkaloid-containing legumes (Erythrina corallodendrum andSpartium junceum) and non-toxic plants (Citrus sinensis, Cucurbita moschata andEuphorbia tirucalli), several polyphagous homopterans,Aphis craccivora (Aphididae),Icerya purchasi, I. aegyptiaca (Margarodidae),Lepidosaphes ulmi (Diaspididae) andPlanococcus citri (Pseudococcidae), and some major natural enemies of these homopterans. Significant reductions in survival due to negative effects of alkaloid containing as compared with non-alkaloidal plants were recorded for the predatorsRodolia cardinalis andChilocorus bipustulatus, but not forCryptolaemus montrouzieri (Coleoptera: Coccinellidae),Chrysoperla carnea (Neuroptera: Chrysopidae) andSympherobius sanctus (Neuroptera: Sympherobiidae). The development time of the larvae or pupae ofR. cardinalis, C. carnea andS. sanctus was longer on the toxic plants than on the non-toxic ones. The percentage of parasitism ofA. craccivora collected from the non-alkaloidal plantsVicia palaestina andMelilotus albus was much higher than that onS. junceum. The parasitoid complexes ofA. craccivora differed between both plant groups. The nutritive value of honeydew ofI. purchasi andA. craccivora, as expressed by the life span ofEncyrtus infelix (Hymenoptera: Encyrtidae) adults, was also investigated. Life spans were significantly longer when the wasps fed on honeydew produced on non-alkaloidal plants (C. sinensis andPittosporum tobira) than on alkaloid containing plants whenI. purchasi — but notA. craccivora — was the producer. It is suggested that the chemical defense ofE. corallodendrum andS. junceum is exploited by polyphagous phytophages to reduce predation. In nature, population growth and density of four of the investigated homopterans are conspicuously high when they developed on the alkaloid containing plant species, and very low on non-alkaloid plants. The efficiency of their natural enemies may be reduced by sequestration of alkaloids (or other toxic plant compounds) or their transfer into excreted honeydew. Therefore it is assumed that a generalist phytophagous homopteran may be protected from its natural enemies, although at different rates of efficiency, if it can safely sequester the host allelochemical when it develops on toxic species within its host range.     

Sequestration of cucurbitacin analogs by New and Old World chrysomelid leaf beetles in the tribe Luperini

Summary Two South American polyphagous leaf beetles,Diabrotica speciosa andCerotoma arcuata, selectively accumulated the bitter tasting compound 23,24-dihydrocucurbitacin D in their body after ingesting root tissues of cucurbit plants. Similarly, three Asian Cucurbitaceae-feeding specialists in the genusAulacophora were found to sequester the same compound. Cucurbitacin analogs were shown to deter feeding by a bird predator, indicating an allomonal role for these compounds in cucurbitacin-associated chrysomelid leaf beetles both of New and Old Worlds. The strong affinity to cucurbitacins, selective sequestration of the analogs and consequent protection from predators suggested an ecological adaptation mechanism developed in common among these two geographically isolated subtribes in the Luperini.     

Effects of Controlled Fire and Livestock Grazing on Bird Communities in East African Savannas

Abstract: In East Africa fire and grazing by wild and domestic ungulates maintain savannas, and pastoralists historically set fires and herded livestock through the use of temporary corrals called bomas. In recent decades traditional pastoral practices have declined, and this may be affecting biodiversity. We investigated the effects of prescribed fires and bomas on savanna bird communities in East Africa during the first and second dry seasons of the year (respectively before and after the rains that mark the onset of breeding for most birds). We compared abundance, richness, and community composition on 9‐ha burned plots, recently abandoned bomas, and control plots in the undisturbed matrix habitat over a 3‐year period. Generally, recently burned areas and abandoned bomas attracted greater densities of birds and had different community assemblages than the surrounding matrix. The effects of disturbances were influenced by interactions between primary productivity, represented by the normalized difference vegetation index, and time. Bird densities were highest and a greater proportion of species was observed on burned plots in the months following the fires. Drought conditions equalized bird densities across treatments within 1 year, and individuals from a greater proportion of species were more commonly observed on abandoned bomas. Yearly fluctuations in abundance were less pronounced on bomas than on burns, which indicate that although fire may benefit birds in the short term, bomas may have a more‐lasting positive effect and provide resources during droughts. Several Palearctic migrants were attracted to burned plots regardless of rainfall, which indicates continued fire suppression may threaten their already‐declining populations. Most notably, the paucity of birds observed on the controls suggests that the current structure of the matrix developed as a result of fire suppression. Traditional pastoralism appears critical to the maintenance of avian diversity in these savannas.     

What Every Conservation Biologist Should Know about Economic Theory

Abstract: The last century has seen the ascendance of a core economic model, which we will refer to as Walrasian economics. This model is driven by the psychological assumptions that humans act only in a self‐referential and narrowly rational way and that production can be described as a self‐contained circular flow between firms and households. These assumptions have critical implications for the way economics is used to inform conservation biology. Yet the Walrasian model is inconsistent with a large body of empirical evidence about actual human behavior, and it violates a number of basic physical laws. Research in behavioral science and neuroscience shows that humans are uniquely social animals and not self‐centered rational economic beings. Economic production is subject to physical laws including the laws of thermodynamics and mass balance. In addition, some contemporary economic theory, spurred by exciting new research in human behavior and a wealth of data about the negative global impact of the human economy on natural systems, is moving toward a world view that places consumption and production squarely in its behavioral and biophysical context. We argue that abandoning the straightjacket of the Walrasian core is essential to further progress in understanding the complex, coupled interactions between the human economy and the natural world. We call for a new framework for economic theory and policy that is consistent with observed human behavior, recognizes the complex and frequently irreversible interaction between human and natural systems, and directly confronts the cumulative negative effects of the human economy on the Earth's life support systems. Biophysical economics and ecological economics are two emerging economic frameworks in this movement.     

Effects of Coffee Management on Deforestation Rates and Forest Integrity

Knowledge about how forest margins are utilized can be crucial for a general understanding of changes in forest cover, forest structure, and biodiversity across landscapes. We studied forest‐agriculture transitions in southwestern Ethiopia and hypothesized that the presence of coffee (Coffea arabica)decreases deforestation rates because of coffee's importance to local economies and its widespread occurrence in forests and forest margins. Using satellite images and elevation data, we compared changes in forest cover over 37 years (1973–2010) across elevations in 2 forest‐agriculture mosaic landscapes (1100 km² around Bonga and 3000 km² in Goma‐Gera). In the field in the Bonga area, we determined coffee cover and forest structure in 40 forest margins that differed in time since deforestation. Both the absolute and relative deforestation rates were lower at coffee‐growing elevations compared with at higher elevations (?10/20% vs. ?40/50% comparing relative rates at 1800 m asl and 2300–2500 m asl, respectively). Within the coffee‐growing elevation, the proportion of sites with high coffee cover (>20%) was significantly higher in stable margins (42% of sites that had been in the same location for the entire period) than in recently changed margins (0% of sites where expansion of annual crops had changed the margin). Disturbance level and forest structure did not differ between sites with 30% or 3% coffee. However, a growing body of literature on gradients of coffee management in Ethiopia reports coffee's negative effects on abundances of forest‐specialist species. Even if the presence of coffee slows down the conversion of forest to annual‐crop agriculture, there is a risk that an intensification of coffee management will still threaten forest biodiversity, including the genetic diversity of wild coffee. Conservation policy for Ethiopian forests thus needs to develop strategies that acknowledge that forests without coffee production may have higher deforestation risks than forests with coffee production and that forests with coffee production often have lower biodiversity value. Efectos de la Administración Cafetalera sobre las Tasas de Deforestación y la Integridad de los Bosques     

Globalization of the Cashmere Market and the Decline of Large Mammals in Central Asia

As drivers of terrestrial ecosystems, humans have replaced large carnivores in most areas, and human influence not only exerts striking ecological pressures on biodiversity at local scales but also has indirect effects in distant corners of the world. We suggest that the multibillion dollar cashmere industry creates economic motivations that link western fashion preferences for cashmere to land use in Central Asia. This penchant for stylish clothing, in turn, encourages herders to increase livestock production which affects persistence of over 6 endangered large mammals in these remote, arid ecosystems. We hypothesized that global trade in cashmere has strong negative effects on native large mammals of deserts and grassland where cashmere‐producing goats are raised. We used time series data, ecological snapshots of the biomass of native and domestic ungulates, and ecologically and behaviorally based fieldwork to test our hypothesis. In Mongolia increases in domestic goat production were associated with a 3‐fold increase in local profits for herders coexisting with endangered saiga (Saiga tatarica).That increasing domestic grazing pressure carries fitness consequences was inferred on the basis of an approximately 4‐fold difference in juvenile recruitment among blue sheep (Pseudois nayaur)in trans‐Himalayan India. Across 7 study areas in Mongolia, India, and China's Tibetan Plateau, native ungulate biomass is now <5% that of domestic species. Such trends suggest ecosystem degradation and decreased capacity for the persistence of native species, including at least 8 Asian endemic species: saiga, chiru (Pantholops hodgsoni), Bactrian camel (Camelus bactrianus), snow leopard(Panthera uncia), khulan(Equus hemionus), kiang (E. kiang), takhi (E. przewalski), and wild yak (Bos mutus). Our results suggest striking yet indirect and unintended actions that link trophic‐level effects to markets induced by the trade for cashmere. Globalización del Mercado de Cachemira y la Declinación de Mamíferos Mayores en Asia Central     

The lichen-rich coastal heath vegetation on the isle of Anholt, Denmark — conservation and management

The high conservational value of the lichen-rich vegetation and landscape of the marine foreland Ørkenen on the isle of Anholt is treated from a Danish as well as a European perspective. The sensitivity of the lichen-rich vegetation to physical disturbance is emphasized. The impact of invasive species such asPinus mugo as well as the effect of atmospheric deposition of nutrients on the heaths at Anholt is described. Considerations related to the development of a management plan for Ørkenen are presented.     

Behavior and ecology of Old World Luperini beetles of the genusAulacophora (Coleoptera: Chrysomelidae)

Summary The attraction of Old World leaf beetles in the genusAulacophora to kairomones and parakairomones which are effective lures for New WorldDiabrotica andAcalymma were investigated. Beetles captured on sticky traps baited with single and multicomponent lures were no different from the control traps for two species ofAulacophora. Yellow colored traps and squash blossoms are attractive toAulacophora beetles which detect sub-microgram quantities of cucurbitacins on silica gel. Leaf feeding behavior and flight activity data are correlated with varietal preference of threeAulacophora species. The common response byDiabrotica andAulacophora to cucurbitacins reinforces the two groups' coevolutionary association with the Cucurbitaceae. The apparent lack of a common response toCucurbita blossom volatiles suggests recent evolutionary pathways are substantially different for these two groups of beetles.     

Use of stochastic patch occupancy models in the California red-legged frog for Bayesian inference regarding past events and future persistence

Assessing causes of population decline is critically important to management of threatened species. Stochastic patch occupancy models (SPOMs) are popular tools for examining spatial and temporal dynamics of populations when presence–absence data in multiple habitat patches are available. We developed a Bayesian Markov chain method that extends existing SPOMs by focusing on past environmental changes that may have altered occupancy patterns prior to the beginning of data collection. Using occupancy data from 3 creeks, we applied the method to assess 2 hypothesized causes of population decline—in situ die-off and residual impact of past source population loss—in the California red-legged frog. Despite having no data for the 20–30 years between the hypothetical event leading to population decline and the first data collected, we were able to discriminate among hypotheses, finding evidence that in situ die-off increased in 2 of the creeks. Although the creeks had comparable numbers of occupied segments, owing to different extinction–colonization dynamics, our model predicted an 8-fold difference in persistence probabilities of their populations to 2030. Adding a source population led to a greater predicted persistence probability than did decreasing the in situ die-off, emphasizing that reversing the deleterious impacts of a disturbance may not be the most efficient management strategy. We expect our method will be useful for studying dynamics and evaluating management strategies of many species.