Two synonymy cases within the genus Neoseiulella (Acari: Phytoseiidae): is the molecular evidence so evident?

Synonymy is considered as a great problem for diversity characterization and further applications, especially for biological control success with regard to the accurate identification of natural enemies. The present study focuses on two synonymy cases of natural enemies, belonging to the family Phytoseiidae, the genus Neoseiulella, specifically five species of this genus: Neoseiulella tiliarum, Neoseiulella formosa, Neoseiulella aceri, Neoseiulella squamiger, and Neoseiulella aceris. Morphological and molecular analyses [12S rRNA, cytochrome b (Cytb) mitochondrial (mt)DNA, internal transcribed spacer DNA] were applied. First, the results obtained support the synonymy of N. tiliarum and N. formosa. Second, because morphological differences (solenostomes occurrence) were observed for the first time between the type material of N. aceris and N. squamiger, the present study does not provide sufficient evidence to synomymize these two species and further analyses are required. Lastly, we assume that N. squamiger and N. aceri are synonyms. However, three groups of specimens, including N. aceri and N. squamiger, were identified by two mitochondrial DNA genes (12S rRNA and Cytb mtDNA). Therefore, the present study highlights the problems encountered when using only mitochondrial genes to diagnose species. The great mtDNA variations observed appear to reflect population differentiation (linked to plant support). This is the first time that such high intraspecific differentiation is be observed within the family Phytoseiidae. Further experiments, such as cross‐breeding and microsatellite DNA marker analyses, are planned to characterize gene flow and reproductive isolation levels within this species. © 2010 The Linnean Society of London, Biological Journal of the Linnean Society, 2010, 101 , 323–344.     

Isolation and characterization of eight microsatellite loci for the study of gene flow between Testudo marginata and Testudo weissingeri (Testudines: Testudinidae)

The taxonomic status of the Greek Testudo species, marginated tortoise (Testudo marginata Schoepff, 1793) and dwarf marginated tortoise (Testudo weissingeri Bour, 1995), is controversed. In order to study the gene flow among these Greek Testudo species, eight polymorphic microsatellite markers were characterized and screened for 32 individuals. The number of alleles observed per locus ranged from two to 19. Observed heterozygosities varied from 0.235 to 0.830. These microsatellite loci were also successfully tested on seven closely related species of Testudinidae. This set of microsatellites offers an efficient tool to investigate genetic differentiation among testudinid species.     

Assessing the risk of primary infection of cereals by barley yellow dwarf virus in autumn in the Rennes basin of France

In the Rennes basin, Rhopalosiphum padi is anholocyclic and represents more than 90% of suction trap catches of potential vectors of barley yellow dwarf virus (BYDV) during autumn. From 1983 to 1987 the possibility of predicting the risk of BYDV infection of batches of barley test seedlings (sampling units) exposed each week from September to December near a 12.2 m high suction trap was investigated. Three kinds of variables were checked as possible predictors: weekly mean or maximum temperatures; weekly catches of R. padi (including or excluding males); and percentage of sampling units infested by aphids. Three contrasting examples were observed: during the first three years (1983–1985), infection was high and its change with time followed temperature, aphid catches and plant infestation changes; in 1986, high numbers of aphids caught and a high proportion of plants infested resulted in only low infection and in 1987, both infestation and infection were very low. Simple linear regression analysis showed that the more reliable predictors of infection were the proportion of infested plants and to a lesser extent the numbers of trapped aphids. Multiple linear regressions including either of the three groups of ‘predicting’ variables did not result in any improvement in the prediction. At a practical level, the use of counts of aphid catches would seem a better compromise between accuracy and consistency of prediction and ease of gathering data than that of plant infestation but any significant improvement of the prediction should be sought in an early estimate of the amount of virus available to aphids before they colonise the plants.     

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.     

Ultrastructural studies of fossil plant cuticles: Ticoa harrisii from the early Cretaceous of Argentina

ARCHANGELSKY, S., TAYLOR, T. N. & KURMANN, M. H., 1985. Ultrastructural studies of fossil plant cuticles: Ticoa harrisii from the early Cretaceous of Argentina. The fine structure of fossil plant cuticles of Cretaceous age demonstrates well preserved layers that are topographically equivalent to those in some extant plants. Cuticle stratification on specialized structures (stomatal apparatus and trichomes) is presented, together with an account of the fine structure of both the upper and lower cuticular membrane. Levels of cuticle stratification are compared with those of extant plants.     

Aboveground herbivory affects indirect defences of brassicaceous plants against the root feeder Delia radicum Linnaeus: laboratory and field evidence

1. Belowground herbivory has recently been shown to disrupt the host location behaviour of aboveground parasitoids and thereby impact plants indirect defences. Reverse interactions, on the other hand, have received little attention so far. 2. Lab and field studies were conducted to examine whether the presence of the leaf herbivore Pieris brassicae Linnaeus on brassicaceous plants influences the response of Trybliographa rapae Westwood, a specialist parasitoid of the root feeder Delia radicum Linnaeus. 3. The present results show that the attraction of the parasitoid towards host‐infested plants disappeared when these plants were also infested by P. brassicae. This absence of attraction was observed both when the complete odour blend or only undamaged leaves from damaged plants were offered, emphasising the role of systemically induced volatiles for host location in T. rapae. 4. Furthermore, the field study revealed that parasitism levels dropped from 30% on root‐infested plants to 4% on double‐infested plants. 5. The present study is the first to confirm that reduced attraction to host‐infested plants as a result of simultaneous attack by below‐ and aboveground herbivores translates into lower levels of parasitism in the field.     

ORAL ASSESSMENT OF HARDNESS BETWEEN ELASTIC AND PLASTIC PRODUCTS

This study examined how people compare the hardness of different materials. Simple models with either elastic or plastic behavior were prepared and controlled mechanically. Six elastomers were compared to 29 plastic dental waxes of different hardness. For each elastic sample, a psychophysical staircase method was used to determine its perceived hardness in comparison to the plastic samples. Single bites were performed and the forces were recorded by a small load-cell placed between the sample and the teeth. Nine subjects. free of dental pathology, participated in this study. Subjects were able to match samples of both materials with a specific stress ratio which depended on the hardness of the elastic samples. Results indicated that people do not use the same sensory cues and, in this case, no clear role of the bite force was established.