Population biology of Carlina vulgaris and Hypochoeris radicata in fragmented European grasslands

The ongoing anthropogenic impact on our landscape, e.g. by intensification of agricultural use and abandonment of extensively used farmland, strongly affects the persistence of many plant and animal species and populations. Many formerly connected habitats were destroyed or became fragmented. As a consequence many populations became extinct and remnant populations became smaller in size and more isolated. These small and isolated populations are at a higher risk of extinction because they are more sensitive to demographic, environmental and genetic stochasticity. Genetic stochasticity, i.e. genetic drift, and inbreeding in small and isolated populations might lead to reduced individual fitness in the short term. In the long term the ability to react to changing environmental conditions might decrease. Moreover, the environmental conditions in remnant habitats might be of lower quality, e.g. due to increasing edge effects. As species become restricted to remnant habitats, effective management for long-term conservation requires a quantitative understanding of the effects of habitat fragmentation on population viability. Most recent studies of the effects of habitat fragmentation were carried out at relatively small geographical scales. In this thesis I present four studies of the effects of habitat fragmentation on plant performance that investigate offspring performance, quantitative genetic variation and local adaptation in populations at a large geographical scale. Populations were studied in several European regions (in Sweden, The Netherlands, Germany, Britain, Czech Republic, Luxembourg and Switzerland). The target species Carlina vulgaris L. and Hypochoeris radicata L. have contrasting life histories with respect to dispersal ability and the frequency of flowering, but both species are widespread in species-rich semi-natural grasslands throughout Europe. Species-rich grasslands have dramatically declined in number and size in the last decades and are thus an excellent system to study effects of habitat fragmentation. In Chapter 2 I study the effects of habitat conditions and population size and isolation on the performance of C. vulgaris from 74 populations in seven European regions, both in natural populations and in a common garden. In the common garden several measures of performance were reduced in plants from small populations and plant size decreased with increasing isolation of the populations, indicating genetic drift and inbreeding depression in small and isolated populations. In the field, only seed set was reduced in small populations. Environmental variables explained most of the variation in plant size among populations in the field. The results suggest that reproduction and offspring performance may be reduced in small populations of C. vulgaris across Europe due to genetic deterioration, and because pollen quality and quantity might be reduced. In Chapter 3 I analyse the variation in several quantitative genetic traits in offspring grown in a common garden from 74 populations of Carlina vulgaris from seven geographical regions and 32 populations of Hypochoeris radicata from three geographical regions. In both species, most traits varied considerably among seed families within populations, among populations within regions and among regions. The overall proportion of phenotypic genetic variation among populations was higher in C. vulgaris (75.8 %) than in H. radicata (50.7 %), suggesting less gene flow between populations in the poorly dispersed C. vulgaris. The results suggest that at the small scale genetic drift or environmental differences that are not related to geographical distances drive population differentiation, whereas at the large scale selective forces closely related to geographical distances are most important for population differentiation. In Chapter 4 population differentiation and local adaptation in Carlina vulgaris is studied at the European scale. Reciprocal transplant experiments were carried out among (regional scale) and within (local scale) five European regions. Only at the regional scale, the individual fitness of C. vulgaris and several other measures of the plant performance were highest if plants grew in their home region. Furthermore, performance of plants decreased with increasing transplant distance. At the local scale, genotype x environment interactions were far less pronounced and were not related to geographical distance between the population of origin and the transplant site. The results of our study suggest that C. vulgaris consists of regionally adapted genotypes and that distance is a good predictor of the extent of adaptive differentiation at large (> 200 km), but not at small scales. Thus, patterns of local adaptation have to be taken into account for the efficient preservation of genetic resources. In Chapter 5 I present a study on the effects of cross-proximity on seed production and offspring performance of Hypochoeris radicata from Germany, Czechia and The Netherlands. Crosses were carried out within plants (selfing), and between plants from the same seed family, from the same population, from different populations of the same region and from different regions. Seed set and germination after inbreeding and crosses between populations were lower than after within population crosses, indicating inbreeding and outbreeding depression. However, crosses between regions resulted in higher seed set than within population crosses. For late traits, there was regional variation in the effects of inbreeding and interpopulation crosses. Our results suggest that outbreeding depression does not necessarily increase with interpopulation distance and that the sensitivity of populations to introgression may vary among regions

Population biology of Carlina vulgaris and Hypochoeris radicata in fragmented European grasslands

The ongoing anthropogenic impact on our landscape, e.g. by intensification of agricultural use and abandonment of extensively used farmland, strongly affects the persistence of many plant and animal species and populations. Many formerly connected habitats were destroyed or became fragmented. As a consequence many populations became extinct and remnant populations became smaller in size and more isolated. These small and isolated populations are at a higher risk of extinction because they are more sensitive to demographic, environmental and genetic stochasticity. Genetic stochasticity, i.e. genetic drift, and inbreeding in small and isolated populations might lead to reduced individual fitness in the short term. In the long term the ability to react to changing environmental conditions might decrease. Moreover, the environmental conditions in remnant habitats might be of lower quality, e.g. due to increasing edge effects. As species become restricted to remnant habitats, effective management for long-term conservation requires a quantitative understanding of the effects of habitat fragmentation on population viability. Most recent studies of the effects of habitat fragmentation were carried out at relatively small geographical scales. In this thesis I present four studies of the effects of habitat fragmentation on plant performance that investigate offspring performance, quantitative genetic variation and local adaptation in populations at a large geographical scale. Populations were studied in several European regions (in Sweden, The Netherlands, Germany, Britain, Czech Republic, Luxembourg and Switzerland). The target species Carlina vulgaris L. and Hypochoeris radicata L. have contrasting life histories with respect to dispersal ability and the frequency of flowering, but both species are widespread in species-rich semi-natural grasslands throughout Europe. Species-rich grasslands have dramatically declined in number and size in the last decades and are thus an excellent system to study effects of habitat fragmentation. In Chapter 2 I study the effects of habitat conditions and population size and isolation on the performance of C. vulgaris from 74 populations in seven European regions, both in natural populations and in a common garden. In the common garden several measures of performance were reduced in plants from small populations and plant size decreased with increasing isolation of the populations, indicating genetic drift and inbreeding depression in small and isolated populations. In the field, only seed set was reduced in small populations. Environmental variables explained most of the variation in plant size among populations in the field. The results suggest that reproduction and offspring performance may be reduced in small populations of C. vulgaris across Europe due to genetic deterioration, and because pollen quality and quantity might be reduced. In Chapter 3 I analyse the variation in several quantitative genetic traits in offspring grown in a common garden from 74 populations of Carlina vulgaris from seven geographical regions and 32 populations of Hypochoeris radicata from three geographical regions. In both species, most traits varied considerably among seed families within populations, among populations within regions and among regions. The overall proportion of phenotypic genetic variation among populations was higher in C. vulgaris (75.8 %) than in H. radicata (50.7 %), suggesting less gene flow between populations in the poorly dispersed C. vulgaris. The results suggest that at the small scale genetic drift or environmental differences that are not related to geographical distances drive population differentiation, whereas at the large scale selective forces closely related to geographical distances are most important for population differentiation. In Chapter 4 population differentiation and local adaptation in Carlina vulgaris is studied at the European scale. Reciprocal transplant experiments were carried out among (regional scale) and within (local scale) five European regions. Only at the regional scale, the individual fitness of C. vulgaris and several other measures of the plant performance were highest if plants grew in their home region. Furthermore, performance of plants decreased with increasing transplant distance. At the local scale, genotype x environment interactions were far less pronounced and were not related to geographical distance between the population of origin and the transplant site. The results of our study suggest that C. vulgaris consists of regionally adapted genotypes and that distance is a good predictor of the extent of adaptive differentiation at large (> 200 km), but not at small scales. Thus, patterns of local adaptation have to be taken into account for the efficient preservation of genetic resources. In Chapter 5 I present a study on the effects of cross-proximity on seed production and offspring performance of Hypochoeris radicata from Germany, Czechia and The Netherlands. Crosses were carried out within plants (selfing), and between plants from the same seed family, from the same population, from different populations of the same region and from different regions. Seed set and germination after inbreeding and crosses between populations were lower than after within population crosses, indicating inbreeding and outbreeding depression. However, crosses between regions resulted in higher seed set than within population crosses. For late traits, there was regional variation in the effects of inbreeding and interpopulation crosses. Our results suggest that outbreeding depression does not necessarily increase with interpopulation distance and that the sensitivity of populations to introgression may vary among regions

Einfluss von HDAC-Inhibitoren auf die tumorinduzierte Angiogenese in der Kolonkarzinomzelllinie Caco-2

Die Angiogenese ist von essentieller Bedeutung für das Wachstum und die hämatogene Metastasierung solider Tumore. Ihre Hemmung stellt eine vielversprechende Methode der Tumortherapie dar. Es werden zunehmend Hinweise dafür gefunden, dass Hemmstoffe von Histondeacetylasen (HDACs) antiangiogene Potenz besitzen. Im Rahmen der vorliegenden Arbeit wurden diesbezüglich Valproat, Butyrat und Trichostatin A untersucht. Die vorgestellten Ergebnisse zeigen, dass diese HDAC-Inhibitoren als wirkungsvolle Hemmstoffe tumorinduzierter Angiogenese gelten können. Anhand verschiedener in vitro Angiogenesemodelle ließ sich zeigen, dass Valproat, Butyrat und Trichostatin A in der Lage sind, angiogeneserelevante Endothelzellfunktionen zu hemmen. So wurden die Proliferation, die Migration und die Ausbildung kapillarähnlicher tubulärer Strukturen von human umbilical vein endothelial cells (HUVECs) durch die Testsubstanzen zum Teil signifikant reduziert. An der Induktion der Angiogenese sind Wachstumsfaktoren wie der fibroblast growth factor (FGF-2) und der vascular endothelial growth factor (VEGF) maßgeblich beteiligt. Im Rahmen dieser Arbeit wurde unter anderem untersucht, ob Valproat, Butyrat und Trichostatin A ihre antiangiogene Wirkung möglicherweise über eine Beeinflussung dieser bedeutenden proangiogenen Faktoren entfalten. Die vorgestellten Ergebnisse zur Sekretions- und Expressionshemmung von FGF-2 und VEGF auf Protein- bzw. mRNA-Ebene bestätigten diese Überlegung. Ein vorgeschaltetes Signalmolekül in der Wachstumsfaktor-induzierten Angiogenese ist der hypoxia inducible factor-1alpha (HIF-1alpha). Es konnte nachgewiesen werden, dass Valproat, Butyrat und Trichostatin A die Expression dieses Transkriptionsfaktors im Gesamthomogenat von Caco-2 Zellen induzieren. Die Aktivität von HIF-1α in der nukleären Caco-2 Fraktion wurde dagegen reduziert. Diese Resultate lassen sich möglicherweise auf eine Hemmung der nukleären Translokation von HIF-1alpha zurückführen. Desweiteren ließ sich zeigen, dass die proteasomale Aktivität im Caco-2 Zelllysat durch Valproat, Butyrat und Trichostatin A zum Teil signifikant vermindert wurde. Dementsprechend liegt der deutlichen zytoplasmatischen Akkumulation des HIF-1alpha Proteins wahrscheinlich auch eine Hemmung der proteasomalen Degradierung durch die Behandlungssubstanzen zugrunde. Als Konsequenz dieser Ergebnisse wurde die Hypothese aufgestellt, dass die antiangiogene Wirkung der Testsubstanzen über eine Unterbrechung des HIF-1alpha Signals vermittelt wird. Zusätzlich konnte gezeigt werden, dass HDAC-Inhibitoren über eine Beeinflussung der PI3K/AKT Signaltransduktionskaskade möglicherweise auch die Synthese von HIF-1alpha stören. Dies konnte zumindest für Butyrat und Trichostatin A belegt werden. Für Valproat sind diesbezüglich weiterführende Untersuchungen nötig.Angiogenesis is of essential importance for the growth and metastasis of solid tumors. Its inhibition may be a valuable approach in cancer therapy, representing an important aspect of future treatment. Recent studies indicate that inhibitors of histondeacetylases are potent antiangiogenic agents. The subject of this work was to evaluate the antiangiogenic effects of the HDAC-inhibitors valproate, butyrate and trichostatin A. Our results indicate that the tested substances supposed to be effective inhibitors of tumor-derived angiogenesis. Valproate, butyrate and trichostatin A appeared to be able to inhibit endothelial cell functions relevant for angiogenesis in different in vitro angiogenesis assays. Proliferation, migration as well as tube formation of HUVECs were suppressed by all tested drugs, at least partly in a significant manner. Angiogenesis is induced by angiogenic growth factors such as fibroblast growth factor (FGF-2) and vascular endothelial growth factor (VEGF). One aim of this study was to find evidence for the thesis that valproate, butyrate and trichostatin A exert their antiangiogenic effects through a modulation of these important angiogenic factors. This consideration could be confirmed by decreased protein and mRNA levels of FGF-2 and VEGF. Hypoxia inducible factor-1alpha (HIF-1alpha) is a proceeding signal molecule of growth factor– induced angiogenesis. Valproate, butyrate and trichostatin A proved to induce the expression of this transcriptional factor in the whole cell lysat of Caco-2 cells. However, the HIF-1alpha DNA-binding activity in the nuclear extract of Caco-2 cells was reduced, which can possibly be explained by an inhibition of nuclear translocation of HIF-1alpha. Further results could show that valproate, butyrate and trichostatin A led to a partly significant suppression of proteasome activity in the Caco-2 cell lysat. Thus, the marked cytoplasmatic accumulation of HIF-1alpha protein, as observed in our experiments, is probably due to the inhibitory effects of valproate, butyrate an trichostatin A on the ubiquitin-proteasome pathway. Summarizing our findings we concluded that the antiangiogenic effects of the tested substances are caused by a disruption of HIF-1alpha signaling. Furthermore we assumed HDAC-inhibitors to be able to influence the HIF-1alpha synthesis by modulating the PI3K/AKT pathway. This could be verified at least for butyrate and trichostatin A. Concerning valproate further examinations are needed

Untersuchungen mit dem Ecdyson-induzierbaren Promotorsystem an humanen Tumorzelllinien

Induzierbare Genexpressionssysteme ermöglichen die Untersuchung von Genfunktionen in Zellen, besonders der dortigen Wirkung toxischer und teratogener Proteine, sowie der regulierten Expression von antisense Sequenzen oder siRNA Sequenzen zur Regulation endogener Genexpression. Durch die präzise Kontrolle der Genexpression können biochemische und physiologische Prozesse reversibel analysiert werden. Das von Drosophila melanogaster stammende endogene Ecdyson-induzierbare Genexpressionssystem, dessen Effizienz bereits in CHO-Zellen (Chinese hamster ovary) gezeigt worden war, sollte auf humane Tumorzelllinien [HCT116 (humanen Colon Carzinom Zellen), Hela (humane Cervix Carzinom Zellen) und HaCat (humanen Keratinozyten Zellen)] Anwendung finden, um nachfolgend Untersuchungen mit antisense oder siRNA Vektoren zum Studium der Genfunktion zu ermöglichen. Mittels Lipofektion bzw. Elektroporation wurde das Ecdyson-induzierbare Rezeptorsystem (pVgRxR) in die Zellen integriert und mit Hilfe der Northern Blot Analyse seine Expression nachgewiesen. Ebenso wurde ein alternativer Reportervektor (pEF-EIR) lipofiziert, bei dem beide Reportergene von einer bizistronischen mRNA exprimiert werden. Zur Identifizierung induzierbarer Zelllinien sollte das Reporterprotein GFP (grün fluoreszierendes Protein) dienen, das mit Hilfe der Fluoreszenzmikroskopie, der Western Blot Analyse wie auch der Immunhistochemie nachgewiesen wurde. Von den drei verwendeten Zelllinien war lediglich bei der HCT116 Zelllinie ein funktionierendes Rezeptorsystem nachweisbar. Allerdings funktionierte das induzierbare Promotorsystem nur in einem Teil der Zellen eines Klons. Als Ergebnis der Arbeit wurde ein Klon von HCT 116 Zellen isoliert, bei dem das Ecdyson-induzierbare Genexpressionssystem mit den genannten Einschränkungen angewendet werden kann

Usages et stratégies de gestion d'Anogeissus leiocarpa, une espèce à usage multiple dans l'Est du Burkina Faso

Für die ländliche Bevölkerung in tropischen Gebieten sind Nichtholzprodukte verschiedenster Baumarten von essenzieller Bedeutung. Die durch Übernutzung und Landnutzungsintensivierungen hervorgerufenen Bedrohungen dieser Nutzholzarten erfordern sowohl ökologische als auch ethnobotanische Studien. Eine wichtige und stark genutzte Nutzholzart in Westafrika ist Anogeissus leiocarpa. Trotz starker Nutzung gibt es erstaunlicherweise kaum detaillierte ethnobotanische Studien über diese Art. In der vorliegenden Studie dokumentieren wir Verwendungen und Managementstrategien von A. leiocarpa bei der Gulimanceba Bevölkerung im Osten Burkina Fasos. Dazu haben wir quantitative ethnobotanische Befragungen bei den Gulimanceba durchgeführt und Unterschiede im Wissen zwischen den Geschlechtern, Generationen und zwischen Bewohnern verschiedener Dörfer untersucht. Die Ergebnisse der Umfragen zeigen, dass A. leiocarpa für 18 verschiedene Zwecke genutzt wird und verdeutlichen die Bedeutung dieser Art für die lokale Bevölkerung. Das Wissen über A. leiocarpa unterschied sich kaum zwischen den Geschlechtern und Generationen, wohingegen geringfügige Unterschiede zwischen den Befragten verschiedener Dörfer ermittelt werden konnten. Obwohl A. leiocarpa nicht aktiv von der lokalen Bevölkerung geschützt wird, lässt sich feststellen, dass die gegenwärtigen lokalen Sammeltechniken und Managementstrategien von A. leiocarpa nachhaltig sind. Allerdings erfordern anhaltende Landnutzungsintensivierungen angepasste Sammel- und Managementtechniken, um das Fortbestehen dieser wichtigen Art zu gewährleisten. Mit Hilfe unserer Ergebnisse und in Kombination mit den Ergebnissen unserer vorherigen ökologischen Studie können angemessene Managementempfehlungen für eine nachhaltige Nutzung von A. leiocarpa formuliert werden. Unsere Studie verdeutlicht die Bedeutung von lokalen, ethnobotanischen Untersuchungen. Mit Hilfe solcher Studien können konkrete Managementstrategien entwickelt werden, die unter den spezifischen Bedingungen anwendbar und tragbar sind.Many people in the semi-arid tropics strongly depend on non-timber forest products (NTFPs) for livelihood. Increasing threats on NTFP-providing tree species, due to land-use intensification and over-harvesting, require ecological studies as well as additional information provided by local people. One important NTFP-providing tree in West Africa is Anogeissus leiocarpa. Even though this species is highly used, ethnobotanical studies on A. leiocarpa are scarce and address mainly qualitative aspects. Our study investigates uses, perceptions of the population development, and management strategies of A. leiocarpa among the Gulimanceba people in eastern Burkina Faso. We conducted a quantitative ethnobotanical survey and investigated distribution of traditional ecological knowledge related to the species on a local scale, i.e. difference in knowledge between villages, genders, and generations. Interviews reveal that A. leiocarpa is harvested by local people for 18 different uses and emphasize its high importance for local people. Ethnobotanical knowledge of A. leiocarpa was mostly evenly spread between genders and generations, while it slightly differed between villages. Although local people did not actively protect A. leiocarpa, current local harvesting modes and management resulted in sustainable use. However, ongoing land-use intensifications require adapted management strategies to guarantee the persistence of this important species. Our results provide, in combination with ecological results of our previous study, appropriate management recommendations. Our study emphasizes the importance of ethnobotanical studies on a local scale level in order to develop management strategies that are reliable in the specific area under the specific circumstances.Les populations des zones semi-arides dépendent fortement des produits forestiers non ligneux (PFNLx) pour la subsistance. L'augmentation des menaces sur les arbres pourvoyeurs de PFNLx en raison de l'intensification de l'utilisation des terres et la surexploitation, nécessitent des études écologiques ainsi que des informations supplémentaires fournies par la population locale. Anogeissus leiocarpa est un des plus importants arbres, pourvoyeur de PFNLx en Afrique de l'Ouest. Malgré sa forte utilisation, les études ethnobotaniques sur A. leiocarpa sont rares et traitent principalement des aspects qualitatifs. Notre étude examine les usages, les perceptions de l'évolution de la population, et les stratégies de gestion d’A. leiocarpa chez les Gulimanceba dans l'Est du Burkina Faso. Nous avons mené une enquête ethnobotanique quantitative et étudié la distribution des connaissances écologiques traditionnelles relatives à l'espèce à une échelle locale; à savoir la différence dans la connaissance entre les villages, le genre et les générations. Les interviews révèlent que A. leiocarpa intervient dans 18 usages différents d’où son importance pour la population locale. Les connaissances ethnobotaniques sur A. leiocarpa étaient équitablement réparties entre le genre et les générations, mais légèrement différentes entre les villages. Bien que A. leiocarpa ne bénéficie pas d’une protection active de la part de la population locale, les modes actuelles de récolte et la gestion qui en résulte, concourent à une utilisation durable. Toutefois, l’intensification de l'utilisation des terres en cours nécessitent des stratégies de gestion adaptée pour garantir la persistance de cette importante espèce. Nos résultats fournissent, en combinaison avec nos études écologiques antérieures, des recommandations pour une gestion appropriées d’A. leiocarpa. Notre étude souligne l'importance des études ethnobotaniques à une échelle locale afin de développer des stratégies de gestion fiables et spécifiques à une zone donnée compte tenu des circonstances spécifiques

Design Recommendations for Web-based Career Guidance Platforms - Let Young Women Experience IT Careers!

Despite a variety of intervention programs in the western society over the last decades, still too few young women are interested in an information technology (IT) career. While looking for career information and guidance, young women consult family and friends but also the internet. Although there is already a plethora of career information websites, those are seldom tailored to the interests of young women. To address the IT-gender gap with the design of a platform that appeals to the needs of the target group, we firstly analyzed existing German websites for career information and guidance. The analysis was framed by literature on women’s IT career choice barriers. Secondly, we evaluated selected websites with focus groups of female students. Finally, we present design recommendations to enhance web-based career information and guidance platforms for young women to raise their interest in IT-related careers

Einführung von SAP-HR - Vernetzung mit Verstrickungspotenzial?

Der folgende Artikel basiert auf realen Erfahrungen aus einer Vielzahl von Projekten der Projektkultur GmbH. Immer ging es um die Einführung oder Anpassung von Systemen des großen Software-Anbieters SAP im Bereich Human Resources. Zum Schutz unserer Kunden und unserer Mitarbeiter erzählen wir Ihnen eine ausgedachte Geschichte. Sie fasst einige unserer Erfahrungen zusammen und hätte genau so passieren können

Alkylidynephosphines : syntheses and reactivity

In the past, different methods have been utilized for the preparation of alkylidynephosphines. Whereas, however, small amounts of thermally instable derivatives might be obtained from reactions in the gas phase, the synthesis of phosphines which are stable under an inert atmosphere, as for instance those with a tert-butyl or a 1-adamantyl substituent at the carbon atom of the PEC group, is best started with tris (trimethylsilyl) phosphine itself or with the more reactive lithium bis (trimethylsilyl) phosphide.2 tetrahydrofuran complex. Treatment of either compound with acyl halides results in the formation of acylbis (trimethylsilyl) phosphines which, at room temperature, rearrange to the corresponding trimethylsilyl [1-(trimethylsiloxy) alkylidene] isomers. As traces of hydrogen halide accelerate the conversion of tris (trimethylsilyl) phosphine to the triacyl derivatives, the use of the lithium phosphide is strongly recommended in all cases where impure acyl halides are used. In the presence of small amounts of solid sodium hydroxide suspended in an etherial solvent, the thus prepared trimethyl[1-(trimethylsiloxy)-alkylidene]phosphines eliminate hexamethyldisiloxane to yield the required alkylidyne compounds. Running the decomposition without a solvent at a higher temperature, Regitz and coworkers were able to improve this method further

Phosphane und Arsane mit Heteroatomen niederer Koordinationszahl

In der anorganischen und elementorganischen Chemie steht gegenwärtig die Frage nach der Existenz, der Synthese und der Reaktivität von Verbindungen, die unter Beteiligung eines Hauptgruppenelementes aus der dritten oder einer höheren Periode eine homo- oder heteronukleare (np-mp)π-Bindung ausbilden und die entgegen der allgemeinen Erwartung bei Zimmertemperatur thermisch stabil sind, im Blickpunkt des Interesses.Während aber unsere Kenntnisse über entsprechende Systeme aus der dritten und vierten Hauptgruppe nur langsam zunehmen, war bei den Alkylidenphosphanen und teilweise auch -arsanen eine überaus rasche Entwicklung zu verzeichnen [2-4]. Nachdem jedoch diese beiden Substanzklassen in den letzten Jahren intensivst bearbeitet worden sind, werden jetzt auch die von verschiedenen Seiten Phosphaalkine genannten Alkylidinphosphane R-C≡P eingehender untersucht. Dabei kommt einer Klärung der Frage, ob sie aufgrund ihrer Reaktivität eher als Homologe der Nitrile anzusehen sind oder ob sie im Sinne der Schrägbeziehungen im Periodensystem Ähnlichkeiten mit Alkinen aufweisen, entscheidende Bedeutung zu