Variation in hybrid gene expression: Implications for the evolution of genetic incompatibilities in interbreeding species

Interbreeding species often produce low-fitness hybrids due to genetic incompatibilities between parental genomes. Whether these incompatibilities reflect fixed allelic differences between hybridizing species, or, alternatively, standing variants that segregate within them, remains unknown for many natural systems. Yet, evaluating these alternatives is important for understanding the origins and nature of species boundaries. We examined these alternatives using spadefoot toads (genus Spea), which naturally hybridize. Specifically, we contrasted patterns of gene expression in hybrids relative to pure-species types in experimentally produced tadpoles from allopatric parents versus those from sympatric parents. We evaluated the prediction that segregating variation should result in gene expression differences between hybrids derived from sympatric parents versus hybrids derived from allopatric parents, and found that 24% of the transcriptome showed such differences. Our results further suggest that gene expression in hybrids has evolved in sympatry owing to evolutionary pressures associated with ongoing hybridization. Although we did not measure hybrid incompatibilities directly, we discuss the implications of our findings for understanding the nature of hybrid incompatibilities, how they might vary across populations over time, and the resulting effects on the evolutionary maintenance - or breakdown - of reproductive barriers between species

Utilisation of QSPR ODT modelling and odour vector modelling to predict Cannabis sativa odour.

Cannabis flower odour is an important aspect of product quality as it impacts the sensory experience when administered, which can affect therapeutic outcomes in paediatric patient populations who may reject unpalatable products. However, the cannabis industry has a reputation for having products with inconsistent odour descriptions and misattributed strain names due to the costly and laborious nature of sensory testing. Herein, we evaluate the potential of using odour vector modelling for predicting the odour intensity of cannabis products. Odour vector modelling is proposed as a process for transforming routinely produced volatile profiles into odour intensity (OI) profiles which are hypothesised to be more informative to the overall product odour (sensory descriptor; SD). However, the calculation of OI requires compound odour detection thresholds (ODT), which are not available for many of the compounds present in natural volatile profiles. Accordingly, to apply the odour vector modelling process to cannabis, a QSPR statistical model was first produced to predict ODT from physicochemical properties. The model presented herein was produced by polynomial regression with 10-fold cross-validation from 1,274 median ODT values to produce a model with R2 = 0.6892 and a 10-fold R2 = 0.6484. This model was then applied to terpenes which lacked experimentally determined ODT values to facilitate vector modelling of cannabis OI profiles. Logistic regression and k-means unsupervised cluster analysis was applied to both the raw terpene data and the transformed OI profiles to predict the SD of 265 cannabis samples and the accuracy of the predictions across the two datasets was compared. Out of the 13 SD categories modelled, OI profiles performed equally well or better than the volatile profiles for 11 of the SD, and across all SD the OI data was on average 21.9% more accurate (p = 0.031). The work herein is the first example of the application of odour vector modelling to complex volatile profiles of natural products and demonstrates the utility of OI profiles for the prediction of cannabis odour. These findings advance both the understanding of the odour modelling process which has previously only been applied to simple mixtures, and the cannabis industry which can utilise this process for more accurate prediction of cannabis odour and thereby reduce unpleasant patient experiences

Why Do Species Co-Occur? A Test of Alternative Hypotheses Describing Abiotic Differences in Sympatry versus Allopatry Using Spadefoot Toads

Areas of co-occurrence between two species (sympatry) are often thought to arise in regions where abiotic conditions are conducive to both species and are therefore intermediate between regions where either species occurs alone (allopatry). Depending on historical factors or interactions between species, however, sympatry might not differ from allopatry, or, alternatively, sympatry might actually be more extreme in abiotic conditions relative to allopatry. Here, we evaluate these three hypothesized patterns for how sympatry compares to allopatry in abiotic conditions. We use two species of congeneric spadefoot toads, Spea multiplicata and S. bombifrons, as our study system. To test these hypotheses, we created ecological niche models (specifically using Maxent) for both species to create a map of the joint probability of occurrence of both species. Using the results of these models, we identified three types of locations: two where either species was predicted to occur alone (i.e., allopatry for S. multiplicata and allopatry for S. bombifrons) and one where both species were predicted to co-occur (i.e., sympatry). We then compared the abiotic environment between these three location types and found that sympatry was significantly hotter and drier than the allopatric regions. Thus, sympatry was not intermediate between the alternative allopatric sites. Instead, sympatry occurred at one extreme of the conditions occupied by both species. We hypothesize that biotic interactions in these extreme environments facilitate co-occurrence. Specifically, hybridization between S. bombifrons females and S. multiplicata males may facilitate co-occurrence by decreasing development time of tadpoles. Additionally, the presence of alternative food resources in more extreme conditions may preclude competitive exclusion of one species by the other. This work has implications for predicting how interacting species will respond to climate change, because species interactions may facilitate survival in extreme habitats

Modes, mechanisms and evidence of bet hedging in rotifer diapause traits

In this contribution, we review our knowledge on bet-hedging strategies associated with rotifer diapause. First, we describe the ecological scenario under which bet hedging is likely to have evolved in three diapause-related traits in monogonont rotifer populations: (1) the timing of sex (because diapausing eggs are produced via sexual reproduction), (2) the sexual reproduction ratio (i.e. the fraction of sexually reproducing females) and (3) the timing of diapausing egg hatching. Then, we describe how to discriminate among bet-hedging modes and discuss which modes and mechanisms better fit the variability observed in these traits in rotifers. Finally, we evaluate the strength of the empirical evidence for bet hedging in the scarce studies available, and we call for the need of research at different levels of biological complexity to fully understand bet hedging in rotifer diapause

Evaluation and Treatment of Iron Deficiency Anemia: A Gastroenterological Perspective

A substantial volume of the consultations requested of gastroenterologists are directed towards the evaluation of anemia. Since iron deficiency anemia often arises from bleeding gastrointestinal lesions, many of which are malignant, establishment of a firm diagnosis usually obligates an endoscopic evaluation. Although the laboratory tests used to make the diagnosis have not changed in many decades, their interpretation has, and this is possibly due to the availability of extensive testing in key populations. We provide data supporting the use of the serum ferritin as the sole useful measure of iron stores, setting the lower limit at 100 μg/l for some populations in order to increase the sensitivity of the test. Trends of the commonly obtained red cell indices, mean corpuscular volume, and the red cell distribution width can provide valuable diagnostic information. Once the diagnosis is established, upper and lower gastrointestinal endoscopy is usually indicated. Nevertheless, in many cases a gastrointestinal source is not found after routine evaluation. Additional studies, including repeat upper and lower endoscopy and often investigation of the small intestine may thus be required. Although oral iron is inexpensive and usually effective, there are many gastrointestinal conditions that warrant treatment of iron deficiency with intravenous iron

Fundamental properties of non-wetting topography

© 2017 Dr. Tomer SimovichThe core principles of wettability were established over 70 years ago by Wenzel, Cassie and Baxter and remain the basis of present understanding of hydrophobicity. While these models are used to describe the contact angle of some functional superhydrophobic surfaces, they fail as a predictive tool. This work establishes that the Cassie-Baxter equation is limited by an inability to evaluate liquid-solid contact area. Using in-situ synchrotron based X-Ray imaging, the behaviour of water at the interface of micro-pillar arrays was observed, quantifying the effect of meniscus penetration between peaks on contact area. It was determined that the wetting line between surface asperities is governed by pillar width, spacing and height. A model was developed incorporating this relationship that predicts the contact angle of all tested superhydrophobic surfaces with a maximum error of 6.7% (average 2.2%). Microscale durability was integrated into this model to compare non-wetting topography with mechanical stability. This predicted that an ideal coating morphology would consist of over-arching microstructure with hierarchically protected nano-roughness. Combining this ideal morphology with the elastic bulk properties of nylon and epoxy, novel coatings were fabricated exhibiting both high durability (2H-6H hardness) and contact angles above 156º. A current limitation surrounding the design and fabrication of superhydrophobic coatings is the depletion of the entrapped air layer (plastron) within 24 hours. Scattered micro-droplets, stabilized by high vapor pressure, were imaged for the first time within the plastron on submerged superhydrophobic surfaces. These droplets, ranging from 20-50 μm, were also observed on the superhydrophobic hairs of the aquatic plant Pistia stratiotes. In such systems, the rate of air dissolution is reduced due to lower partial pressure of gaseous species in the plastron, resulting in increased longevity by an order of magnitude. Despite increased longevity, these plastrons still gradually decay over time. To address this, a method involving minimal localised heating (1-2ºC) was developed to replenish the plastron and indefinitely maintain superhydrophobicity. This approach is an environmentally sustainable and scalable solution for long term underwater applications

Fundamental properties of non-wetting topography

© 2017 Dr. Tomer SimovichThe core principles of wettability were established over 70 years ago by Wenzel, Cassie and Baxter and remain the basis of present understanding of hydrophobicity. While these models are used to describe the contact angle of some functional superhydrophobic surfaces, they fail as a predictive tool. This work establishes that the Cassie-Baxter equation is limited by an inability to evaluate liquid-solid contact area. Using in-situ synchrotron based X-Ray imaging, the behaviour of water at the interface of micro-pillar arrays was observed, quantifying the effect of meniscus penetration between peaks on contact area. It was determined that the wetting line between surface asperities is governed by pillar width, spacing and height. A model was developed incorporating this relationship that predicts the contact angle of all tested superhydrophobic surfaces with a maximum error of 6.7% (average 2.2%). Microscale durability was integrated into this model to compare non-wetting topography with mechanical stability. This predicted that an ideal coating morphology would consist of over-arching microstructure with hierarchically protected nano-roughness. Combining this ideal morphology with the elastic bulk properties of nylon and epoxy, novel coatings were fabricated exhibiting both high durability (2H-6H hardness) and contact angles above 156º. A current limitation surrounding the design and fabrication of superhydrophobic coatings is the depletion of the entrapped air layer (plastron) within 24 hours. Scattered micro-droplets, stabilized by high vapor pressure, were imaged for the first time within the plastron on submerged superhydrophobic surfaces. These droplets, ranging from 20-50 μm, were also observed on the superhydrophobic hairs of the aquatic plant Pistia stratiotes. In such systems, the rate of air dissolution is reduced due to lower partial pressure of gaseous species in the plastron, resulting in increased longevity by an order of magnitude. Despite increased longevity, these plastrons still gradually decay over time. To address this, a method involving minimal localised heating (1-2ºC) was developed to replenish the plastron and indefinitely maintain superhydrophobicity. This approach is an environmentally sustainable and scalable solution for long term underwater applications