Increasing experience with the LIFT procedure in Crohn's disease patients with complex anal fistula.

BACKGROUND: Surgical management of anal fistulas in Crohn's disease (CD) is associated with high failure rates, and treatment options are limited due to ongoing proctitis, multiple tracts, and concern for incontinence and non-healing wounds. The aim of this study was to investigate the healing rate of ligation of the inters-sphincteric fistula tract (LIFT) for anal fistulas in Crohn's disease and identify prognostic factors for healing. METHODS: This prospective analysis compared long-term healing rates of CD patients undergoing LIFT for anal fistulas. Consecutive patients with CD who underwent LIFT procedure at our institution, in the period from March 2012 to September 2019 were included. The main outcome was anal fistula healing rate. RESULTS: The study cohort of 46 patients (mean age of 34.2 ± 13.0 years, 18 (40%) males). After a mean follow-up time of 33 ± 28 months, fistula healing was seen in 30 (65%) patients. A total of 8 patients were noted to have inter-sphincteric recurrence and 8 patients had trans-sphincteric recurrence. Smoking at the time of surgery was significantly associated with LIFT failure (HR 3.18, 95% CI 1.18-8.61, p = 0.02). Other factors, such as age, sex, race, disease duration and location, type of fistula history of proctitis, preoperatively use of biologics or a seton, and previous repair attempts, did not appear to influence LIFT healing. Although not statistically significant, there was a trend toward increase in failure among patients with active proctitis at the time of surgery (HR 1.97, 95% CI 0.71-5.42, p = 0.19). CONCLUSION: Our increasing experience with LIFT for anal fistula in CD demonstrates a higher rate of healing (65%) than previously reported (48%). Smoking appears to negatively influence healing of LIFT in CD.

Mechanisms of Bacterial Tolerance and Persistence in the Gastrointestinal and Respiratory Environments.

Pathogens that infect the gastrointestinal and respiratory tracts are subjected to intense pressure due to the environmental conditions of the surroundings. This pressure has led to the development of mechanisms of bacterial tolerance or persistence which enable microorganisms to survive in these locations. In this review, we analyze the general stress response (RpoS mediated), reactive oxygen species (ROS) tolerance, energy metabolism, drug efflux pumps, SOS response, quorum sensing (QS) bacterial communication, (p)ppGpp signaling, and toxin-antitoxin (TA) systems of pathogens, such as Escherichia coli, Salmonella spp., Vibrio spp., Helicobacter spp., Campylobacter jejuni, Enterococcus spp., Shigella spp., Yersinia spp., and Clostridium difficile, all of which inhabit the gastrointestinal tract. The following respiratory tract pathogens are also considered: Staphylococcus aureus, Pseudomonas aeruginosa, Acinetobacter baumannii, Burkholderia cenocepacia, and Mycobacterium tuberculosis Knowledge of the molecular mechanisms regulating the bacterial tolerance and persistence phenotypes is essential in the fight against multiresistant pathogens, as it will enable the identification of new targets for developing innovative anti-infective treatments.

Honeybee dietary neonicotinoid exposure is associated with pollen collection from agricultural weeds.

Neonicotinoid insecticides have been linked to bee declines. However, tracking the primary exposure route for bees in the field has proven to be a major logistical challenge, impeding efforts to restore pollinator health in agricultural landscapes. We quantified neonicotinoid concentrations and botanical species composition in 357 pollen samples collected from 114 commercial honeybee colonies placed along a gradient of agricultural intensity between June and September. Neonicotinoid concentrations increased through the season, peaking at the end of August. As a result, concentrations in pollen were negatively associated with collection from woody and crop plants that flower early-mid season, and positively associated with collection from herbaceous plants that flower mid-late season. Higher clothianidin and thiamethoxam residues were correlated with samples containing a greater proportion of pollen collected from agricultural weeds. The percentage of agricultural land within 1500 m was positively correlated with thiamethoxam concentration; however, this spatial relationship was far weaker than the relationship with the proportion of pollen collected from herbaceous plants. These results indicate that both plant species identity and agricultural dominance are important in determining honeybee neonicotinoid exposure through the pollen diet, but that uncultivated plants associated with agriculture are the source of the greatest acute exposure.

Genomic and Biochemical Characterization of Acinetobacter Podophage Petty Reveals a Novel Lysis Mechanism and Tail-Associated Depolymerase Activity.

The increased prevalence of drug-resistant, nosocomial Acinetobacter infections, particularly from pathogenic members of the Acinetobacter calcoaceticus-baumannii complex, necessitates the exploration of novel treatments such as phage therapy. In the present study, we characterized phage Petty, a novel podophage that infects multidrug-resistant Acinetobacter nosocomialis and Acinetobacter baumannii Genome analysis reveals that phage Petty is a 40,431-bp ϕKMV-like phage, with a coding density of 92.2% and a G+C content of 42.3%. Interestingly, the lysis cassette encodes a class I holin and a single-subunit endolysin, but it lacks canonical spanins to disrupt the outer membrane. Analysis of other ϕKMV-like genomes revealed that spaninless lysis cassettes are a feature of phages infecting Acinetobacter within this subfamily of bacteriophages. The observed halo surrounding Petty's large clear plaques indicated the presence of a phage-encoded depolymerase capable of degrading capsular exopolysaccharides (EPS). The product of gene 39, a putative tail fiber, was hypothesized to possess depolymerase activity based on weak homology to previously reported phage tail fibers. The 101.4-kDa protein gene product 39 (gp39) was cloned and expressed, and its activity against Acinetobacter EPS in solution was determined. The enzyme degraded purified EPS from its host strain A. nosocomialis AU0783, reducing its viscosity, and generated reducing ends in solution, indicative of hydrolase activity. Given that the accessibility to cells within a biofilm is enhanced by degradation of EPS, phages with depolymerases may have enhanced diagnostic and therapeutic potential against drug-resistant Acinetobacter strains.IMPORTANCE Bacteriophage therapy is being revisited as a treatment for difficult-to-treat infections. This is especially true for Acinetobacter infections, which are notorious for being resistant to antimicrobials. Thus, sufficient data need to be generated with regard to phages with therapeutic potential, if they are to be successfully employed clinically. In this report, we describe the isolation and characterization of phage Petty, a novel lytic podophage, and its depolymerase. To our knowledge, it is the first phage reported to be able to infect both A. baumannii and A. nosocomialis The lytic phage has potential as an alternative therapeutic agent, and the depolymerase could be used for modulating EPS both during infections and in biofilms on medical equipment, as well as for capsular typing. We also highlight the lack of predicted canonical spanins in the phage genome and confirm that, unlike the rounding of lambda lysogens lacking functional spanin genes, A. nosocomialis cells infected with phage Petty lyse by bursting. This suggests that phages like Petty employ a different mechanism to disrupt the outer membrane of Acinetobacter hosts during lysis.

Interkingdom signal indole inhibits Pseudomonas aeruginosa persister cell waking.

AIMS: Persister cells are stressed cells that have transient tolerance to antibiotics; these cells undergo no genetic change, but instead, their tolerance is due to reduced metabolism. Unfortunately, little is known about how persisters resuscitate, so we explored the waking of cells in the presence of the interkingdom signal indole. METHODS AND RESULTS: To generate a large population of persister cells, we induced the persister phenotype in the opportunistic pathogen Pseudomonas aeruginosa by pretreating cells with carbonyl cyanide m-chlorophenylhydrazone to reduce translation by depleting ATP levels, and found, via single cell observations, that proline is sufficient to wake the persister cells. P. aeruginosa is often present in the gastrointestinal tract, and indole from commensal bacteria such as Escherichia coli has been shown to inhibit P. aeruginosa quorum sensing and pathogenicity without influencing growth. Furthermore, indole is not toxic to P. aeruginosa persister cells. However, we find here that physiological concentrations of indole inhibit P. aeruginosa persister cell resuscitation with an efficiency of higher than 95%. Critically, when contacted with E. coli stationary-phase cultures, the indole produced by E. coli completely inhibits persister cell resuscitation of P. aeruginosa. CONCLUSIONS: Therefore, E. coli has devised a method to outcompete its competitors by preventing their resuscitation with indole. SIGNIFICANCE AND IMPACT OF THE STUDY: This work provides insight into why indole is produced by commensal bacteria.

Toxins of toxin/antitoxin systems are inactivated primarily through promoter mutations.

AIMS: Given the extreme toxicity of some of the toxins of toxin-antitoxin (TA) systems, we were curious how the cell silences toxins, if the antitoxin is inactivated or independent toxins are obtained via horizontal gene transfer. METHODS AND RESULTS: Growth curves of Escherichia coli K12 BW25113 harbouring plasmid pCA24N to produce RalR, MqsR, GhoT or Hha toxins, showed toxin inactivation after 3 h. Sequencing plasmids from these cultures revealed toxin inactivation occurred primarily due to consistent deletions in the promoter. The lack of mutation in the structural genes was corroborated by a bioinformatics analysis of 1000 E. coli genomes which showed both conservation and little variability in the four toxin genes. For those strains that lacked a mutation in the plasmid, single nucleotide polymorphism analysis was performed to identify that chromosomal mutations iraM and mhpR inactivate the toxins GhoT and MqsR/GhoT respectively. CONCLUSION: We find that the RalR (type I), MqsR (type II), GhoT (type V) and Hha (type VII) toxins are inactivated primarily by a mutation that inactivates the toxin promoter or via the chromosomal mutations iraM and mhpR. SIGNIFICANCE AND IMPACT OF THE STUDY: This study demonstrates toxins of TA systems may be inactivated by mutations that primarily affect the toxin gene promoter instead of the toxin structural gene.

Limited phenological and dietary overlap between bee communities in spring flowering crops and herbaceous enhancements.

Wild bee populations have undergone declines in recent years across much of the Western world, and these declines have the potential to limit yield in pollination-dependent crops. Highbush blueberry, Vaccinium corymbosum, and tart cherry, Prunus cerasus, are spring-blooming crops that rely on the movement of pollen by bees and other insects for pollination. Wild bee populations can be increased on farmland by providing floral resources, but whether the addition of these plants translates into increased pollinator density on crop flowers has not been documented in most cropping systems. To determine the importance of providing additional floral resources for wild bee pollinator communities, we selected blueberry fields and tart cherry orchards with and without herbaceous floral enhancements in western Michigan, USA. The bee communities visiting crop flowers, enhancements and control grassy field margins were sampled over a 5-yr period. In addition, the pollen diets of the most abundant wild bee crop pollinators were quantified across Michigan to better understand their foraging niches and to identify potentially important alternative host plants. The presence of floral enhancements did not increase the abundance of wild bees on either blueberry or cherry flowers during bloom. The bee community visiting blueberry was evenly composed of short-season bees that fly only during the spring and long-season bees that fly in both spring and summer. In contrast, the bee community visiting cherry was dominated by short-season spring bees. The majority of pollen collected by the wild bee communities visiting blueberry and cherry was from spring-flowering woody plants, with limited use of the herbaceous enhancements. Enhancements attracted greater abundance and species richness of bees compared to control areas, including twice as many floral specialists. Conserving summer-flying, grassland-associated bees is an appropriate goal for pollinator conservation programs. However, herbaceous enhancements may not provide adequate resources for the wild bees that pollinate spring-flowering crops. This study demonstrates that an examination of the pollen collected by wild bees across their flight periods can identify plant species to help them persist in intensively managed landscapes.

Interactive effects of age and respiratory virus on severe lower respiratory infection.

We investigated risk factors for severe acute lower respiratory infections (ALRI) among hospitalised children 8 months were at greater risk from influenza-associated ICU admissions and long hospital stay. Children with ADV had increased LOS across all ages. In the first 2 years of life, the effects of different viruses on ALRI severity varies with age. Our findings help to identify specific ages that would most benefit from virus-specific interventions such as vaccines and antivirals.

Experiences of adolescent lung transplant recipients: A qualitative study.

Many young transplant recipients experience psychological distress and adjustment difficulties, yet there is little research investigating lung transplantation from the recipients' perspective. This qualitative study aimed to explore experiences of young people who underwent lung transplantation. Semi-structured interviews were conducted with six lung transplant recipients (aged 15-18). Interviews were analysed using IPA, a qualitative research approach examining how people make sense of their major life experiences. The analysis revealed three master themes: "Living with Dodgy Lungs" outlined how participants dealt with their experiences, managing through accepting or discussing their feelings with others, although talking was often difficult. "The Big Deal" reflected participants' experiences of the process, their expectations, and the contrast of their lives pre- and post-transplant. Inherent in their accounts was the profound meaning ascribed to transplantation, the emotional turmoil, and impact on their lives. "A Sense of Self" illustrated participants' developing identities within their social contexts and at times isolating experiences. The results highlight key areas where adolescent lung transplant recipients could be supported by clinicians, enabling the promotion of psychological well-being. Examples include supporting identity integration post-transplant, facilitating social inclusion, considering alternative means of support, and involving adolescents in healthcare decisions.

CA19-9 decrease at 8 weeks as a predictor of overall survival in a randomized phase III trial (MPACT) of weekly nab-paclitaxel plus gemcitabine versus gemcitabine alone in patients with metastatic pancreatic cancer.

BACKGROUND: A phase I/II study and subsequent phase III study (MPACT) reported significant correlations between CA19-9 decreases and prolonged overall survival (OS) with nab-paclitaxel plus gemcitabine (nab-P + Gem) treatment for metastatic pancreatic cancer (MPC). CA19-9 changes at week 8 and potential associations with efficacy were investigated as part of an exploratory analysis in the MPACT trial. PATIENTS AND METHODS: Untreated patients with MPC (N = 861) received nab-P + Gem or Gem alone. CA19-9 was evaluated at baseline and every 8 weeks. RESULTS: Patients with baseline and week-8 CA19-9 measurements were analyzed (nab-P + Gem: 252; Gem: 202). In an analysis pooling the treatments, patients with any CA19-9 decline (80%) versus those without (20%) had improved OS (median 11.1 versus 8.0 months; P = 0.005). In the nab-P + Gem arm, patients with (n = 206) versus without (n = 46) any CA19-9 decrease at week 8 had a confirmed overall response rate (ORR) of 40% versus 13%, and a median OS of 13.2 versus 8.3 months (P = 0.001), respectively. In the Gem-alone arm, patients with (n = 159) versus without (n = 43) CA19-9 decrease at week 8 had a confirmed ORR of 15% versus 5%, and a median OS of 9.4 versus 7.1 months (P = 0.404), respectively. In the nab-P + Gem and Gem-alone arms, by week 8, 16% (40/252) and 6% (13/202) of patients, respectively, had an unconfirmed radiologic response (median OS 13.7 and 14.7 months, respectively), and 79% and 84% of patients, respectively, had stable disease (SD) (median OS 11.1 and 9 months, respectively). Patients with SD and any CA19-9 decrease (158/199 and 133/170) had a median OS of 13.2 and 9.4 months, respectively. CONCLUSION: This analysis demonstrated that, in patients with MPC, any CA19-9 decrease at week 8 can be an early marker for chemotherapy efficacy, including in those patients with SD. CA19-9 decrease identified more patients with survival benefit than radiologic response by week 8.

Variations in Neisseria meningitidis carriage by socioeconomic status: a cross-sectional study.

BACKGROUND: Deprivation is associated with an increased risk of invasive Neisseria meningitidis disease, but little is known about the relationship between deprivation and asymptomatic carriage of N. meningitidis. This analysis was conducted to examine the relationship between meningococcal carriage and deprivation. METHODS: As part of a rapid meningococcal carriage prevalence study conducted in West Cumbria to investigate an apparent cluster of invasive meningococcal disease, data were collected on lifestyle and social factors, including area-level indicators of socioeconomic status, to identify factors associated with meningococcal carriage. RESULTS: In a multivariable log binomial regression model adjusted for age, lower socioeconomic status was significantly associated with higher prevalence of meningococcal carriage. A 1-unit increase in Index of Multiple Deprivation (2010) score was associated with a 1.7% increase in meningococcal carriage prevalence (95% confidence interval 0.3-3.0%). Age was the only significant predictor of carriage of Neisseria lactamica. CONCLUSIONS: Living in a deprived area is associated with increased carriage of Group B meningococcus. Deprivation is an important factor to consider in the evaluation of the effectiveness and cost-effectiveness of the introduction of new meningococcal B vaccines and the development and implementation of immunization policies. Further work is required to understand whether deprivation has an effect on meningococcal carriage through other factors such as smoking.

Three dimensional simulation of the magnetic stress in a neutron star crust.

We present the first fully self-consistent three dimensional model of a neutron star's magnetic field, generated by electric currents in the star's crust via the Hall effect. We find that the global-scale field converges to a dipolar Hall-attractor state, as seen in recent axisymmetric models, but that small-scale features in the magnetic field survive even on much longer time scales. These small-scale features propagate toward the dipole equator, where the crustal electric currents organize themselves into a strong equatorial jet. By calculating the distribution of magnetic stresses in the crust, we predict that neutron stars with fields stronger than 10^{14} G can still be subject to starquakes more than 10^{5} yr after their formation.

A comparison of techniques for assessing farmland bumblebee populations.

Agri-environment schemes have been implemented across the European Union in order to reverse declines in farmland biodiversity. To assess the impact of these schemes for bumblebees, accurate measures of their populations are required. Here, we compared bumblebee population estimates on 16 farms using three commonly used techniques: standardised line transects, coloured pan traps and molecular estimates of nest abundance. There was no significant correlation between the estimates obtained by the three techniques, suggesting that each technique captured a different aspect of local bumblebee population size and distribution in the landscape. Bumblebee abundance as observed on the transects was positively influenced by the number of flowers present on the transect. The number of bumblebees caught in pan traps was positively influenced by the density of flowers surrounding the trapping location and negatively influenced by wider landscape heterogeneity. Molecular estimates of the number of nests of Bombus terrestris and B. hortorum were positively associated with the proportion of the landscape covered in oilseed rape and field beans. Both direct survey techniques are strongly affected by floral abundance immediately around the survey site, potentially leading to misleading results if attempting to infer overall abundance in an area or on a farm. In contrast, whilst the molecular method suffers from an inability to detect sister pairs at low sample sizes, it appears to be unaffected by the abundance of forage and thus is the preferred survey technique.

Validation of a technique for estimating organ doses for kilovoltage cone-beam CT of the prostate using the PCXMC 2.0 patient dose calculator.

The use of cone beam CT in common radiotherapy treatments is increasing with the growth of image guided radiotherapy. Whilst the benefits that this technology offers are clear, such as improved patient positioning prior to treatment, it is always important to consider the implications of such intensive imaging regimes on the patient, especially when considering the fundamental radiation protection requirements for justification and optimisation.The purpose of this study was to develop a technique that uses readily available dose calculation software (PCXMC 2.0) to estimate the organ and effective doses that result from these types of examination in prostate treatments on the Varian OBI system. It has been shown that by separating these types of examinations into 28 different projections, with a range of x-ray beam qualities, it is possible to reproduce the complex geometry that is used on these imaging systems in PCXMC i.e. asymmetric radiation field with a half bowtie filter rotating 360° around the patient.This new technique has been validated with thermo-luminescent dosimeter measurements in the Rando anthropomorphic phantom, and has been shown to give excellent agreement with this established method (R(2) = 0.995). This technique will prove to be valuable to radiotherapy departments that are looking to optimise their CBCT imaging protocols as it allows a rapid evaluation of the impact of any changes on patient dose. It also serves to further highlight the levels of dose that these types of patient are subject to when having daily CBCT scans as part of the treatment, which further reinforces the need for optimisation of both patient dose and image quality on these systems.

A practical method to standardise and optimise the Philips DoseRight 2.0 CT automatic exposure control system.

Given the increasing use of computed tomography (CT) in the UK over the last 30 years, it is essential to ensure that all imaging protocols are optimised to keep radiation doses as low as reasonably practicable, consistent with the intended clinical task. However, the complexity of modern CT equipment can make this task difficult to achieve in practice. Recent results of local patient dose audits have shown discrepancies between two Philips CT scanners that use the DoseRight 2.0 automatic exposure control (AEC) system in the 'automatic' mode of operation. The use of this system can result in drifting dose and image quality performance over time as it is designed to evolve based on operator technique. The purpose of this study was to develop a practical technique for configuring examination protocols on four CT scanners that use the DoseRight 2.0 AEC system in the 'manual' mode of operation. This method used a uniform phantom to generate reference images which form the basis for how the AEC system calculates exposure factors for any given patient. The results of this study have demonstrated excellent agreement in the configuration of the CT scanners in terms of average patient dose and image quality when using this technique. This work highlights the importance of CT protocol harmonisation in a modern Radiology department to ensure both consistent image quality and radiation dose. Following this study, the average radiation dose for a range of CT examinations has been reduced without any negative impact on clinical image quality.

New Asian Andrena species, with notes on the subgenus Cnemidandrena (Hymenoptera: Andrenidae).

Asia is the worlds largest continent and comprises most of the Holarctic biogeographic region. The genus Andrena is principally distributed through the Holarctic, but it remains understudied in Asia. The subgenus Cnemidandrena Hedicke, 1933 is distributed across Asia with some species reaching south to the Tibetan Plateau. However, some southern members display an unusual morphology, including A. (Cnemidandrena) kishidai chagyabensis Wu, 1982 (newly recorded for Bhutan, India, and Nepal) and A. (Cnemidandrena) granulitergorum Tadauchi & Xu, 2002 (newly recorded for Nepal). The male of A. granulitergorum is described for the first time, A. (Cnemidandrena) rufina Morawitz, 1876 is reported from Kyrgyzstan, Afghanistan, and Kashmir for the first time, and possible senior synonyms for Asian A. (Cnemidandrena) are suggested. To contribute to an improved understanding of localised Asian Andrena diversity, the following new species are described: A. (Cnemidandrena) textrix sp. nov. from China, A. (incertae sedis) liebigi sp. nov. and A. (Troandrena) monfaredi sp. nov. from Iran, and A. (incertae sedis) quercorum sp. nov. from Turkey. These results further confirm that additional taxonomic work is needed to harmonise Andrena species concepts across the different biogeographic regions of Asia.

Review of clinical presentation and diagnosis of mucopolysaccharidosis IVA.

Mucopolysaccharidosis type IVA (MPS IVA) was described in 1929 by Luis Morquio from Uruguay and James Brailsford from England, and was later found as an autosomal recessive lysosomal storage disease. MPS IVA is caused by mutations in the gene encoding the enzyme, N-acetylgalactosamine-6-sulfate sulfatase (GALNS). Reduced GALNS activity results in impaired catabolism of two glycosaminoglycans (GAGs), chondroitin-6-sulfate (C6S) and keratan sulfate (KS). Clinical presentations of MPS IVA reflect a spectrum of progression from a severe "classical" phenotype to a mild "attenuated" phenotype. More than 180 different mutations have been identified in the GALNS gene, which likely explains the phenotypic heterogeneity of the disorder. Accumulation of C6S and KS manifests predominantly as short stature and skeletal dysplasia (dysostosis multiplex), including atlantoaxial instability and cervical cord compression. However, abnormalities in the visual, auditory, cardiovascular, and respiratory systems can also affect individuals with MPS IVA. Diagnosis is typically based on clinical examination, skeletal radiographs, urinary GAG, and enzymatic activity of GALNS in blood cells or fibroblasts. Deficiency of GALNS activity is a common assessment for the laboratory diagnosis of MPS IVA; however, with recently increased availability, gene sequencing for MPS IVA is often used to confirm enzyme results. As multiple clinical presentations are observed, diagnosis of MPS IVA may require multi-system considerations. This review provides a history of defining MPS IVA and how the understanding of the disease manifestations has changed over time. A summary of the accumulated knowledge is presented, including information from the International Morquio Registry. The classical phenotype is contrasted with attenuated cases, which are now being recognized and diagnosed more frequently. Laboratory based diagnoses of MPS IVA are also discussed.

The genetic basis of speciation in the Giliopsis lineage of Ipomopsis (Polemoniaceae).

One of the most powerful drivers of speciation in plants is pollinator-mediated disruptive selection, which leads to the divergence of floral traits adapted to the morphology and behavior of different pollinators. Despite the widespread importance of this speciation mechanism, its genetic basis has been explored in only a few groups. Here, we characterize the genetic basis of pollinator-mediated divergence of two species in genus Ipomopsis, I. guttata and I. tenuifolia, using quantitative trait locus (QTL) analyses of floral traits and other variable phenotypes. We detected one to six QTLs per trait, with each QTL generally explaining small to modest amounts of the phenotypic variance of a backcross hybrid population. In contrast, flowering time and anthocyanin abundance (a metric of color variation) were controlled by a few QTLs of relatively large effect. QTLs were strongly clustered within linkage groups, with 26 of 37 QTLs localized to six marker-interval 'hotspots,' all of which harbored pleiotropic QTLs. In contrast to other studies that have examined the genetic basis of pollinator shifts, our results indicate that, in general, mutations of small to modest effect on phenotype were involved. Thus, the evolutionary transition between the distinct pollination modes of I. guttata and I. tenuifolia likely proceeded incrementally, rather than saltationally.

Elevated rates of dietary generalization in eusocial lineages of the secondarily herbivorous bees.

BACKGROUND: Within the Hymenoptera, bees are notable for their relationship with flowering plants, being almost entirely dependent on plant pollen and nectar. Though functionally herbivorous, as a result of their role as pollinators, bees have received comparatively little attention as models for insect herbivory. Bees often display dietary specialization, but quantitative comparison against other herbivorous insects has not previously been conducted. RESULTS: In the most comprehensive analysis to date for 860 bee species, dietary specialization amounted to 50.1% of studied species collecting pollen from between 1 and 2 botanical families with a relatively long tail of dietary generalists, with 11.1% of species collecting from more than 10 botanical families. This distribution deviated from the truncated Pareto distribution of dietary breadth seen in other herbivorous insect lineages. However, this deviation was predominantly due to eusocial bee lineages, which show a range of dietary breadths that conformed to a normal distribution, while solitary bees show a typical truncated distribution not strongly different from other herbivorous insects. We hypothesize that the relatively low level of dietary specialization in bees as a whole reflects the relaxation of the constraints typically observed in herbivorous insects with a comparatively reduced importance of plant chemistry and comparatively increased importance of phenology and foraging efficiency. The long flight periods of eusocial bees that are necessary to allow overlapping generations both allows and necessitates the use of multiple flowering resources, whereas solitary bees with short flight periods have more limited access to varied resources within a constrained activity period. CONCLUSIONS: Collectively, solitary bees show slightly lower specialization compared to other herbivorous insects, possibly due to their balanced relationship with plants, rather than direct antagonism such as seen in the direct consumption of plant tissues. An additional factor may be the mediocre diversity of bees at low latitudes combined with low levels of dietary specialization, whereas these areas typically display a high rate of specialization by herbivorous insects in general. Though the most important factors structuring dietary specialization in bees appear to differ from many other herbivorous insects, solitary bees show a surprisingly similar overall pattern of dietary specialization.