Tree migration in the dynamic, global vegetation model LPJ-GM 1.0: Efficient uncertainty assessment and improved dispersal kernels

The prediction of species geographic redistribution under climate change (i.e. range shifts) has been addressed by both experimental and modelling approaches and can be used to inform efficient policy measures on the functioning and services of future ecosystems. Dynamic Global Vegetation Models (DGVMs) are considered state-of-the art tools to understand and quantify the spatio-temporal dynamics of ecosystems at large scales and their response to changing environments. They can explicitly include local vegetation dynamics relevant to migration (establishment, growth, seed production), species-specific dispersal abilities and the competitive interactions with other species in the new environment. However, the inclusion of more detailed mechanistic formulations of range shift processes may also widen the overall uncertainty of the model. Thus, a quantification of these uncertainties is needed to evaluate and improve our confidence in the model predictions. In this study, we present an efficient assessment of parameter and model uncertainties combining low-cost analyses in successive steps: local sensitivity analysis, exploration of the performance landscape at extreme parameter values, and inclusion of relevant ecological processes in the model structure. This approach was tested on the newly-implemented migration module of the state-of-the-art DGVM, LPJ-GM 1.0. Estimates of post-glacial migration rates obtained from pollen and macrofossil records of dominant European tree taxa were used to test the model performance. The results indicate higher sensitivity of migration rates to parameters associated with the dispersal kernel (dispersal distances and kernel shape) compared to plant traits (germination rate and maximum fecundity) and highlight the importance of representing rare long-distance dispersal events via fat-tailed kernels. Overall, the successful parametrization and model selection of LPJ-GM will allow simulating plant migration with a more mechanistic approach at larger spatial and temporal scales, thus improving our efforts to understand past vegetation dynamics and predict future range shifts in a context of global change.

Numerical Description of Jet and Duct Ventilation in Underground Garage after LPG Dispersion

Contamination of toxic and odorous gases emitted from stacks in buildings located in an urban environment are potential health hazards to citizens. A simulation using the computational fluid dynamic technique may provide detailed data on the flammable region and spatial dispersion of released gases. Concentrations or emissions associated with garage sources and garage-to-house migration rates are needed to estimate potential exposures and risk levels. Therefore, the aim of the study was to use an original mathematical model to predict the most accurate locations for LPG sensors in an underground garage for vehicles powered with LPG. First, the three-dimensional geometry of an underground garage under a multi-family building was reconstructed. Next, two types of ventilation, jet and duct, were considered, and different sources of LPG leakage were assumed. Then, the Ansys Fluent software was applied as a solver, and the same initial value of released LPG (5 kg) was assumed. As a simplification, and to avoid the simulation of choked outflow, the emission from a large area was adopted. The results showed stagnation areas for duct ventilation in which gas remained for both the jet and duct ventilation. Moreover, it was observed that the analyzed gas would gather in the depressions of the ground in the underground garage, for example in drain grates, which may create a hazardous zone for the users of the facility. Additionally, it was observed that for jet ventilation, turbulence appearance sometimes generated differentiated gas in an undesirable direction. The simulation also showed that for blowing ventilation around the garage, and for higher LPG leakage, a higher cloud of gas that increased probability of ignition and LPG explosion was formed. Meanwhile, for jet ventilation, a very low concentration of LPG in the garage was noticed. After 35 s, LPG concentration was lower than the upper explosive limit. Therefore, during the LPG leakage in an underground garage, jet ventilation was more efficient in decreasing LPG gas to the non-explosive values.

Distinguishing gene flow between malaria parasite populations

Measuring gene flow between malaria parasite populations in different geographic locations can provide strategic information for malaria control interventions. Multiple important questions pertaining to the design of such studies remain unanswered, limiting efforts to operationalize genomic surveillance tools for routine public health use. This report examines the use of population-level summaries of genetic divergence (FST) and relatedness (identity-by-descent) to distinguish levels of gene flow between malaria populations, focused on field-relevant questions about data size, sampling, and interpretability of observations from genomic surveillance studies. To do this, we use P. falciparum whole genome sequence data and simulated sequence data approximating malaria populations evolving under different current and historical epidemiological conditions. We employ mobile-phone associated mobility data to estimate parasite migration rates over different spatial scales and use this to inform our analysis. This analysis underscores the complementary nature of divergence- and relatedness-based metrics for distinguishing gene flow over different temporal and spatial scales and characterizes the data requirements for using these metrics in different contexts. Our results have implications for the design and implementation of malaria genomic surveillance studies.

Interregional Mobility of Latin American Immigrants in Canada: Explorations Using Tax Filer Data

Using data from the Longitudinal Immigration Database (IMDB), which links tax filer information to provinces of landing information and current regions, the author carried out data explorations regarding the interregional mobility of 98,440 Latin American immigrants arriving in Canada between 2000 and 2014. These were observed in the tax year 2014. The interregional mobility of citizens from 15 citizenship countries was examined: Argentinians, Bolivians, Brazilians, Chileans, Colombians, Cubans, Ecuadorians, Salvadoreans, Guatemalans, Hondurans, Mexicans, Nicaraguans, Peruvians, Uruguayans, and Venezuelans. Immigrants were allowed entry into Canada under various immigrant intake classes such as economic, family, and refugee. Examination of retention and net migration rates showed that Alberta and British Columbia were among those who benefited the most from Latino immigrant inflows during the observation period. About one in five Latinos had moved outside their original landing region by the tax year 2014. Citizens of various nationalities left the Atlantic, Quebec and Manitoba regions for other ones. Interregional mobility was found the highest among males, earlier arrival cohort members, those with higher educational levels and economic principal applicants. Colombian citizens were the most mobile group while Nicaraguans, Bolivians, and Ecuadorians were the least mobile. The regional triangle constituted by Alberta, Ontario, and Quebec was found to be the dominant one in the network of all migratory exchanges. Tracking the interregional mobility of Latin American immigrants to Canada after arrival provides interesting insights into how this particular immigrant population is redistributed, how it may respond to the needs of regional economies, and also speaks to the success of immigrant integration and resettlement of Latin American immigrants in particular regions of Canada.

P-OGC24 Comparison of the histopathological regression after neoadjuvant FLOT versus ECX in resectable gastroesophageal adenocarcinoma

Background Neoadjuvant chemotherapy is a key component in the treatment of resectable oesophagogastric cancer (OGC). Histopathological tumour regression is associated with a prognostic benefit in OGC. There is increased usage of the FLOT regimen as part of neoadjuvant chemotherapy (NAC) for these tumours. The initial phase 2 trial demonstrated complete pathological response (pCR) in 15% for FLOT versus 6% for ECX but there is no data outside a trial setting. The aim of this study was to evaluate the differences in pCR and the extent of downstaging between patients receiving FLOT versus ECX in the neoadjuvant setting. Methods Consecutive patients treated for OGC in a single, high-volume UK centre between 2018 and 2021 were identified from a contemporaneously maintained database. Patients underwent 3 cycles of ECX or 4 cycles of FLOT as part of NAC. Histopathological tumour regression was assessed by the Mandard classification. A comparison of T- and N stage migration between FLOT and ECX was performed. Major pCR was defined as TRG 1-2 based on the Mandard classification. Results The study included 162 patients. 6/84 (7.1%) patients receiving ECX and 5/78 (6.4%) patients receiving FLOT achieved a pCR (p = 0.853). 11/84 (13.1%) patients in the ECX group and 12/78 (15.4%) patients in the FLOT group achieved a major pCR (p = 0.677). With regards to stage migration by T-stage, 36 (42.9%) patients were downstaged and 6 patients (7.1%) were upstaged with ECX. Amongst FLOT patients, 42 (53.8%) were downstaged and 8 (10.3%) upstaged (p = 0.189). When comparing N-stage, 29 (34.5%) patients achieved downstaging and 28 (33.3%) were upstaged with ECX. 30 (38.5%) patients were downstaged and 20 (25.6%) were upstaged with FLOT (0.563). Conclusions There was no significant difference in pCR and stage migration rates between patients receiving neoadjuvant ECX and FLOT. pCR rates were lower than previously reported, and it is unclear if the difference in prognosis will translate comparable outcomes between patients receiving ECX versus FLOT.

Migration and Remittances in South Africa

The chapter draws from two data sources to describe patterns and trends of internal migration and remittances in South Africa and explore what these mean for rural households. These are the National Income Dynamics Study (NIDS 2008–17) and the South African Population Research Infrastructure Network (2000–17). NIDS data show that at a national level there are high levels of non-resident household membership. As much as 24 per cent of African rural households have a non-resident member. This reflects temporary migration, especially of young adults. SAPRIN shows that temporary migration rates remain persistent over time, while definitive migration shows a gradual decline in incidence after 2003. Some temporary migrants send remittances, mostly of money, but also clothes and food. The study shows amounts averaging R1,100 per month from female migrants and R1,500 per month from male migrants in 2017. These can play a crucial role in food security for the poorest rural households and in improving human capital in better-off rural households. What has not been explored here are costs to the household of temporary migration, which help to explain why more households do not send temporary migrants. These include financial costs, but the main two areas of concern are health and social connection.

Country-Specific Magnitudes of Migration between Rural and Urban Sectors

Across seventy-four countries, six migration propensities of men and women are tabulated in this chapter: notably, for gross and net, lifetime and five-year flow, rural-urban and urban-rural moves. China is purported to have the highest rate of rural-urban migration in recent history, but neither reliable estimates nor sufficient data to permit computations appear to be available. The conventional wisdom is that India has a low rural-urban migration rate, but our estimates contradict this claim. The five-year flow rates are only loosely correlated with lifetime movements. It is important to understand the situation in each country at the time of enumeration, and these specific circumstances are described in the second half of the chapter. Gross rural-urban migration rates increase at higher urbanization levels, but net rural-urban migration proves positive virtually everywhere. Yet a decomposition for twenty-two countries indicates that reclassification of rural areas as urban is far more important than net rural-urban moves in incremental urbanization.

Reproductive isolation via polygenic local adaptation in sub-divided populations: effect of linkage disequilibria and drift

This paper considers how local adaptation and reproductive isolation between hybridizing populations is influenced by linkage disequilibria (LD) between multiple divergently selected loci in scenarios where both gene flow and genetic drift degrade local adaptation. It shows that the combined effects of multi-locus LD and genetic drift on allele frequencies at selected loci and on heterozygosity at neutral loci are predicted accurately by incorporating (deterministic) effective migration rates into the diffusion approximation (for selected loci) and into the structured coalescent (for neutral loci). Theoretical approximations are tested against individual-based simulations and used to investigate the conditions for the maintenance of local adaptation on an island subject to one-way migration from a differently adapted mainland, and in an infinite-island population with two different habitats under divergent selection. The analysis clarifies the conditions under which LD between sets of locally deleterious alleles allows these to be collectively eliminated despite drift, causing sharper and (under certain conditions) shifted migration thresholds for loss of adaptation. Local adaptation also has counter-intuitive effects on neutral (relative) divergence: FST is highest for a pair of subpopulations belonging to the same (rare) habitat, despite the lack of reproductive isolation between them.

Climate-assisted persistence of tropical fish vagrants in temperate marine ecosystems

Rising temperatures and extreme climate events are propelling tropical species into temperate marine ecosystems, but not all species can persist. Here, we used the heatwave-driven expatriation of tropical Black Rabbitfish (Siganus fuscescens) to the temperate environments of Western Australia to assess the ecological and evolutionary mechanisms that may entail their persistence. Population genomic assays for this rabbitfish indicated little genetic differentiation between tropical residents and vagrants to temperate environments due to high migration rates, which were likely enhanced by the marine heatwave. DNA metabarcoding revealed a diverse diet for this species based on phytoplankton and algae, as well as an ability to feed on regional resources, including kelp. Irrespective of future climate scenarios, these macroalgae-consuming vagrants may self-recruit in temperate environments and further expand their geographic range by the year 2100. This expansion may compromise the health of the kelp forests that form Australia’s Great Southern Reef. Overall, our study demonstrates that projected favourable climate conditions, continued large-scale genetic connectivity between populations, and diet versatility are key for tropical range-shifting fish to establish in temperate ecosystems.

Migration, remittances and child education in Ghana. Evidence from a longitudinal study

Evidence on the time-varying effects of migration, remittances and child education in African contexts remains scarce. This study employs panel data to examine educational outcomes – school enjoyment, and class ranking – of children whose parents migrated internally or internationally and who received in-kind remittances, monetary remittances, or both. The data were collected in 2013, 2014, and 2015 on a panel of school going children and youths aged from 12 to 21 in two urban areas with high out-migration rates in Ghana: Kumasi and Sunyani (N = 741). The panel includes children of both migrant and non-migrant parents. Results indicate dynamic patterns of sending remittances over years, with preferences converging towards sending both in-kind and monetary remittances by internal and international migrant parents. Overall, the education of children benefits when they receive both in-kind and monetary remittances. The positive effects are further enhanced when remittances are directly invested in child education. The absence of remittances has more negative effects on child education, especially for girls. This study gives a more nuanced understanding of the dynamic and intertwined associations between parental migration, remittances and the education of children in transnational families.