Mexico through a superdiversity lens: already-existing diversity meets new immigration

New migration flows to Mexico are challenging long-established sociocultural configurations. So far, most studies on immigrants in Mexico have focused on singular ethno-national groups rather than paying attention to the intermingling of people. This paper presents an examination of diversification processes occurring in Guadalajara, Mexico. We contend that these are particularly strained because of the continuing frictions with which the country has to deal due to its already-existing diversity. The many forms of discrimination and racism that many Mexicans are subjected to by their co-nationals are often extended to new arrivals. The increasing complexity of migrant inflows challenges established forms of prejudice in everyday interactions. We argue in this paper that the use of superdiversity as a lens to study diversification processes allows us to better understand the changing dynamics currently taking place in Mexico.     

Genetic structure in insular and mainland populations of house sparrows (Passer domesticus) and their hemosporidian parasites

Small and isolated populations usually exhibit low levels of genetic variability, and thus, they are expected to have a lower capacity to adapt to changes in environmental conditions, such as exposure to pathogens and parasites. Comparing the genetic variability of selectively neutral versus functional loci allows one to assess the evolutionary history of populations and their future evolutionary potential. The genes of the major histocompatibility complex (MHC) control immune recognition of parasites, and their unusually high diversity is genes which is likely driven by parasite‐mediated balancing selection. Here, we examined diversity and differentiation of neutral microsatellite loci and functional MHC class I genes in house sparrows (Passer domesticus), living in six insular and six mainland populations, and we aimed to determine whether their diversity or differentiation correlates with the diversity and the prevalence of infection of hemosporidian parasites. We found that island bird populations tended to have lower neutral genetic variability, whereas MHC variability gene was similar between island and mainland populations. Similarly, island populations tended to show greater genetic differentiation than mainland populations, especially at microsatellite markers. The maintenance of MHC genetic diversity and its less marked structure in the island populations could be attributed to balancing‐selection. The greater MHC differentiation among populations was negatively correlated with similarity in blood parasites (prevalence and diversity of parasite strains) between populations. Even at low prevalence and small geographical scale, haemosporidian parasites might contribute to structure the variability of immune genes among populations of hosts.     

Using Heading date 1 preponderant alleles from indica cultivars to breed high‐yield,high‐quality japonica rice varieties for cultivation in south China

Heading date 1 (Hd1) is an important gene for the regulation of flowering in rice, but its variation in major cultivated rice varieties, and the effect of this variation on yield and quality, remains unknown. In this study, we selected 123 major rice varieties cultivated in China from 1936 to 2009 to analyse the relationship between the Hd1 alleles and yield‐related traits. Among these varieties, 19 haplotypes were detected in Hd1, including two major haplotypes (H8 and H13) in the japonica group and three major haplotypes (H14, H15 and H16) in the indica group. Analysis of allele frequencies showed that the secondary branch number was the major aimed for Chinese indica breeding. In the five major haplotypes, SNP₃₁₆(C‐T) was the only difference between the two major japonica haplotypes, and SNP₄₉₅(C‐G) and SNP₆₁₄(G‐A) are the major SNPs in the three indica haplotypes. Association analysis showed that H16 is the most preponderant allele in modern cultivated Chinese indica varieties. Backcrossing this allele into the japonica variety Chunjiang06 improved yield without decreasing grain quality. Therefore, our analysis offers a new strategy for utilizing these preponderant alleles to improve yield and quality of japonica varieties for cultivation in the southern areas of China.     

生物类专业课程思政教学改革初探——以生物化学为例

课程思政教学改革近两年来获得广泛关注。如何在专业课教学中融入思政元素以达到二者协同育人的目的,是值得我们思考的问题。生物化学与微生物学、细胞生物学等课程具有显著的共性和关联,是生物类专业的重要基础课程。结合本科生生物化学课堂教学中的具体例子,本文介绍了课程思政教学改革的经验,重点探讨如何发掘专业知识点的思政内涵,为相关生物类专业课程思政教学改革提供参考。     

Many loci make light work: High individual diversity despite low population diversity and random mating at class I MHC in a Critically Endangered island songbird

Multi‐cellular organisms are under constant attack from parasites, making immune defence a critical aspect of fitness. In vertebrate animals, genes of the major histocompatibility complex (MHC) determine the breadth of pathogens to which individuals can respond. Having many MHC alleles can confer better protection against infectious disease, and balancing selection at MHC is widespread. Indeed, MHC loci are famously variable, with some populations harbouring thousands of alleles (Biedrzycka et al., 2018; Robinson, Soormally, Hayhurst, & Marsh, 2016). MHC has also long fascinated behavioural ecologists because mate choice—for example, preferring MHC‐dissimilar partners—may amplify the effects of natural selection (Penn & Potts, 1999). But despite keen interest in the evolutionary ecology of MHC, extensive duplication (Minias, Pikus, Whittingham, & Dunn, 2019) has made these genes challenging to study. In a From the Cover article in this issue of Molecular Ecology, Stervander, Dierickx, Thorley, Brooke, and Westerdahl (2020) characterizes class I MHC in a Critically Endangered songbird, relating genotype to mate choice and survivorship. By inferring copy number and patterns of allelic co‐segregation, the authors pave the way to elucidating the genomic architecture of MHC in this bottlenecked population. These insights help reconcile apparently counterintuitive findings: no effect of MHC genotype on mate choice or survival, and high MHC diversity within individuals despite low diversity at the population level. The latter finding is cause for optimism regarding conservation prospects. Moreover, these results suggest that ancient duplication events can have longstanding effects on the adaptive landscapes of natural and sexual selection.     

Major histocompatibility complex variation is similar in little brown bats before and after white‐nose syndrome outbreak

White‐nose syndrome (WNS), caused by the fungal pathogen Pseudogymnoascus destructans (Pd), has driven alarming declines in North American hibernating bats, such as little brown bat (Myotis lucifugus). During hibernation, infected little brown bats are able to initiate anti‐Pd immune responses, indicating pathogen‐mediated selection on the major histocompatibility complex (MHC) genes. However, such immune responses may not be protective as they interrupt torpor, elevate energy costs, and potentially lead to higher mortality rates. To assess whether WNS drives selection on MHC genes, we compared the MHC DRB gene in little brown bats pre‐ (Wisconsin) and post‐ (Michigan, New York, Vermont, and Pennsylvania) WNS (detection spanning 2014–2015). We genotyped 131 individuals and found 45 nucleotide alleles (27 amino acid alleles) indicating a maximum of 3 loci (1–5 alleles per individual). We observed high allelic admixture and a lack of genetic differentiation both among sampling sites and between pre‐ and post‐WNS populations, indicating no signal of selection on MHC genes. However, post‐WNS populations exhibited decreased allelic richness, reflecting effects from bottleneck and drift following rapid population declines. We propose that mechanisms other than adaptive immunity are more likely driving current persistence of little brown bats in affected regions.     

A comparison of bovine lymphocyte antigens

In Canberra, 31 antigens have been described on the surface of bovine lymphocytes. Seven antigens are subgroups of other antigens. Eleven antigens are similar to the eleven antigens which have been described in Melbourne. Fourteen antigens are similar to twelve international-workshop antigens and two European-workshop antigens.     

Population structure and geographical subdivision of the Leishmania major vector Phlebotomus papatasi as revealed by microsatellite variation

Abstract Multi‐locus microsatellite typing (MLMT) has been employed to infer the population structure of Phlebotomus papatasi (Scopoli) (Diptera: Psychodidae) sandflies and assign individuals to populations. Phlebotomus papatasi sandflies were collected from 35 sites in 15 countries. A total of 188 P. papatasi individuals were typed using five microsatellite loci, resulting in 113 different genotypes. Unique microsatellite signatures were observed for some of the populations analysed. Comparable results were obtained when the data were analysed with Bayesian model and distance‐based methods. Bayesian statistic‐based analyses split the dataset into two distinct genetic clusters, A and B, with further substructuring within each. Population A consisted of five subpopulations representing large numbers of alleles that were correlated with the geographical origins of the sandflies. Cluster B comprised individuals collected in the Middle East and the northern Mediterranean area. The subpopulations B1 and B2 did not, however, show any further correlation to geographical origin. The genetic differentiation between subpopulations was supported by F statistics showing statistically significant (Bonferroni‐corrected P < 0.005) values of 0.221 between B2 and B1 and 0.816 between A5 and A4. Identification of the genetic structure of P. papatasi populations is important for understanding the patterns of dispersal of this species and to developing strategies for sandfly control.