Aphanomyces astaci mtDNA: insights into the pathogen’s differentiation and its genetic diversity from other closely related oomycetes

The causative agent of crayfish plague, Aphanomyces astaci (Saprolegniales, Oomycota), is one of the 100 world’s worst invasive alien species and represents a major threat to freshwater crayfish species worldwide. A better understanding of the biology and epidemiology of A. astaci relies on the application of efficient tools to detect the pathogen and assess its genetic diversity. In this study, we validated the specificity of two recently developed PCR-based approaches used to detect A. astaci groups. The first relies on the analysis of mitochondrial ribosomal rnnS (small) and rnnL (large) subunit sequences and the second, of sequences obtained by using genotype-specific primers designed from A. astaci whole genome sequencing. For this purpose, we tested the specificity against 76 selected isolates, including other oomycete species and the recently described species Aphanomyces fennicus, which, when used in nrITS-based specific tests for A. astaci, is known to result in a false positive. Under both approaches, we were able to efficiently and accurately identify A. astaci and its genetic groups in both pure cultures and clinical samples. We report that sequence analysis of the rnnS region alone is sufficient for the identification of A. astaci and a partial characterization of haplogroups. In contrast, the rnnL region alone is not sufficiently informative for A. astaci identification as other oomycete species present sequences identical to those of A. astaci.     

Liver-Fat Accumulation and Insulin Resistance in Obese Women with Previous Gestational Diabetes

Objective: We determined whether fat accumulation in the liver is associated with features of insulin resistance independent of obesity. Research Methods and Procedures: We recruited 27 obese nondiabetic women in whom liver fat (LFAT) content was determined by proton spectroscopy, intra-abdominal and subcutaneous fat by magnetic resonance imaging, and insulin sensitivity by the euglycemic insulin clamp technique. The women were divided based on their median LFAT content (5%) to groups with low (3.2 ± 0.3%) and high (9.8 ± 1.5%) liver fat. The groups were almost identical with respect to age (36 ± 1 vs. 38 ± 1 years in low vs. high-LFAT), body mass index (32.2 ± 0.6 vs. 32.8 ± 0.5 kg/m²), waist-to-hip ratio, intra-abdominal, subcutaneous, and total fat content. Results: Women with high LFAT had features of insulin resistance including higher fasting serum triglyceride (1.93 ± 0.21 vs. 1.11 ± 0.09 mM, p < 0.01) and insulin (14 ± 3 vs. 10 ± 1 mU/L, p < 0.05) concentrations than women with low LFAT. The group with high LFAT also had higher 24-hour blood pressures, and lower whole-body insulin sensitivity compared with the low-LFAT group. Discussion: In obese women with previous gestational diabetes, LFAT, rather than any measure of body composition, is associated with features of insulin resistance.     

Integral projection models perform better for small demographic data sets than matrix population models: a case study of two perennial herbs

1. Matrix population models are widely used to describe population dynamics, conduct population viability analyses and derive management recommendations for plant populations. For endangered or invasive species, management decisions are often based on small demographic data sets. Hence, there is a need for population models which accurately assess population performance from such small data sets.
2. We used demographic data on two perennial herbs with different life histories to compare the accuracy and precision of the traditional matrix population model and the recently developed integral projection model (IPM) in relation to the amount of data.
3. For large data sets both matrix models and IPMs produced identical estimates of population growth rate (λ). However, for small data sets containing fewer than 300 individuals, IPMs often produced smaller bias and variance for λ than matrix models despite different matrix structures and sampling techniques used to construct the matrix population models.
4. Synthesis and applications . Our results suggest that the smaller bias and variance of λ estimates make IPMs preferable to matrix population models for small demographic data sets with a few hundred individuals. These results are likely to be applicable to a wide range of herbaceous, perennial plant species where demographic fate can be modelled as a function of a continuous state variable such as size. We recommend the use of IPMs to assess population performance and management strategies particularly for endangered or invasive perennial herbs where little demographic data are available.     

Are habitat loss,predation risk and climate related to the drastic decline in a Siberian flying squirrel population? A 15-year study

To devise effective conservation actions, it is important to know which factors are associated with the population parameters of a declining population. Using mark–recapture methods, we estimated the annual population size, growth rate and survival probability of an ear-tagged flying squirrel population over a 15-year period in a 4,500 ha study area in western Finland. The species is considered vulnerable, but detailed knowledge concerning population sizes or trends is lacking. The population parameters and changes therein were regressed against habitat availability, an indicator of predation pressure, and mean winter temperature (an indicator of climate change), to reveal potential reasons for trends in the population. The best-fit models suggested the annual growth rate to be below one, and on average it was 0.93 (±0.06; SE) across the 15-year period. The survival probability was about 0.22 (±0.03) for juveniles and 0.50 (±0.03) for adults. The population size of adult flying squirrels decreased from 65 (±11) individuals in 1995 to 29 (±6) individuals in 2009. The number of flying squirrels was associated with the amount of available habitat, but the decline in population size was more rapid than the loss of habitat area. If the current decreasing trend in habitat availability continues, the population might become extinct by the year 2020. To halt the population decline, it is necessary to refrain from clear-cutting mature spruce stands until new suitable habitats develop from the maturation of younger forests.