Determinants of mating and sperm‐transfer success in a simultaneous hermaphrodite

The number of mating partners an individual has within a population is a crucial parameter in sex allocation theory for simultaneous hermaphrodites because it is predicted to be one of the main parameters influencing sex allocation. However, little is known about the factors that determine the number of mates in simultaneous hermaphrodites. Furthermore, in order to understand the benefits obtained by resource allocation into the male function it is important to identify the factors that predict sperm‐transfer success, i.e. the number of sperm a donor manages to store in a mate. In this study we experimentally tested how social group size (i.e. the number of all potential mates within a population) and density affect the number of mates and sperm‐transfer success in the outcrossing hermaphroditic flatworm Macrostomum lignano. In addition, we assessed whether these parameters covary with morphological traits, such as body size, testis size and genital morphology. For this we used a method, which allows tracking sperm of a labelled donor in an unlabelled mate. We found considerable variation in the number of mates and sperm‐transfer success between individuals. The number of mates increased with social group size, and was higher in worms with larger testes, but there was no effect of density. Similarly, sperm‐transfer success was affected by social group size and testis size, but in addition this parameter was influenced by genital morphology. Our study demonstrates for the first time that the social context and the morphology of sperm donors are important predictors of the number of mates and sperm‐transfer success in a simultaneous hermaphrodite. Based on these findings, we hypothesize that sex allocation influences the mating behaviour and outcome of sperm competition.     

Pedogenesis, permafrost, and soil moisture as controlling factors for soil nitrogen and carbon contents across the Tibetan Plateau

We investigated the main parameters [e.g. mean annual air temperature , mean annual soil temperature, mean annual precipitation, soil moisture (SM), soil chemistry, and physics] influencing soil organic carbon (C_org), soil total nitrogen (N_t) as well as plant available nitrogen (N_min) at 47 sites along a 1200 km transect across the high‐altitude and low‐latitude permafrost region of the central‐eastern Tibetan Plateau. This large‐scale survey allows testing the hypothesis that beside commonly used ecological variables, diversity of pedogenesis is another major component for assessing carbon (C) and nitrogen (N) cycling. The aim of the presented research was to evaluate consequences of permafrost degradation for C and N stocks and hence nutrient supply for plants, as the transect covers all types of permafrost including heavily degraded areas and regions without permafrost. Our results show that SM is the dominant parameter explaining 64% of C_org and 60% of N variation. The extent of the effect of SM is determined by permafrost, current aeolian sedimentation occurring mostly on degraded sites, and pedogenesis. Thus, the explanatory power for C and N concentrations is significantly improved by adding CaCO₃ content (P=0.012 for C_org; P=0.006 for N_t) and soil texture (P=0.077 for C_org; P=0.015 for N_t) to the model. For soil temperature, no correlations were detected indicating that in high‐altitude grassland ecosystems influenced by permafrost, SM overrides soil temperature as the main driving parameter at landscape scale. It was concluded from the current study that degradation of permafrost and corresponding changes in soil hydrology combined with a shift from mature stages of pedogenesis to initial stages, have severe impact on soil C and plant available N. This may alter biodiversity patterns as well as the development and functioning of the ecosystems on the Tibetan Plateau.     

Alien herbivores and native parasitoids: rapid developments and structure of the parasitoid and inquiline complex in an invading gall wasp Andricus quercuscalicis (Hymenoptera: Cynipidae)

Abstract.

• 1 Rapid and substantial changes have occurred in the parasitoid and inquiline community associated with the agamic galls of Andricus quercuscalicis since it invaded Britain in the late 1950s. The number of parasitoid and inquiline species has risen from one to thirteen over a 15-year period. Although the number of species has been relatively consistent over the last 8 years, the species composition has changed considerably and in a highly characteristic way during this period.
• 2 The parasitoid complex can be divided into two broadly distinct sets of parasitoid species; one set attacks only the gall former whereas the other set concentrates on the inquilines living in the wall of the gall.
• 3 The most dramatic change, however, is in the abundance of inquilines which were reported to be virtually absent in earlier studies on this community in Britain. Over a period of only 5 years, between 1988 and 1993, inquiline attack rose from less than 0.01 to an average of 0.26 inquilines per gall. The intensity of inquiline attack is geographically heterogenous, with high inquiline numbers restricted to south-east England. Because of the relatively high specificity of the parasitoids, high inquiline abundance is positively correlated with parasitoid species richness in knopper galls.
• 4 Parasitism rates, particularly on the gall former, were generally low (<10%). Over the last 5 years, however, seven parasitoid species have been consistently recorded and the mortality caused by these species has increased continuously. The species composition of the community associated with this alien gall wasp in Britain has quickly converged to the community known from its native range in continental Europe. Parasitoid species known to attack the galls of A.quercuscalisis on the continent have been recorded from it in Britain for the first time mainly in areas where inquilines have recently become abundant.
• 5 Since rates of parasitism of the gall former are still low, parasitoids are unlikely to play a major role in the population dynamics of this invading gall wasp at present, but the rapidly increasing inquiline and parasitoid attack could be a source of increased mortality for native cynipid species which are the alternative hosts of those parasitoid species.

     

The effect of light intensity and daylength on the β-dimethylsulphoniopropionate (DMSP) content of marine green macroalgae from Antarctica*

Abstract. The β-dimethylsulphoniopropionate (DMSP) concentrations of 5 Antarctic green algae grown at 2, 30 and 55 μmol photons m^?2 s^?1 were determined during a period of one year, cultivated under fluctuating daylengths mimicking the conditions of the natural habitat at King George Island. Antarctica. The intracellular DMSP content of all species decreased simultaneously with decreasing daylengths and vice versa. Additionally, the DMSP level was affected by the light intensity: the higher the photon fluence rate the greater the algal DMSP concentration. Under conditions of darkness, there was a degradation of the DMSP pool in members of the Acrosiphoniales, while the DMSP content in members of the Ulvales did not change. The results indicate a light-dependent DMSP accumulation in algae. Therefore, they may help to explain the seasonal variability of DMSP and its cleavage product dimethylsulphide (DMS) in coastal waters.     

How internal waves influence the vertical distribution of zooplankton

1. We present data with a high spatio‐temporal resolution from a 72‐h field survey in Bautzen Reservoir (Saxony, Germany). The aims of this survey were to observe hydrophysical processes during a period of unstable stratification in spring and investigate the effect of wind‐induced internal waves on the vertical distribution of zooplankton. 2. Wind velocities up to 10 m s⁻¹ caused a strong downwelling event of warm water at the sampling site and led to the generation of internal waves with an amplitude of 4 m. 3. The zooplankton community, which was dominated by Daphnia galeata, inhabited epilimnetic waters. Downwelling enlarged the thickness of the epilimnetic layer and, hence, led to high zooplankton abundances down to relatively deep water strata indicating lateral transport of zooplankton. As a consequence, area‐specific zooplankton abundances increased considerably (max. fourfold) during downwelling. 4. We conclude that classical limnological field sampling, such as for monitoring purposes, can lead to severely biased estimates of zooplankton abundance due to the interfering effects of hydrophysical processes like internal waves. 5. Backscattering strengths measured by a simultaneously deployed Acoustic Doppler Current Profiler (600 kHz) were found to be correlated with estimated zooplankton abundances based on plankton samples.     

Mitochondrial RNA Polymerase from <Emphasis Type="Italic">Neurospora crassa</Emphasis>

The enzyme consists of a single polypeptide chain of molecular weight of 64,000 and tends to form heavy aggregates. It is sensitive to rifampicin and resistant to α-amanitin. It prefers native mitochondrial DNA and d(AT) copolymer as template.     

New ankylosaurian material from the Upper Cretaceous of Transylvania

Ankylosaurian remains from the Transylvanian Basin, Romania, are extremely rare. More than 100 years after the discovery of the first and only better-known assemblage, namely the type material of Struthiosaurus transylvanicus, new ankylosaurian material has been discovered in the Maastrichtian of the Ha?eg Basin, as well as at another locality (Vurp?r), in the Transylvanian Basin, that is described here. The material consists of one tooth in a small jaw fragment (from the Ha?eg Basin) and at least two accummulations of associated, as well as several isolated, postcranial elements (from Vurp?r). No diagnostic elements are preserved that would overlap with the type of S. transylvanicus, so we cannot assign any of the new specimens to this species. The tooth shows marked differences compared to those of other anklyosaurs including S. austriacus and Hungarosaurus in having only six, more or less equally sized, apically pointed cusps separated by deep grooves. The postcranial material from Vurp?r represents at least three different individuals. The humerus is the most diagnostic element among the postcranial remains being most similar both in size and morphology to humeri referred to as Struthiosaurus from different European localities, thus here we refer the humerus and probably associated elements preserved in one assemblage to as cf. Struthiosaurus sp.; the remaining specimens from Vurp?r are retained as Nodosauridae indet. Histological studies have confirmed the adult nature of all sampled bones in the Vurp?r ankylosaur material suggesting that these fully grown animals were of similar size to Struthiosaurus, a small-bodied nodosaurid the ontogenetic status of which, however, has never been investigated histologically. The obviously diminished body size of the Transylvanian ankylosaurs compared to other members of the clade could be explained by insular dwarfism using the same histology-based argument as presented for Magyarosaurus.