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The synthesis and in vitro evaluation of a squarate hydroxamate-coumarin conjugate, 12, as a chemodosimeter for Fe(III) and other oxidants, such as Cr(VI) and Ce(IV), is described. As 12 was originally designed to become a chelation-enhanced fluorescence (CHEF)-type sensor for Fe(III), the competence of the squarate diamide platform to relay a CHEF response was demonstrated using a zinc-binding, cyclen-substituted squarate coumarin amide. Due to a photo electron transfer process, 12 possesses a low fluorescence yield. Upon exposure of 12 to Fe(III) (or other oxidants), an irreversible 9-fold fluorescence intensity increase is observed as the result of an oxidation/hydrolysis reaction. The (aminomethyl)coumarin portion of 12 is oxidized to an iminocoumarin that hydrolyzes to produce a highly fluorescent coumarinaldehyde. Fe(III) acts as a catalyst in this transformation, thereby enhancing the sensitivity of the system for the detection of Fe(III) down to 1 ppm in aqueous buffer solution. The identities of the major reaction products between 12 and Fe(III) were proven by independent synthesis.

Sorex araneus, the Common shrew, is a species with more than 70 karyotypic races, many of which form parapatric hybrid zones, making it a model for studying chromosomal speciation. Hybrids between races have reduced fitness, but microsatellite markers have demonstrated considerable gene flow between them, calling into question whether the chromosomal barriers actually do contribute to genetic divergence. We studied phenotypic clines across two hybrid zones with especially complex heterozygotes. Hybrids between the Novosibirsk and Tomsk races produce chains of nine and three chromosomes at meiosis, and hybrids between the Moscow and Seliger races produce chains of eleven. Our goal was to determine whether phenotypes show evidence of reduced gene flow at hybrid zones. We used maximum likelihood to fit tanh cline models to geometric shape data and found that phenotypic clines in skulls and mandibles across these zones had similar centers and widths as chromosomal clines. The amount of phenotypic differentiation across the zones is greater than expected if it were dissipating due to unrestricted gene flow given the amount of time since contact, but it is less than expected to have accumulated from drift during allopatric separation in glacial refugia. Only if heritability is very low, Ne very high, and the time spent in allopatry very short, will the differences we observe be large enough to match the expectation of drift. Our results therefore suggest that phenotypic differentiation has been lost through gene flow since post-glacial secondary contact, but not as quickly as would be expected if there was free gene flow across the hybrid zones. The chromosomal tension zones are confirmed to be partial barriers that prevent differentiated races from becoming phenotypically homogenous.

The Moscow and Seliger chromosomal races of the common shrew differ by Robertsonian fusions and possibly whole‐arm reciprocal translocations (WARTs) such that their F1 hybrids produce a chain‐of‐eleven configuration at meiosis I and are expected to suffer substantial infertility. Of numerous hybrid zones that have been described in the common shrew, those between the Moscow and Seliger races involve the greatest chromosomal difference. We collected 211 individuals from this zone to generate a total dataset of 298 individuals from 187 unique global positioning system (GPS) locations within the vicinity of interracial contact. We used a geographic information system (GIS) to map the location of the hybrid zone, which follows a direct route between two lakes, as would be anticipated from tension zone theory. Even within the central area of the hybrid zone, there is a much higher frequency of pure race individuals than hybrid, making this a clear example of a bimodal zone in the sense of Jiggins & Mallet (2000). The zone runs through good habitat for common shrews, but nevertheless it is very narrow (standard cline widths: 3–4 km), as would be anticipated from low hybrid fitness. There is clear potential for an interruption to gene flow and build‐up of reproductive isolation. As found in some other hybrid zones, there is a high frequency of novel genetic variants, in this case, new chromosomal rearrangements. Here, we report a de novo Robertsonian fission and a de novo reciprocal translocation, both for the first time in the common shrew. There is an extraordinarily high frequency of de novo mutations recorded in F1 hybrids in the zone and we discuss how chromosomal instability may be associated with such hybrids. The occurrence of a de novo Robertsonian fission is of considerable significance because it provides missing evidence that fissions are the basis of the novel acrocentric forms found and apparently selected for in certain common shrew hybrid zones.