Response of adult parasitoids ofBemisia tabaci (Hom.: Aleyrodidae) to leaf residues of selected cotton insecticides

The contact toxicity of eight insecticides to adults of four parasitoids of the sweetpotato whiteflyBemisia tabaci was evaluated in the laboratory. Two common Texas species,Eretmocerus sp. andEncarsia pergandiella Howard, and two exotic species,Eretmocerus mundus Mercet from Spain andEncarsia formosa Gahan from Greece were tested. Insecticides, applied as sprays to greenhouse-grown cotton plants at recommended rates were amitraz (Ovasyn^®), azinphosmethyl (Guthion^®), bifenthrin (Capture^®), buprofezin (Applaud^®), cypermethrin (Ammo^®), methyl parathion and thiodicarb (Larvin^®), with a water control. Parasitoid adults were confined on discs cut from leaves (1) sprayed the same day and (2) sprayed two days previously. Survival in both treatments was measured two and four days following exposure. Significant differences in toxicity were detected among the insecticides. Buprofezin was not toxic to any of the four parasitoids. When caged on leaves sprayed two days previously, only amitraz of the remaining compounds allowed significant general parasitoid survival after two days.E. mundus exhibited the greatest overall tolerance to insecticides, with 40% or more surviving 48 hr after confinement on leaves sprayed with amitraz, thiodicarb and cypermethrin. Survival was generally much reduced after 96 hr. In a separate test, fresh residues of endosulfan (Thiodan^®) were highly toxic at the two rates tested, but two day old residues at the lower rate allowed 76.7% survival ofE. mundus and 35% survival ofE. pergandiella after 48 hrs.     

Craterellus fallax, a Black Trumpet mushroom from eastern North America with a broad host range

Phylogenetic analysis of ITS sequences of members of the Craterellus cornucopioides complex (Black Trumpet mushrooms) supports the taxonomic separation of Craterellus fallax apart from C. cornucopioides, with which it has been synonymized in the past. Examination of Pinus virginiana ectomycorrhizal (ECM) root tips and sequence comparison with other insufficiently identified environmental sequences from roots of Tsuga, Quercus, and possibly Castanea supports a broad host range in North America for the ECM symbiont C. fallax. This is the first molecular confirmation of an ECM symbiont with P. virginiana, which associates with a wide diversity of ECM fungi, and the first report of a Cantharellaceae symbiont with this tree, an eastern North American two-needled pine. Three unique species in the C. cornucopioides complex are recovered based on phylogenetic analysis: C. fallax, C. cornucopioides, and an unidentified Craterellus species similar to C. fallax but smaller in stature with smaller spores.     

Genetic linkage between a sexually selected trait and X chromosome meiotic drive

Previous studies on the stalk-eyed fly, Cyrtodiopsis dalmanni, have shown that males with long eye-stalks win contests and are preferred by females, and artificial selection on male relative eye span alters brood sex-ratios. Subsequent theory proposes that X-linked meiotic drive can catalyse the evolution of mate preferences when drive is linked to ornament genes. Here we test this prediction by mapping meiotic drive and quantitative trait loci (QTL) for eye span. To map QTL we genotyped 24 microsatellite loci using 1228 F2 flies from two crosses between lines selected for long or short eye span. The crosses differed by presence or absence of a drive X chromosome, X(D), in the parental male. Linkage analysis reveals that X(D) dramatically reduces recombination between X and X(D) chromosomes. In the X(D) cross, half of the F2 males carried the drive haplotype, produced partially elongated spermatids and female-biased broods, and had shorter eye span. The largest QTL mapped 1.3cM from drive on the X chromosome and explained 36% of the variation in male eye span while another QTL mapped to an autosomal region that suppresses drive. These results indicate that selfish genetic elements that distort the sex-ratio can influence the evolution of exaggerated traits.     

<Emphasis Type="Italic">Scoredist</Emphasis>: A simple and robust protein sequence distance estimator

Background  

Distance-based methods are popular for reconstructing evolutionary trees thanks to their speed and generality. A number of methods exist for estimating distances from sequence alignments, which often involves some sort of correction for multiple substitutions. The problem is to accurately estimate the number of true substitutions given an observed alignment. So far, the most accurate protein distance estimators have looked for the optimal matrix in a series of transition probability matrices, e.g. the Dayhoff series. The evolutionary distance between two aligned sequences is here estimated as the evolutionary distance of the optimal matrix. The optimal matrix can be found either by an iterative search for the Maximum Likelihood matrix, or by integration to find the Expected Distance. As a consequence, these methods are more complex to implement and computationally heavier than correction-based methods. Another problem is that the result may vary substantially depending on the evolutionary model used for the matrices. An ideal distance estimator should produce consistent and accurate distances independent of the evolutionary model used.     

Improved profile HMM performance by assessment of critical algorithmic features in SAM and HMMER

Background  

Profile hidden Markov model (HMM) techniques are among the most powerful methods for protein homology detection. Yet, the critical features for successful modelling are not fully known. In the present work we approached this by using two of the most popular HMM packages: SAM and HMMER. The programs' abilities to build models and score sequences were compared on a SCOP/Pfam based test set. The comparison was done separately for local and global HMM scoring.