Strong Barriers Research Articles

Causes and Consequences of Bacteriophage Diversification via Genetic Exchanges across Lifestyles and Bacterial Taxa.

Bacteriophages (phages) evolve rapidly by acquiring genes from other phages. This results in mosaic genomes. Here, we identify numerous genetic transfers between distantly related phages and aim at understanding their frequency, consequences, and the conditions favoring them. Gene flow tends to occur between phages that are enriched for recombinases, transposases, and nonhomologous end joining, suggesting that both homologous and illegitimate recombination contribute to gene flow. Phage family and host phyla are strong barriers to gene exchange, but phage lifestyle is not. Even if we observe four times more recent transfers between temperate phages than between other pairs, there is extensive gene flow between temperate and virulent phages, and between the latter. These predominantly involve virulent phages with large genomes previously classed as low gene flux, and lead to the preferential transfer of genes encoding functions involved in cell energetics, nucleotide metabolism, DNA packaging and injection, and virion assembly. Such exchanges may contribute to the observed twice larger genomes of virulent phages. We used genetic transfers, which occur upon coinfection of a host, to compare phage host range. We found that virulent phages have broader host ranges and can mediate genetic exchanges between narrow host range temperate phages infecting distant bacterial hosts, thus contributing to gene flow between virulent phages, as well as between temperate phages. This gene flow drastically expands the gene repertoires available for phage and bacterial evolution, including the transfer of functional innovations across taxa.

Corridors as a tool for linking habitats – Shortcomings and perspectives for plant conservation

Habitat fragmentation and isolation are considered important causes of biodiversity loss in cultural landscapes. To counter the negative effects of fragmentation such as reduced connectivity and increased risks of population extinction due to stochastic processes and genetic erosion, it has been proposed to establish linear ecological corridors to facilitate dispersal between isolated habitat patches. We summarise the current knowledge on the potential benefits and limitations of corridors for reducing the negative effects of habitat fragmentation on plant populations. We address the opportunities and problems that are associated with linear corridors and advocate the use of semi-open corridors as an alternative that might overcome some shortcomings of conventional corridors for plants. Observational and experimental studies have found that various types of linear corridors can increase plant dispersal. Other linear structures such as paths, roads, railways and streams may also function to a certain extent as corridors, although mostly for widespread species. Because plants are highly dependent on external agents such as animals or wind to reach new habitats, the effectivity of corridors is strongly influenced by their structural features and suitability for animal dispersers. However, many plant species can only use corridors for long-distance dispersal if they can also use them as stepping stone habitats where they can establish, grow, reproduce and then disperse further. This dispersal critically depends on suitable light conditions and disturbance regimes, and on a sufficient width of a corridor to reduce edge effects. Thus, hedgerows appear to be suitable corridors for some forest species but are too narrow for forest specialists from the interior of woodlands. Corridors do not only have positive effects but may also facilitate the spread of invasive species. Moreover, a potentially underestimated negative effect of linear corridors is that they may actually create new dispersal barriers when they intersect other habitats. For example, linear woodland corridors that intersect grasslands may successfully connect patches of woodland but simultaneously form strong barriers for grassland species and increase the fragmentation of their populations. As an alternative to linear corridors, we recommend “semi-open corridors” that simultaneously connect patches of both open habitats and woodlands and promote the dispersal of species of both types of habitat. This idea is based on the various types of semi-open landscapes in Europe that have been formed by grazing with livestock, resulting in a mosaic of open habitats, groups of trees or shrubs and small woodland patches, and are characterised by a high diversity of environmental conditions on a small scale. Wide corridors of such semi-open habitats may avoid the strong edge and barrier effects associated with linear corridors and provide suitable stepping stone habitats for species with different habitat requirements.

Uncovering endemism in a lake of invasive species introgression.

Species distributions are rapidly being altered by human globalisation and movement. As species are moved across biogeographic boundaries, human-mediated secondary contacts between historically allopatric taxa may promote hybridisation between closely related native and introduced species. The outcomes of hybridisation are diverse from strong reproductive barriers to gene flow to genome-wide admixture that may enhance (Fitzpatrick et al., 2010; Mesgaran et al., 2016; Valencia-Montoya et al., 2020) or impede (Kovach et al., 2016) invasive spread. For native species, introgressive hybridisation may disassemble locally adapted genomes, and in extreme cases, extensive asymmetric introgression may lead to the 'genomic extinction' of endemic diversity (Rhymer & Simberloff, 1996; Todesco et al., 2016). Undoubtedly, introgressive hybridisation can rapidly alter the evolution of introduced and endemic populations. This is a major conservation issue (Leitwein, Duranton, Rougemont, Gagnaire, & Bernatchez, 2020), with the greatest potential consequences on small, range-restricted native populations where introduced species may reach higher relative densities (Currat, Ruedi, Petit, & Excoffier, 2008). In this issue of Molecular Ecology, Blackwell et al. (2020) explore the history of divergence and admixture between the highly invasive Nile tilapia, Oreochromis niloticus, and a recently discovered Oreochromis lineage that is endemic to the coastal lakes of southern Tanzania. Oreochromis tilapias belong to the African cichlids and the most diverse family of vertebrates (Cichlidae), with almost 2000 species inhabiting the Great Lakes and river environments of Eastern Africa (Kocher, 2004; McGee et al., 2020). By analysing previously unrecognised cichlid diversity from southern lakes, Blackwell et al. (2020) provide novel evidence for how introgressive hybridisation with introduced species can alter native genetic makeup, illustrating the potential susceptibility of Tanzania's endemic biodiversity to genetic threats from introduced taxa.

Mediating role diet self-efficacy plays in the relationship between social support and diet self-management for patients with type 2 diabetes

BackgroundIt has previously been established that patients who have strong barriers to their diet self-management are more likely to have weak social support; however, the key mechanisms underlying the association between these two variables have not yet been established. This study aims to examine the potential role that diet self-efficacy plays in the relationship between social support and diet behavior in patients with type 2 diabetes mellitus (T2DM).MethodsIt was a cross-sectional survey. Three hundred-eighty patients diagnosed with T2DM were recruited for this study from five community health centers in China. The Chronic Disease Resource Scale (CIRS), Cardiac Diet Self-efficacy Scale (CDSE), and Food Control Behavior Scale (FCBS) were used to estimate participants’ utilization of social resources, diet self-efficacy, and diet self-management, respectively. The data were analyzed utilizing structural equation modelling.ResultsThe results suggest that both higher levels of social support and diet self-efficacy are related to higher levels of diet self-management. The mediating effect that diet self-efficacy has on the relationship between social support and diet self-management was significant (β = .30, p < .05), explaining 55.68% of the total effect of social support on diet self-management.ConclusionsDiet self-efficacy plays a mediating role in the association between social support and diet behavior in patients with type 2 diabetes mellitus.

First-principle study of Ti2XS2 (X = C/N) MXenes as high capacity anodes for rechargeable potassium-ion batteries

Potassium-ion batteries (KIBs) are potential substitutions of lithium-ion batteries, considering the superiority of K in abundance and safety compared with lithium. Recently, the MXenes emerged as a significant class of two-dimensional materials in energy storage applications. Herein we investigated the performances of two S-functionalized MXenes (S-MXenes), Ti2CS2 and Ti2NS2, as anodes for KIBs through first-principle calculations. The results show that both S-MXenes possess metallic nature and structural integrity. Besides, the two functionalized structures exhibit strong adsorptions and low diffusion energy barriers, suggesting fast charge–discharge rates. By reaching the ultimate structural configurations, the theoretical capacities are as high as 312 mAh/g with low but positive open circuit voltage. All the performances reveal that the S-MXenes are promising anode materials for KIBs and expand their application as electrode materials.

Reconfigurable Manufacturing Development: Insights on Strategic, Tactical, and Operational Challenges

The paper provides empirical insight on how changeable and reconfigurable manufacturing system concepts can be developed to meet requirements in manufacturing companies, as well as the related organizational and technical challenges. The findings reveal that there are still strong barriers towards the wider implementation of reconfigurability and that a paradigm shift in industry is required, e.g., in terms of managing stepwise investments, organizational culture and mindset, approaches to production development, organizational structures, and knowledge on changeability and reconfigurability.

Barriers to Accurate Fluid Measurement in Perioperative Patients: A Mixed Methods Approach

BackgroundSurgeons depend on fluid intake and output (I/O) measurements for assessment of resuscitation and fluid balance during the perioperative period. Frequently, these measurements are taken by Registered Nurses (RNs) and/or Patient Care Technicians (PCTs). There is variability in the accuracy and consistency of these measurements across nursing units. The goal of this study is to establish what barriers exist in obtaining accurate fluid measurements and potential solutions. Materials and methodsA mixed-method, sequential study design was utilized. First, a survey was conducted at a tertiary care institution of 8 nonintensive care nursing units assessing the perceptions of RNs (n = 85) and PCTs (n = 38) regarding fluid intake and output measurements for surgical patients. Four focus groups were then conducted to expand upon the results of the survey. Fourteen participants (10 RNs and 4 PCTs) were interviewed, and transcripts were analyzed by three reviewers. Qualitative data were manually coded by reviewers using a hierarchical methodology. ResultsSurvey response rate was 40.6%. The strongest barriers in the survey were patient load and staff time limitations. About half (49%) of the respondents acknowledged that fluid measurements were inaccurate half of the time. PCTs spend more time collecting and charting I/Os and have higher patient loads (P < 0.001) than RNs. PCTs noted more difficulty with complex patients (P = 0.017) and devices for outputs (P = 0.004). PCT’s (94%) handwrite data prior to electronic entry. One-third of nurses reported direct electronic entry (P < 0.001). Overall, 71% would prefer to chart in patient’s rooms. Most (80%) of respondents received <5 h of fluids-related training at the time they were hired.Cronbach’s alpha for three focus group reviewers was 0.84 (95% CI 0.693-0.923). Themes included understaffing, lack of training, a high percentage of traveling nurses, and poor communication regarding new orders. Recommended solutions to improve I/Os included in-room kiosks for electronic entry and relief of staffing burdens. ConclusionsFluid I/O measurement accuracy and efficiency may be improved by increased staffing, educational programs, and computer access, streamlining of order sets, simplicity of EMR data entry, and a standardized process for measuring, recording, and charting I/Os.

No impact of previous evidence advocating openness to talk to children about their imminent death.

Communication is as important as the drug and the knife in medical care, particularly when patients are facing life-threatening conditions. However, the ability to communicate effectively has been commonly associated with strong emotional barriers among healthcare professionals and family members. Studies that have focused on paediatric oncology have showed that openness about the transition from curative to palliative care is frequently avoided (1,2). As long ago as the 1980s a paper in this journal reported that children often wanted to share their thoughts and feelings at the end of life, but that adults often failed to recognise that need (3).

Epistemological Profile of Chemical Bonding: Evaluation of Knowledge Construction in High School

This work aims to evaluate the evolution of chemical bonding concepts of high school students at public schools in southern Brazil. For this, we built the epistemological profile of each student who took part in a teaching-learning sequence (TLS) about this topic, based on the foundations of Bachelard’s theory. Following the principles of the qualitative survey, we applied questionnaires to monitor the students’ ideas. The results revealed that the construction of knowledge took place by overcoming epistemological obstacles linked to the realist and empiricist philosophical zones. Most students (55.2%) presented a mostly rationalist profile at the end of the research, but misconceptions already found in the literature constitute strong barriers to the construction of knowledge, among which the nature of chemical bonds and chemical stability stand out.

High site fidelity does not equate to population genetic structure for common goldeneye and Barrow's goldeneye in North America

Delineation of population structure provides valuable information for conservation and management of species, as levels of demographic and genetic connectivity not only affect population dynamics but also have important implications for adaptability and resiliency of populations and species. Here, we measure population genetic structure and connectivity across the ranges of two sister species of sea ducks: Barrow's goldeneye Bucephala islandica and common goldeneye B. clangula. We use two different marker types: 7–8 nuclear microsatellite loci assayed across 229 samples and 3678 double digest restriction‐site associated DNA sequencing (ddRAD‐seq) loci assayed across 61 samples. First, both datasets found no evidence of genetic structure within common or Barrow's goldeneye, including between North American and European samples of common goldeneye. These results are in contrast with previous mitochondrial DNA, band recovery and telemetry data which suggest that goldeneyes are structured across their range. We posit that the discordance between autosomal genetic markers and other data types suggests that males, possibly subadult males, may be maintaining genetic connectivity across each species' respective ranges. Next, although mate choice consequences resulting from inter‐specific brood parasitism was hypothesized to cause some level of gene flow between goldeneye species, we only identified a single F1 hybrid with no further evidence of contemporary or historical gene flow. Despite ddRAD‐seq demographic analyses which recovered an optimum evolutionary model of split‐with‐migration (i.e. secondary contact), estimates of gene flow were &lt;&lt;1 migrant per generation in both directions. Together, we conclude that either strong ecological barriers or assortative mating are likely playing a role in preventing further backcrossing. Finally, demographic analyses estimated a relatively deep divergence time between Barrow's goldeneye and common goldeneye of ~1.6 million years before present and suggests that the genomes of both species have been under similar evolutionary constraints.

Do border walls work?: security, insecurity and everyday economy in the Turkish-Syrian borderlands

ABSTRACT Border walls are often seen as preferable options to improve security by providing strong barriers against the movement of people. Although these barriers are never absolute and remain porous, they are still appealing, which raises the question about who benefits when border walls are introduced. This article questions whether and for whom border walls work by focusing on the new Turkish-Syrian border wall in Hatay. Through an ethnographic investigation of border politics and the effects of increasing surveillance on residents of the border, it examines the socio-economic and political impact of the wall on local life. Second, it shows how the wall has led to a significant increase in migrant smuggling, which indicates improvements in security in one policy area may lead to a worsening situation in others. It concludes that the wall reinforces the state’s claim of sovereignty but fails to be an effective security measure for border residents or refugees.

Genetic variation of a widespread subdominant tree species (Acer campestre L.) in Bosnia and Herzegovina

Tree species of minor commercial importance are mostly neglected both in large-scale genetic surveys and gene conservation programs. Gene conservation measures of forest trees focus on the preservation of intra-species genetic variability, which is a prerequisite of species’ adaptive evolutionary potential enabling it to survive unfavourable conditions. Therefore, variation levels within populations as well as inter-population differentiation patterns need to be assessed under various geographical and evolutionary setups. We studied genetic variation of a widespread, but subdominant tree species, Acer campestre L., in 25 populations located close to the rear edge of the Holocene colonisation in Bosnia and Herzegovina at ten nuclear microsatellite loci. Genetic differentiation within this region was very weak, indicating a lack of strong barriers to gene flow despite range fragmentation. In spite of this, significant isolation by distance was revealed, along with isolation by environment related to temperature. We suggest phenological isolation as the explanation of isolation by environment. Moreover, the group of sub-Mediterranean populations appeared to diverge from the interior populations: they exhibit higher gene diversity, form a separate cluster in the neighbour-joining tree based on chord genetic distances, and show different proportions of gene pools identified by the Bayesian analysis of population structure. As the territory under study is located close to several important glacial refugia for tree species, an origin from different refugial populations may explain the pattern of weak but recognisable genetic differentiation between interior and sub-Mediterranean populations. A genetic bottleneck in several sub-Mediterranean populations was attributed to more recent colonisation events. The results suggest that genetic differentiation associated with the origin from different glacial refugia was not erased by gene flow even in rear-edge populations, and needs to be taken into consideration in gene conservation programs.

Pif1, RPA, and FEN1 modulate the ability of DNA polymerase δ to overcome protein barriers during DNA synthesis

Successful DNA replication requires carefully regulated mechanisms to overcome numerous obstacles that naturally occur throughout chromosomal DNA. Scattered across the genome are tightly bound proteins, such as transcription factors and nucleosomes, that are necessary for cell function, but that also have the potential to impede timely DNA replication. Using biochemically reconstituted systems, we show that two transcription factors, yeast Reb1 and Tbf1, and a tightly positioned nucleosome, are strong blocks to the strand displacement DNA synthesis activity of DNA polymerase δ. Although the block imparted by Tbf1 can be overcome by the DNA-binding activity of the single-stranded DNA-binding protein RPA, efficient DNA replication through either a Reb1 or a nucleosome block occurs only in the presence of the 5'-3' DNA helicase Pif1. The Pif1-dependent stimulation of DNA synthesis across strong protein barriers may be beneficial during break-induced replication where barriers are expected to pose a problem to efficient DNA bubble migration. However, in the context of lagging strand DNA synthesis, the efficient disruption of a nucleosome barrier by Pif1 could lead to the futile re-replication of newly synthetized DNA. In the presence of FEN1 endonuclease, the major driver of nick translation during lagging strand replication, Pif1-dependent stimulation of DNA synthesis through a nucleosome or Reb1 barrier is prevented. By cleaving the short 5' tails generated during strand displacement, FEN1 eliminates the entry point for Pif1. We propose that this activity would protect the cell from potential DNA re-replication caused by unwarranted Pif1 interference during lagging strand replication.

Evolution of multiple postzygotic barriers between species of the Mimulus tilingii complex.

Species are often defined by their ability to interbreed (i.e., Biological Species Concept), but determining how and why reproductive isolation arises between new species can be challenging. In the Mimulus tilingii species complex, three species (M. caespitosa, M. minor, and M. tilingii) are largely allopatric and grow exclusively at high elevations (>2000m). The extent to which geographic separation has shaped patterns of divergence among the species is not well understood. In this study, we determined that the three species are morphologically and genetically distinct, yet recently diverged. Additionally, we performed reciprocal crosses within and between the species and identified several strong postzygotic reproductive barriers, including hybrid seed inviability, F1 hybrid necrosis, and F1 hybrid male and female sterility. In this study, such postzygotic barriers are so strong that a cross between any species pair in the M. tilingii complex would cause nearly complete reproductive isolation. We consider how geographical and topographical patterns may have facilitated the evolution of several postzygotic barriers and contributed to speciation of closely related members within the M. tilingii species complex.

Single- and multi-layer arsenene as an anode material for Li, Na, and K-ion battery applications

Revealing ideal electrode materials with required functionalities is a crucial step to develop high-performance alkali-ion batteries. In this study, we investigate the potential of single- (SL) and multi-layer (ML) arsenene phases (buckled and symmetric washboard) to be used as an anode material by means of abinitio calculations. The interaction of alkali metal atoms (M: Li, Na, and K) with arsenene is examined to reveal strong adatom-electrode binding and low diffusion barriers. Provided that the initial crystalline patterns are maintained, the possible M orderings (MxAs) are investigated for varying ion concentrations (x). The structural deformations and the decrease in formation energy with increasing x indicate probable structural transformations. The abinitio molecular dynamics simulations confirm that the ordered patterns are prone to instability and crystalline to amorphous transition is induced at ambient temperature. The calculated (average) open-circuit voltages are between 0.65–0.98 V with the specific capacity range of 358–715 mAhg−1 for SL- and ML-MxAs. Strong metal-electrode interaction, fast diffusion, and desired voltage range suggest arsenene as a promising anode material for alkali-ion batteries to be utilized in low charging voltage applications.

Spatial Energy Planning: A Review

Despite the fact that some renewable energy (RE) technologies are already techno-economically viable, the high spatial dilution nature of their sources, together with aspects beyond the techno-economic ones (such as environmental, social, cultural, and other aspects), can become strong constraints and barriers when it comes to their integration into electric systems. Therefore, with the objective of determining whether studies on spatial energy planning (SEP) are addressing these issues, a systematic review has been carried out to address whether SEP studies are considering aspects beyond the techno-economic ones when integrating RE technologies and, if they are being considered, how they are addressed in their analyses and what criteria, factors, and indicators of the aspects that are employed. Apart from the revelation that the concept of SEP has been included within high-quality scientific literature for less than ten years, SEP seems to be an unexploited tool with the potential to provide significant insight into a planning process that could prevent conflicts when integrating RE technologies into electric systems. This would be useful for decision-makers and for accelerating a sustainable energy transition.

Family medicine physicians' report strong support, barriers and preferences for Registered Dietitian Nutritionist care in the primary care setting.

Previous studies have examined barriers (e.g. time) for Family Medicine Providers (FMPs) to provide nutrition and lifestyle counseling, however, to date no studies have examined access or interest to Registered Dietitian Nutritionist (RDN) care for patients. The objective of this study was to explore FMP access, referral practices, barriers and preferences for RDN care. A cross-sectional online survey, with content and face validation was conducted with Family Medicine Departments within large academic health care systems in the Southeastern United States. The main variables of interest included: FMP access, interest, current referrals and referral preferences for RDN care, barriers to referrals and overall perceptions regarding RDN care. Descriptive analysis of close-ended responses was performed with SPSS 26.0. Open-ended responses were analysed using inductive content analysis. Over half of the respondents (n = 151) did not have an RDN on-site (64%) yet were highly interested in integrating an RDN (94.9%), with reported preferences for full-time on-site, part-time on-site or off-site RDN care (49.1%, 39.5% and 11.4% respectively). The greatest reported barriers to RDN referrals were perceived cost for the patient (64.47%) and uncertainty how to find a local RDN (48.6%). The most consistent theme reported in the open-ended responses were concerns regarding reimbursement, e.g. 'Insurance does not cover all of the ways I would like to use an RDN'. FMPs report interest and value in RDN services despite multiple perceived barriers accessing RDNs care. Opportunities exist for interprofessional collaboration between dietetic and FMP professional groups to address barriers.

10 Oral - Chemoprevention for breast cancer: A survey of the views of Australian women and clinicians

Background: Chemoprevention for women at elevated risk of breast cancer is endorsed by international guidelines. This study examined the uptake of chemoprevention by Australian women at increased risk and aimed to identify modifiable barriers and facilitators for both patients and clinicians. Material and Methods: 1,113 participants enrolled in the Kathleen Cuningham Foundation Consortium for Research into Familial Breast Cancer Follow-Up Study (kConFab FUS) and at ≥16% lifetime risk of BC (≥1.5 times the average population risk) were mailed a 68-item survey. 130 currently practising breast surgeons and 394 family doctors (FDs) who reportedly provided care for kConFab-FUS participants were sent a 49-item survey. Surveys were developed based on the theoretical domains framework. Results: 725 participants (65%) and 221 (42%) clinicians responded (147 (37%) FDs, 74 (57%) breast surgeons). The median age of participants was 55 years. Most (84%) were at moderately increased risk (<3 times population risk). Ten women (1.4%) had taken chemoprevention. Possible side effects, lack of information and preferring the adoption of a healthy lifestyle alone were the three strongest barriers. The 20-year reduction in BC risk with tamoxifen was the most important facilitator, followed by desire to stay healthy for their family and having an abnormal breast biopsy. Most patients preferred to get information from a cancer genetics centre (CGC) (38%) followed by their FD (33%). Most surgeons knew about chemoprevention (97%), but 35% of FDs did not; 7% and 74%, respectively, were not confident in providing chemoprevention information. The majority of FDs (75%) and breast surgeons (89%) thought discussing chemoprevention should be part of their role. For FDs the strongest barriers were insufficient knowledge and lack of confidence. For breast surgeons, the strongest barriers were medication side-effects and lack of consultation time. Clear guidelines and strong family history were facilitators for both clinician groups. FDs identified that availability of better tools to select suitable patients would be a strong facilitator. Conclusions: Chemoprevention uptake is low in Australia by international standards. This study identified barriers and facilitators not previously noted in the literature and that could suggest interventions. However, as in other studies, improving both clinician and patient knowledge may be the most important driver of interventions. Upskilling FDs is important as, in Australia, moderate risk women are not generally eligible for CGC consultation (despite their preference for one). Providing FDs and patients with tailored education resources and tools (such as iPrevent- www.petermac.org/iprevent) to improve their confidence and awareness of chemoprevention may reduce the gap between evidence and implementation. Conflict of interest: Other Substantive Relationships: KAP has a patent “System and Process of Cancer Risk Estimation” (Australian Innovation Patent) issued regarding iPrevent.

The feasibility of recruiting and retaining men who have sex with men and transgender women in a multinational prospective HIV prevention research cohort study in sub-Saharan Africa (HPTN 075).

IntroductionMen who have sex with men (MSM) and transgender women (TGW) in sub‐Saharan Africa (SSA) are profoundly affected by HIV with high HIV prevalence and incidence. This population also faces strong social stigma and legal barriers, potentially impeding participation in research. To date, few multi‐country longitudinal HIV research studies with MSM/TGW have been conducted in SSA. Primary objective of the HIV Prevention Trials Network (HPTN) 075 study was to assess feasibility of recruiting and retaining a multinational prospective cohort of MSM/TGW in SSA for HIV prevention research.MethodsHPTN 075, conducted from 2015 to 2017, was designed to enroll 400 MSM/TGW at four sites in SSA (100 per site: Kisumu, Kenya; Blantyre, Malawi; Cape Town, South Africa; and Soweto, South Africa). The number of HIV‐positive persons was capped at 20 per site; HIV‐positive persons already in care were excluded from participation. The one‐year study included five biobehavioural assessments. Community‐based input and risk mitigation protocols were included in study design and conduct.ResultsOf 624 persons screened, 401 were enrolled. One in five participants was classified as transgender. Main reasons for ineligibility included: (a) being HIV positive after the cap was reached (29.6%); (b) not reporting anal intercourse with a man in the preceding three months (20.6%); and (c) being HIV positive and already in care (17.5%). Five (1.2%) participants died during the study (unrelated to study participation). 92.9% of the eligible participants (368/396) completed the final study visit and 86.1% participated in all visits. The main, overlapping reasons for early termination included being (a) unable to adhere to the visit schedule, predominantly because of relocation (46.4%), and (b) unable to contact the participant (32.1%). Participants reported strong motivation to participate and few participation barriers. Four participants reported social harms (loss of confidentiality and sexual harassment by study staff) that were successfully addressed.ConclusionsHPTN 075 successfully enrolled a multinational sample of MSM/TGW in SSA in a prospective HIV prevention research study with a high retention rate and few documented social harms. This supports the feasibility of conducting large‐scale research trials in this population to address its urgent, unmet HIV prevention needs.

Post-pollination barriers enable coexistence of pollinator-sharing ornithophilous Erica species.

Some evolutionary radiations produce a number of closely-related species that continue to coexist. In such plant systems, when pre-pollination barriers are weak, relatively strong post-pollination reproductive barriers are required to maintain species boundaries. Even when post-pollination barriers are in place, however, reproductive interference and pollinator dependence may strengthen selection for pre-pollination barriers. We assessed whether coexistence of species from the unusually speciose Erica genus in the fynbos biome, South Africa, is enabled through pre-pollination or post-pollination barriers. We also tested for reproductive interference and pollinator dependence. We investigated this in natural populations of three bird-pollinated Erica species (Erica plukenetii, E. curviflora and E. coccinea), which form part of a large guild of congeneric species that co-flower and share a single pollinator species (Orange-breasted Sunbird Anthobaphes violacea). At least two of the three pre-pollination barriers assessed (distribution ranges, flowering phenology and flower morphology) were weak in each species pair. Hand-pollination experiments revealed that seed set from heterospecific pollination (average 8%) was significantly lower than seed set from outcross pollination (average 50%), supporting the hypothesis that species boundaries are maintained through post-pollination barriers. Reproductive interference, assessed in one population by applying outcross pollen three hours after applying heterospecific pollen, significantly reduced seed set compared to outcross pollen alone. This may drive selection for traits that enhance pre-pollination barriers, particularly given that two of the three species were self-sterile, and therefore pollinator dependent. This study suggests that post-pollination reproductive barriers could facilitate the coexistence of congeneric species, in a recent radiation with weak pre-pollination reproductive barriers.