Brood size manipulations in Great Horned Owls Bubo virginianus: are predators food limited at the peak of prey cycles?

The reproduction of raptors strongly depends on food resources. It is unclear whether predators experience superabundant food during cyclic peaks of prey populations. In order to test this hypothesis, four pairs of Great Horned Owls Bubo virginianus with two young were subjected to brood size manipulations during high densities of cyclic Snowshoe Hare Lepus americanus populations in southwestern Yukon, Canada. Broods older than 35 days were temporarily enlarged by one, and then by two, young. No effects were observed when one owlet was added, but the addition of two young resulted in significant weight losses in manipulated broods. Females with enlarged broods moved farther from their nest sites at night, presumably reflecting increased hunting effort, and also spent less time near the nest during the day. Food additions to enlarged broods returned the parental behaviour to normal. We conclude that these large predators did not experience superabundant food at this stage of the breeding season during a peak in cyclic prey.     

Linking environmental warming to the fitness of the invasive clam Corbicula fluminea

Climate warming is discussed as a factor that can favour the success of invasive species. In the present study, we analysed potential fitness gains of moderate warming (3 °C above field temperature) on the invasive clam Corbicula fluminea during summer and winter. The experiments were conducted under seminatural conditions in a bypass-system of a large river (Rhine, Germany). We showed that warming in late summer results in a significant decrease in the clams' growth rates (body mass and shell length increase) and an increase in mortality rate. The addition of planktonic food dampens the negative effect of warming on the growth rates. This suggests that the reason for the negative growth effect of temperature increase in late summer is a negative energetic balance caused by an enhanced metabolic rate at limited food levels. Warming during early summer revealed contrasting effects with respect of body mass (no warming effect) and shell length (increased shell growth with warming). This differential control of both parameters further enhances the loss of the relative (size-specific) body mass with warming. In contrast, warming in winter had a consistently positive effect on the clams' growth rate as demonstrated in two independent experiments. Furthermore, the reproduction success (as measured by the average number of larvae per clam) during the main breeding period (April) was strongly enhanced by experimental warming during winter, i.e. by eight times during the relatively cold winter 2005/2006 and by 2.6 times during the relatively warm winter 2007/2008. This strong, positive effect of moderate winter warming on the clams' fitness is probably one reason for the recent invasion success of C. fluminea in the northern hemisphere. However, warm summer events might counteract the positive winter warming effect, which could balance out the fitness gains.     

Physical illness in patients with severe mental disorders. II. Barriers to care, monitoring and treatment guidelines, plus recommendations at the system and individual level

Physical disorders are, compared to the general population, more prevalent in people with severe mental illness (SMI). Although this excess morbidity and mortality is largely due to modifiable lifestyle risk factors, the screening and assessment of physical health aspects remains poor, even in developed countries. Moreover, specific patient, provider, treatment and system factors act as barriers to the recognition and to the management of physical diseases in people with SMI. Psychiatrists can play a pivotal role in the improvement of the physical health of these patients by expanding their task from clinical psychiatric care to the monitoring and treatment of crucial physical parameters. At a system level, actions are not easy to realize, especially for developing countries. However, at an individual level, even simple and very basic monitoring and treatment actions, undertaken by the treating clinician, can already improve the problem of suboptimal medical care in this population. Adhering to monitoring and treatment guidelines will result in a substantial enhancement of physical health outcomes. Furthermore, psychiatrists can help educate and motivate people with SMI to address their suboptimal lifestyle, including smoking, unhealthy diet and lack of exercise. The adoption of the recommendations presented in this paper across health care systems throughout the world will contribute to a significant improvement in the medical and related psychiatric health outcomes of patients with SMI.     

Genetic variation of Saxifraga paniculata Mill. (Saxifragaceae): molecular evidence for glacial relict endemism in central Europe

Saxifraga paniculata Mill. is an amphi-atlantic species that is widely distributed in the Alps but also occurs with disjunct populations in central Europe. These isolated populations are considered to be glacial relicts. In the study presented here, we analysed the genetic variation within and between populations of Saxifraga paniculata in central Europe to test whether the molecular data give evidence for the supposed relict endemism. We used RAPD analysis and the analysis of molecular variance (AMOVA) technique to investigate 30 populations of Saxifraga paniculata from different locations in central Europe and adjacent geographical areas. In the RAPD analysis, 319 fragments could be amplified of which 91.2% were polymorphic. The percentage of polymorphic bands within populations correlated significantly with population size, indicating a higher level of inbreeding in small populations. AMOVA revealed 43.60% of the variation within populations, only 15.45% between populations within locations, and 40.95% between locations. Genetic distance between locations (Φ_ST) correlated significantly with the geographical distance between locations, giving evidence for geographical isolation. In an UPGMA cluster analysis, based on RAPD data, the populations were grouped together according to their location. The results exhibit a strong genetic differentiation which is obviously due to genetic drift in the isolated populations. Our study therefore gives evidence for glacial relict endemism of Saxifraga paniculata in central Europe.  © 2003 The Linnean Society of London, Biological Journal of the Linnean Society , 2003, 80, 11–21.     

Disturbance history influences the distribution of stream invertebrates by altering microhabitat parameters: a field experiment

1. We investigated the effects of local disturbance history and several biotic and abiotic habitat parameters on the microdistribution of benthic invertebrates after an experimental disturbance in a flood‐prone German stream. 2. Bed movement patterns during a moderate flood were simulated by scouring and filling stream bed patches (area 0.49 m²) to a depth of 15–20 cm. Invertebrates were investigated using ceramic tiles as standardized substrata. After 1, 8, 22, 29, 36 and 50 days, we sampled one tile from each of 16 replicates of three bed stability treatments (scour, fill and stable controls). For each tile, we also determined water depth, near‐bed current velocity, the grain size of the substratum beneath the tile, epilithic algal biomass and standing stock of particulate organic matter (POM). 3. Shortly after disturbance, total invertebrate density, taxon richness and density of the common taxa Baetis spp. and Chironomidae were highest in stable patches. Several weeks after disturbance, by contrast, Baetis spp. and Hydropsychidae were most common in fill and Leuctra spp. in scour patches. The black fly Simulium spp. was most abundant in fill patches from the first day onwards. Community evenness was highest in scour patches during the entire study. 4. Local disturbance history also influenced algal biomass and POM standing stock at the beginning of the experiment, and water depth, current velocity and substratum grain size throughout the experiment. Scouring mainly exposed finer substrata and caused local depressions in the stream bed characterized by slower near‐bed current velocity. Algal biomass was higher in stable and scour patches and POM was highest in scour patches. In turn, all five common invertebrate taxa were frequently correlated with one or two of these habitat parameters. 5. Our results suggest that several ‘direct’ initial effects of local disturbance history on the invertebrates were subsequently replaced by ‘indirect’ effects of disturbance history (via disturbance‐induced changes in habitat parameters such as current velocity or food).