Teasing apart the joint effect of demography and natural selection in the birth of a contact zone

Vast population movements induced by recurrent climatic cycles have shaped the genetic structure of plant species. This is especially true in Scandinavia that was repeatedly glaciated. During glacial periods trees were confined to refugia, south and east of the ice sheet, from which they recolonized Scandinavia as the ice melted away. This multi-pronged recolonization led to large contact zones in most species. We leverage large genomic data from 5000 trees to reconstruct the demographic history of Norway spruce (Picea abies) and test for the presence of natural selection during the recolonization process and the establishment of the contact zone. Sweden is today made up of two large genetic clusters, a southern one originating from the Baltics and a Northern one originating from Northern Russia. The contact zone delineating these two clusters closely matches the limit between two major climatic regions. This suggests that natural selection contributed to the establishment and the maintenance of the contact zone. To test this hypothesis we first used Approximate Bayesian Computation; an Isolation-with migration model with genomewide linked selection fits the data better than a purely neutral one. Secondly, we identified loci characterized by both extreme allele frequency differences between geographic regions and association to the variables defining the climatic zones. These loci, many of which are related to phenology, form clusters present on all linkage groups. Altogether, the current genetic structure reflects the joint effect of climatic cycles, recolonization and selection on the establishment of strong local adaptation and con-tact zones.

Technological Features of the Liquid-Solid State of the Boundary Layer in the Processes of Bimetallic Products

The hydrodynamic and thermal state in the contact zone of the layers of a bimetallic product obtained by pouring liquid iron onto a solid steel billet, which changes in time and is responsible for the strength of the diffusion joint and the geometric parameters of the transition layer, has been investigated. Simplified analytical dependences, mathematical modeling data and experimental results of the liquid phase existence time in the contact zone based on research of the melt velocities during pouring and changes in the thermal field are presented. It is shown that simplified calculations data coincide in order and are close in values ​​to the calculations of mathematical modeling and experimental data, which makes it possible to use them for preliminary rough estimates by technologists and metallurgists.

About One of the Approaches for the Research of the Stress-Strain State of a Flange Connection with a Seal Made of an Alloy with Shape Memory

Design features of a flange connection with a seal made of an alloy with shape memory and the most commonly used methods of researching of the stress-strain state of such connections are estimated. Alternative approach for stress-strain state analysis is proposed, it is based on modeling of the contact zone of the sealing surfaces by means of an equivalent gap between the layers, the value of which changes during axial compression of the multilayer ring and goes into tension. Formulas for determining of contact stresses at the border of layers, which take into consideration the variable physical and mechanical properties of the materials of each layer are presented.

International Schools as Models for Educators to Dismantle Oppression and Promote Social Justice

International-mindedness is a strategy employed by international schools (IS) to create environments successfully promoting social justice, cultural diversity, and tolerance. The composition of the student body forces accommodation and assimilation of multiple cultures, backgrounds, and languages into one location or contact zone. The purpose of the study is to understand how IS navigate, manage, and lead educators and students from different races, genders, religions, and socioeconomic statuses by promoting equity and creating an environment with zero tolerance for discrimination. However, social justice gaps in education in general still exist, and practical applications and strategies to embrace diversity and equalize the marginalized are lacking. This chapter provides strategies as to how educators worldwide can benefit from approaches used by IS for social justice and tangible strategies used by IS to promote ethical-international-mindedness and decrease discrimination.

Modeling of thermal processes in the contact zones of fuel elements

In this work, using two specific examples, a general approach to the mathematical modeling of thermal processes in the contact zones of fuel elements in the development and optimization of various technological processes, systems and devices is considered. In the first example, a mathematical model of heat transfer in the contact zone (metal-hybrid thermal interface) between the heat-generating element and the heat-dissipating radiator is considered. In the second case, the thermal process in the processing of materials with a bonded diamond tool in the contact zone "diamond grain – binder – processed material" is considered and analyzed. The general approach to modeling thermal processes in the contact zones of various fuel elements makes it possible to optimize the parameters of technological processing modes and the correct operating conditions for products and systems

THE FRONTER AND IT’S COMPONENTS IN HISTORICAL GEOGRAPHY OF UKRAINE

The purpose of the article is to define the concept of the frontier and its components in the historical geography of Ukraine. The concept of FJ Turner's frontier was substantiated in the researches of Ukrainian historians M. Hrushevskyі, S. Rudnytsky, and J. Dashkevych. The source base of the study consists of scientific and cartographic works of historians and geographers. Several aspects of the spatial representation of the frontier are considered – directly in the name "Ukraine", which was identified with the peripheral land and as an integral part of the Ukrainian lands – the Black Sea, the Wild Field, Sloboda Ukraine. It is established that the concept of the frontier as a border or border strip can be considered in the context of the problems of historical geography, and the Ukrainian lands are at the intersection of different border contact zones. The frontier plays a significant role in shaping the ethnic composition of the population, as the contact zone of different ethnic groups is usually formed in such frontline or border areas. A peculiar phenomenon in the context of this concept is part of the Southern Ukrainian territory – Budjak. The opinion is substantiated that the majority of the Ukrainian territory is considered to be a zone of continuous historicalgeographical and chronological frontier.

Strefa kontaktu, czyli interaktywne relacje antropologa w terenie

Based on the classic concept developed by M.L. Pratt and the author’s experience of fieldwork in Africa, this article discusses methods of building a contact zone during anthropological field research. Under the conditions of such research, a limited space of mutual, lasting, interactive relations is created between the anthropologist and the local social environment. The contact zone understood in this way is produced discursively and practiced physically. The time factor and coordination of the anthropologist’s availa- bility with the rhythm of life in the studied community are paramount. The contact zone may have different scope and social depth – it will be shallow, scattered and short-lived in field research covering an extensive area, but will acquire an interactive depth during an “intensive habitation”, when an anthropologist shares everyday life with the studied community.

Phenotypic differentiation of the slow worm lizards (Squamata: Anguis) across their contact zone in Central Europe

Background The application of molecular-phylogenetic approaches to taxonomy has had a dramatic effect on our understanding of the diversity of reptiles. These approaches have allowed researchers to reveal previously hidden lineages as well as taxonomic overestimation in morphologically plastic taxa. Slow worms, legless lizards of the genus Anguis (Squamata: Anguidae), were previously considered to comprise either one or two species, and morphology-based intraspecific taxonomy of Anguis fragilis remained controversial throughout the 20th century. After the discovery of deep genetic divergences within the genus, its taxonomy was reconsidered, and as a result, five extant species have been recognized. In order to better understand the patterns of their interspecific differentiation, here we studied phenotypic differences between the two most widespread of them—A. fragilis and A. colchica, and their putative hybrids across the contact zone of both species in Central Europe. Methods We used multivariate and univariate statistics and analyzed ten metric, eleven meristic, and six categorical phenotypic variables in material comprising a total of 326 individuals. We also genotyped individuals from the contact zone for one mitochondrial and two nuclear DNA fragments in order to delineate the distribution of individuals of hybrid and non-hybrid origin. The clines in morphological traits were studied using HZAR. Results We show that the two species are morphologically differentiated. Anguis fragilis has a less robust head, fewer scales covering the body, lower frequency of the external ear opening presence, lower frequency of separated prefrontal scales, higher frequency of prefrontal scales in contact with each other, and body coloration more similar to the juvenile coloration than A. colchica. Slow worms from the contact/hybrid zone are characterized by an intermediate morphology, with more similarities to A. fragilis than to A. colchica. Discussion None of the analyzed characters alone proved to be fully diagnostic, although more than 90% of all individuals could be successfully assigned to one or another species based on numbers of scales around the body. Our results indicate concordant, coincident, and steep clines in character states change. We present several hypotheses on the origin and evolutionary maintenance of the morphological divergence between both species and suggest that different evolutionary histories of the taxa rather than recently acting selection explain the observed morphological variation.

Genomics Reveal Admixture and Unexpected Patterns of Diversity in a Parapatric Pair of Butterflies

We studied the evolutionary relationship of two widely distributed parapatric butterfly species, Melitaea athalia and Melitaea celadussa, using the ddRAD sequencing approach, as well as genital morphology and mtDNA data. M. athalia was retrieved as paraphyletic with respect to M. celadussa. Several cases of mito-nuclear discordance and morpho-genetic mismatch were found in the contact zone. A strongly diverged and marginally sympatric clade of M. athalia from the Balkans was revealed. An in-depth analysis of genomic structure detected high levels of admixture between M. athalia and M. celadussa at the contact zone, though not reaching the Balkan clade. The demographic modelling of populations supported the intermediate genetic make-up of European M. athalia populations with regards to M. celadussa and the Balkan clade. However, the dissimilarity matrix of genotype data (PCoA) suggested the Balkan lineage having a genetic component that is unrelated to the athalia-celadussa group. Although narrowly sympatric, almost no signs of gene flow were found between the main M. athalia group and the Balkan clade. We propose two possible scenarios on the historical evolution of our model taxa and the role of the last glacial maximum in shaping their current distribution. Finally, we discuss the complexities regarding the taxonomic delimitation of parapatric taxa.