Steuernde Parameter der Vegetationszusammensetzung in Savannenökosystemen anhand von Untersuchungen im Khomas Hochland, Namibia

Ziel der Arbeit ist es herauszufinden, welche Umweltfaktoren zur Ausbildung kleinräumiger Vegetationsstrukturen in Savannen beitragen. Dazu wurden im Zeitraum von Oktober bis Dezember 2010 im Khomas Hochland von Namibia vegetationsökologische Untersuchungen durchgeführt. Die Aufnahmen umfassten auf zwei unterschiedlichen Beweidungsgebieten insgesamt 72 Flächen, die zur Verdeutlichung der Vegetationsveränderungen im Übergang von der Trocken- zur Regenzeit zum Teil mehrmals aufgenommen wurden. Des Weiteren wurden klimatische Faktoren an einem offenen Grasstandort und einem Standort unterhalb der Baumkrone gemessen und Bodenproben für die anschließenden Laboruntersuchungen entnommen. Die Auswertung der Vegetationszusammensetzung und der Beeinflussung durch die verschiedenen Parameter fand mithilfe Methoden der multivariaten Statistik statt. Mittels Klassifikationsanalyse der Flächen auf Basis des Isopamalgorithmus und der SMW-Analyse der Transekte wurden hierbei Ähnlichkeitsbeziehungen der Vegetation der Aufnahmeflächen ermittelt und Zusammenhänge mit den einwirkenden Umweltparametern anhand von NMDS-Ordinationen untersucht. Es konnte eine maßgebende Beeinflussung der Vegetationszusammensetzung durch die Beweidung nachgewiesen werden. Die Beweidungsgebiete bestehen aus einem Mosaik von stark beeinträchtigten Bereichen und Flächen mit einer relativ stabilen Klimaxgesellschaft. Der Einfluss der Gehölze auf die Vegetationsverteilung ist anhand der Klassifikationsanalysen nicht eindeutig nachzuweisen. Durch die Auswertung der Transekte kann jedoch in einem Abstand von drei bis fünf Metern vom Baum eine Veränderung der Vegetationszusammensetzung und der Lebensformen festgestellt werden. Bei den Bodenparametern konnte ausgehend vom Baum zur offenen Grasfläche eine Abnahme der elektrischen Leitfähigkeit, des pH-Wertes, der Phosphat- und Stickstoffgehalte sowie der K-Sättigung und eine Zunahme der Mg-Sättigung festgestellt werden. Mit Ausnahme der Fe- und Al-Sättigungen wurden bei allen Umweltfaktoren steuernde Einflüsse auf die Vegetationszusammensetzung bestimmt.The aim of this work is to determine the contribution of environmental factors to the formation of small-scale vegetation structure in savannas in the transition from dry to rainy season. For this purpose vegetation-environmental investigations were carried out in the Khomas Highlands in Namibia (Oct.-Dec. 2010). The recordings included 72 plots in two different grazing areas. Furthermore, climatic factors on an open grassland site and a site below the canopy were measured and in addition soil samples were taken for subsequent laboratory testing. For the organisation of plant data and the correlation to environmental parameters, methods of multivariate statistics including isopam-classifications, NMDS-ordination and SMW-analysis were used. A decisive influence on the vegetation composition was detected by the grazing area. Both grazing areas consist of a mosaic of heavily affected areas and areas with a relatively stable climax plant community. The influence of trees on vegetation distribution was demonstrated on the basis of the classification analysis. By evaluating the transects, a change in vegetation composition and life forms can be found at a distance of three to five meters from the tree. As a further result, measurements of soil parameters sampled on the transects show changes from stem outward into the open grassland. Soils located below tree crowns were characterised by higher concentrations of phosphate, nitrogen and potassium saturation, higher amounts of electrical conductivity, a reduced magnesium saturation and a lower pH-value. With the exception of the iron and aluminium saturation, in all environmental parameters a controlling influence on vegetation composition was determined

Konzept OER-Zertifizierung an österreichischen Hochschulen

Das Ergebnis der Arbeitsgruppe „Open Educational Resources“ ist ein Konzept zur OER-Zertifizierung an österreichischen Hochschulen. Dazu wird unterschieden in eine zweistufige Zertifizierung für Hochschullehrende und eine dreistufige Zertifizierung für Hochschulen. Der Umsetzungsvorschlag sieht dafür digitale Open Badges vor, die von einer zentralen Stelle bereits in der nächsten Leistungsvereinbarungsperiode (2019–2021) vergeben werden sollen

The Cercal Organ May Provide Singing Tettigoniids a Backup Sensory System for the Detection of Eavesdropping Bats

Conspicuous signals, such as the calling songs of tettigoniids, are intended to attract mates but may also unintentionally attract predators. Among them bats that listen to prey-generated sounds constitute a predation pressure for many acoustically communicating insects as well as frogs. As an adaptation to protect against bat predation many insect species evolved auditory sensitivity to bat-emitted echolocation signals. Recently, the European mouse-eared bat species Myotis myotis and M. blythii oxygnathus were found to eavesdrop on calling songs of the tettigoniid Tettigonia cantans. These gleaning bats emit rather faint echolocation signals when approaching prey and singing insects may have difficulty detecting acoustic predator-related signals. The aim of this study was to determine (1) if loud self-generated sound produced by European tettigoniids impairs the detection of pulsed ultrasound and (2) if wind-sensors on the cercal organ function as a sensory backup system for bat detection in tettigoniids. We addressed these questions by combining a behavioral approach to study the response of two European tettigoniid species to pulsed ultrasound, together with an electrophysiological approach to record the activity of wind-sensitive interneurons during real attacks of the European mouse-eared bat species Myotis myotis. Results showed that singing T. cantans males did not respond to sequences of ultrasound pulses, whereas singing T. viridissima did respond with predominantly brief song pauses when ultrasound pulses fell into silent intervals or were coincident with the production of soft hemi-syllables. This result, however, strongly depended on ambient temperature with a lower probability for song interruption observable at 21°C compared to 28°C. Using extracellular recordings, dorsal giant interneurons of tettigoniids were shown to fire regular bursts in response to attacking bats. Between the first response of wind-sensitive interneurons and contact, a mean time lag of 860 ms was found. This time interval corresponds to a bat-to-prey distance of ca. 72 cm. This result demonstrates the efficiency of the cercal system of tettigoniids in detecting attacking bats and suggests this sensory system to be particularly valuable for singing insects that are targeted by eavesdropping bats

Global and regional molecular epidemiology of HIV-1, 1990–2015: a systematic review, global survey, and trend analysis

International audienceGlobal genetic diversity of HIV-1 is a major challenge to the development of HIV vaccines. We aimed to estimate the regional and global distribution of HIV-1 subtypes and recombinants during 1990–2015.We searched PubMed, EMBASE (Ovid), CINAHL (Ebscohost), and Global Health (Ovid) for HIV-1 subtyping studies published between Jan 1, 1990, and Dec 31, 2015. We collected additional unpublished HIV-1 subtyping data through a global survey. We included prevalence studies with HIV-1 subtyping data collected during 1990–2015. We grouped countries into 14 regions and analysed data for four time periods (1990–99, 2000–04, 2005–09, and 2010–15). The distribution of HIV-1 subtypes, circulating recombinant forms (CRFs), and unique recombinant forms (URFs) in individual countries was weighted according to the UNAIDS estimates of the number of people living with HIV (PLHIV) in each country to generate regional and global estimates of HIV-1 diversity in each time period. The primary outcome was the number of samples designated as HIV-1 subtypes A, B, C, D, F, G, H, J, K, CRFs, and URFs. The systematic review is registered with PROSPERO, number CRD42017067164.This systematic review and global survey yielded 2203 datasets with 383 519 samples from 116 countries in 1990–2015. Globally, subtype C accounted for 46·6% (16 280 897/34 921 639 of PLHIV) of all HIV-1 infections in 2010–15. Subtype B was responsible for 12·1% (4 235 299/34 921 639) of infections, followed by subtype A (10·3%; 3 587 003/34 921 639), CRF02_AG (7·7%; 2 705 110/34 921 639), CRF01_AE (5·3%; 1 840 982/34 921 639), subtype G (4·6%; 1 591 276/34 921 639), and subtype D (2·7%; 926 255/34 921 639). Subtypes F, H, J, and K combined accounted for 0·9% (311 332/34 921 639) of infections. Other CRFs accounted for 3·7% (1 309 082/34 921 639), bringing the proportion of all CRFs to 16·7% (5 844 113/34 921 639). URFs constituted 6·1% (2 134 405/34 921 639), resulting in recombinants accounting for 22·8% (7 978 517/34 921 639) of all global HIV-1 infections. The distribution of HIV-1 subtypes and recombinants changed over time in countries, regions, and globally. At a global level during 2005–15, subtype B increased, subtypes A and D were stable, and subtypes C and G and CRF02_AG decreased. CRF01_AE, other CRFs, and URFs increased, leading to a consistent increase in the global proportion of recombinants over time.Global and regional HIV diversity is complex and evolving, and is a major challenge to HIV vaccine development. Surveillance of the global molecular epidemiology of HIV-1 remains crucial for the design, testing, and implementation of HIV vaccines