Convergence, Constraint and the Role of Gene Expression During Adaptive Radiation: Floral Anthocyanins in Aquilegia

Convergent phenotypes are testament to the role of natural selection in evolution. However, little is known about whether convergence in phenotype extends to convergence at the molecular level. We use the independent losses of floral anthocyanins in columbines (Aquilegia) to determine the degree of molecular convergence in gene expression across the anthocyanin biosynthetic pathway (ABP). Using a phylogeny of the North American Aquilegia clade, we inferred six independent losses of floral anthocyanins. Via semiquantitative reverse transcriptase-polymerase chain reaction (RT-PCR), we monitored developmental and tissue-specific variation in expression of the six major structural ABP loci in three Aquilegia species, two that produce anthocyanins (A+) and one that does not (A-). We then compared ABP expression in petals of old-bud and pre-anthesis flowers of 13 Aquilegia species, eight wild species and two horticultural lines representing seven independent A- lineages as well as three wild A+ species. We only found evidence of down-regulation of ABP loci in A- lineages and losses of expression were significantly more prevalent for genes late in the pathway. Independent contrast analysis indicates that changes in expression of dihydroflavonol reductase (DFR) and anthocyanidin synthase (ANS) are strongly phylogenetically correlated consistent with the multilocus targets of trans-regulatory elements in the ABP of other systems. Our findings strongly suggest that pleiotropy constrains the evolution of loss of floral anthocyanins to mutations affecting genes late in the ABP mostly through convergent changes in regulatory genes. These patterns support the hypothesis that rapid evolutionary change occurs largely through regulatory rather than structural mutations

Geographic genetic structure of Iberian columbines (gen. Aquilegia)

Southern European columbines (genus Aquilegia)are involved in active processes of diversification, and the Iberian Peninsula offers a privileged observatory to witness the process. Studies on Iberian columbines have provided significant advances on species diversification,but we still lack a complete perspective of the genetic diversification in the Iberian scenario. This work explores how genetic diversity of the genus Aquilegia is geographically structured across the Iberian Peninsula. We used Bayesian clustering methods, principal coordinates analyses, and NJ phenograms to assess the genetic relationships among 285 individuals from 62 locations and detect the main lineages. Genetic diversity of Iberian columbines consists of five geographically structured lineages, corresponding to different Iberian taxa. Differentiation among lineages shows particularly complex admixture patterns at Northeast and highly homogeneous toward Northwest and Southeast. This geographic genetic structure suggests the existence of incomplete lineage sorting and interspecific hybridization as could be expected in recent processes of diversification under the influence of quaternary postglacial migrations. This scenario is consistent with what is proposed by the most recent studies on European and Iberian columbines, which point to geographic isolation and divergent selection by habitat specialization as the main diversification drivers of the Iberian Aquilegia complex

The Racist Pandemic. A Semantico-Pragmatic Study of Anti-Asian Overtones in COVID-19-related Twitter Discourse

2019 saw the emergence of a new human pathogen, SARS-CoV-2, which causes a disease currently known as COVID-19. There are, however, other names which expose the Asian origin of the virus. These ways of reference – although discouraged by the scientific community – still remain in frequent use in various COVID-19-related discourses. Such names explicitly point to the geographical place of origin of the virus, but at the same time are likely to provoke associations and solidify pre-existing stereotypes about Asians as well as strengthen misconceptions about the virus itself. The intention of the use of terms such as Chinese virus may be purely referential, but they are, nonetheless, marked with accusatory or downright racist overtones. The present paper is maintained within the Critical Discourse Analysis (CDA) framework (van Dijk 1993), as CDA aims specifically to examine the ways in which discourses shape power relations, maintain social stigmas, perpetuate stereotypes and widen inequalities. We use CDA as a framework for conducting a semantic analysis of expressions such as Asian virus, Chinese virus, Sinovirus or Wuhan virus used on Twitter. Specifically, we intend to select the usages that are unequivocally intentional and whose aim is not only to emphasise the geographical origin of the virus, but also to justify blaming China for the global pandemic that SARS-CoV-2 eventually has caused. We have found that potentially harmful names such as Chinese virus have been used intentionally and are accompanied by even more blatant cases of defamatory and accusatory language targeting the Chinese. It is even more significant, as the proliferation of anti-Asian hate speech has culminated in a serious aftermath in the form of anti-Asian violence, especially in the US

The bearing of mutant and cross specificity on the pattern of intragenic recombination

Four white-spored allelic mutants ofAscobolus immersuswere used to study the effect of mutant and cross specificity on the recombination pattern in intragenic crosses.In the locus studied no correlation was found between the position of mutants on the map and their basic conversion frequencies. One of the mutants evidently caused an increase of conversion frequency of the two others. Crossing-over in intragenic recombination may be mutant-specific as revealed by using two mutants which give no recombinants when crossed with each other. The frequency of crossing-over was higher in crosses in repulsion than in coupling involving the same pairs of mutants. Polarization observed in two-point crosses was due in some instances predominantly to differences in basic conversion frequencies of the mutants used, and in others to the relative position of the mutated sites. Mutants located in the central part of the studied region were those which converted most frequently in two-point crosses. No reciprocal conversions were observed.A number of recombinant asci resulting from two or more separate but highly correlated recombinational events within a gene were found.</jats:p