The role of pollinator attracting scent in the sexually deceptive orchids Ophrys chestermanii, O. normanii and O. tenthredinifera

Sexual deception of male bees is one of the most remarkable mechanisms of pollination (Ackermann 1986, Proctor & al. 1996). Flowers of the orchid genus Ophrys mimic females of their pollinator species, usually bees and wasps, to attract males, which try to copulate with the flowers. During this so-called “pseudocopulation” the male removes the pollinia and transfers them to another flower to ensure pollination. Apart from visual and tactile cues, floral scent was shown to be most important for eliciting mating behaviour in males (Kullenberg 1961, Schiestl & al. 1999, Ayasse & al. 2003). Pollination in Ophrys is highly specific and usually each Ophrys species attracts only one pollinator species (Paulus & Gack 1990). The high degree of specialization provides the means of reproductive isolation between the intercrossable Ophrys-species (Ehrendorfer 1980). The complex odour-bouquets released by the flowers are species-specific and often consist of more than 100 different chemical compounds (Borg-Karlson & al. 1985, Ayasse 2006). Speciation in Ophrys-orchids may be brought about by changes in the pollinator attracting floral scent. The attraction of a new pollinator may act as a pre-zygotic isolation barrier (Stebbins 1970, Paulus & Gack 1990, Soliva & al. 2001). We investigated three sympatrically occuring Ophrys-species on Sardinia. O. chestermanii and O. normanii are endemic and are both pollinated by males of the bumblebee B. vestalis. O. tenthredinifera is pollinated by Eucera nigrilabris. There are different opinions concerning the taxonomic status of O. normanii. It has been described as an actual hybrid between O. chestermanii and O. tenthredinifera (Wood 1983). Paulus & Gack (1995) suggested that it is an own species, that either has developed from a hybrid between O. chestermanii and O. normanii or that has evolved by radiation from O. tenthredinifera. By conducting behavioural-tests with B. vestalis males, performing gas chromatographic analyses and electrophysiological studies we wanted to identify pollinator attracting scent and to clarify the taxonomic status of O. normanii.Sexualtäuschorchideen der Gattung Ophrys (Orchidaceae) imitieren die Weibchen ihrer Bestäuber in Duft, Form und Farbe. Insektenmännchen versuchen mit dem Labellum der Blüte zu kopulieren und transportieren den Pollen von Blüte zu Blüte, wodurch die Orchidee bestäubt wird. In dieser Arbeit untersuchten wir die Bestäuber anlockenden Duftstoffe der beiden endemisch auf Sardinien vorkommenden Arten O. normanii und O. chestermanii, die beide von Bombus vestalis Männchen (Hymenoptera: Apidae) bestäubt werden und von O. tenthredinifera, die Eucera nigrilabris (Hymenoptera: Apidae) zur Bestäubung anlockt. O. normanii wurde von Wood (1983) als Primärhybride beschrieben. Nach Paulus und Gack (1995) handelt es sich um eine hybridogene Art oder um eine Art die durch Abspaltung von O. tenthredinifera entstanden ist. Das Ziel der Untersuchungen war die Identifizierung Männchen-anlockender Verbindungen. Die Attraktivität der drei Arten für B. vestalis Männchen sollte Hinweise auf den Artstatus von O. normanii geben. In Biotests mit B. vestalis-Männchen lösten Blütenextrakte von O. normanii und O. chestermanii ebenso wie B. vestalis-Weibchen Kopulationsverhalten der Männchen aus, nicht jedoch Extrakte von O. tenthredinifera. Folglich handelt es sich bei O. normanii nicht um einen aktuellen Hybriden zwischen O. chestermanii und O. tenthredinifera. Ein Vergleich der GC-EAD-aktiven Duftbouquets mittels Diskriminanzanalyse ergab große Ähnlichkeiten zwischen O. normanii und O. chestermanii für die Substanzklassen der Ester, Alkohole und Fettsäuren, die daher vermutlich eine Schlüsselfunktion bei der Bestäuberanlockung haben

Genetic monogamy in burrowing parrots ?

Masello J, Sramkova A, Quillfeldt P, Epplen JT, Lubjuhn T. Genetic monogamy in burrowing parrots ? Journal of Avian Biology. 2002;33(1):99-103.We report on a first DNA fingerprinting study of paternity in a Psittaciform bird, the burrowing parrotCyanoliseus patagonus. In two consecutive breeding seasons, a total of 49 families was sampled, of which 11 breeding pairs were investigated each of two years. Extra‐pair paternity was not encountered suggesting that burrowing parrots are socially as well as genetically monogamous. Strict genetic monogamy is comparatively rare in birds and occurs predominantly in some groups of non‐passeriformes all of which exhibit long reproductive lifespans and essential paternal care. Psittaciformes fit this pattern. We conclude that paternal care plays a crucial role in the evolution and maintenance of genetic monogamy in the study species. Cases of intraspecific brood parasitism are rarely observed

Truly hypervariable DNA fingerprints due to exceptionally high mutation rates

Lubjuhn T, Sramkova A, Masello J, Quillfeldt P, Epplen JT. Truly hypervariable DNA fingerprints due to exceptionally high mutation rates. ELECTROPHORESIS. 2002;23(4):517-519.The power of DNA fingerprinting is due to comparatively high mutation rates of minisatellite and microsatellite DNA sequences. Studying the mating system of a parrot species (Burrowing Parrots, Cyanoliseus patagonus) using oligonucleotide probes, we observed mutation rates that are several orders of magnitude higher than those described anywhere in the literature. Most plausibly, the respective values are based on 3–4 loci with mutation rates of up to 100%

Long distance dispersal shaped patterns of human genetic diversity in Eurasia

Most previous attempts at reconstructing the past history of human populations did not explicitly take geography into account, or considered very simple scenarios of migration and ignored environmental information. However, it is likely that the Last Glacial Maximum (LGM) affected the demography and the range of many species, including our own. Moreover, long-distance dispersal (LDD) may have been an important component of human migrations, allowing fast colonization of new territories and preserving high levels of genetic diversity. Here, we use a high-quality microsatellite dataset genotyped in 22 populations to estimate the posterior probabilities of several scenarios for the settlement of the Old World by modern humans. We considered models ranging from a simple spatial expansion to others including LDD and a LGM-induced range contraction, as well as Neolithic demographic expansions. We find that scenarios with LDD are much better supported by data than models without LDD. Nevertheless, we show evidence that LDD events to empty habitats were strongly prevented during the settlement of Eurasia. This unexpected absence of LDD ahead of the colonization wave front could have been caused by an Allee effect, either due to intrinsic causes such as an inbreeding depression built during the expansion, or to extrinsic causes such as direct competition with archaic humans. Overall, our results suggest only a relatively limited effect of the LGM-contraction on current patterns of human diversity. This is in clear contrast with the major role of LDD migrations, which have potentially contributed to the intermingled genetic structure of Eurasian populations

The scaling of genetic diversity in a changing and fragmented world

Most species do not live in a constant environment over space or time. Their environment is often heterogeneous with a huge variability in resource availability and exposure to pathogens or predators, which may affect the local densities of the species. Moreover, the habitat might be fragmented, preventing free and isotropic migrations between local sub-populations (demes) of a species, making some demes more isolated than others. For example, during the last ice age populations of many species migrated towards refuge areas from which re-colonization originated when conditions improved. However, populations that could not move fast enough or could not adapt to the new environmental conditions faced extinctions. Populations living in these types of dynamic environments are often referred to as metapopulations and modeled as an array of subdivisions (or demes) that exchange migrants with their neighbors. Several studies have focused on the description of their demography, probability of extinction and expected patterns of diversity at different scales. Importantly, all these evolutionary processes may affect genetic diversity, which can affect the chance of populations to persist. In this chapter we provide an overview on the consequences of fragmentation, long-distance dispersal, range contractions and range shifts on genetic diversity. In addition, we describe new methods to detect and quantify underlying evolutionary processes from sampled genetic data

Soft hydrogel zwitterionic coatings minimize fibroblast and macrophage adhesion on polyimide substrates

Minimizing the foreign body reaction to polyimide-based implanted devices has a pivotal role for several biomedical applications. In this work we propose materials exhibiting non-biofouling properties and a Young's modulus reflecting the one of soft human tissues. We describe the synthesis, characterization and in vitro validation of poly(carboxybetaine) hydrogel coatings covalently attached to polyimide substrates via a photolabile 4-azidophenyl group, incorporated in poly(carboxybetaine) chains at two concentrations of 1.6 and 3.1 mol.%. The presence of coatings was confirmed by attenuated total reflectance Fourier-transform infrared spectroscopy. White light interferometry was used to evaluate coating continuity and thickness (resulting between 3 and 6 μm in dry conditions). Confocal laser scanning microscopy allowed to quantify the thickness of the swollen hydrogel coatings that ranged between 13 and 32 μm. The different hydrogel formulations resulted in stiffness values ranging from 2 to 19 kPa, and led to different fibroblasts and macrophages responses tested in vitro. Both cell types showed a minimum adhesion on the softest hydrogel type. In addition, both the overall macrophage activation and cytotoxicity were observed to be negligible for all the tested material formulations. These results are a promising starting point towards future advanced implantable systems. In particular, such technology paves the way to novel neural interfaces able to minimize the fibrotic reaction, once implanted in vivo, and to maximize their long-term stability and functionality

Membrane-depolarizing channel blockers induce selective glioma cell death by impairing nutrient transport and unfolded protein/amino acid responses.

Glioma-initiating cells (GIC) are considered the underlying cause of recurrences of aggressive glioblastomas, replenishing the tumor population and undermining the efficacy of conventional chemotherapy. Here we report the discovery that inhibiting T-type voltage-gated Ca2+ and KCa channels can effectively induce selective cell death of GIC and increase host survival in an orthotopic mouse model of human glioma. At present, the precise cellular pathways affected by the drugs affecting these channels are unknown. However, using cell-based assays and integrated proteomics, phosphoproteomics, and transcriptomics analyses, we identified the downstreamsignaling events these drugs affect. Changes in plasma membrane depolarization and elevated intracellular Na+, which compromised Na+-dependent nutrient transport, were documented. Deficits in nutrient deficit acted in turn to trigger the unfolded protein response and the amino acid response, leading ultimately to nutrient starvation and GIC cell death. Our results suggest new therapeutic targets to attack aggressive gliomas