Multiple introductions and population structure during the rapid expansion of the invasive Sahara mustard (Brassica tournefortii).

The specific mechanisms that result in the success of any species invasion case are difficult to document. Reproductive strategies are often cited as a primary driver of invasive success, with human activities further facilitating invasions by, for example, acting as seed vectors for dispersal via road, train, air, and marine traffic, and by producing efficient corridors for movement including canals, drainages, and roadways. Sahara mustard (Brassica tournefortii) is a facultative autogamous annual native to Eurasia that has rapidly invaded the southwestern United States within the past century, displacing natives, and altering water-limited landscapes in the southwest. We used a genotyping-by-sequencing approach to study the population structure and spatial geography of Sahara mustard from 744 individuals from 52 sites across the range of the species' invasion. We also used herbaria records to model range expansion since its initial introduction in the 1920s. We found that Sahara mustard occurs as three populations in the United States unstructured by geography, identified three introduction sites, and combined herbaria records with genomic analyses to map the spread of the species. Low genetic diversity and linkage disequilibrium are consistent with self-fertilization, which likely promoted rapid invasive spread. Overall, we found that Sahara mustard experienced atypical expansion patterns, with a relatively constant rate of expansion and without the lag phase that is typical of many invasive species.

Cigarette smokers' classification of tobacco products.

INTRODUCTION: Cigarette consumption has declined in the USA. However, cigar consumption has increased. This may be due in part to some cigarette smokers switching to filtered cigars as a less expensive substitute for cigarettes. Additionally, some cigarette smokers may perceive and consume little filtered cigars as cigarettes. The purpose of this study was to determine how cigarette smokers classify tobacco products when presented with photographs of those products. METHODS: An online survey was conducted with a sample of 344 self-identified cigarette smokers. Respondents were presented with pictures of various types of tobacco products, both with and without packaging, and then asked to categorise them as either a cigarette, little cigar, cigarillo, cigar or machine-injected roll-your-own cigarette (RYO). Respondents were also asked about their tobacco use and purchasing behaviour. RESULTS: Overall, respondents had difficulty distinguishing between cigarettes, little cigars, cigarillos and RYO. When presented with images of the products without packaging, 93% of respondents identified RYO as a cigarette, while 42% identified a little cigar as a cigarette. Additionally, respondents stated that they would consider purchasing little cigars as substitutes for cigarettes because of the price advantage. CONCLUSIONS: The results of this survey suggest that when presented with photographs of tobacco products, large proportions of current smokers were unable to differentiate between cigarettes, little cigars, cigarillos, RYO and cigars. Findings have implications for existing public health efforts targeting cigarette smokers, and underscore the need to review current definitions of tobacco products and federal excise taxes on such products.

A novel method for detecting licking behavior during recording of electrophysiological signals from the brain.

We have developed a novel method for detecting licking at a fluid well that is compatible with behavioral neurophysiology. This method uses off-the-shelf fiber optic technology to introduce a light beam through the fluid-air interface of a fluid bolus in a well. A self-adjusting optical sensor detects licking as disturbances in the amplified light surface within the interface when the fluid is disturbed. The proper configuration of fluid well and fiber optics will reliably detect licking and introduce no artifacts into simultaneous high-impedance recordings of extracellular neural activity. This method is also compatible with delivery of multiple fluids to the same well. Unlike present methods of detecting licking in neurophysiological experiments, our approach does not involve the passage of current or capacitance changes in which the animal forms part of a circuit, nor does it require movement of the licking apparatus or any other response beyond the actual licking of the fluid. As a result, noise artifacts in the unit recordings do not occur, and the sensor is highly resistant to artifacts caused by exploration or licking at the fluid well in the absence of liquid. We present neural recording data from units in the nucleus accumbens demonstrating these properties of the lick detector.