Role of Caribbean Islands in the diversification and biogeography of Neotropical Heraclides swallowtails

Numerous hypotheses on the evolution of Neotropical biodiversity have stimulated research to provide a better understanding of diversity dynamics and distribution patterns of the region. However, few studies integrate molecular and morphological data with complete sampling of a Neotropical group, and so there has been little synthesis of the multiple processes governing biodiversity through space and time. Here, a total‐evidence phylogenetic approach is used to reconstruct the evolutionary history of the butterfly subgenus Heraclides. We used DNA sequences for two mitochondrial genes and one nuclear gene and coded 133 morphological characters of larvae and adults. A robust and well‐resolved phylogeny was obtained using several analytical approaches, while molecular dating and biogeographical analyses indicated an early Miocene origin (22 Mya) in the Caribbean Islands. We inferred six independent dispersal events from the Caribbean to the mainland, and three from the mainland to the Caribbean, and we suggest that cooling climates with decreasing sea levels may have contributed to these events. The time‐calibrated tree is best explained by a museum model of diversity in which both speciation and extinction rates remained constant through time. By assessing both continental and fine‐scale biodiversity patterns, this study provides new findings, for instance that islands may act as source of diversity rather than as a sink, to explain spatio‐temporal macroevolutionary processes within the Neotropical region.     

Relationship between Sevoflurane Plasma Concentration,Clinical Variables and Bispectral Index Values during Cardiopulmonary Bypass

Background

Anesthetic administration is increasingly guided by electroencephalography (EEG)-based monitoring, such as the bispectral index (BIS). However, during cardiopulmonary bypass (CPB), factors other than the administered hypnotic agents may influence EEG signals, and their effects on BIS values are unknown.

Methods

This report is a secondary analysis of data from a prospective, controlled interventional study comparing the effect of sevoflurane administration guided by BIS monitoring (group Sevo_BIS) and constant administration of sevoflurane (group Sevo_1.8Vol%) during CPB. Sevoflurane plasma concentration (SPC) was measured using gas chromatography. The relationships of BIS to SPC, CPB pump flow, arterial pressure, hematocrit, temperature, time on CPB, and patient characteristics were analysed.

Results

No association was observed between BIS values and SPC in group Sevo_BIS. In group Sevo_1.8Vol%, a 40 μg ml^-1 increase in SPC, which encompassed the entire range of observed values of the SPC in this analysis, was associated with a decrease of 3.6 (95% confidence interval (CI): 1.1–6.1) in BIS values (p = 0.005). Each increase in CPB time of 10 minutes was associated with an increase in BIS values of 0.25 (95%CI: 0.11–0.39, p<0.001). Path analysis revealed that the BIS values of Sevo_BIS patients were 5.3 (95%CI: 3.2–7.5) units higher than those of Sevo_1.8Vol% patients (p<0.001), which was the strongest effect on BIS values. Path analysis revealed a slope of 0.5 (95%CI: 0.3–0.7) BIS units per 1°C body temperature (p<0.001).

Conclusion

BIS monitoring is insensitive to clinically relevant changes in SPC in individual patients during CPB.     

Systematic Review and Meta-Analysis of Response Rates and Diagnostic Yield of Screening for Type 2 Diabetes and Those at High Risk of Diabetes

Background

Screening for type 2 diabetes (T2DM) and individuals at risk of diabetes has been advocated, yet information on the response rate and diagnostic yield of different screening strategies are lacking.

Methods

Studies (from 1998 to March/2015) were identified through Medline, Embase and the Cochrane library and included if they used oral glucose tolerance test (OGTT) and WHO-1998 diagnostic criteria for screening in a community setting. Studies were one-step strategy if participants were invited directly for OGTT and two, three/four step if participants were screened at one or more levels prior to invitation to OGTT. The response rate and diagnostic yield were pooled using Bayesian random-effect meta-analyses.

Findings

47 studies (422754 participants); 29 one-step, 11 two-step and seven three/four-step were identified. Pooled response rate (95% Credible Interval) for invitation to OGTT was 65.5% (53.7, 75.6), 63.1% (44.0, 76.8), and 85.4% (76.4, 93.3) in one, two and three/four-step studies respectively. T2DM yield was 6.6% (5.3, 7.8), 13.1% (4.3, 30.9) and 27.9% (8.6, 66.3) for one, two and three/four-step strategies respectively. The number needed to invite to the OGTT to detect one case of T2DM was 15, 7.6 and 3.6 in one, two, and three/four-step strategies. In two step strategies, there was no difference between the response or yield rates whether the first step was blood test or risk-score. There was evidence of substantial heterogeneity in rates across study populations but this was not explained by the method of invitation, study location (rural versus urban) and developmental index of the country in which the study was performed.

Conclusions

Irrespective of the invitation method, developmental status of the countries and or rural/urban location, using a multi-step strategy increases the initial response rate to the invitation to screening for diabetes and reduces the number needed to have the final diagnostic test (OGTT in this study) for a definite diagnosis.     

Repeated Reticulate Evolution in North American Papilio machaon Group Swallowtail Butterflies

Hybridization between distinct populations or species is increasingly recognized as an important process for generating biodiversity. However, the interaction between hybridization and speciation is complex, and the diverse evolutionary outcomes of hybridization are difficult to differentiate. Here we characterize potential hybridization in a species group of swallowtail butterflies using microsatellites, DNA sequences, and morphology, and assess whether adaptive introgression or homoploid hybrid speciation was the primary process leading to each putative hybrid lineage. Four geographically separated hybrid populations were identified in the Papilio machaon species group. One distinct mitochondrial DNA clade from P. machaon was fixed in three hybrid taxa (P. brevicauda, P. joanae, and P. m. kahli), while one hybrid swarm (P. zelicaon x machaon) exhibited this hybrid mtDNA clade as well as widespread parental mtDNA haplotypes from both parental species. Microsatellite markers and morphology showed variable admixture and intermediacy, ranging from signatures of prolonged differential introgression from the paternal species (P. polyxenes/P. zelicaon) to current gene flow with both parental species. Divergences of the hybrid lineages dated to early- to mid-Pleistocene, suggesting that repeated glaciations and subsequent range shifts of parental species, particularly P. machaon hudsonianus, facilitated initial hybridization. Although each lineage is distinct, P. joanae is the only taxon with sufficient evidence (ecological separation from parental species) to define it as a homoploid hybrid species. The repetition of hybridization in this group provides a valuable foundation for future research on hybridization, and these results emphasize the potential for hybridization to drive speciation in diverse ways.     

Distinct role of subcomplexes of the COPI coat in the regulation of ArfGAP2 activity

COPI vesicles serve for transport of proteins and membrane lipids in the early secretory pathway. Their coat protein (coatomer) is a heptameric complex that is recruited to the Golgi by the small GTPase Arf1. Although recruited en bloc, coatomer can be viewed as a stable assembly of an adaptin‐like tetrameric subcomplex (CM4) and a trimeric ‘cage’ subcomplex (CM3). Following recruitment, coatomer stimulates ArfGAP‐dependent GTP hydrolysis on Arf1. Here, we employed recombinant coatomer subcomplexes to study the role of coatomer components in the regulation of ArfGAP2, an ArfGAP whose activity is strictly coatomer‐dependent. Within CM4, we define a novel hydrophobic pocket for ArfGAP2 interaction on the appendage domain of γ₁‐COP. The CM4 subcomplex (but not CM3) is recruited to membranes through Arf1 and can subsequently recruit ArfGAP2. Neither CM3 nor CM4 in itself is effective in stimulating ArfGAP2 activity, but stimulation is regained when both subcomplexes are present. Our findings point to a distinct role of each of the two coatomer subcomplexes in the regulation of ArfGAP2‐dependent GTP hydrolysis on Arf1, where the CM4 subcomplex functions in GAP recruitment, while, similarly to the COPII system, the cage‐like CM3 subcomplex stimulates the catalytic reaction.     

Nectarivory by the plant-tissue feeding predator Macrolophus pygmaeus Rambur (Heteroptera: Miridae): Nutritional redundancy or nutritional benefit?

Most predators and parasitoids feed on plant-provided food (nectar, pollen) or engage in herbivory during at least part of their life stages. Plant feeding by these insects plays an important role in driving predator-herbivore dynamics. Thus, understanding the effects of plant feeding on omnivores could be an important element in improving biological control strategies. The mirid Macrolophus pygmaeus is an omnivorous heteropteran predator of whitefly and other pests. Unlike other predators that need to seek out accessible nectar to meet their carbohydrate requirements, mirid bugs can access the plant's carbohydrate resources by feeding directly on plant tissues. Leaf and stem feeding could be seen as a nutritional surrogate that allows mirids to become independent of nectar availability. However, to date feeding experiments have not yet considered nectar feeding by these mirid predators. In this study we demonstrate that M. pygmaeus survival is prolonged on broad bean plants featuring extrafloral nectar as compared to broad bean with extrafloral nectaries removed, irrespective of the presence of cattail pollen. Survival on extrafloral nectar was comparable to the survival by individuals kept on broad bean provided with eggs of Ephestia kuehniella as prey. Also, a greater proportion of mirid females laid eggs when extrafloral nectar was available as compared to those confined on nectariless plants without supplemental food.     

Decreased neoblast progeny and increased cell death during starvation-induced planarian degrowth

The development of a complex multicellular organism requires a careful coordination of growth, cell division, cell differentiation and cell death. All these processes must be under intricate and coordinated control, as they have to be integrated across all tissues. Freshwater planarians are especially plastic, in that they constantly replace somatic tissues from a pool of adult somatic stem cells and continuously undergo growth and degrowth as adult animals in response to nutrient availability. During these processes they appear to maintain perfect scale of tissues and organs. These life history traits make them an ideal model system to study growth and degrowth. We have studied the unique planarian process of degrowth. When food is not available, planarians are able to degrow to a minimum size, without any signs of adverse physiological outcomes. For example they maintain full regenerative capacity. Our current knowledge of how this is regulated at the molecular and cellular level is very limited. Planarian degrowth has been reported to result from a decrease in cell number rather than a decrease in cell size. Thus one obvious explanation for degrowth would be a decrease in stem cell proliferation. However evidence in the literature suggests this is not the case. We show that planarians maintain normal basal mitotic rates during degrowth but that the number of stem cell progeny decreases during starvation and degrowth. These observations are reversed upon feeding, indicating that they are dependent on nutritional status. An increase in cell death is also observed during degrowth, which is not rapidly reversed upon feeding. We conclude that degrowth is a result of cell death decreasing cell numbers and that the dynamics of neoblast self-renewal and differentiation adapt to nutrient conditions to allow maintenance of the neoblast population during the period of starvation.     

Design and characterization of auxotrophy-based amino acid biosensors

Efficient and inexpensive methods are required for the high-throughput quantification of amino acids in physiological fluids or microbial cell cultures. Here we develop an array of Escherichia coli biosensors to sensitively quantify eleven different amino acids. By using online databases, genes involved in amino acid biosynthesis were identified that - upon deletion - should render the corresponding mutant auxotrophic for one particular amino acid. This rational design strategy suggested genes involved in the biosynthesis of arginine, histidine, isoleucine, leucine, lysine, methionine, phenylalanine, proline, threonine, tryptophan, and tyrosine as potential genetic targets. A detailed phenotypic characterization of the corresponding single-gene deletion mutants indeed confirmed that these strains could neither grow on a minimal medium lacking amino acids nor transform any other proteinogenic amino acid into the focal one. Site-specific integration of the egfp gene into the chromosome of each biosensor decreased the detection limit of the GFP-labeled cells by 30% relative to turbidometric measurements. Finally, using the biosensors to determine the amino acid concentration in the supernatants of two amino acid overproducing E. coli strains (i.e. ΔhisL and ΔtdcC) both turbidometrically and via GFP fluorescence emission and comparing the results to conventional HPLC measurements confirmed the utility of the developed biosensor system. Taken together, our study provides not only a genotypically and phenotypically well-characterized set of publicly available amino acid biosensors, but also demonstrates the feasibility of the rational design strategy used.     

The effect of different dietary sugars and honey on longevity and fecundity in two hyperparasitoid wasps

In nature adult insects, such as parasitic wasps or 'parasitoids' often depend on supplemental nutritional sources, such as sugars and other carbohydrates, to maximize their life-expectancy and reproductive potential. These food resources are commonly obtained from animal secretions or plant exudates, including honeydew, fruit juices and both floral and extra-floral nectar. In addition to exogenous sources of nutrition, adult parasitoids obtain endogenous sources from their hosts through 'host-feeding' behavior, whereby blood is imbibed from the host. Resources obtained from the host contain lipids, proteins and sugars that are assumed to enhance longevity and/or fecundity. Here we conducted an experiment exploring the effects of naturally occurring sugars on longevity and fecundity in the solitary hyperparasitoids, Lysibia nana and Gelis agilis. Although both species are closely related, L. nana does not host-feed whereas G. agilis does. In a separate experiment, we compared reproduction and longevity in G. agilis reared on either honey, a honey-sugar 'mimic', and glucose. Reproductive success and longevity in both hyperparasitoids varied significantly when fed on different sugars. However, only mannose- and water-fed wasps performed significantly more poorly than wasps fed on four other sugar types. G. agilis females fed honey produced twice as many progeny as those reared on the honey-sugar mimic or on glucose, whereas female longevity was only reduced on the mimic mixture. This result shows not only that host feeding influences reproductive success in G. agilis, but also that non-sugar constituents in honey do. The importance of non-sugar nutrients in honey on parasitoid reproduction is discussed.     

Cutting edge: impaired MHC class I expression in mice deficient for Nlrc5/class I transactivator

MHC class I and class II are crucial for the adaptive immune system. Although regulation of MHC class II expression by CIITA has long been recognized, the mechanism of MHC class I transactivation has been largely unknown until the recent discovery of NLRC5/class I transactivator. In this study, we show using Nlrc5-deficient mice that NLRC5 is required for both constitutive and inducible MHC class I expression. Loss of Nlrc5 resulted in severe reduction in the expression of MHC class I and related genes such as β(2)-microglobulin, Tap1, or Lmp2, but did not affect MHC class II levels. IFN-γ stimulation could not overcome the impaired MHC class I expression in Nlrc5-deficient cells. Upon infection with Listeria monocyogenes, Nlrc5-deficient mice displayed impaired CD8(+) T cell activation, accompanied with increased bacterial loads. These findings illustrate critical roles of NLRC5/class I transactivator in MHC class I gene regulation and host defense by CD8(+) T cell responses.