We investigated the detoxification strategies of Helicoverpa armigera and Heliothis virescens, which allow them to feed successfully on cotton plants that produce toxic gossypol as a chemical defense compound. First, we tested CYP6AE14, a proposed candidate enzyme for gossypol detoxification, for its ability to detoxify gossypol. In incubation assays with gossypol and heterologously expressed CYP6AE14 no metabolites were detected. Our data show that CYP6AE14 is not directly involved in gossypol metabolism, at least under the assay conditions tested, but rather takes part in the general stress response of the herbivores to plant toxins. Second, we discovered that H. armigera and H. virescens excrete a large proportion (50%) of unmetabolized gossypol in the feces, but additionally metabolize gossypol by glycosylation. Analysis of larval feces revealed three monoglycosylated and up to five diglycosylated gossypol isomers when larvae fed on gossypol-supplemented diet. Based on their expression patterns we selected H. armigera candidate UGT genes and functionally expressed the respective proteins in insect cells. In enzymatic assays, we showed that UGT41B3 and UGT40D1 are capable of glycosylating gossypol mainly to a diglycosylated gossypol isomer that is characteristic for H. armigera and is absent in H. virescens feces. We offer novel insights into the detoxification mechanism of the plant defensive toxin, gossypol, by two generalist herbivores.

This paper aims to expand our understanding on the success factors of small businesses, which comprise of more than 90 percent of all businesses in U.S. in 2016. One of the most critical issues behind small business success is the competition, which becomes increasingly intense. Not only small businesses fiercely compete with larger competitors (e.g. Emergence of mega-retailers such as Wal-Mart has intensified the competition in the grocery industry, and, as a result, many mom and pop stores have gone out of business.), but also the competition against each other (i.e. competition between small businesses) becomes increasingly aggressive. Yet, the current literature in marketing have less investigated the issue of competition between small businesses, while issues on competition between small and large businesses have been somewhat explored. Another phenomenon in small business that has not received much attention is the competition between generalist and specialist firms. This phenomenon of specialist versus generalist competition is in fact frequently observed in many industries. Therefore, we study competition between small businesses, focusing on the competition between generalist and specialist small businesses. We examine how competitive intensity, as well as market environmental factors, affect the performance of small businesses. Specifically, we decompose the competitive intensity into two types, one between generalists and the other between specialists, in order to identify the differential effects of competition between generalist and specialist, and examine their impacts on the generalist and specialist performance. Given the research questions above, we develop the following hypotheses based on the past research in marketing. First, we expect competition has a positive effect on generalist performance, while we expect the opposite effect on specialist performance. We also expect that the effect of competition becomes weaker, as the competition becomes more intense. That is, the positive (negative) impact of competition on generalist (specialist) performance becomes less significant as there are more competitors in the market. We further expect that competition between the same type of businesses (e.g. between generalists) has a positive effect on their performance, while competition between the difference types (e.g. between generalist and specialist) has a negative effect on their performance. Moreover, we expect that market environmental factors have differential effects on the performance of generalist and specialist. To test the aforementioned hypotheses on the small business competition between generalist and specialist, we collected data from the health care industry on private physician practices (offices) in Korea. Out data contain, for each practice, monthly sales, number of doctors, number of nurses, type of practice, number of beds and zip code it is located in. We also have data on average consumer spending, average medical spending, percentage of patients over sixty years old for each zip code. Moreover, we have data on competition between the same type of offices (e.g. between generalists and between specialists) and competition between different types (e.g. between generalist and specialist). Note that our data collected from the Korean health care industry fit our research questions well. First, the majority of medical service providers in Korea are small private practices with an average number of two doctors, and the share of generalist and specialist practices are about half-and-half. Second, unlike the U.S. health care industry, generalist physicians in Korea usually practice a number of different fields, while specialist physicians focus on their own specialties. Third, patients in Korea do not usually distinguish between generalist and specialist offices, and they do not usually have a primary care physician. As a result, patients can easily switch between physicians, and in fact the switching is highly likely, as all medical information is centralized by government. Our main findings are as follows. First, we find that competition has a positive effect on generalist performance, while it has a negative effect on specialist performance. Specifically, we find that generalist benefits from competition with both generalist and specialist, while specialist suffers from the competition with both specialist and generalist. As competition becomes intense, meaning the number of physician offices increases, it would attract more patients to visit the area where physician offices are clustered (clustering effect), while it becomes easier for patients to switch from one to the other nearby offices. In particular, as generalist usually treats multiple fields (specialties), generalist tends to benefit from the patients who switch from specialist. In other words, generalists benefit from competition, as they free ride on clustering of physicians including specialists, while specialists would suffer from competition. Second, our findings show that as the competition becomes more intense, its effect on business performance becomes weaker. That is, a high level of competition weakens the benefits and damages imposed on the performance of generalist and specialist, respectively. When there are more physician offices to switch, the effect of free riding becomes weaker, as patients have more options to choose from. Thus, the benefit of generalist from free riding becomes weaker, as well as the negative effect on specialist performance. Moreover, our findings suggest that market environmental factors do influence the business performance. Specifically, the performance of both generalist and specialist improves as the number of doctors increases. However, an increase in the number of nurses has a different effect on generalist and specialist. Employing a larger group of nurses has a negative effect on generalist because it might cause the operation of the office to be less efficient. However, since specialist’s practice usually involves a more technical and sophisticated processes, a larger group of nurses could make the office more efficient having a positive impact on the sales performance. Similarly, we find the effects of other environmental factors have differential impacts on the performance of specialist versus generalist.

Temperature and nutrition are the two most important environmental factors influencing growth and survival in immature insects. There is ample evidence of interactions between these two factors but still little is known how changes in thermal environment affect feeding and nutrient utilization insect ectotherms. The aim of this study is to investigate the potential effects of ambient temperature on food selection and post-ingestive nutritional physiology in a generalist-feeding caterpillar of Spodorptera litura. Two separate experiments were performed. The first was a food choice experiment in which caterpillars were maintained through their final larval stadium under one of three constant temperatures(20,25,30°) and given a choice between two nutritionally unbalanced diets that differed in protein(p) and carbohydrate(c) content (p42:c0 vs p7:c35 and p35:c7 vs p7:c35). In the second experiment, caterpillars were kept at the same thermal conditions as the first experiment but received a single diet from three no-choice feeding treatments(p35:c7,p21:c21and p7:c35). When raised at the highest temperature (30C), caterpillars from the choice experiment selected significantly more carbohydrate than those on lower temperatures whereas protein intake did not differ significantly between caterpillars across three test temperatures. Results from the no-choice experiment showed that lipid storage efficiency was reduced when caterpillars were maintained at the highest temperature(30C). In both experiments, growth rate increased progressively with rising temperature. However, there was a significant temperature-by-diet interaction, with growth rates increasing more rapidly on p21:c21 diet than on the other diets(p35:c7 and p7:c35). Our results demonstrate that caterpillars adjust their nutrient preference to meet the increased energetic demand at high ambient temperature.

The aim of this research was to demonstrate whether generalist-feeding caterpillars of Spodoptera exigua (Hübner) regulate their nutrient intake when faced with nutritionally variable food conditions. Six, chemically-defined diets were prepared that differed in the composition of protein and digestible carbohyrate:42% protein with 0% carbohydrate by dry mass(p42:c0), p35:c7, p28:c5.6, p7:c35, p5.6:c28 and p0:42. A total of 288 newly-ecdysed final instar(5th) caterpillars were collected and assigned randomly into 7 food pairing treatments, in which they were allowed to choose between two diet block:one with high P:C ratio and the other with low ratio [1) p42:c0 vs. p0:c42, 2) p42:c0 vs. p7:c35, 3) p35:c7 vs. p0:c42, 4) p35:c7 vs. p7:c35, 5) p35:c7 vs. p5.6:c28, 6) p28:c5.6 vs. p7:c35 and 7) p28:c5.6 vs. p5.6:c28]. Various aspects of food intake and larval performance variables were measured for each insect, including larval survival, stadium duration, pupal mass and body lipid composition. Results showed that the intake of protein and carbohydrate self-composed by caterpillars in all treatments converged to a point in a bivariate nutrient plot and the ratio of protein to carbohydrate averaged over these converging intake points was close to 1:1. This indicates that S. exigua caterpillars have capacity to balance their nutrient intake by defending their species-specific ‘intake target’ despite the differences in amount and proportion of nutrients available in each food choice treatment.