Chemotropism by isolated ring traps ofDactylella doedycoides

Summary Uninflated ring traps ofD. doedycoides were mechanically detached from the mycelium and placed on agar near dead or moribund nematodes. Some rings were then induced to inflate by exposure to chlorobutanol. All produced hyphae which grew towards the prey, eventually differentiating into feeding hyphae which digested the carcass if the worm had been killed by dessication, or enveloping it, if it had been killed by heat. The pattern and dynamics of hyphal growth differed in inflated and uninflated rings.     

Changes in interface pressures and shear stresses over time on trans-tibial amputee subjects ambulating with prosthetic limbs: comparison of diurnal and six-month differences

For trans-tibial amputees maintenance over time of a quality fit of the prosthesis to the residual limb is an important clinical challenge. The purpose of this research was to compare diurnal and long-term (5 weeks to 6 months) interface stress changes as well as variance in the change in cross-sectional area down the length of the residual limb. If long-term changes were simply accentuated diurnal fluctuations then this result would suggest similar treatment methods should be used for both conditions. Interface pressures and shear stresses at 13 sites and residual limb shape were measured on eight trans-tibial amputee subjects using patellar-tendon-bearing prostheses. Data were collected at diurnal intervals (within the same day at least 5 h apart) as well as at long-term intervals (5, 10, 15, 20, and 25 weeks apart). Absolute diurnal interface stress changes were not significantly different from those at 5-weeks intervals but were significantly smaller than those at 15, 20, and 25-weeks intervals. Mean interface stress changes increased significantly (p<0.05) for increased session-to-session intervals. Variance of the change in cross-sectional area down the length of the residual limb was significantly smaller for diurnal intervals than for 6-months intervals, indicating that long-term changes were more localized than diurnal changes. These results indicate that long-term changes are not simply accentuated diurnal fluctuations, suggesting that different treatment methods should be used to treat each condition.     

Genetic constraints on wing pattern variation in Lycaeides butterflies: A case study on mapping complex,multifaceted traits in structured populations

Patterns of phenotypic variation within and among species can be shaped and constrained by trait genetic architecture. This is particularly true for complex traits, such as butterfly wing patterns, that consist of multiple elements. Understanding the genetics of complex trait variation across species boundaries is difficult, as it necessitates mapping in structured populations and can involve many loci with small or variable phenotypic effects. Here, we investigate the genetic architecture of complex wing pattern variation in Lycaeides butterflies as a case study of mapping multivariate traits in wild populations that include multiple nominal species or groups. We identify conserved modules of integrated wing pattern elements within populations and species. We show that trait covariances within modules have a genetic basis and thus represent genetic constraints that can channel evolution. Consistent with this, we find evidence that evolutionary changes in wing patterns among populations and species occur in the directions of genetic covariances within these groups. Thus, we show that genetic constraints affect patterns of biological diversity (wing pattern) in Lycaeides, and we provide an analytical template for similar work in other systems.     

Genetic Variation within Clonal Lineages of Phytophthora infestans Revealed through Genotyping-By-Sequencing,and Implications for Late Blight Epidemiology

Genotyping-by-sequencing (GBS) was performed on 257 Phytophthora infestans isolates belonging to four clonal lineages to study within-lineage diversity. The four lineages used in the study were US-8 (n = 28), US-11 (n = 27), US-23 (n = 166), and US-24 (n = 36), with isolates originating from 23 of the United States and Ontario, Canada. The majority of isolates were collected between 2010 and 2014 (94%), with the remaining isolates collected from 1994 to 2009, and 2015. Between 3,774 and 5,070 single-nucleotide polymorphisms (SNPs) were identified within each lineage and were used to investigate relationships among individuals. K-means hierarchical clustering revealed three clusters within lineage US-23, with US-23 isolates clustering more by collection year than by geographic origin. K-means hierarchical clustering did not reveal significant clustering within the smaller US-8, US-11, and US-24 data sets. Neighbor-joining (NJ) trees were also constructed for each lineage. All four NJ trees revealed evidence for pathogen dispersal and overwintering within regions, as well as long-distance pathogen transport across regions. In the US-23 NJ tree, grouping by year was more prominent than grouping by region, which indicates the importance of long-distance pathogen transport as a source of initial late blight inoculum. Our results support previous studies that found significant genetic diversity within clonal lineages of P. infestans and show that GBS offers sufficiently high resolution to detect sub-structuring within clonal populations.     

Temperature Adaptability of Psychrotrophic Pseudomonas

The rate of oxidation of glucose and alanine at low temperatures by washed cells of psychrotrophic strains of Pseudomonas is related to growth temperature.     

Bayesian estimation of genomic clines

We developed a Bayesian genomic cline model to study the genetic architecture of adaptive divergence and reproductive isolation between hybridizing lineages. This model quantifies locus‐specific patterns of introgression with two cline parameters that describe the probability of locus‐specific ancestry as a function of genome‐wide admixture. ‘Outlier’ loci with extreme patterns of introgression relative to most of the genome can be identified. These loci are potentially associated with adaptive divergence or reproductive isolation. We simulated genetic data for admixed populations that included neutral introgression, as well as loci that were subject to directional, epistatic or underdominant selection, and analysed these data using the Bayesian genomic cline model. Under many demographic conditions, underdominance or directional selection had detectable and predictable effects on cline parameters, and ‘outlier’ loci were greatly enriched for genetic regions affected by selection. We also analysed previously published genetic data from two transects through a hybrid zone between Mus domesticus and M. musculus. We found considerable variation in rates of introgression across the genome and particularly low rates of introgression for two X‐linked markers. There were similarities and differences in patterns of introgression between the two transects, which likely reflects a combination of stochastic variability because of genetic drift and geographic variation in the genetic architecture of reproductive isolation. By providing a robust framework to quantify and compare patterns of introgression among genetic regions and populations, the Bayesian genomic cline model will advance our understanding of the genetics of reproductive isolation and the speciation process.     

The n = 1 constraint in population genomics

A key objective of population genomics is to identify portions of the genome that have been shaped by natural selection rather than by neutral divergence. A previously recognized but underappreciated challenge to this objective is that observations of allele frequencies across genomes in natural populations often correspond to a single, unreplicated instance of the outcome of evolution. This is because the composition of each individual genomic region and population is expected to be the outcome of a unique array of evolutionary processes. Given a single observation, inference of the evolutionary processes that led to the observed state of a locus is associated with considerable uncertainty. This constraint on inference can be ameliorated by utilizing multi-allelic (e.g. DNA haplotypes) rather than bi-allelic markers, by analysing two or more populations with certain models and by utilizing studies of replicated experimental evolution. Future progress in population genomics will follow from research that recognizes the 'n = 1 constraint' and that utilizes appropriate and explicit evolutionary models for analysis.