Adaptations of Central Amazon Tree Species to Prolonged Flooding: Root Morphology and Leaf Longevity

Abstract: Várzeas are species-rich forest communities of the Central Amazon floodplains, inhabited by highly adapted tree species that can withstand long flooding periods. The leaf shedding behaviour and morphological traits that may contribute to adaptation to low oxygen levels were studied at the Ilha de Marchantaria on the lower Solimoes-Amazonas river, Brazil, and in greenhouse experiments with cuttings of six tree species typical of the Amazon floodplain. Comparison of deciduousness in situ revealed that four of the species under investigation, Salix martiana , Tabernaemontana juruana , Laetia corymbulosa and Pouteria glomerata , are able to maintain their leaf system during the aquatic period. Adventitious roots were formed by S. martiana and T. juruana , but anatomical characteristics differed between the species. Whereas S. martiana developed lysigenous aerenchyma in its roots during aerobic and anaerobic growth, only small intercellular spaces of schizogenous origin were formed in the root cortex of T. juruana . Similar to the latter species, such spaces were constitutively formed in the deciduous species Crateva benthami and Vitex cymosa . Suberin deposits were observed in tangential and radial cell walls of the hypodermis of roots from T. juruana , L. corymbulosa and P. glomerata . Suberin deposits were less pronounced in roots of S. martiana and absent in V. cymosa and C. benthami . The data show that different, almost contrasting, survival mechanisms have evolved in roots of plants with similar life forms in the same habitat. The results further suggest that the morphological traits of the investigated trees are causally linked with the in situ leaf shedding behaviour.     

Learning to discriminate between infochemicals from different plant-host complexes by the parasitoids Cotesia glomerata and C. rubecula

Comparison of closely related species can elucidate adaptive differences in species characteristics. The present study compares the effect of experience on the host-finding behaviour of two Cotesia (Hymenoptera: Braconidae) parasitoid species that differ in their degree of specialization. After multiple experiences with host larvae, females of the generalist parasitoid Cotesia glomerata showed a clear preference for volatiles from Pieris brassicae-infested Brussels sprouts leaves over P. rapae-infested Brussels sprouts leaves in two-choice tests (preference learning at herbivore level). A single experience with a host did not lead to such preferences.Experience of adult C. glomerata with different P. brassicae-infested cabbage varieties or nasturtium (Tropaeolum majus L.) led to preferences for the experienced plant-host complex in most cases (preference learning at plant level). No effect of rearing plant (early adult learning) on plant preference was found.In contrast to the generalist C. glomerata, females of the specialist C. rubecula did not show preference learning at the herbivore level. At the plant level, experience with different P. rapae-infested cabbage varieties in no case resulted in a difference in preference between treatments. The results support the hypothesis that learning plays a more important role in searching in generalists than in specialist parasitoids. The behaviour of the generalist C. glomerata was more easily changed by experience than that of the specialist C. rubecula.     

鸭茅种质资源多样性研究进展

鸭茅是世界范围内广泛栽培的一种重要禾本科牧草,具有高产、优质、耐荫性强等特性。我国的野生鸭茅资源十分丰富,分布广泛,基因资源优良,但有关鸭茅的研究报导相对较少。为了更好地开发利用这一优良的牧草资源,本从形态学、细胞学和分子水平对国内外鸭茅种质资源多样性的研究进行了综述,并对今后我国的鸭茅研究工作提出了建议。     

Sequential rapid adaptation of indigenous parasitoid wasps to the invasive butterfly Pieris brassicae

The introduction of a new species can change the characteristics of other species within a community. These changes may affect discontiguous trophic levels via adjacent trophic levels. The invasion of an exotic host species may provide the opportunity to observe the dynamics of changing interspecific interactions among parasitoids belonging to different trophic levels. The exotic large white butterfly Pieris brassicae invaded Hokkaido Island, Japan, and quickly spread throughout the island. Prior to the invasion, the small white butterfly P. rapae was the host of the primary parasitoid Cotesia glomerata, on which both the larval hyperparasitoid Baryscapus galactopus and the pupal hyperparasitoid Trichomalopsis apanteroctena depended. At the time of the invasion, C. glomerata generally laid eggs exclusively in P. rapae. During the five years following the invasion, however, the clutch size of C. glomerata in P. rapae gradually decreased, whereas the clutch size in P. brassicae increased. The field results corresponded well with laboratory experiments showing an increase in the rate of parasitism in P. brassicae. The host expansion of C. glomerata provided the two hyperparasitoids with an opportunity to choose between alternative hosts, that is, C. glomerata within P. brassicae and C. glomerata within P. rapae. Indeed, the pupal hyperparasitoid T. apanteroctena shifted its preference gradually to C. glomerata in P. brassicae, whereas the larval hyperparasitoid B. galactopus maintained a preference for C. glomerata in P. rapae. These changes in host preference may result from differential suitability of the two host types. The larval hyperparasitoid preferred C. glomerata within P. rapae to C. glomerata within P. brassicae, presumably because P. brassicae larvae attacked aggressively, thereby hindering the parasitization, whereas the pupal hyperparasitoid could take advantage of the competition-free resource by shifting its host preference. Consequently, the invasion of P. brassicae has changed the host use of the primary parasitoid C. glomerata and the pupal hyperparasitoid T. apanteroctena within a very short time.     

Combined exposure to hydroelectric expansion,climate change and forest loss jeopardies amphibians in the Brazilian Amazon

Aim

Human‐driven impacts constantly threat amphibians, even in largely protected regions such as the Amazon. The Brazilian Amazon is home to a great diversity of amphibians, several of them currently threatened with extinction. We investigated how climate change, deforestation and establishment of hydroelectric dams could affect the geographic distribution of Amazonian amphibians by 2030 and midcentury.

Location

The Brazilian Amazon.

Methods

We overlapped the geographic distribution of 255 species with the location of hydroelectric dams, models of deforestation and climate change scenarios for the future.

Results

We found that nearly 67% of all species and 54% of species with high degree of endemism within the Legal Brazilian Amazon would lose habitats due to the hydroelectric overlapping. In addition, deforestation is also a potential threat to amphibians, but had a smaller impact compared to the likely changes in climate. The largest potential range loss would be caused by the likely increase in temperature. We found that five amphibian families would have at least half of the species with over 50% of potential distribution range within the Legal Brazilian Amazon limits threatened by climate change between 2030 and 2050.

Main conclusions

Amphibians in the Amazon are highly vulnerable to climate change, which may cause, directly or indirectly, deleterious biological changes for the group. Under modelled scenarios, the Brazilian Government needs to plan for the development of the Amazon prioritizing landscape changes of low environmental impact and economic development to ensure that such changes do not cause major impacts on amphibian species while reducing the emission of greenhouse gases.

     

A comparison of attack rates in a native and an introduced population of the parasitoid Cotesia glomerata

The attack rate of a population of the braconid parasitoid Cotesia glomerata, introduced into the USA over 100 years ago as a parasitoid of Pieris rapae, was compared with that of a native British population, which normally attacks P. brassicae, and with that of a P. rapae specialist, Cotesia rubecula. British C. glomerata attacked P. brassicae at a much higher rate than it attacked P. rapae. In comparison with British C. glomerata, C. rubecula showed a higher attack rate with P. rapae. American C. glomerata attacked P. rapae at a slightly higher rate than did British C. glomerata, but not at as high a rate as that achieved by C. rubecula. The differences in each comparison were statistically significant. The possible causes of the differences between British and American C. glomerata attacking P. rapae are discussed. They may be due to genetic or environmental effects. Egg load did not appear to be a factor limiting the number of hosts parasitized under the conditions of the experiments.     

Effects of suspended sediment and desiccation on the benthic tailwater community in the Colorado River, USA

We demonstrated that differences in habitatrequirements by C. glomerata and Oscillatoria havea profound bottom-up influence on the foodweb in thetailwaters below Glen Canyon Dam in the Colorado Riverthrough Grand Canyon National Park, USA. We examinedthe effects of suspended sediment and desiccation onthe colonization sequence of Cladophora glomerata andOscillatoria spp. and the consequent effects onmacroinvertebrates in each algal community in a seriesof reciprocal transplants in the regulated ColoradoRiver, AZ. Our experiments showed that C. glomeratagrows best in continuously submerged, clear-water,stable habitats, whereas Oscillatoria forms densemat-like matrices of trichomes and sand in varialzones and habitats with high suspended sedimentstypical of many southwestern USA streams. Varial zoneconditions have a stronger influence on communitystructure than habitats with high suspended sediments. Recruitment by chironomid larvae was less dependent onC. glomerata and less affected by suspended sedimentand periodic desiccation than Gammarus lacustris. Weestimated the energy from macroinvertebrate biomassassociated with tufts of C. glomerata to be an orderof magnitude higher than that in Oscillatoriamatrices. Therefore, loss of C. glomerata andreplacement of habitat more suitable for Oscillatoriaas a result of regulated flows indirectly reducespotential energy flow in the Colorado Riverfoodweb.     

Ecotype differentiation and coexistence of two parapatric tetraploid subspecies of cocksfoot (Dactylis glomerata) in the Alps

Two tetraploid subspecies of Dactylis glomerata L., subsp. reichenbachii (Hausm.) Stebbins et Zohary and subsp. glomerata , occur in the French Alps. The former is confined to dolomitic, south-facing, alpine lawns above 2000 m, whereas the latter occurs in non-dolomitic habitats in subalpine meadows mainly below 1900 m. Previous studies of allozyme variation have shown that genetic introgression between the two subspecies occurs over large areas. By contrast, morphologically intermediate individuals only occur in an extremely narrow area, suggesting that the morphological and physiological differences between the two subspecies is of adaptive significance. A reciprocal clone transplant experiment was set up to examine (1) any genetic differences between subspecies indicative of ecotypic differentiation in relation to habitat characteristics and (2) the level of phenotypic plasticity in the two subspecies. Genetic differentiation was confirmed by a statistically significant taxon × site interaction effect in anova for all traits studied. The glomerata populations produced more tillers, longer leaves and higher culms in all sites, especially in their home environment. However, reichenbachii populations produced more seeds than the glomerata populations in the original reichenbachii environment, suggesting ecotypic differentiation between the two subspecies. This result might also explain why the glomerata subspecies is unable to colonize dolomitic habitats occupied by the reichenbachii subspecies. The reichenbachii populations showed less plasticity than the glomerata populations for leaf length and floriferous tiller number, a result which is discussed in the context of the response of plants from productive and non-productive habitats to environmental variation.     

Relationships between parasitoid host range and host defence: a comparative study of egg encapsulation in two related parasitoid species

Abstract. Parasitoid host range may proceed from traits affecting host suitability, traits affecting parasitoid foraging behaviour, or both. We tested the hypothesis that encapsulation can be used as a reliable indicator of parasitoid host range in two closely related larval endoparasitoids of Lepidoptera. Cotesia glomerata (L.) (Hymenoptera: Braconidae) is gregarious and a generalist on several species of Pieridae, whereas C. rubecula (Marshall) is solitary and specific to Pieris rapae (L.). We determined the effects of host species ( Pieris brassicae (L.), P. napi (L.) and P. rapae ) (Lepidoptera: Pieridae) and host developmental stage (early first, second and third instar) on encapsulation of parasitoid eggs. Host species and parasitoid species, as well as the resulting interaction between these two factors had significant effects on encapsulation of Cotesia eggs. Encapsulation in Pieris hosts was much lower for C. glomerata (<34%, except for second and third instar of P. rapae ) than for C. rubecula (>32%), even when the latter was parasitizing P. rapae. Encapsulation increased with the age of the larvae, although the only significant difference was for C. glomerata. Overall, P. rapae showed a stronger encapsulation reaction than P. brassicae and P. napi. Encapsulation levels of C. glomerata corresponded well to patterns of female host species and host age preference for oviposition and parasitoid larval performance. In contrast, percentages of encapsulation of C. rubecula were not consistent with host preference and host suitability. We argue that encapsulation alone is unlikely to provide a sufficient explanation for C. glomerata and C. rubecula host range.     

Allelochemical stress inhibits growth, leaf water relations, PSII photochemistry, non-photochemical fluorescence quenching, and heat energy dissipation in three C3 perennial species

In this study, the effect of two allelochemicals, benzoxazolin-2(3H)-one (BOA) and cinnamic acid (CA), on different physiological and morphological characteristics of 1-month-old C(3) plant species (Dactylis glomerata, Lolium perenne, and Rumex acetosa) was analysed. BOA inhibited the shoot length of D. glomerata, L. perenne, and R. acetosa by 49%, 19%, and 19% of the control. The root length of D. glomerata, L. perenne, and R. acetosa growing in the presence of 1.5 mM BOA and CA was decreased compared with the control. Both allelochemicals (BOA, CA) inhibited leaf osmotic potential (LOP) in L. perenne and D. glomerata. In L. perenne, F(v)/F(m) decreased after treatment with BOA (1.5 mM) while CA (1.5 mM) also significantly reduced F(v)/F(m) in L. perenne. Both allelochemicals decreased ΦPSII in D. glomerata and L. perenne within 24 h of treatment, while in R. acetosa, ΦPSII levels decreased by 72 h following treatment with BOA and CA. There was a decrease in qP and NPQ on the first, fourth, fifth, and sixth days after treatment with BOA in D. glomerata, while both allelochemicals reduced the qP level in R. acetosa. There was a gradual decrease in the fraction of light absorbed by PSII allocated to PSII photochemistry (P) in R. acetosa treated with BOA and CA. The P values in D. glomerata were reduced by both allelochemicals and the portion of absorbed photon energy that was thermally dissipated (D) in D. glomerata and L. perenne was decreased by BOA and CA. Photon energy absorbed by PSII antennae and trapped by 'closed' PSII reaction centres (E) was decreased after CA exposure in D. glomerata. BOA and CA (1.5 mM concentration) decreased the leaf protein contents in all three perennial species. This study provides new understanding of the physiological and biochemical mechanisms of action of BOA and CA in one perennial dicotyledon and two perennial grasses. The acquisition of such knowledge may ultimately provide a rational and scientific basis for the design of safe and effective herbicides.     

Characterization and control of thread mould in cheese

AIMS: The origin of a mould responsible for the contamination of an Argentinian cheese factory was identified and several antifungal treatments were assessed. METHODS AND RESULTS: Moulds were isolated and identified from vacuum-packed hard cheeses, from the environment and from the surfaces of the factory. A suspension conidia test containing different fungicides was performed; another assay involved the fumigation with p-OH fenilsalicidamide. Only Phoma glomerata was found in all of the mouldy cheeses, and was also obtained from different environments and machine surfaces. The most effective treatments against P. glomerata isolates were 0.5% (w/v) natamycin and 2% (v/v) parabens. Fumigation with p-OH fenilsalicidamide showed no satisfactory results. CONCLUSION: P. glomerata is an important thread mould-contaminating agent in vacuum-packed hard cheeses. Significance and Impact of the Study: Taking into account the survival of the conidia of the P. glomerata isolates to different antifungal treatments, the sources of contamination need to be controlled by designing a good factory layout.     

Does Manipulation by the Parasitoid Wasp Cotesia glomerata (L.) Cause Attachment Behaviour of Host Caterpillars on Cocoon Clusters?

Some parasitoid wasps appear to control the behaviour of their hosts. However, altered behaviours of parasitised hosts are not necessarily caused by parasitoids but are sometimes the result of traumatic side effects of parasitism. However, it was difficult for us to discriminate the cause of host's behaviours between manipulation by parasitoids and traumatic side effects. Larvae of the parasitoid wasp Cotesia glomerata form cocoon clusters after egression from the parasitised host caterpillar Pieris brassicae . Following parasitoid egression, host caterpillars survive for several days and remain near the cocoon clusters. These caterpillars may repel solitary pteromalid hyperparasitoid wasps, Trichomalopsis apanteloctena , that attempt to parasitise fresh C. glomerata pupae. We allowed hyperparasitoids to attack cocoon clusters in the field and laboratory and then assessed the costs and benefits to C. glomerata of attachment by the parasitised caterpillars. The eclosion success of C. glomerata in cocoon clusters with attached caterpillars was higher than that in clusters without attached caterpillars in both field and laboratory experiments. This difference was attributed to shorter hyperparasitoid visits to cocoon clusters with attached host caterpillars. However, large cluster size was potentially costly for host attachment, because the duration of host caterpillar attachment decreased with increasing numbers of C. glomerata per caterpillar. This trade-off may be related to shortages of fat body resources, which are shared between the development of wasp larvae and the survival of host caterpillars. Therefore, we concluded that caterpillar attachment satisfied some requirements of host manipulation by C. glomerata .     

A new species of Simaba (Simaroubaceae) from Pará, Brazil,with a key to the species north of the Amazon River

A new species,Simaba cavalcantei, is described and illustrated. It is considered to be intermediate between sectionsGrandiflorae andFloribundae and is distinguished from potentially sympatric species in a key to the species occurring north of the Amazon River.     

中国西南横断山区的野生鸭茅资源

中国西南横断山区广泛分布野生鸭茅资源,包括鸭茅亚种和喜马拉雅鸭茅亚种。二者的分布范围相近,但在形态及物候发育等方面存在明显差异,鸭茅亚种的主要农艺性状优于喜马拉雅鸭茅亚种。两个亚种在人工控制条件下可以杂交形成三倍体后代,但自然状态下尚未发现二者杂交的确切证据。近年来,中国加强了对两个鸭茅亚种的基础研究,但从保护和利用研究角度出发,开展的工作较少。从来源角度分析,喜马拉雅鸭茅亚种为当地起源类型,鸭茅亚种为外来归化种的可能性较大。由于喜马拉雅鸭茅面临鸭茅亚种的竞争威胁,因此应加强中国喜马拉雅鸭茅亚种野生资源的保护和开发利用研究。     

Effects of a 4 °C increase in temperature on partitioning of leaf area and dry mass, root respiration and carbohydrates

1. Plants of Bellis perennis, Dactylis glomerata and Poa annua were grown from seed in controlled-environment cabinets at either 16 or 20 °C; at the higher temperature all three species had increased total dry mass and leaf area when assessed on the basis of chronological time. On the basis of thermal time (summation of degree-days above 0 °C; days °C) temperature decreased the dry mass in P. annua.
2. Partitioning was assessed as a change in the allometric coefficients relating shoot and root dry mass, leaf and plant mass, leaf area and plant mass, and leaf area and leaf mass. Of the 12 relationships examined only three were affected by temperature: there was increased partitioning towards the shoot relative to the root in D. glomerata and increased partitioning towards leaf area rather than leaf mass in D. glomerata and B.perennis .
3. Root respiration was unaffected by temperature of growth in D. glomerata and P.annua but was lower in B. perennis grown at elevated temperature.
4. Root respiration acclimated to temperature in P. annua and B. perennis (i.e. when measured at the same temperature, respiration was higher in plants grown at 16 °C).
5. Root soluble carbohydrate concentration was unaffected by temperature of growth in any of the species. Feeding sucrose to the roots for a short period had no effect on the rate of respiration of B. perennis or D. glomerata but increased root respiration of P. annua .     

鸭茅种质资源遗传多样性的ISSR研究

采用ISSR分子标记技术对来自国内及亚洲、欧洲、美洲9个国家共50份鸭茅品种(系)进行遗传多样性研究。12个引物共扩增出多态性带101条, 平均每个引物扩增的多态带数为8.41条, 多态性条带比率(PPB)为86.3%, 材料间遗传相似系数范围在0.6116到0.9290间。这说明鸭茅具有较丰富的遗传多样性。根据研究结果进行了聚类分析和主成分分析, 可将50份鸭茅材料分为5大类, 来自于相同洲的鸭茅能聚在一类, 中国和美国的鸭茅品种(系)能分别聚在同一类, 呈现出一定的地域性分布规律。并对鸭茅种质资源的收集保存提出建议。     

Revision and phylogeny of the bee genus Paratetrapedia Moure,with description of a new genus from the Andean Cordillera (Hymenoptera,Apidae, Tapinotaspidini)

The bee genus Paratetrapedia represents a commonly collected group of bees and is especially diverse in forested areas of the Neotropics. Its taxonomy has remained poorly understood because of a lack of modern revisionary work and numerous species described as Tetrapedia whose type specimens have not been re‐examined in recent times. Here, a comprehensive study was carried out to review the taxonomy of the genus Paratetrapedia and to investigate cladistically the relationships amongst its species. Eighteen new species of Paratetrapedia are described, giving a total of 32 species in the genus. A phylogenetic analysis of the species of Paratetrapedia was carried out using 61 morphological characters for 41 terminal taxa. The phylogenetic results confirmed the monophyly of Paratetrapedia and allowed the recognition of five species groups: the lugubris, moesta, bicolor, lineata, and flavipennis groups. Nasutopedia gen. nov. , recognized as the sister group of Paratetrapedia and with its distribution restricted to the western forested portions of the Andean highlands, is proposed based on distinct morphology, its placement in the phylogenetic tree, and biogeographical patterns. Species of Paratetrapedia are especially diverse in the Amazon Forest; the eastern Brazilian Atlantic Forest contains four endemic species, and one species is endemic to the Cerrado of central Brazil. Paratetrapedia shows a biogeographical pattern similar to other Neotropical groups of bees and birds, with wide distribution and high diversity in lowland forests and whose sister taxon occurs on highlands of north‐western portions of the Andean cordillera. Identification keys for males and females of all species are provided, as well as distribution maps and illustrations of general external morphology and genitalia. © 2011 The Linnean Society of London, Zoological Journal of the Linnean Society, 2011, 162 , 351–442.     

Oil and gas projects in the Western Amazon: threats to wilderness, biodiversity, and indigenous peoples

Background

The western Amazon is the most biologically rich part of the Amazon basin and is home to a great diversity of indigenous ethnic groups, including some of the world''s last uncontacted peoples living in voluntary isolation. Unlike the eastern Brazilian Amazon, it is still a largely intact ecosystem. Underlying this landscape are large reserves of oil and gas, many yet untapped. The growing global demand is leading to unprecedented exploration and development in the region.

Methodology/Principal Findings

We synthesized information from government sources to quantify the status of oil development in the western Amazon. National governments delimit specific geographic areas or “blocks” that are zoned for hydrocarbon activities, which they may lease to state and multinational energy companies for exploration and production. About 180 oil and gas blocks now cover ∼688,000 km² of the western Amazon. These blocks overlap the most species-rich part of the Amazon. We also found that many of the blocks overlap indigenous territories, both titled lands and areas utilized by peoples in voluntary isolation. In Ecuador and Peru, oil and gas blocks now cover more than two-thirds of the Amazon. In Bolivia and western Brazil, major exploration activities are set to increase rapidly.

Conclusions/Significance

Without improved policies, the increasing scope and magnitude of planned extraction means that environmental and social impacts are likely to intensify. We review the most pressing oil- and gas-related conservation policy issues confronting the region. These include the need for regional Strategic Environmental Impact Assessments and the adoption of roadless extraction techniques. We also consider the conflicts where the blocks overlap indigenous peoples'' territories.     

The epiphytic microbiota of the globally widespread macroalga Cladophora glomerata (Chlorophyta, Cladophorales)

? Premise of the study: The filamentous chlorophyte Cladophora produces abundant nearshore populations in marine and freshwaters worldwide, often dominating periphyton communities and producing nuisance growths under eutrophic conditions. High surface area and environmental persistence foster such high functional and taxonomic diversity of epiphytic microfauna and microalgae that Cladophora has been labeled an ecological engineer. We tested the hypotheses that (1) Cladophora supports a structurally and functionally diverse epiphytic prokaryotic microbiota that influences materials cycling and (2) mutualistic host-microbe interactions occur. Because previous molecular sequencing-based analyses of the microbiota of C. glomerata found as western Lake Michigan beach drift had identified pathogenic associates such as Escherichia coli, we also asked if actively growing lentic C. glomerata harbors known pathogens. ? Methods: We used 16S rRNA gene amplicon pyrosequencing to examine the microbiota of C. glomerata of Lake Mendota, Dane, Wisconsin, United States, during the growing season of 2011, at the genus- or species-level to infer functional phenotypes. We used correlative scanning electron and fluorescence microscopy to describe major prokaryotic morphotypes. ? Key results: We found microscopic evidence for diverse bacterial morphotypes, and molecular evidence for ca. 100 distinct sequence types classifiable to genus at the 80% confidence level or species at the 96-97% level within nine bacterial phyla, but not E. coli or related human pathogens. ? Conclusions: We inferred that bacterial epiphytes of lentic C. glomerata have diverse functions in materials cycling, with traits that indicate the occurrence of mutualistic interactions with the algal host.     

Trypanosoma cruzi IV Causing Outbreaks of Acute Chagas Disease and Infections by Different Haplotypes in the Western Brazilian Amazonia

Background

Chagas disease is an emergent tropical disease in the Brazilian Amazon Region, with an increasing number of cases in recent decades. In this region, the sylvatic cycle of Trypanosoma cruzi transmission, which constitutes a reservoir of parasites that might be associated with specific molecular, epidemiological and clinical traits, has been little explored. The objective of this work is to genetically characterize stocks of T. cruzi from human cases, triatomines and reservoir mammals in the State of Amazonas, in the Western Brazilian Amazon.

Methodology/Principal Findings

We analyzed 96 T. cruzi samples from four municipalities in distant locations of the State of Amazonas. Molecular characterization of isolated parasites from cultures in LIT medium or directly from vectors or whole human blood was performed by PCR of the non-transcribed spacer of the mini-exon and of the 24 S alfa ribosomal RNA gene, RFLP and sequencing of the mitochondrial cytochrome c oxidase subunit II (COII) gene, and by sequencing of the glucose-phosphate isomerase gene. The T. cruzi parasites from two outbreaks of acute disease were all typed as TcIV. One of the outbreaks was triggered by several haplotypes of the same DTU. TcIV also occurred in isolated cases and in Rhodnius robustus. Incongruence between mitochondrial and nuclear phylogenies is likely to be indicative of historical genetic exchange events resulting in mitochondrial introgression between TcIII and TcIV DTUs from Western Brazilian Amazon. TcI predominated among triatomines and was the unique DTU infecting marsupials.

Conclusion/Significance

DTU TcIV, rarely associated with human Chagas disease in other areas of the Amazon basin, is the major strain responsible for the human infections in the Western Brazilian Amazon, occurring in outbreaks as single or mixed infections by different haplotypes.