Non-reciprocal cross-incompatibility in Trichogramma deion

In non-reciprocal cross-incompatibility (NRCI), the crossing of a female of a strain A with a male of a strain B results in hybrid offspring, whereas the reciprocal cross produces few or no hybrids. Only females are of hybrid origin in Hymenoptera because they arise from fertilized eggs; males arise from unfertilized (haploid) eggs. Crosses between many strains of Trichogramma deion showed some degree of NRCI. Crosses between a T. deion culture collected in Seven Pines, California (SVP) with one from Marysville, California (MRY) showed an extreme form of NRCI in which practically no female offspring was produced when MRY females were crossed with SVP males. The reciprocal cross produced a close to normal proportion of female and male offspring. Detailed studied of this cross indicated that 1) the female offspring produced in the compatible interstrain cross were not the result of parthenogenesis but were true hybrids, 2) the incompatible interstrain cross did not produce female offspring because fertilized eggs died during development, 3) the death of these eggs could not be prevented by either antibiotic or temperature treatment, 4) cytoplasmically inherited factors causing NRCI could be discounted because backcrossed females with the genome of MRY and the cytoplasm of SVP, exhibit the NRCI relationship characteristic of their genome. Therefore the NRCI between these strains appears to be caused by a modification coded for by the nuclear genes of MRY that results in incompatibility when SVP sperm fertilizes MRY eggs. In addition the level of incompatibility in crosses between the SVP females and MRY males is temperature sensitive, the higher the rearing temperature the lower the level of compatibility.     

Selection against immigrants in wild seabird populations

Immigration is a major demographic parameter shaping population dynamics and is an important driver of eco‐evolutionary patterns, but the fitness consequences for individuals following their settlement to a new population (immigrants) remain poorly tested in wild animal populations, particularly among long‐lived species. Here we show that immigrants have a lower fitness than residents in three wild seabird populations (wandering albatross Diomedea exulans, southern fulmar Fulmarus glacialoides, snow petrel Pagodroma nivea). Across all species and during a 32‐year period, immigrants made on average ?9 to 29% fewer breeding attempts, had 5–31% fewer fledglings, had 2–16% lower breeding success and produced 6–46% fewer recruits. Female immigration and male residency were also favored through differences in breeding performance. We provide evidence for selection against immigrants in wild populations of long‐lived species and our results are consistent with female‐biased dispersal in birds being driven by asymmetric limiting resources and the competitive ability of dispersers vs. non‐dispersers.     

Stagnant immigrant social networks and cycles of exploitation

Based on over four years of ethnographic research among street vendors in Los Angeles and on interviews with family members of vendors and former vendors living in Mexico, this article examines the influence of a sending community and its social networks on migrant outcomes in the USA. These social networks affect migration patterns, ease entry into the fruit-vending business but also facilitate exploitation. Furthermore, these social networks do not always function as effective conduits of information because its members, due to feelings of shame or embarrassment, often fail to add to the existing body of knowledge. As a result, international migration patterns, job placement and exploitative practices do not change or improve for subsequent migrants. This creates a cycle in which social networks become stagnant and successively fail to function as effective conduits of information and resources in ways that might help network members equally and in the aggregate.     

Clubs of culture and capital: immigrant and second-generation incorporation in a new destination school

The influx of Latin American immigrants into the US South since the early 1990s has changed the demographic face of the region, particularly among school-aged populations where the rate of growth among Latinos has been the fastest. Despite an emerging literature addressing changing racial and ethnic relations in the New US South, relatively little research has addressed the incorporation of Latino youths within southern schools. Relying on data from a four-year ethnographic and in-depth interview study in one North Carolina town, findings suggest powerful benefits of ethnic-identity based clubs for Latino youths in new immigrant destination schools. While both Latino and African American respondents faced discrimination within their community, Latino students received more formal support at school, which helped shield them from the negative impacts of discrimination.     

‘Our fellow Africans make our lives hell’: the lives of Congolese and Nigerians living in Johannesburg

Xenophobia in post-apartheid South Africa has become a major issue. Much of the hostility is directed at Africans from countries north of Southern Africa who are often easily distinguishable due to their physical features, distinctive dress and inability to speak the indigenous languages. This article focuses on immigrants and asylum seekers from two countries, Nigeria and the Democratic Republic of Congo. Both groupings have experienced significant antagonism and prejudice from the local population, more especially from black South Africans. The article describes and analyses the interaction of the two groupings in question with the local populace and authorities. What is argued is that during the apartheid era the restrictions on black immigration meant that the number of black foreigners was limited. Since 1990, however, there has been a substantial increase in illegal and legal migration from Southern African countries and countries further north. This increase, in a context of growing unemployment and crime, limited infrastructural growth and fiscal resources, has intensified xenophobia against foreign Africans. The article is mainly based on in-depth interviews with Nigerian and Congolese informants living in Johannesburg's inner city.     

Evolution of postzygotic reproductive isolation in galliform birds: analysis of first and second hybrid generations and backcrosses

The process of speciation is a crucial aspect of evolutionary biology. In this study, we analysed the patterns of evolution of postzygotic reproductive isolation in Galliformes using information on hybridization and genetic distance among species. Four main patterns arose: (1) hybrid inviability and sterility in F₁ hybrids increase as species diverge; (2) the presence of geographical overlap does not affect the evolution of postzygotic isolation; (3) the galliforms follow Haldane's rule; (4) hybrid inviability is higher in F₂ than in F₁ hybrids, but does not appear to be increased in the backcrosses. This study contributes to the growing evidence suggesting that the patterns of evolution of postzygotic isolation and the process of speciation are shared among avian groups (and animals in general). In particular, our results support the notion of F₂ hybrid inviability as being key for the maintenance of species genetic integrity when prezygotic isolation barriers are overcome in closely related species, in which postzygotic isolation in the F₁ hybrid might still not be fully developed. To the contrary, hybrids from backcrosses did not show serious inviability problems (at least not more than F₁ hybrids), demonstrating that they could generate gene flow among bird species. © 2013 The Linnean Society of London, Biological Journal of the Linnean Society, 2013, 110 , 528–542.     

Structural and genetic studies of the proliferation disrupter genes of Drosophila simulans and D. melanogaster

To examine whether structural and functional differences exist in the proliferation disrupter (prod) genes between Drosophila simulans and D. melanogaster, we analyzed and compared both genes. The exon–intron structure of the genes was found to be the same – three exons were interrupted by two introns, although a previous report suggested that only one intron existed in D. melanogaster. The prod genes of D. simulans and D. melanogaster both turn out to encode 346 amino acids, not 301 as previously reported for D. melanogaster. The numbers of nucleotide substitutions in the prod genes was 0.0747 ±  per synonymous site and 0.0116 ± 0.0039 per replacement site, both comparable to those previously known for homologous genes between D. simulans and D. melanogaster. Genetic analysis demonstrated that D. simulans PROD can compensate for a deficiency of D. melanogaster PROD in hybrids. The PRODs of D. simulans and D. melanogaster presumably share the same function and a conserved working mechanism. The prod gene showed no significant interaction with the lethality of the male hybrid between these species. This revised version was published online in July 2006 with corrections to the Cover Date.     

Sexual isolation evolves faster than hybrid inviability in a diverse and sexually dimorphic genus of fish (Percidae: Etheostoma)

Abstract .Theory predicts that sexual (or behavioral) isolation will be the first form of reproductive isolation to evolve in lineages characterized by sexual selection. Here I directly compare the rate of evolution of sexual isolation with that of hybrid inviability in a diverse and sexually dimorphic genus of freshwater fish. The magnitude of both sexual isolation and hybrid inviability were quantified for multiple pairs of allopatric species. Rates of evolution were inferred by comparing genetic distances of these species pairs with the magnitude of each form of reproductive isolation: the slope of the regression of genetic distance on the magnitude of reproductive isolation represents the rate of evolution. Of the two forms of isolation, the magnitude of sexual isolation exhibited the steeper slope of regression, indicating that sexual isolation will tend to evolve to completion earlier than hybrid inviability, strictly as a by-product of evolution in geographically isolated populations. Additional evidence from the literature is used to qualitatively compare rates of evolution of sexual isolation with that of other forms of reproductive isolation. Preliminary comparisons support the prediction that sexual isolation will evolve more rapidly than other forms. Because Etheostoma is characterized by striking sexual dimorphism, these results are consistent with the hypothesis that sexual selection for exaggerated mate-recognition characters causes the relatively rapid evolution of sexual isolation.     

Rhetoric of Exclusion and Racist Violence in a Catalan Secondary School

Drawing on ethnographic research in a secondary school in Catalonia, Spain, this article analyzes the relationship between racist violence against students of African origin and racist ideologies held by students, described as a rhetoric of exclusion. I argue for a more detailed and painstaking characterization of students' ethnic discourses as a means of understanding the diversity of these discourses and their connection to intergroup relations.     

Diaspora and the Anthropology of Latino Education: Challenges, Affinities, and Intersections

In this article, I highlight the challenges, tensions, and affinities between Latino educational anthropology and diaspora studies. Some of the urgent questions include attention to new Latino destinations, transnationalism, and Latino diversity. It concludes by suggesting future pathways through Latina feminist thought.