Randomly Amplified Polymorphic DNA (RAPD) and Isoenzyme Analysis of Trypanosoma rangeli Strains

ABSTRACT. Sixteen Trypanosoma rangeli strains were compared by isoenzyme and randomly amplified polymorphic DNA (RAPD) analysis. Eight strains were isolated from either Rhodnius prolixus or Homo sapiens from Honduras, Colombia and Venezuela. Another eight strains were isolated from either Panstrongylus megistus or the rodent Echimys dasythrix from the State of Santa Catarina, southern Brazil. All six T. rangeli strains isolated from P. megistus were co-infections with Trypanosoma cruzi , demonstrating an overlap of the sylvatic cycles of these parasites and that the accurate identification of species is of utmost importance. Both isoenzyme and RAPD analysis revealed two distinct groups of T. rangeli strains, one formed by the strains from Santa Catarina and the other, by the strains from Honduras, Colombia and Venezuela. With the five enzymes used, all the strains from Santa Catarina had identical profiles which overlapped with those of the other regions only in the pattern obtained with malic enzyme. Analysis of 138 RAPD bands by means of an unweighted pair group method analysis (UPGMA) phenogram using the Dice similarity coefficient allowed the separation of the two groups based on their divergence at a lower level of similarity than the phenon line. We show that the identification of T. cruzi and T. rangeli in naturally mixed infections is readily achieved by either RAPD or isoenzyme analysis.     

Plant neighbours mediate bird predation effects on arthropod abundance and herbivory

相似文献   

Effects of Recreation and Hunting on Flushing Distance of Capercaillie

Abstract: The capercaillie (Tetrao urogallus) in Central Europe is an endangered species of grouse that is thought to be highly susceptible to human disturbance, possibly causing local populations to decline. We investigated the behavioral response of capercaillie in the Black Forest, Germany, and the French Pyrenees to an off-trail hiker by measuring flushing distances. Flushing distance varied with capercaillie sex, visibility of the hiker, intensity of winter tourism, and hunting pressure. Independent of the study area, males flushed at consistently longer distances than females, and lower visual blocking between bird and hiker resulted in longer flushing distances. Capercaillie flew at longer distances from an approaching hiker in areas with high intensity of winter tourism or hunting pressure than in undisturbed areas. We recommend the establishment of regulations requiring hikers to stay on trails and to close trails where intertrail distances fall below 100 m (90% of all flushing events appeared within 50 m). Furthermore, planting or preserving evergreen conifer trees in dense rows along critical parts of disturbance sources, reducing the degree of visibility between capercaillie and recreationists would increase habitat for capercaillie in forests with predictable recreation activities.     

Patterns of macroinvertebrate traits along three glacial stream continuums

1. Glacier‐fed streams are characterised by low spatial but high temporal heterogeneity, manifested in seasonal and diurnal discharge and suspended sediment peaks induced by glacial runoff. These streams shelter macroinvertebrate communities adapted to such harsh environmental conditions. Studies relating macroinvertebrate traits to environmental conditions in glacial streams could provide important insights into the structure and function of glacial stream communities. 2. From data collected in three glacial streams from the central Swiss and southern French Alps, we analysed the relationships among six biological traits to define five groups of macroinvertebrate taxa with similar suites of traits. 3. The longitudinal distribution of the five groups and of individual traits was analysed, as well as their variation according to a glaciality index combining water temperature, conductivity, suspended solids and substrate stability. 4. The trait diversity along the three streams showed a strong upstream‐downstream gradient. The upper reaches were dominated by a single group of taxa characterised by small, crawling, deposit feeders. The other trait‐based groups appeared progressively downstream. 5. Changes in the relative frequency of trait‐based groups along the glaciality gradient highlighted the dominance of all‐rounder resistant/resilient traits in the three streams and confirmed that environmental conditions in the glacial streams are too harsh or uniform to allow macroinvertebrate communities to develop alternative suites of traits. The findings are discussed in relation to the question of trait coding in the available literature.     

A single‐stranded conformational polymorphism (SSCP)‐derived quantitative variable to monitor the virulence of a Barley yellow dwarf virus‐PAV (BYDV‐PAV) isolate during adaptation to the TC14 resistant wheat line

A standardized single‐stranded conformational polymorphism (SSCP) procedure is proposed as an alternative to the time‐consuming biological characterization of Barley yellow dwarf virus‐PAV (BYDV‐PAV) isolates. Using this procedure, six of 21 overlapping regions used to scan the viral genome gave patterns specific to ‘4E’ (avirulent) or ‘4T’ (‘4E’‐derived virulent) isolates. The calibration of samples and integration of SSCP patterns corresponding to the nucleotide region 1482–2023 allowed the estimation of P_T values that reflect the proportions of a ‘4T’‐specific band. Analysis of the biological (area under the pathogen progress curve) and molecular (P_T) data suggested a positive linear relation between these variables. Moreover, sequence analysis of the nucleotide region 1482–2023 highlighted the presence of a nucleotide polymorphism (C/A₁₈₃₅) which can be considered as a candidate for virus–host interactions linked to the monitored virulence. According to these parameters, P_T values associated with ‘4E’‐ and ‘4T’‐derived populations show that: (i) long‐term infection of a BYDV‐PAV isolate on the ‘TC14’ resistant host leads to the fixation of virulent individuals in viral populations; and (ii) the introduction of susceptible hosts in successive ‘TC14’ infections results in the maintenance of low virulence of the populations. Thus, the presented study demonstrates that SSCP is a useful tool for monitoring viral populations during the host adaptation process. The described impact of host alternation provides new opportunities for the use of the ‘TC14’ resistance source in BYDV‐resistant breeding programmes. This study is part of the global effort made by the scientific community to propose sustainable alternatives to the chemical control of this viral disease.     

Does synovigeny confer reproductive plasticity upon a parasitoid wasp that is faced with variability in habitat richness?

Understanding the factors that constrain the reproductive success of animals and their demographics requires detailed insight into the processes of resource acquisition and allocation in relation to habitat richness. Parasitoid wasp females are valuable models in this respect because their lifetime reproductive success is closely tied to host availability. Parasitoids that manufacture eggs throughout adult life (i.e. ‘synovigenic’ species) and characteristically acquire nutrients via feeding are predicted to be plastic in their allocation to egg manufacture. Using the synovigenic parasitoid wasp Venturia canescens, we tested whether this prediction holds when females are faced with variation in the availability of both hosts and food. Laboratory experiments were conducted to determine how environmental variation affects parasitoid reproductive success and the lifetime dynamics of egg load and of major nutrient types. Our results, surprisingly, show that female V. canescens lacks a significant degree of reproductive plasticity under our experimental conditions. In particular, allocation of resources to reproduction was high irrespective of host availability. We attribute this lack of flexibility to the low energy content of V. canescens' eggs and to features peculiar to the ecology of this species. Our findings shed new light on the physiological factors that constrain parasitoid lifetime reproductive success. © 2011 The Linnean Society of London, Biological Journal of the Linnean Society, 2011, 104 , 621–632.     

Plasticity of ontogenetic trajectories in cyprinids: a source of evolutionary novelties

Research in evolutionary developmental (evo‐devo) biology is making an increasingly important contribution to our understanding of the molecular mechanisms underlying the establishment of complex morphological traits. Deciphering the ontogenetic trajectories leading to the differentiation of sister species (and the existence of hybrids) is a new challenge in our understanding of speciation processes. In the present study, we characterized the ontogenetic trajectory of lower lip morphology in two cyprinid species and their hybrids. Chondrostoma toxostoma has an arched lower lip and a generalist diet. Chondrostoma nasus has a straight lower lip and a specialist diet. An analysis of 99 C. toxostoma, 99 C. nasus and 25 first‐generation (F₁) hybrid individuals demonstrated that the difference between arched and straight lip morphology was found to depend strongly on the height/width ratio of the lower lip. A comparison of the ontogenetic trajectories of these morphometric traits showed that the height of the lower lip was isometric to body length in both species, whereas developmental changes involving an acceleration and a hypermorphosis of the widening of the lower lip led to a straight lip morphology in C. nasus. F₁ hybrids were characterized by an extreme phenotype resulting from a rate of lower lip widening slower than that in the two parent species. Therefore, we rejected a codominance hypothesis and concluded that the first stage of hybridization provides the foundations of evolutionary novelty. These results have important evolutionary implications because lower lip shape is linked to dietary behaviour in many fish species. © 2012 The Linnean Society of London, Biological Journal of the Linnean Society, 2012, 106 , 342–355.     

Tug of war between continental gene flow and rearing site philopatry in a migratory bird: the sex-biased dispersal paradigm reconsidered

Nonrandom dispersal has been recently advanced as a mechanism promoting fine-scale genetic differentiation in resident populations, yet how this applies to species with high rates of dispersal is still unclear. Using a migratory species considered a classical example of male-biased dispersal (the greater snow goose, Chen caerulescens atlantica ), we documented a temporally stable fine-scale genetic clustering between spatially distinct rearing sites (5–30 km apart), where family aggregates shortly after hatching. Such genetic differentiation can only arise if, in both sexes, dispersal is restricted and nonrandom, a surprising result considering that pairing occurs among mixed flocks of birds more than 3000 km away from the breeding grounds. Fine-scale genetic structure may thus occur even in migratory species with high gene flow. We further show that looking for genetic structure based on nesting sites only may be misleading. Genetically distinct individuals that segregated into different rearing sites were in fact spatially mixed during nesting. These findings provide new, scale-dependent links between genetic structure, pairing, and dispersal and show the importance of sampling different stages of the breeding cycle in order to detect a spatial genetic structure.