Morphometric Variation as an Indicator of Genetic Interactions between Black-capped and Carolina Chickadees at a Contact Zone in the Appalachian Mountains

We studied hybridization and introgression between Black-capped (Poecile atricapillus) and Carolina (P. carolinensis) chickadees along two transects in the Appalachians using four genetic markers and multivariate analysis of morphology. Genetic data revealed that at least 58% of the birds in the center of each transect were of mixed ancestry and that recombinant genotypes predominated among hybrids, demonstrating that hybridization is frequent and that many hybrids are fertile. Genetic clines generally were steep and coincident in position, but introgression was evident well beyond the range interface. Introgression was higher at the one autosomal locus surveyed than in mitochondrial DNA or in two sexlinked markers, suggesting that the hybrid zone is a conduit for gene flow between the two forms at some loci. On a broad scale, morphometric variation was concordant with genetic variation. Clines in morphological variation based on principal components (PC) scores were steep and coincident with genetic clines. Also, a strong correlation within a population between PC scores and an individual\u27s genetic makeup suggested that a large amount of morphological variation was genetically determined. However, morphological analysis indicated that hybrids were uncommon on one transect, whereas genetic data clearly showed that they were common on both. In addition, patterns of morphological variation were equivocal regarding introgression across the hybrid zone. Thus, genetic data provided a complementary and more detailed assessment of hybridization, largely due to the discrete nature of genetic variation. Genetic markers are useful in understanding hybridization and introgression, but diagnostic markers may underestimate average gene flow if selection against hybrids maintains steep clines at diagnostic loci. To gain a clearer picture of the genome-wide effects of hybridization. A much larger number of loci must be assayed, including non-diagnostic ones

Reproductive Isolation and Cryptic Introgression in a Sky Island Enclave of Appalachian Birds

Reproductive isolation is central to the speciation process, and cases where the strength of reproductive isolation varies geographically can inform our understanding of speciation mechanisms. Although generally treated as separate species, Black-capped chickadees (Poecile atricapillus) and Carolina chickadees (P. carolinensis) hybridize and undergo genetic introgression in many areas where they come into contact across the eastern United States and in the northern Appalachian Mountains. The Great Smoky Mountains harbor the last large breeding population of atricapillus in the southern Appalachians, isolated from the species’ main range by nearly 200 km. This population is believed to be reproductively isolated from local carolinensis due to an unusual, behaviorally mediated elevational range gap, which forms during the breeding season and may function as an incipient reproductive isolating mechanism. We examined the effectiveness of this putative isolating mechanism by looking for genetic introgression from carolinensis in Great Smoky Mountain atricapillus. We characterized this population and parental controls genetically using hundreds of amplified fragment length polymorphism (AFLP) loci as well as mitochondrial DNA (mtDNA) sequence data from cytochrome-b. Great Smoky Mountain atricapillus have experienced nuclear genetic introgression from carolinensis, but at much lower levels than other populations near the hybrid zone to the north. No mitochondrial introgression was detected, in contrast to northern contact areas. Thus, the seasonal elevational range gap appears to have been effective in reducing gene flow between these closely related taxa

An Assessment of Song Admixture as an Indicator of Hybridization in Black-capped Chickadees (Poecile atricapillus) and Carolina Chickadees (Poecile carolinensis)

Vocal admixture often occurs where differentiated populations or species of birds meet. This may entail song sympatry, bilingually singing birds, and songs with intermediate or atypical characteristics. Different levels of vocal admixture at the range interface between Black-capped Chickadees (Poecile atricapillus) and Carolina Chickadees (P. carolinensis) have been interpreted as indicating that hybridization is frequent at some locations but not others. However, song ontogeny in these birds has a strong nongenetic component, so that inferences regarding hybridization based on vocal admixture require confirmation. We used diagnostic genetic markers and quantitative analyses of song to characterize population samples along two transects of the chickadee contact zone in the Appalachian Mountains. More than 50% of individuals at the range interface were of hybrid ancestry, yet only 20% were observed to be bilingual or to sing atypical songs. Principal component analysis revealed minimal song intermediacy. This result contrasts with an earlier analysis of the hybrid zone in Missouri that found considerable song intermediacy. Re-analysis of the Missouri data confirmed this difference. Correlation between an individual\u27s genetic composition and its song type was weak in Appalachian hybrid populations, and genetic introgression in both forms extended far beyond the limits of vocal admixture. Therefore, song is not a reliable indicator of levels of hybridization or genetic introgression at this contact zone. Varying ecological factors may play a role in producing variable levels of song admixture in different regions of the range interface

Reactivity of a Sterically Unencumbered α-Borylated Phosphorus Ylide towards Small Molecules

The influence of substituents on α‐borylated phosphorus ylides (α‐BCPs) has been investigated in a combined experimental and quantum chemical approach. The synthesis and characterization of Me$_{3}$PC(H)B(iBu)$_{2}$ (1), consisting of small Me substituents on phosphorous and iBu residues on boron, is reported. Compound 1 is accessible through a novel synthetic approach, which has been further elucidated through DFT studies. The reactivity of 1 towards various small molecules was probed and compared with that of a previously published derivative, Ph$_{3}$PC(Me)BEt$_{2}$ (2). Both α‐BCPs react with NH$_{3}$ to undergo heterolytic N−H bond cleavage. Different di‐ and trimeric ring structures were observed in the reaction products of 1 with CO and CO$_{2}$. With PhNCO and PHNCS, the expected insertion products [Me$_{3}$PC(H)(PhNCO)B(iBu)$_{2}$] and [Me$_{3}$PC(H)(PhNCS)B(iBu)$_{2}$], respectively, were isolated

Machine learning a model for RNA structure prediction

RNA function crucially depends on its structure. Thermodynamic models currently used for secondary structure prediction rely on computing the partition function of folding ensembles, and can thus estimate minimum free-energy structures and ensemble populations. These models sometimes fail in identifying native structures unless complemented by auxiliary experimental data. Here, we build a set of models that combine thermodynamic parameters, chemical probing data (DMS and SHAPE) and co-evolutionary data (direct coupling analysis) through a network that outputs perturbations to the ensemble free energy. Perturbations are trained to increase the ensemble populations of a representative set of known native RNA structures. In the chemical probing nodes of the network, a convolutional window combines neighboring reactivities, enlightening their structural information content and the contribution of local conformational ensembles. Regularization is used to limit overfitting and improve transferability. The most transferable model is selected through a cross-validation strategy that estimates the performance of models on systems on which they are not trained. With the selected model we obtain increased ensemble populations for native structures and more accurate predictions in an independent validation set. The flexibility of the approach allows the model to be easily retrained and adapted to incorporate arbitrary experimental information

Gesundheitsentwicklung in Deutschland bis 2037: Eine volkswirtschaftliche Kostensimulation

Die Studie zeigt, wie sich die direkten Kosten, das heißt die Kosten, die für die Behandlung von Krankheiten aufgewendet werden müssen und die indirekten Krankheitskosten, das heißt die Kosten durch den krankheitsbedingten Arbeitsausfall von Erwerbstätigen, aufgrund der Demografie verändern werden und welche Kostensenkungen dabei eine verbesserte Gesundheit bewirken kann. Dabei wurden zwei Simulationen durchgeführt, die jeweils auf einer Bevölkerungsprognose des Statistischen Bundesamtes beruhen. --

Strategy for the Implementation of an Industrial Land Bank

The City of Cleveland plans to create a long-term vision for industrial and commercial land reuse in order to better serve the business and neighborhood interests of its citizens. The implementation of an industrial land bank is one critical way in which to fulfill this goal. This study aimed to develop a strategy to aid the city in the operation and management of rehabilitating commercial and industrial properties for reuse. The objectives of the project were to: * Incorporate a strategy understood by senior managers at the city that identifies a broad economic redevelopment vision, especially for brownfields. * Include in the plan strategies for financing the acquisition and/or transfer of properties into the land bank. * Establish elements in the plan to include both short- and long-term implementation

The naturally occurring N6-threonyl adenine in anticodon loop of Schizosaccharomyces pombe tRNA(i) causes formation of a unique U-turn motif

Modified nucleosides play an important role in structure and function of tRNA. We have determined the solution structure of the anticodon stem–loop (ASL) of initiator tRNA of Schizosaccharomyces pombe. The incorporation of N6-threonylcarbamoyladenosine at the position 3′ to the anticodon triplet (t(6)A37) results in the formation of a U-turn motif and enhances stacking interactions within the loop and stem regions (i.e. between A35 and t(6)A37) by bulging out U36. This conformation was not observed in a crystal structure of tRNAi including the same modification in its anticodon loop, nor in the solution structure of the unmodified ASL. A t(6)A modification also occurs in the well studied anti-stem–loop of lys-tRNA(UUU). A comparison of this stem–loop with our structure demonstrates different effects of the modification depending on the loop sequence

Habitat characterization and spatial distribution of Anopheles sp. mosquito larvae in Dar es Salaam (Tanzania) during an extended dry period

INTRODUCTION: By 2030, more than 50% of the African population will live in urban areas. Controlling malaria reduces the disease burden and further improves economic development. As a complement to treated nets and prompt access to treatment, measures targeted against the larval stage of Anopheles sp. mosquitoes are a promising strategy for urban areas. However, a precise knowledge of the geographic location and potentially of ecological characteristics of breeding sites is of major importance for such interventions. METHODS: In total 151 km(2 )of central Dar es Salaam, the biggest city of Tanzania, were systematically searched for open mosquito breeding sites. Ecologic parameters, mosquito larvae density and geographic location were recorded for each site. Logistic regression analysis was used to determine the key ecological factors explaining the different densities of mosquito larvae. RESULTS: A total of 405 potential open breeding sites were examined. Large drains, swamps and puddles were associated with no or low Anopheles sp. larvae density. The probability of Anopheles sp. larvae to be present was reduced when water was identified as "turbid". Small breeding sites were more commonly colonized by Anopheles sp. larvae. Further, Anopheles gambiae s.l. larvae were found in highly organically polluted habitats. CONCLUSIONS: Clear ecological characteristics of the breeding requirements of Anopheles sp. larvae could not be identified in this setting. Hence, every stagnant open water body, including very polluted ones, have to be considered as potential malaria vector breeding sites