Diagnostic validation of selected serological tests for detecting scrub typhus

Clinical diagnosis of scrub typhus is often difficult because the symptoms are very similar to those of other febrile illness such as dengue, leptospirosis, malaria and other viral hemorrhagic fevers. Though better diagnostic tests are available for rickettsial diseases and scrub typhus elsewhere, the Weil–Felix test is still commonly used in India, mainly because microimmunofluorescence assays (M‐IFA) were not available in India till recently and relevant staff had insufficient training. The present study was performed to investigate the performance of M‐IFA, IgM ELISA, and Weil–Felix test on 546 non‐repeated serum samples from subjects suspected of having scrub typhus. One hundred and forty‐three of these 546 samples were positive by M‐IFA; these cases were also confirmed clinically to have scrub typhus based on their dramatic responses to doxycycline therapy. IgM ELISA was positive in 122 of the 143 M‐IFA positive cases and the Weil–Felix test in 96. Though the Weil–Felix test is a heterophile agglutination test, it was found in this study to have good specificity but far too little sensitivity to use as a routine diagnostic test. IgM ELISA can be a good substitute for M‐IFA. Incorporation of multiple prototype antigens on M‐IFA slides is likely one of the reasons for its superior performance. As newer and better diagnostic assays become available for scrub typhus diagnosis in developed countries, it will be imperative to also use such tests in other endemic countries to prevent over‐ or under‐diagnosis of scrub typhus.     

Evaluating long-term introduction success of the Florida scrub endemic Crotalaria avonensis (Fabaceae) using a decade of demographic data

Introductions are a critical tool in the recovery of many imperiled species, yet adequate evaluation and development of best practices has lagged. Importantly, long-term post-introduction data are typically lacking, as well as suitable comparisons to wild populations to provide a baseline against which to assess performance. Here, we report on three experimental introductions of Crotalaria avonensis (Fabaceae), a federally endangered perennial herb that is narrowly endemic to scrub of the Lake Wales Ridge in peninsular Florida, U.S.A. We synthesize 10 years of post-introduction monitoring at both the introduced and a nearby, protected wild population to (1) develop best practices for conservation, and (2) evaluate the success of the introduction. First, our study identified best practices that included using transplants propagated from stem cuttings, as well as several factors that may increase seed germination such as habitat choice, seed burial, and litter addition. Second, during the 10 years following the introduction, population density in the introduced population was higher than in a nearby protected, wild population, and a comparison of vital rates revealed that this result was due to relatively high clonal and seedling recruitment rates in the introduced population. Furthermore, the source population, which occurred on unprotected lands, precipitously declined during this time period, further highlighting the importance of safeguarding plants from that population. We report that a new, growing population of C. avonensis has been established to date, with important implications for the species' conservation as well as how introductions are evaluated.     

黄土区露天煤矿排土场不同微地貌土壤种子库特征

黄土区露天煤矿排土场边坡水力冲刷强烈,不同植被恢复模式与水力作用耦合形成的不同微地貌可通过对种子的不同拦截作用而影响植被的恢复及发展。为了探讨排土场不同微地貌对种子的拦截效益及不同植被恢复模式的恢复潜力,选取不同恢复模式下形成的细沟、丛岛和草带三种微地貌为研究对象,以邻近裸坡为对照,研究不同微地貌土壤种子库特征及其拦截力。结果表明：（1）在不同微地貌中土壤种子库均以一年生藜科和禾本科植物为主;丛岛微生境的土壤种子库中有较丰富的物种和较高的多样性指数。（2）各微地貌的土壤种子库均具有表层聚集现象;草带微地貌中的土壤种子库总储量最大,且草带的0-2 cm土层处的土壤种子库密度显著高于各微地貌的各个土层（P<0.05）。（3）细沟和丛岛在上坡位对种子的拦截效果更好,草带在下坡位对种子的拦截效果更好。综上所述,沙蒿恢复模式形成的丛岛有利于增加土壤种子库的物种多样性,草带有利于增加土壤种子库的储量,故在黄土区排土场进行植被恢复时可以利用不同微地貌对土壤种子库分布特征的优势构建适宜的复合植被恢复模式。     

Feedbacks of Soil Inoculum of Mycorrhizal Fungi Altered by N Deposition on the Growth of a Native Shrub and an Invasive Annual Grass

Anthropogenic nitrogen (N) deposition causes shifts in vegetation types as well as species composition of arbuscular mycorrhizal (AM) fungi and other soil microorganisms. A greenhouse experiment was done to determine whether there are feedbacks between N-altered soil inoculum and growth of a dominant native shrub and an invasive grass species in southern California. The region is experiencing large-scale loss of Artemisia californica shrublands and replacement by invasive annual grasses under N deposition. Artemisia californica and Bromus madritensis ssp. rubens were grown with soil inoculum from experimental plots in a low N deposition site that had (1) N-fertilized and (2) unfertilized soil used for inoculum, as well as (3) high-N soil inoculum from a site exposed to atmospheric N deposition for four decades. All treatments plus a nonmycorrhizal control were given two levels of N fertilizer solution. A. californica biomass was reduced by each of the three inocula compared to uninoculated controls under at least one of the two N fertilizer solutions. The␣inoculum from the N-deposition site caused the greatest growth depressions. By contrast, B.␣madritensis biomass increased with each of the three inocula under at least one, or both, of the N solutions. The different growth responses of the two plant species may be related to the types of AM fungal colonization. B. madritensis was mainly colonized by a fine mycorrhizal endophyte, while A. californica had primarily coarse endophytes. Furthermore, A. californica had a high level of septate, nonmycorrhizal root endophytes, while B. madritensis overall had low levels of these endophytes. The negative biomass response of A. californica seedlings to high N-deposition inoculum may in part explain its decline; a microbially-mediated negative feedback may occur in this system that causes poor␣seedling growth and establishment of A.␣californica in sites subject to N deposition and B. madritensis invasion.     

Scrub typhus caused by Shimokoshi type Orientia tsutsugamushi showing variant 56‐kDa type‐specific antigen gene sequence in Tohoku region,Japan

In 2018, a patient was diagnosed with Shimokoshi type scrub typhus in Yamagata Prefecture, Japan. The causative pathogen was likely a variant type because 43 (8.3%) of 521 deduced amino acid sequences of the 56‐kDa type‐specific antigen (TSA) were different from those of the Shimokoshi prototype strain. The patient's paired sera showed low antibody titers against the Shimokoshi prototype strain. Two cases of scrub typhus reported in the Tohoku region during 2011–2012 also involved the same 56‐kDa TSA gene sequence. These findings suggest the presence of diversity in Shimokoshi type Orientia tsutsugamushi, which may impede the laboratory diagnosis of scrub typhus.     

Grass invasion causes rapid increases in ecosystem carbon and nitrogen storage in a semiarid shrubland

Accurately predicting terrestrial carbon (C) and nitrogen (N) storage requires understanding how plant invasions alter cycling and storage. A common, highly successful type of plant invasion occurs when the invasive species is of a distinctly different functional type than the native dominant plant, such as shrub encroachment throughout the western United States and annual grass invasions in Mediterranean shrublands, as studied here. Such invasions can dramatically transform landscapes and have large potential to alter C and N cycling by influencing storage in multiple pools. We used a manipulation of non‐native annual grass litter within a shrub‐dominated habitat in southern California (coastal sage scrub, CSS) to study how grass invasion alters ecosystem C and N storage. We added, removed, or left unchanged grass litter in areas of high and low invasion, then followed soil and vegetation changes. Grass litter greatly increased C and N storage in soil, aboveground native and non‐native biomass. Aboveground litter storage increased due to the greater inputs and slower decomposition of grass litter relative to shrub litter; shading by grass litter further reduced decomposition of both non‐native and native litter, which may be due to reduced photodegradation. Soil C and N pools in areas of high litter increased ～20% relative to low litter areas in the two years following manipulation and were generally sinks for C and N, while areas with low litter were sources. We synthesize our results into a C cycle of invaded and uninvaded areas of CSS and link changes in storage to increases in the soil fungi : bacteria ratio, increased plant inputs, and decreased litter loss. Overall, we show that grasses, especially through their litter, control important abiotic and biotic mechanisms governing C and N storage, with widespread implications for C sequestration and N storage in semiarid systems undergoing grass or shrub invasions.     

Combining genetic and geospatial analyses to infer population extinction in mygalomorph spiders endemic to the Los Angeles region

Although hyperdiverse groups like terrestrial arthropods are almost certainly severely impacted by habitat fragmentation and destruction, few studies have formally documented such effects. In this paper, we summarize the results of a multifaceted research approach to assess the magnitude and importance of anthropogenic population extinction on the narrowly endemic trapdoor spider genus Apomastus . We used geographical information systems modeling to reconstruct the likely historical distribution of Apomastus , and used molecular phylogeographic data to discern population genetic structure and detect genetic signatures of population extinction. In combination, these complementary lines of inference support direct observations of population extinction, and lead us to conclude that population extinction via urbanization has played an important role in defining the modern-day distribution of Apomastus species. This population loss implies coincident loss of genetic and adaptive diversity within this genus, and more generally, suggests a loss of ground-dwelling arthropod population diversity throughout the Los Angeles Basin. Strategies for minimizing this loss are proposed.     

Carbohydrate storage in five resprouting Florida scrub plants across a fire chronosequence

Most research analyzing nonstructural carbohydrate (NSC) concentrations on resprouter species in fire-controlled ecosystems has concentrated on how NSC concentrations recover immediately after fire. However, we know little of the effect of long periods without fire on NSC concentrations. In order to assess the effect of different periods of time-since-fire on resprouter species, we studied carbohydrate concentrations (total [NSC], soluble sugars [SS] and nonsoluble sugars [NSS]) in five resprouting species with contrasting trends of abundance across a chronosequence of time-since-fire (0.5-40 yr) in Florida. Carbohydrate concentrations were highest in species with specialized reserve organs. [SS] was mainly explained by factors related to plant size, whereas time-since-fire was the main factor explaining [NSS]. Changes in [NSS] and [NSC] were correlated with the time-since-fire abundance patterns. Variation in [NSS] carbohydrates can be related to the structural development of vegetation, with only those species capable of accessing full light able to accumulate carbohydrates, whereas subordinate plants show reductions in the [NSS] carbohydrate fractions. In areas with long intervals between fires, this carbohydrate reduction could affect subsequent postfire resprouting vigour, although this remains to be confirmed.     

Genetic change following fire in populations of a seed-banking perennial plant

Disturbances such as fire have the potential to remove genetic variation, but seed banks may counter this loss by restoring alleles through a reservoir effect. We used allozyme analysis to characterize genetic change in two populations of the perennial Hypericum cumulicola, an endemic of the fire-prone Florida scrub. We assessed genetic variation before and 1, 2, and 3 years after fire that killed nearly all aboveground plants. Populations increased in size following fire, with most seedlings likely recruited from a persistent seed bank. Four of five loci were variable. Most alleles were present in low frequencies, but our large sample sizes allowed detection of significant trends. Expected heterozygosity increased, and allele presence and allele frequencies showed marked shifts following fire. The post-fire seedling cohort contained new alleles to the study and one new allele to the species. Population differentiation between the two study sites did not change. Our study is the first to directly documents genetic changes following fire, a dominant ecological disturbance worldwide, and is also one of the few to consider shifts in a naturally recruiting post-disturbance seedling cohort. We demonstrate the potential of seed banks to restore genetic variation lost between disturbances. Our study demonstrates that rapid genetic change can occur with disturbance and that fire can have positive effects on the genetics of rare species.