Introduction: Interrogating the 'everyday' politics of emotions in international relations

The focus on the everyday in this Special Issue reveals different kinds of emotional practices, their political effects and their political contestation within both micro- and macro-politics in international relations. The articles in this Special Issue address the everyday negotiation of emotions, shifting between the reproduction of hegemonic structures of feelings and emancipation from them. In other words, the everyday politics of emotions allows an exploration of who gets to express emotions, what emotions are perceived as (il)legitimate or (un)desirable, how emotions are circulated and under what circumstances. Consequently, we identify two thematic strands which emerge as central to an interrogation of ‘everyday’ emotions in international relations and which run through each of the contributions: first, an exploration of the relationship between individual and collective emotions and, second, a focus on the role of embodiment within emotions research and its relationship with the dynamics and structures of power

Genetic admixture despite ecological segregation in a North African sparrow hybrid zone (Aves, Passeriformes, Passer domesticus × Passer hispaniolensis)

Under different environmental conditions, hybridization between the same species might result in different patterns of genetic admixture. Particularly, species pairs with large distribution ranges and long evolutionary history may have experienced several independent hybridization events over time in different zones of overlap. In birds, the diverse hybrid populations of the house sparrow (Passer domesticus) and the Spanish sparrow (Passer hispaniolensis) provide a striking example. Throughout their range of sympatry, these two species do not regularly interbreed; however, a stabilized hybrid form (Passer italiae) exists on the Italian Peninsula and on several Mediterranean is‐ lands. The spatial distribution pattern on the Eurasian continent strongly contrasts the situation in North Africa, where house sparrows and Spanish sparrows occur in close vicinity of phenotypically intermediate populations across a broad mosaic hy‐ brid zone. In this study, we investigate patterns of divergence and admixture among the two parental species, stabilized and nonstabilized hybrid populations in Italy and Algeria based on a mitochondrial marker, a sex chromosomal marker, and 12 micros‐ atellite loci. In Algeria, despite strong spatial and temporal separation of urban early‐ breeding house sparrows and hybrids and rural late‐breeding Spanish sparrows, we found strong genetic admixture of mitochondrial and nuclear markers across all study populations and phenotypes. That pattern of admixture in the North African hybrid zone is strikingly different from i) the Iberian area of sympatry where we observed only weak asymmetrical introgression of Spanish sparrow nuclear alleles into local house sparrow populations and ii) the very homogenous Italian sparrow population where the mitogenome of one parent (P. domesticus) and the Z‐chromosomal marker of the other parent (P. hispaniolensis) are fixed. The North African sparrow hybrids provide a further example of enhanced hybridization along with recent urbanization and anthropogenic land‐use changes in a mosaic landscape.Fil: Päckert, Martin. Leibniz Institution for Biodiversity and Earth System Research, Dresden; AlemaniaFil: Ait Belkacem, Abdelkrim. Université de Djelfa; ArgeliaFil: Wolfgramm, Hannes. Leibniz Institution for Biodiversity and Earth System Research, Dresden; AlemaniaFil: Gast, Oliver. Institute of Vertebrate Biology Brno y Masaryk University ; República ChecaFil: Canal Piña, David. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Ciencias de la Tierra y Ambientales de La Pampa. Universidad Nacional de La Pampa. Facultad de Ciencias Exactas y Naturales. Instituto de Ciencias de la Tierra y Ambientales de La Pampa; ArgentinaFil: Giacalone, Gabriele. Cooperativa Silene; ItaliaFil: Lo Valvo, Mario. Universita Degli Studi Di Palermo.; ItaliaFil: Vamberger, Melita. Leibniz Institution for Biodiversity and Earth System Research, Dresden; AlemaniaFil: Wink, Michael. Ruprecht Karls Universitat Heidelberg.; AlemaniaFil: Martens, Jochen. Johannes Gutenberg Universitat Mainz; AlemaniaFil: Stuckas, Heiko. Leibniz Institution for Biodiversity and Earth System Research, Dresden; Alemani

Effects of interspecific gene flow on the phenotypic variance–covariance matrix in Lake Victoria Cichlids

Quantitative genetics theory predicts adaptive evolution to be constrained along evolutionary lines of least resistance. In theory, hybridization and subsequent interspecific gene flow may, however, rapidly change the evolutionary constraints of a population and eventually change its evolutionary potential, but empirical evidence is still scarce. Using closely related species pairs of Lake Victoria cichlids sampled from four different islands with different levels of interspecific gene flow, we tested for potential effects of introgressive hybridization on phenotypic evolution in wild populations. We found that these effects differed among our study species. Constraints measured as the eccentricity of phenotypic variance–covariance matrices declined significantly with increasing gene flow in the less abundant species for matrices that have a diverged line of least resistance. In contrast, we find no such decline for the more abundant species. Overall our results suggest that hybridization can change the underlying phenotypic variance–covariance matrix, potentially increasing the adaptive potential of such populations

Evidence for Mito-Nuclear and Sex-Linked Reproductive Barriers between the Hybrid Italian Sparrow and Its Parent Species

Studies of reproductive isolation between homoploid hybrid species and their parent species have rarely been carried out. Here we investigate reproductive barriers between a recently recognized hybrid bird species, the Italian sparrow Passer italiae and its parent species, the house sparrow P. domesticus and Spanish sparrow P. hispaniolensis. Reproductive barriers can be difficult to study in hybrid species due to lack of geographical contact between taxa. However, the Italian sparrow lives parapatrically with the house sparrow and both sympatrically and parapatrically with the Spanish sparrow. Through whole-transcriptome sequencing of six individuals of each of the two parent species we identified a set of putatively parent species-diagnostic single nucleotide polymorphism (SNP) markers. After filtering for coverage, genotyping success (>97%) and multiple SNPs per gene, we retained 86 species-informative, genic, nuclear and mitochondrial SNP markers from 84 genes for analysis of 612 male individuals. We show that a disproportionately large number of sex-linked genes, as well as the mitochondria and nuclear genes with mitochondrial function, exhibit sharp clines at the boundaries between the hybrid and the parent species, suggesting a role for mito-nuclear and sex-linked incompatibilities in forming reproductive barriers. We suggest that genomic conflict via interactions between mitochondria and sex-linked genes with mitochondrial function ("mother's curse") at one boundary and centromeric drive at the other may best explain our findings. Hybrid speciation in the Italian sparrow may therefore be influenced by mechanisms similar to those involved in non-hybrid speciation, but with the formation of two geographically separated species boundaries instead of one. Spanish sparrow alleles at some loci have spread north to form reproductive barriers with house sparrows, while house sparrow alleles at different loci, including some on the same chromosome, have spread in the opposite direction to form barriers against Spanish sparrows

Effect of Species Interaction on Beak Integration in an Avian Hybrid Species Complex

Theory predicts that variability in size and the shape of a morphological trait should often be stable both at the intra- and interspecific level. We studied variation in beak integration among several populations of two species of the genus Passer, a hybrid species, the Italian sparrow (Passer italiae) and one of its parents, the Spanish sparrow (Passer hispaniolensis). We show that the general shape of the beak has been conserved in these two species and that hybrid speciation has had no major effects on beak integration. However, in young, sympatric populations, phenotypic integration between beak height and length decreased significantly, to the extent that these two dimensions apparently became independent. This displacement in phenotypic integration seems to be accompanied with changes in the distribution of phenotypic variation at the univariate level. This suggests that while beak shape may have been constrained over evolutionary time-scales and major hybridization events (i.e. the formation of the hybrid Italian sparrow), under specific selection regimes linked to secondary contact, it can evolve rapidly