Source Population Research Articles

To weight or not to weight? The effect of selection bias in 3 large electronic health record-linked biobanks and recommendations for practice.

To develop recommendations regarding the use of weights to reduce selection bias for commonly performed analyses using electronic health record (EHR)-linked biobank data. We mapped diagnosis (ICD code) data to standardized phecodes from 3 EHR-linked biobanks with varying recruitment strategies: All of Us (AOU; n = 244071), Michigan Genomics Initiative (MGI; n = 81243), and UK Biobank (UKB; n = 401167). Using 2019 National Health Interview Survey data, we constructed selection weights for AOU and MGI to represent the US adult population more. We used weights previously developed for UKB to represent the UKB-eligible population. We conducted 4 common analyses comparing unweighted and weighted results. For AOU and MGI, estimated phecode prevalences decreased after weighting (weighted-unweighted median phecode prevalence ratio [MPR]: 0.82 and 0.61), while UKB estimates increased (MPR: 1.06). Weighting minimally impacted latent phenome dimensionality estimation. Comparing weighted versus unweighted phenome-wide association study for colorectal cancer, the strongest associations remained unaltered, with considerable overlap in significant hits. Weighting affected the estimated log-odds ratio for sex and colorectal cancer to align more closely with national registry-based estimates. Weighting had a limited impact on dimensionality estimation and large-scale hypothesis testing but impacted prevalence and association estimation. When interested in estimating effect size, specific signals from untargeted association analyses should be followed up by weighted analysis. EHR-linked biobanks should report recruitment and selection mechanisms and provide selection weights with defined target populations. Researchers should consider their intended estimands, specify source and target populations, and weight EHR-linked biobank analyses accordingly.

Reinforcements in the face of ongoing threats: a case study from a critically small carnivore population

AbstractReinforcements are a well‐established tool for alleviating small population pressures of inbreeding and genetic diversity loss. Some small populations also suffer from specific threats that pose a discrete selective pressure, like diseases. Uncertainty about reinforcing diseased populations exists, as doing so may increase disease prevalence and disrupt potential adaptive processes. However, without assisted gene flow, isolated populations are at high risk of extinction. Tasmanian devils (Sarcophilus harrisii) are a useful case study to test whether reinforcements can alleviate small‐population pressures where there is an ongoing disease pressure. We investigated demographic, genome‐wide and functional genetic diversity, and disease consequences of reinforcing a small population (<20 animals) that was severely impacted by devil facial tumour disease. Released animals from one source population successfully bred with incumbent individuals, tripling the population size, improving genome‐wide and functional diversity and introducing 26 new putatively functional alleles, with no common alleles lost and no increase in disease prevalence. Results suggest, in the case of Tasmanian devils, reinforcements can alleviate small‐population pressures without increasing disease prevalence. Because no common functional alleles were lost, it is likely that any adaptive processes in response to the disease may still occur in the reinforced population, perhaps even with greater efficiency due to reduced genetic drift (due to larger population size). Our study is presented as a comprehensive worked example of the IUCN's guidelines for monitoring reinforcements, to showcase the value of genetic monitoring in a richly monitored system and provide realistic approaches to test similar questions in other taxa.

Matching field-based ranges in brackish water gradients with experimentally derived salinity tolerances of Conrad’s false mussel (Mytilopsis leucophaeata cochleata) and zebra mussel (Dreissena polymorpha)

The invasive alien false mussels Mytilopsis leucophaeata cochleata and Dreissena polymorpha (Dreissenidae) have established populations in the North Sea canal in the Netherlands that connects the harbours of Amsterdam with the North Sea. The favourable and unfavourable salinity ranges of both species were earlier studied in long-term outdoor mesocosm experiments. Their occurrence in salinity gradients in estuaries or canals connecting seaways to freshwater harbours provides information on their salinity tolerance under field conditions. By the combination of laboratory experiments and field data using the same source population a high predictability can be expected for establishment of the gradients facilitated by constructions. The reliability of experimentally derived salinity-tolerance limits for both dreissenid species was tested using data on their distribution in a salinity gradient of the littoral zone along the North Sea canal. The mussels used for the survival experiments in mesocosms were also collected from this canal. Favourable salinity ranges for adult survival in the mesocosms were 0.2 – 17.5 for M. leucophaeata cochleata and 0.2 – 6.0 for D. polymorpha. Unfavourable salinities were outside these ranges and led to high and fast mortality of these species. Mytilopsis leucophaeata cochleata was present over nearly the whole length of the North Sea canal with the highest densities close to the sea sluices where also the highest salinities and water temperatures were measured. Their densities in the canal decreased gradually at larger distances from the sea. Dreissena polymorpha co-exists with M. leucophaeata cochleata at the east end of the canal with low salinity due to the influence of freshwater of the river Rhine. The occurrence of D. polymorpha was restricted to a salinity below 4 and M. leucophaeata cochleata only occurred at a salinity above 1.5 (maximum value measured in the canal 9.2). Shorter salinity gradients with lower salinity ranges provided additional information on the co-existence of both species. Co-existence was observed at a salinity range of 1.5–3.3 (own data), 1.0–3.5 (Van Couwelaar and Van Dijk 1989), both in the North Sea canal, and 0.2–2.8, in the Canal through Voorne (Janssen and Janssen-Kruit 1967). These data correspond with studies of both species by Walton (1996) in the Hudson River (salinity range 0–3). Found salinity ranges in the North Sea canal for both species match with the tolerance results obtained by mesocosm experiments. A new invading dreissenid mussel Dreissena rostriformis bugensis and a mytilid Ischadium recurvum occur in the North Sea canal since 2006 and 2012, respectively. Competition between recent and earlier invaders is likely when salinity tolerances are similar. It has already been observed that D. rostriformis bugensis outcompetes D. polymorpha under freshwater conditions (Bij de Vaate et al. 2014; Matthews et al. 2014). Ischadium recurvum has the potential to colonize large parts of the canal and to be a strong competitor of M. leucophaeata cochleata (Goud et al. 2019). Since January 2022, the new ‘Zeesluis IJmuiden’ with the biggest locks in the world is in use, affecting the probability of population establishment of new introduced and invasive alien mussel species.

Understanding the temporal dynamics of invasive late blight populations in India for improved management practices.

The microbial oomycete pathogen, Phytophthora infestans causes severe epidemics of potato late blight in crops globally. Disease management benefits from an understanding of the diversity of pathogen populations. In this study, we explore the dynamics of P. infestans populations in the late blight-potato agro-ecosystem across the Indian subcontinent. Investigations of the macroecological observations at the field level and microbial ecological principles provided insights into future pathogen behaviour. We use a comprehensive simple sequence repeat allele dataset to demonstrate that an invasive clonal lineage called EU_13_A2 has dominated populations over 14 years across India, Bangladesh, and Pakistan. Increasing levels of sub-clonal variation were tracked over time and space and, for the first time, populations in Asia were also compared to the source populations from Europe. Within India, a regional pathogen population structure was observed with evidence for local migration, cross-border movement between surrounding countries, and introductions via imports. There was also evidence of genetic drift and between-season transmission of more strongly pathogenic sub-clones with a complete displacement of some sub-clonal types. The limited introduction of novel genotypes and the use of resistant potato cultivars could contribute to the dominance of the 13_A2 lineage. The insights will contribute to the management of the pathogen in these key global potato production regions.

An arcsecond view at 1–2 GHz into the Galactic Bulge

Abstract We present the results of a high angular resolution (1.1”) and sensitivity (maximum of ∼0.1 mJy) radio survey at 1–2 GHz in the Galactic Bulge. This complements the X-ray Chandra Galactic Bulge Survey, and investigates the full radio source population in this dense Galactic region. Radio counterparts to sources at other wavelengths can aid in classification, as there are relatively few types of objects that are reasonably detectable in radio at kiloparsec distances, and even fewer that are detected in both X-rays and radio. This survey covers about 3 square degrees of the Galactic Bulge Survey area (spanning the Galactic coordinate range of −3○ < l < +3○ and +1.6○ < b < +2.1○) as a first look into this region of the Galaxy with this combination of frequency, resolution, and sensitivity. Spectral indices within the observed band of 1–2 GHz were calculated for each source to assist in determining its emission mechanism. We find 1617 unique sources in the survey, 25 of which are radio counterparts to X-ray sources, and about 100 of which are steep-spectrum (α ≲ −1.4) point sources that are viable pulsar candidates. Four radio sources are of particular interest: a compact binary; an infrared transient with an inverted radio spectrum; a potential transitional millisecond pulsar candidate; and a very steep spectrum radio source with an X-ray and bright infrared counterpart. We discuss other notable sources, including possible radio transients, potential new planetary nebulae, and active galactic nuclei.

Prevalence of the Gingival Phenotype in Adults and Associated Risk Factors: A Systematic Review of the Literature

The relevance of assessing the gingival phenotype prior to the initiation of periodontal, orthodontic, or prosthetic therapy has been clearly demonstrated. However, publications on this subject are either old or concerned with the means of assessing the gingival phenotype or the main factors likely to modify it. The main objective of this systematic review of the literature was therefore to investigate the prevalence of different gingival phenotypes in adults in good general health and with a healthy periodontium. A systematic review of the literature was performed following the guidelines of PRISMA recommendations using an electronic search strategy on four databases (PubMed, Scopus, Cochrane Library, and Embase) complemented by a manual search. Three independent authors were involved in study selection, data extraction, and bias assessment. Results: Of 807 articles, 17 of them, published between 2012 and 2023, involving 3277 subjects from 11 countries and 9766 dental sites, fulfilled the inclusion criteria. The prevalence of the gingival phenotype could not be determined at the level of an individual or a dental arch because all the publications assessed this phenotype only at the level of certain dental sectors, and were not chosen at random. The maxillary central incisors and maxillary or mandibular first molar sectors were associated with a high and thick gingival phenotype, independently of the dental morphology, gender, and age of adult subjects. Furthermore, in these regions, this gingival phenotype tended to be associated with a thick vestibular bone table. In contrast, maxillary and mandibular incisors and premolars more often had a thin gingival phenotype. For other teeth, the results were less conclusive. It is important not to rely solely on the overall appearance of the dentition but to independently assess the thickness and height of the gingiva at each dental site requiring intervention. Finally, this study highlights a key point, namely the need for further longitudinal studies to determine the prevalence in healthy adults. For practicality and feasibility reasons, these studies should be designed according to therapeutic needs, dental sector by dental sector, and within homogeneous source populations. PROSPERO registration: CRD 42023392602.

The LOFAR Two-metre Sky Survey: The nature of the faint source population and SFR-radio luminosity relation using Prospector

Abstract Spectral energy distribution (SED) fitting has been extensively used to determine the nature of the faint radio source population. Recent efforts have combined fits from multiple SED-fitting codes to account for the host galaxy and any active nucleus that may be present. We show that it is possible to produce similar-quality classifications using a single energy-balance SED fitting code, Prospector, to model up to 26 bands of UV–far-infrared aperture-matched photometry for ∼31,000 sources in the ELAIS-N1 field from the LOFAR Two-Metre Sky Survey (LoTSS) Deep fields first data release. One of a new generation of SED-fitting codes, Prospector accounts for potential contributions from radiative active galactic nuclei (AGN) when estimating galaxy properties, including star formation rates (SFRs) derived using non-parametric star formation histories. Combining this information with radio luminosities, we classify 92 per cent of the radio sources as a star-forming galaxy, high-/low-excitation radio galaxy, or radio-quiet AGN and study the population demographics as a function of 150 MHz flux density, luminosity, SFR, stellar mass, redshift and apparent r-band magnitude. Finally, we use Prospector SED fits to investigate the SFR–150 MHz luminosity relation for a sample of ∼133,000 3.6 μm-selected z < 1 sources, finding that the stellar mass dependence is significantly weaker than previously reported, and may disappear altogether at log10(SFR/M⊙ yr−1) > 0.5. This approach makes it significantly easier to classify radio sources from LoTSS and elsewhere, and may have important implications for future studies of star-forming galaxies at radio wavelengths.

Lessons learned from using wild-caught and captive-reared lesser scaup (Aythya affinis) in captive experiments

Abstract Waterfowl are housed in captivity for research studies that are infeasible in the wild. Accommodating the unique requirements of semi-aquatic species in captivity while meeting experimental design criteria for research questions can be challenging and may have unknown effects on animal health. Thus, testing and standardizing best husbandry and care practices for waterfowl is necessary to facilitate proper husbandry and humane care while ensuring reliable and repeatable research results. To inform husbandry practices for captive-reared and wild-caught lesser scaup (Aythya affinis; hereafter, scaup), we assessed body mass and fat composition across two different aspects of husbandry, source population (captive-reared or wild caught), and housing densities (birds/m2). Our results suggest that housing scaup at low densities (≤0.6 m2/bird, P=0.049) relative to other species can minimize negative health effects. Captive-reared scaup were heavier (P=0.027) with greater body fat (P<0.001) and exhibited fewer signs of stress during handling than wild-caught scaup. In our experience, scaup which are captive-reared from eggs collected in the wild were better for long-term captivity studies as they maintained body mass between and recovered lost body mass following trials. Researchers would benefit from carefully evaluating the tradeoffs of using short- and long-term captive methods on their research question before designing projects, husbandry practices, and housing facilities for waterfowl.

Functional traits differ across an invasive tree species’ native, introduced, and invasive populations

AbstractIt is often speculated that non-native invasive species undergo rapid changes in their phenotypic properties (i.e., traits) that provide adaptive advantage in their new environment. However, few studies have directly compared traits of invasive non-native species with their native counterparts to reveal whether such phenotypic changes occur, and which stages of initial introduction and subsequent invasion contribute to these shifts. We studied trait variation of an invasive tree, Pinus contorta, which is native to northwestern North America and invasive in the Patagonia region of South America (i.e., Argentina and Chile). Commercial plantations of P. contorta were introduced extensively in Patagonia from the 1970s onward, from an unknown seed origin within the Pacific Northwest, USA, where three sub-species are found, including subsp. contorta, latifolia, and murrayana. We employed a home-versus-away study approach, where we compared mean growth, defense, and reproduction trait values, and mean within-stand trait variation (Coefficient of Variation, CV) of Patagonia plantations, with the three native sub-species. We further compared mean traits, and trait CVs between invasive P. contorta and the Patagonia plantations from which they escaped. Patagonia plantations shared the most similar mean trait values with subsp. latifolia and murrayana, suggesting possible source populations. However, both mean trait values and trait CVs of Patagonia plantations differed from all three native sub-species, indicating potential founder effects, population bottlenecks, and/or plastic responses to their new environment that occurred during or after introduction. We also found evidence for selective change during invasion; however, these differences did not suggest growth traits were prioritized over defense traits, which was inconsistent with hypotheses that invaders exhibit an evolutionary trade-off between defense traits and growth traits. Our study highlights that processes occurring both at first introduction and establishment, as well as the subsequent invasion phase can influence the phenotype of successful invaders.

Salivary Diagnosis of Dental Caries: A Systematic Review

The activity of dental caries, combined with its multifactorial etiology, alters salivary molecule composition. The present systematic review was developed to answer the following question: “Are salivary biomarkers reliable for diagnosis of dental caries?”. Following the “Preferred Reporting Item for Systematic Reviews and Meta-analysis” (PRISMA) guidelines, the review was conducted using multiple database research (Medline, Web of Science, and Scopus). Studies performed on healthy subjects with and without dental caries and providing detailed information concerning the clinical diagnosis of caries (Decayed, Missing, Filled Teeth-DMFT and International Caries Detection and Assessment System-ICDAS criteria) were included. The quality assessment was performed following a modified version of the Joanna Briggs Institute Prevalence Critical Appraisal Checklist. The protocol was registered in the International Prospective Register of Systematic Reviews (PROSPERO, ID: CRD42022304505). Sixteen papers were included in the review. All studies reported statistically significant differences in the concentration of salivary molecules between subjects with and without caries (p < 0.05). Proteins were the most investigated molecules, in particular alpha-amylase and mucins. Some studies present a risk of bias, such as identifying confounding factors and clearly defining the source population. Nevertheless, the 16 papers were judged to be of moderate to high quality. There is evidence that some salivary compounds studied in this review could play an important diagnostic role for dental caries, such as salivary mucins, glycoproteins (sCD14), interleukins (IL-2RA, 4,-13), urease, carbonic anhydrase VI, and urea.

Population-based study of eclampsia: Lessons learnt to improve maternity care.

Among hypertensive disorders of pregnancy (HDP), eclampsia is a rare but serious event, often considered avoidable. Detailed assessment of the adequacy of care for the women who have eclampsia can help identify opportunities for improvement and for prevention of the associated adverse maternal and neonatal outcomes. 1/ To estimate the incidence and describe the characteristics of women with eclampsia and to compare them with those of women with non-eclamptic hypertensive disorders of pregnancy (HDP)-related severe maternal morbidity (SMM) and of control women without SMM 2/ To analyse the quality of management in women who had eclampsia, at various stages of their care pathway. It was a planned ancillary analysis of the EPIMOMS population-based study, conducted in six French regions in 2012-2013. Among the 182,309 maternities of the source population, all women with eclampsia (n = 51), with non-eclamptic HDP-related SMM (n = 351) and a 2% representative sample of women without SMM (n = 3,651) were included. Main outcome was the quality of care for eclampsia assessed by an independent expert panel at three different stages of management: antenatal care, care for pre-eclampsia and care for eclampsia. The eclampsia incidence was 2.8 per 10,000 (95%CI 2.0-4.0). Antenatal care was considered completely inadequate or substandard in 39% of women, as was pre-eclampsia care in 76%. Care for eclampsia was judged completely inadequate or substandard in 50% (21/42), mainly due to inadequate use of magnesium sulphate. The high proportion of inadequate quality of care underlines the need for an evidence-based standardisation of care for HDP.

Histologic, metabolomic, and transcriptomic differences in fir trees from a peri-urban forest under chronic ozone exposure.

Urbanization modifies ecosystem conditions and evolutionary processes. This includes air pollution, mostly as tropospheric ozone (O3), which contributes to the decline of urban and peri-urban forests. A notable case are fir (Abies religiosa) forests in the peripheral mountains southwest of Mexico City, which have been severely affected by O3 pollution since the 1970s. Interestingly, some young individuals exhibiting minimal O3-related damage have been observed within a zone of significant O3 exposure. Using this setting as a natural experiment, we compared asymptomatic and symptomatic individuals of similar age (≤15 years old; n = 10) using histologic, metabolomic, and transcriptomic approaches. Plants were sampled during days of high (170 ppb) and moderate (87 ppb) O3 concentration. Given that there have been reforestation efforts in the region, with plants from different source populations, we first confirmed that all analyzed individuals clustered within the local genetic group when compared to a species-wide panel (Admixture analysis with ~1.5K SNPs). We observed thicker epidermis and more collapsed cells in the palisade parenchyma of needles from symptomatic individuals than from their asymptomatic counterparts, with differences increasing with needle age. Furthermore, symptomatic individuals exhibited lower concentrations of various terpenes (ß-pinene, ß-caryophylene oxide, α-caryophylene, and ß-α-cubebene) than asymptomatic trees, as evidenced through GC-MS. Finally, transcriptomic analyses revealed differential expression for 13 genes related to carbohydrate metabolism, plant defense, and gene regulation. Our results indicate a rapid and contrasting phenotypic response among trees, likely influenced by standing genetic variation and/or plastic mechanisms. They open the door to future evolutionary studies for understanding how O3 tolerance develops in urban environments, and how this knowledge could contribute to forest restoration.

Main-belt and Trojan asteroid phase curves from the ATLAS survey

Abstract Sparse and serendipitous asteroid photometry obtained by wide field surveys such as the Asteroid Terrestrial-impact Last Alert System (ATLAS) is a valuable resource for studying the properties of large numbers of small Solar System bodies. We have gathered a large database of ATLAS photometry in wideband optical cyan and orange filters, consisting of 9.6× 107 observations of 4.5× 105 main belt asteroids and Jupiter Trojans. We conduct a phase curve analysis of these asteroids considering each apparition separately, allowing us to accurately reject outlying observations and to remove apparitions and asteroids not suitable for phase curve determination. We obtain a dataset of absolute magnitudes and phase parameters for over 100,000 selected asteroids observed by ATLAS, ∼66 000 of which had sufficient measurements to derive colours in the ATLAS filters. To demonstrate the power of our dataset we consider the properties of the Nysa-Polana complex, for which the ATLAS colours and phase parameters trace the S-like and C-like compositions amongst family members. We also compare the properties of the leading and trailing groups of Jupiter Trojans, finding no significant differences in their phase parameters or colours as measured by ATLAS, supporting the consensus that these groups were captured from a common source population during planetary migration. Furthermore, we identify ∼9000 asteroids that exhibit large shifts in derived absolute magnitude between apparitions, indicating that these objects have both elongated shapes and spin axes with obliquity ∼90 degrees.

Serial founder effects slow range expansion in an invasive social insect

Invasive populations often experience founder effects: a loss of genetic diversity relative to the source population, due to a small number of founders. Even where these founder effects do not impact colonization success, theory predicts they might affect the rate at which invasive populations expand. This is because secondary founder effects are generated at advancing population edges, further reducing local genetic diversity and elevating genetic load. We show that in an expanding invasive population of the Asian honey bee (Apis cerana), genetic diversity is indeed lowest at range edges, including at the complementary sex determiner, csd, a locus that is homozygous-lethal. Consistent with lower local csd diversity, range edge colonies had lower brood viability than colonies in the range centre. Further, simulations of a newly-founded and expanding honey bee population corroborate the spatial patterns in mean colony fitness observed in our empirical data and show that such genetic load at range edges will slow the rate of population expansion.

Establishment success of the reinforced population of Gran Canaria Blue Chaffinch Fringilla polatzeki

AbstractThe Gran Canaria Blue Chaffinch is the rarest forest passerine in the western Palaearctic with a population reduced to a single locality, Inagua, in the west of the island. After a forest fire, some birds were established in another location and a reinforcement programme was launched with the aim of consolidating this new population. Between 2010 and 2019, 194 Blue Chaffinches were released in the pine forest of La Cumbre, in the centre of the island and at a higher altitude than the previous one. Birds of two origins were used for this action: captive-bred birds were released using “soft” release methods, and wild-caught birds from the Inagua source population were released using “hard” release methods. Survival of radio-tagged birds (20–42 days of battery life) was high and similar between the two groups. Wild-caught birds occupied 12–15 times more surface area than captive-bred birds that remained close to supplementary feeding sites. All translocated birds displayed breeding behaviour in the following breeding season, although the rate of contribution to the new population was significantly lower for wild-caught birds (21% compared to 54% for captive-bred birds). This disparity can be partly attributed to nearly one-fifth of the wild-caught birds returning to Inagua. We conclude that the establishment phase of the Blue Chaffinch reinforced program in Gran Canaria has been successful. To retain wild-caught birds and deter their return to the source population, we recommend employing methods akin to the soft-release techniques utilized for captive-bred birds. Ongoing monitoring of the enhanced population, collecting data on survival and breeding success, will enable the evaluation of the long-term success of the translocation program.

Variation in resting respiration rate of Brook Trout among source populations: Implications for bioenergetic models

AbstractObjectiveOur objective was to compare wild and hatchery sourced Brook Trout Salvelinus fontinalis to determine the importance of source population on routine respiration rate (RRR), the major cost term in bioenergetic models.MethodsWe evaluated intraspecific variation in RRRs of one hatchery and four wild Brook Trout populations. Hatchery fish were obtained from the Bowden State Fish Hatchery in Elkins, West Virginia, and were the basis for the previously published bioenergetics model for the species. Wild fish were obtained from four headwater streams in West Virginia. Using intermittent respirometry, we measured and analyzed RRRs sequentially at 20, 16, and 12°C. Measures on hatchery fish were censored to restrict the dataset to similar sizes and temperatures as used with the wild populations. We used a suite of mixed effects models and one linear model to compare RRRs of hatchery fish with wild fish, as well as to determine whether wild populations differed.ResultWe found that the RRR of hatchery fish was double that of wild fish over the range of 12–20°C. Within the wild populations, the RRR of the Potomac drainage fish was lower than two of the three Ohio drainage populations despite all steams falling within 55 km of each other.ConclusionOur findings suggest that selective pressures at the hatchery, as well as factors that influence thermal regimes in wild populations, likely influence RRR in Brook Trout. More research is needed to identify correlates related to intraspecific variation in fish respiration rates. Most fish bioenergetics models are not based on, or calibrated to, the specific population to which they are applied. Therefore, we encourage greater efforts be expended to calibrate and validate such models in the future.

Greener leaves from northern trees: Latitudinal compensation in riparian cottonwoods

Narrowleaf cottonwoods (Populus angustifolia) occur in disjunct populations along rivers in a north-south corridor of the Rocky Mountain regions from Alberta, Canada, to Arizona, USA. This distribution should allow genetic divergence to provide localized ecophysiological adaptation. To test this, we compared 167 genotypes in ten source populations from across the full latitudinal range of 16° (1800 km). Replicated clonal saplings were grown for three years in a common garden at the northern range limit, where we found that shoot characteristics were correlated with the latitude of origin. Southern populations displayed increased height and stem diameter (populations: r2 = 0.489 and 0.472) due to extended in-leaf growing seasons. However, this produced a phenological mismatch, with increased fall frost injury and shoot die-back. With increasing latitude of origin there were foliar differences across the populations, with higher chlorophyll content (chl, r2 = 0.836), nitrogen (N, r2 = 0.429), and leaf mass per area (LMA, r2 = 0.474). Similar latitudinal correspondences were observed across the individual genotypes, again with the strongest correlation for chl (r2 = 0.188). Across the genotypes, chl was positively correlated with leaf length, width, area, and mass, and especially with foliar N (r2 = 0.354), which was also correlated with foliar δ13C (r2 = 0.230). The heritable correspondences between source latitude and foliar characteristics could enable vigorous photosynthesis during the shorter, northern growing season, providing latitudinal compensation. Conversely, slower photosynthesis would reduce the foliar aging rate, enabling leaf function through the longer, southern growing season. The alternate foliar strategies could accommodate the limited ‘leafspan’, or leaf lifespan. This adaptive variation in foliar physiology would impact natural or assisted northward migration of cottonwood populations in response to climate change. It could also be useful for poplar breeding, with northern genotypes contributing genes to increase photosynthetic capacity. Finally, groupings of the populations based on the combined ecophysiological traits were very consistent with genetically defined ecotypes, supporting the evolution of subspecies types within this obligate riparian tree.

Recruitment strategies used to enrol healthy volunteers in the first pneumococcal human infection study in Africa: Lessons from Blantyre, Malawi

Background Human infection studies (HIS) also known as Controlled Human Infection Models (CHIM) are a relatively new concept in African countries to clinicians, scientists, and communities alike. We have introduced HIS/CHIM studies to Malawi during the last four years by developing an experimental human pneumococcal carriage model. This CHIM was used to test the efficacy of a licensed 13-valent Pneumococcal Conjugate Vaccine (PCV13) against experimental nasal pneumococcal carriage. Traditional and digital recruitment strategies into this novel trial were explored. Objectives To describe various methods of recruitment in this first CHIM study in Malawi. Methods The clinical trial within the context of which these data were recorded was registered with the Pan African Clinical Trials Registry (REF: PACTR202008503507113) on 03 August 2020. The project was conducted at the Malawi Liverpool Wellcome Programme (MLW) in Blantyre, Malawi between April 2021, and September 2022. Source populations were college students and community members within Blantyre. Recruitment strategies included sharing study information in written or visual form, community sensitization meetings, snowball contacts (word of mouth from previous volunteers), branded clothing and participating in radio and television programs. Results 299 volunteers attended screening clinic, of whom 278 were recruited. Sixty-six recruited volunteers (23.7%) were college students and 212 (76.3%) were from the community. Snowball word-of-mouth contacting was the most successful recruitment strategy, with 201 (72.3%) participants recruited using this method. 195 (70.1%) were men of whom 149 (76.4%) joined the study through snowballing. Conclusion or recommendation Using a variety of recruitment strategies led to successful recruitment in this novel controlled human infection study. Most participants were recruited through snowballing.

How transportability analysis can be useful for cumulative theory testing in management research

Moving management science forward by publishing research aimed at theory testing and refinement is the mission of the Journal of Management Scientific Reports. One way to test and refine a theory is through constructive replication studies. If X→Y (the causal effect of X on Y) is found in an initial study, what assumptions and mechanisms are required to expect that X→Y would also be found in a subsequent study, when the population differs between the initial and subsequent studies? What structural discrepancies between source and target populations would render transporting the knowledge obtained from one study to another impossible? Whereas generalizability is concerned with making inferences based on a possibly biased sample drawn from a focal population about the focal population, transportability refers to the conditions under which a transfer of causal knowledge across populations is valid. Researchers now have access to methods for identifying the conditions under which causal information learned from experiments would be valid in studies where ideal experiments cannot be conducted and where only passive observations can be collected. In this commentary, I explain how transportability analysis and its associated diagnostic tools from machine learning and artificial intelligence can be useful for cumulative theory testing in management research.

On the Rigidly Precessing, Eccentric Gas Disk Orbiting the White Dwarf SDSS J1228+1040

Metal pollution onto white dwarfs is a widespread phenomenon that remains puzzling. Some of these white dwarfs also harbor gaseous debris disks. Emission lines from these disks open a unique window to the physical properties of the polluting material, lending insights into their origin. We model the emission line kinematics for the gas disk around SDSS J1228+1040, a system that has been monitored for over two decades. We show that the disk mass is strongly peaked at 1 R ⊙ (modulo the unknown inclination), and the disk eccentricity decreases from a value of 0.44 at the inner edge, to nearly zero at the outer edge. This eccentricity profile is exactly what one expects if the disk is in a global eccentric mode, precessing rigidly under general relativity and gas pressure. The precession period is about two decades. We infer that the mass of the gas disk is roughly equivalent to that of a 50 km rocky body, while the mass of the accompanying dust disk is likely insignificant. The disk eccentricity confirms an origin in tidal disruption, while the short disk diffusion time suggests that the disruption event happened a few centuries ago. Moreover, we argue that the initial orbit for the disrupted body, and that of its putative planetary perturber, fall within an astronomical unit around the white dwarf. The total mass of the source population is likely orders of magnitude more massive than our own Asteroid belt and does not seem to exist around main-sequence stars.