The Drosophilids of a Pristine Old-Growth Northern Hardwood Forest

The current study summarizes the results of a species inventory survey for drosophilid flies (family Drosophilidae, order Diptera) in a primeval forest in northern Michigan. The two main goals of the investigation were to list the species inhabiting the Huron Mountain Club and to collect live specimens for the illustrations in the book Drosophilids of the Midwest and Northeast . From 2014 to 2016, I found 22 drosophilid species, which belong to the two subfamilies Steganinae and Drosophilinae. Future long-term studies are planned to test how the drosophilid populations respond to climate change

Reservas corporales y tasa de preñez del ciervo colorado introducido en Patagonia (Argentina) después de un período de sequía

El ciervo rojo (Cervus elaphus) fue introducido en Patagonia en la década de 1920 y ha alcanzado densidades altas en ciertas áreas del ecotono entre el bosque y la estepa. Se especuló que las condiciones de severa sequía del verano-otoño de 1999 podían tener un efecto negativo sobre la reproducción del ciervo rojo. Las necropsias de 50 hembras adultas revelaron una tasa de preñez de solo 56%, comparado con un 98% en 1992–1998 o un 100% en 1996–1997 en otra población similar. La distribución de edades de hembras preñadas reflejó la importancia de no haber gestado durante el ciclo anterior. Las hembras primíparas de dos años tuvieron una tasa de preñez de 77%, mientras que ninguna de las hembras con crías lactantes estaba preñada. Normalmente, el mayor éxito reproductivo se observa en las clases de mediana edad, lo que reduce la probabilidad de preñez durante periodos de stress, lo cual se reflejó en este estudio en la distribución de edades de las hembras no-gestantes. Sin embargo, la circunferencia a la altura del pecho (como índice del tamaño corporal) no fue diferente entre las hembras gestantes y las no gestantes. Las reservas de grasa corporal estuvieron severamente agotadas en la mayoría de los animales, independientemente de su condición reproductiva. La relación entre crías y hembras adultas en el otoño siguiente fue de 30%, en comparación con 58% en 1991–1992. En la otra población, la relación fue de 28% en el otoño siguiente, indicando que el efecto de la sequía tuvo carácter regional. Los resultados sugieren que estas poblaciones de ciervo rojo tienen densidades a las cuales pueden experimentar fácilmente limitaciones de tipo nutricional debido a un fenómeno ambiental singular como un período de sequía. Aunque la tasa de reclutamiento se redujo drásticamente a través de la escasez de comida, el efecto podría ser temporario, hasta terminar la sequía, y los ciervos rojos podrían continuar ejerciendo una presión intensiva sobre la vegetación si no disminuyen las densidades de la población a través de la caza regular u otra forma de control.Red deer (Cervus elaphus) were introduced to Patagonia in the 1920´s and have reached high densities in certain areas of the forest-steppe ecotone. Severe drought conditions during summer/autumn of 1999 were suspected to have an impact on reproduction of red deer. Necropsies of 50 adult females revealed a pregnancy rate of only 56% as compared to 98% in 1992-98 or 100% in 1996/7 in a comparable population. The age distribution of pregnant females reflected the importance of not having been pregnant during the previous cycle. The primiparous  2 year-old females had a 77% pregnancy rate whereas none of  the lactating females were pregnant. Normally a higher reproductive success occurs for middle age classes, thereby reducing the chances of becoming pregnant during stress periods which was reflected in this study in the age distribution of non-pregnant females. Chest girths as an index of body size, however, were not different for pregnant and non-pregnant females. Body fat reserves were severely depleted in most animals irrespective of reproductive status. The calf-to-adult female ratio in the following autumn was 30% as compared to 58% in 1991/2. The ratio in a comparable population was 28% in the following autumn, indicating that the effect of the drought was regional. The results suggest that these red deer populations occur at densities where they can easily become food-limited through a singular environmental phenomenon such as a drought period. Although the recruitment rate was drastically reduced through such food shortage, the effect might be of short duration as the drought terminates and red deer may continue to exert intensive pressure on the flora causing subsequent damage if population densities are not lowered through continuous hunting or other control means.Fil: Fluck, Werner Thomas. Administración de Parques Nacionales. Parque Nacional ; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin

Offspring sex ratio of introduced red deer in Patagonia, Argentina after an intensive drought

Red deer (Cervus elaphus) introduced to Patagonia have reached high densities in the forest-steppe ecotone. Drought conditions during 1998/99 were suspected to impact subsequent reproductive performance. Necropsies of 50 adult females during winter 1999 revealed lowered pregnancy rates and lactation in 32% of non-pregnant as opposed to 0% among pregnant females. There were no signs of fetal resorptions or abortions. The fetal sex ratio (20m:8f) deviates significantly from unity, and mothers with female or male fetuses averaged 6,7 and 5,2 years, respectively (P=0.14). However, 90% of primiparous females (2,5 years old) had males, the following age class had all females, the middle age class (5-8 years old) had all males, and older females had equally male or female fetuses. These females were at borderline of body condition allowing conception and thus were at extremely low levels of condition during breeding. The male-biased fetal sex ratio contrasts reports of other studies that only females in best condition tend to have male-biased offspring. However, ambivalent results from other studies may stem from not having evaluated body fat reserves and reproductive tracts, or studies done during environmental conditions not extreme enough. The present results also indicate that red deer populations occur at densities where they can easily become food-limited through a singular environmental phenomenon such as a drought. Although recruitment rates would be drastically reduced through such temporary food shortage, red deer will recuperate rapidly and will continue to exert intensive pressure on the flora causing subsequent damage if population densities are not lowered through hunting.Fil: Fluck, Werner Thomas. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin

Non-LTE Spectral Analysis of Extremely Hot Post-AGB Stars: Constraints for Evolutionary Theory

Spectral analysis by means of Non-LTE model-atmosphere techniques has arrived at a high level of sophistication: fully line-blanketed model atmospheres which consider opacities of all elements from H to Ni allow the reliable determination of photospheric parameters of hot, compact stars. Such models provide a crucial test of stellar evolutionary theory: recent abundance determinations of trace elements like, e.g., F, Ne, Mg, P, S, Ar, Fe, and Ni are suited to investigate on AGB nucleosynthesis. E.g., the strong Fe depletion found in hydrogen-deficient post-AGB stars is a clear indication of an efficient s-process on the AGB where Fe is transformed into Ni or even heavier trans iron-group elements. We present results of recent spectral analyses based on high-resolution UV observations of hot stars.Comment: 6 pages, 2 figure

Time Variation in the Tail Behaviour of Bund Futures Returns

The literature on the tail behaviour of asset prices focuses mainly on the foreign exchange and stock markets, with only a few papers dealing with bonds or bond futures. The present paper addresses this omission. We focus on three questions: (i) Are heavy tails a relevant feature of the distribution of BUND futures returns? (ii) Is the tail behaviour constant over time? (iii) If it is not, can we use the tail index as an indicator for financial market risk and does it add value in addition to classical indicators? The answers to these questions are (i) yes, (ii) no, and (iii) yes. We find significant heaviness of the tails of the Bund future returns. The tail index is on average around 3, implying the nonexistence of the forth moments. With the aid of a recently developed test for changes in the tail behaviour we identify several breaks in the degree of heaviness of the return tails. Interestingly, the tails of the return distribution do not move in parallel to realised volatility. This suggests that the tails of futures returns contain information for risk management that complements those gained from more standard statistical measures. -- Die Literatur über Extreme der Renditeverteilung hat sich bisher überwiegend mit Wechselkursen und Aktienkursen befasst. Die Kurse von Rentenwerten oder Terminkontrakten auf Rentenwerte haben hingegen bisher kaum Beach- tung erfahren. Das vorliegende Arbeitspapier versucht diese Lücke zu schließen. Unser Augenmerk gilt dabei insbesondere drei Fragen: (i) Haben die Ren- diteverteilungen von Terminkontrakten auf Bundeswertpapiere "fat tails"? (ii) Ist die Wahrscheinlichkeit extremer Kursbewegungen im Zeitablauf kon- stant? (iii) Kann ein Tail-Index Informationen Äuber den Grad von Marktun- sicherheit liefern, die klassische Indikatoren wie die VolatilitÄat nicht liefern können? Die Antworten zu diesen drei Fragen sind (i) ja, (ii) nein und (iii) ja. Wir finden ein signifikantes "fat tails" Phänomen in der Renditeverteilung von BUND Future Kontrakten. Ein Tail-Index von circa 3 impliziert, dass das vierte und alle höheren Momente der Verteilung nicht existieren. Mit Hilfe kürzlich entwickelter Tests finden wir Brüche der Tail-Stärke der Ren- diteverteilungen. Interessanterweise bewegt sich der Tail-Index nicht immer in die gleiche Richtung wie die Volatilität. Dies lässt vermuten, dass die Betrachtung der Tails dem Risikomanagement Informationen liefert, die mit herkömmlichen Verfahren nicht gewonnen werden kÄonnen.

How wacky is the DAX? The changing structure of German stock market volatility

In this paper we investigate the volatility structure of the German stock market index DAX and its constituents. Using a recently developed test, we find a volatility break in 1997. Interestingly, not only is the volatility higher after 1997 but the volatility persistence also increased. That means that there is a greater likelihood of high volatility days being followed by further high volatility days. An immediate consequence is that the tails of the distribution of stock market returns become fatter or that the probability of extreme price movements becomes greater. The break in volatility is not only a phenomenon of the index itself; the returns of the underlying equities also show a volatility break. If the volatility is decomposed into market and firm-specific or idiosyncratic components, the idiosyncratic volatility is shown to have increased much more than the market volatility. This is probably connected to the declining correlations among individual stock returns and has implications for portfolio diversification. When analysing potential reasons for the break in volatility, we find that the increase in the volatility of the German stock market cannot be attributed to international spillovers alone. Domestic factors which may help to explain the break in volatility are the growing number of institutional investors and the increase in the volatility of longer-term interest rates. -- Dieses Arbeitspapier analysiert Veränderungen der Volatilität des Deutschen Aktienindex (DAX) und der in ihm enthaltenen Aktienwerte. Ein kürzlich entwickelter Test zeigt einen Bruch im Ausmaß der Schwankungen der Aktienrenditen im Jahr 1997 an. Seitdem nahm nicht nur die Volatilität der täglichen Aktienrenditen deutlich zu, sondern es stieg auch deren Persistenz an. Das heißt, auf Tage mit hohen Schwankungen folgen jetzt viel häufiger Tage mit ebenfalls hoher Volatilität. Die ebenso höhere Wahrscheinlichkeit extremer Preisschwankungen zeigt sich darin, dass die Verteilung der Aktienkurserträge deutlich mehr Masse in den Rändern aufweist. Interessanterweise läst sich der Bruch in der Volatilitä nicht nur im Index, sondern auch bei fast allen Einzelwerten etwa zum selben Zeitpunkt nachweisen. Eine Zerlegung der Volatilität in eine Marktkomponente und eine firmenspezifische oder idiosynkratische Komponente zeigt desweiteren, dass letztere viel stärker angestiegen ist als das systematische oder Marktrisiko. Im Zusammenhang damit stehen die gesunkenen Korrelationen zwischen den Einzelaktien; diese haben Auswirkungen auf die Risikodiversifikation eines Portfolios. Als mögliche Ursachen für den Anstieg der Volatilität können nicht allein Übertragungen von Schwankungen anderer internationaler Märkte, insbesondere des amerikanischen Marktes, gelten. Heimische Faktoren, die helfen können den Bruch in der Dynamik der Schwankungen der Aktienerträge zu erklären, sind die zunehmende Rolle institutioneller Investoren am Aktienmarkt und die steigende Volatilität von Langfristzinsen.market and idiosyncratic volatility,test on break in volatility dynamics,institutional ownership