Ontogenetic correlates of diet in Malagasy lemurs

There is a well-documented relationship between development and other life-history parameters among anthropoid primates. Smaller-bodied anthropoids tend to mature more rapidly than do larger-bodied species. Among anthropoids of similar body sizes, folivorous species tend to grow and mature more quickly than do frugivorous species, thus attaining adult body size at an earlier age. This pattern conforms to the expectations of Janson and van Schaik's "ecological risk aversion hypothesis," which predicts that rates of growth and maturation should vary in inverse relation to the intensity of intraspecific feeding competition. According to the ecological risk aversion hypothesis (RAH), species experiencing high intraspecific feeding competition will grow and mature slowly to reduce the risk of mortality due to food shortages. Species experiencing low levels of intraspecific feeding competition will shorten the juvenile period to reduce the overall duration of this high-risk portion of the life cycle. This paper focuses on development and maturation in lemurs. We show that folivorous lemurs (such as indriids) grow and mature more slowly than like-sized frugivorous lemurs (e.g., most lemurids), but tend to exhibit faster dental development. Their dental developmental schedules are accelerated on an absolute scale, relative to craniofacial growth, and relative to particular life-history landmarks, such as weaning. Dental development has a strong phylogenetic component: even those lemurids that consume substantial amounts of foliage have slower dental development than those indriids that consume substantial amounts of fruit. Implications of these results for the RAH are discussed, and an explanation for this hypothesis' failure to predict lemur growth schedules is offered. We propose that the differing developmental schedules of folivorous and frugivorous lemurs may reflect different solutions to the ecological problem of environmental instability: some rely on a strategy of low maternal input and slow returns, while others rely on a strategy of high maternal input and fast returns.     

The antifungal drug voriconazole is an efficient inhibitor of brain cholesterol 24S-hydroxylase in vitro and in vivo

Cholesterol 24S-hydroxylase (CYP46A1) is of key importance for cholesterol homeostasis in the brain. This enzyme seems to be resistant toward most regulatory factors and at present no drug effects on its activity have been described. The crystal structures of the substrate-free and substrate-bound CYP46A1 were recently determined (Mast et al., Crystal structures of substrate-bound and substrate-free cytochrome P450 46A1, the principal cholesterol hydroxylase in the brain. Proc. Natl. Acad. Sci. USA. 2008. 105: 9546–9551). These structural studies suggested that ligands other than sterols can bind to CYP46A1. We show here that the antifungal drug voriconazole binds to the enzyme in vitro and inhibits CYP46A1-mediated cholesterol 24-hydroxylation with a Ki of 11 nM. Mice treated with daily intraperitoneal injections of voriconazole for 5 days had high levels of voriconazole in the brain and significantly reduced brain levels of 24S-hydroxycholesterol. The levels of squalene, lathosterol, and HMG-CoA reductase mRNA were reduced in the brain of the voriconazole-treated animals as well, indicating a reduced cholesterol synthesis. Most of this effect may be due to a reduced utilization of cholesterol by CYP46A1. One of the side-effects of voriconazole is visual disturbances. Because CYP46A1 is also expressed in the neural retina, we discuss the possibility that the inhibition of CYP46A1 by voriconazole contributes to these visual disturbances.     

Effects of biotic disturbances on forest carbon cycling in the United States and Canada

Forest insects and pathogens are major disturbance agents that have affected millions of hectares in North America in recent decades, implying significant impacts to the carbon (C) cycle. Here, we review and synthesize published studies of the effects of biotic disturbances on forest C cycling in the United States and Canada. Primary productivity in stands was reduced, sometimes considerably, immediately following insect or pathogen attack. After repeated growth reductions caused by some insects or pathogens or a single infestation by some bark beetle species, tree mortality occurred, altering productivity and decomposition. In the years following disturbance, primary productivity in some cases increased rapidly as a result of enhanced growth by surviving vegetation, and in other cases increased slowly because of lower forest regrowth. In the decades following tree mortality, decomposition increased as a result of the large amount of dead organic matter. Net ecosystem productivity decreased immediately following attack, with some studies reporting a switch to a C source to the atmosphere, and increased afterward as the forest regrew and dead organic matter decomposed. Large variability in C cycle responses arose from several factors, including type of insect or pathogen, time since disturbance, number of trees affected, and capacity of remaining vegetation to increase growth rates following outbreak. We identified significant knowledge gaps, including limited understanding of carbon cycle impacts among different biotic disturbance types (particularly pathogens), their impacts at landscape and regional scales, and limited capacity to predict disturbance events and their consequences for carbon cycling. We conclude that biotic disturbances can have major impacts on forest C stocks and fluxes and can be large enough to affect regional C cycling. However, additional research is needed to reduce the uncertainties associated with quantifying biotic disturbance effects on the North American C budget.     

Species- and clone-specific responses to environmental stimuli in the cladocerans Bosmina cornuta and B. pellucida - a comparison with Daphnia

We studied the variation of small-scale swimming behaviour in eight Bosmina cornuta and ten B. pellucida clones in response to key environmental factors to test whether swimming behaviour and genotypes are linked in non-Daphnia cladocerans. We quantified (1) the short-term responses to changes in temperature, light intensity and pH, (2) the response to long-term temperature acclimation, and (3) the pH-related survival rates. Vertical swimming activity S was quantified in cuvette experiments as crossings of a line at 2 cm height per individual an hour. S differed significantly among species and conspecific clones. At any temperature, light intensity and pH tested, B. cornuta (clone variation: 40-58 crossings/ind.× h) showed a higher vertical swimming activity than B. pellucida (clone variation: 25-48 crossings/ind.× h). A short-term change of water temperature (range tested: 10-25°C) only affected S of B. cornuta, whereas that of B. pellucida remained unaltered. In contrast, S increased with rising temperature following long-term temperature acclimation (range tested: 10-20°C) in both species. Swimming activity was inversely related to the light intensity (range tested: 60-60,000 lux), but decrease of activity was stronger in B. pellucida (44 → 12 crossings/ind × h) than in B. cornuta (50 → 40 crossings/ind.× h). Short-term changes of pH (range tested: 4-6) did not influence swimming activity in any species, although a prolonged exposure (24 h) to pH 4 was lethal. Thus, Bosmina showed behavioural responses which permit to distinguish between the species and which are related to their seasonal succession and distribution pattern.     

Understanding seagrass resilience in temperate systems: the importance of timing of the disturbance

Temperate seagrass meadows form valuable ecosystems in coastal environments and present a distinct seasonal growth. They are threatened by an increasing amount of stressors, potentially affecting their capacity to recover from disturbances. We hypothesized that their resilience to disturbances is affected by seasonal dynamics. Hence, we investigated the effect of the timing of the disturbance on seagrass Leaf Area Index (as a proxy for presence, or ‘visible’ status), recovery from disturbance (as a proxy for meadow resilience), and rhizome carbohydrates (as a proxy for longer term resilience) by a series of four disturbance-recovery field experiments spread over the growing season at two sites in Shandong Province, China. During the course of the growing season, we found the highest recovery at the start of the growing season, lowest recovery when Leaf Area Index peaked around mid-growing season, and intermediate recovery when Leaf Area Index decreased at the end of the growing season. Rhizome carbohydrates were not affected by disturbances during any of the four experimental periods and could not explain the low recovery during mid-growing season. The two sites differed in exposure and in the occurrence of incidents like a green tide and storms, which affected recovery. However, general patterns were similar; timing strongly influenced the indicator of meadow resilience and its correlation with presence during the two main seagrass growth phases. Our results emphasize the importance of carefully considering timing in the evaluation of seagrass resilience in temperate systems. Furthermore, our study implies that, to effectively protect seagrass beds, conservation management should aim at avoiding disturbances particularly during the peak of the growing season, when resilience is lowest.     

Dangerous life at the edge: Implications of seed predation for roadside revegetation

Question

Anthropogenic edges caused by transport infrastructure such as dirt roads and trails (also known as Soft Linear Developments; SLD) are pervasive in almost every terrestrial ecosystem. Revegetating these edges may reduce some of their negative effects, such as their permeability to biological invasions and detrimental effects on wildlife, potentially becoming suitable habitat for a broad range of species. Selecting species with low post‐dispersal seed predation rates may improve the effectiveness of revegetation programmes.

Location

Mediterranean scrublands in SW Spain.

Methods

We made offerings of a total of 16,000 seeds of eight species of fleshy‐fruit shrubs both along SLD edges and scrubland interiors in two independent blocks in each of three distant locations. Using four types of selective enclosure, we assessed the relative contribution of three seed predator guilds (ants, rodents and birds) to seed predation rates both along SLD edges and scrubland interiors.

Results

The effects of anthropogenic edges on seed predation rates were species‐specific. The large and hard‐seeded species Chamaerops humilis was not predated at all. Juniperus phoenicea and Corema album seeds had higher predation rates in scrubland interiors than in edges. The small‐seeded Rubus ulmifolius experienced relatively low seed predation rates compared to the other species. Predation rates for this species were higher along SLD edges than in scrubland interiors. Ants were the main seed predators in the area, and showed marked preferences for J. macrocarpa and C. album seeds at both SLD edges and scrubland interiors.

Conclusions

Our results show the strong context‐dependency of seed predation rates in both SLD edges and scrubland interiors, and thus the importance of well spatially and temporally replicated studies. Species with large and hard seeds may be good candidates for roadside revegetation programmes. However, the relative suitability of plant species would depend on the seed predator community. Our findings confirm that studies on seed predation may help planning cost‐effective species selection for edge revegetation efforts worldwide.     

Structure and stand development in three subalpine Norway spruce (Picea abies (L.) Karst.) stands in Paneveggio (Trento, Italy)

1. Three permanent plots (100×0 m) were established in the subalpine Norway spruce (Picea abies (L.) Karst.) forest of Paneveggio in the spring of 1993, to begin a long-term forest ecosystem research project. The main purpose of these plots was to provide information about subalpine Norway spruce stand dynamics and to provide suggestions for close-to-nature silviculture. 2. The three stands were selected to represent the most common forest structures in the Paneveggio forest. The first stand is close to forestry roads, has a relatively regular and continuous canopy, and thinning and cutting operations only ended in the 1980s; the second stand is far from forest roads and has developed without anthropogenic influence for several decades; the third one is located at the present upper limit of the pure spruce forest and, apparently, was heavily used in the past as a pasture. 3. The first step in the investigation was to describe the structure and to study the history of the three stands using both written evidence from manage- ment plans and biological archives from tree rings. 4. The stands in plots 1 and 2 began to establish after a disturbance that removed part of the previous stands according to dendroecological studies, which are partially supported by written evidence. The remaining parts of these stands were eliminated by two major disturbances that occurred during the following decades. Written records about the use of the forest lead us to assume that the initial disturbances that occurred in the two stands were logging activities as a part of a group shelterwood system. The stand in plot 2 has developed without significant human interference for about half a century as confirmed by the presence of many dead trees. The stand in plot 3 consists of old trees that were part of an open stand and a secondary population that established after cessation of grazing. 5. The study has confirmed that dendroecological techniques can be used to identify occurrence and intensity of previous disturbance in forests stands, although at Paneveggio it is difficult to distinguish between natural and anthropogenic disturbances in the tree ring record. The presence of human activity necessitates investigation of multiple lines of evidence. 6. Paneveggio's forest management plans were useful in the interpretation of the data obtained through dendroecological analysis, although events did not always correspond because data from the management plans (yearly thinning, felling, wind-throw damage) never gave stand-level details, but applied to areas of several hectares. Despite these limitations, the information included in the management plans is of crucial importance in studying stand history and only by using all these sources of information is it possible to delineate the most important features of the history and disturbance that affected the origin and subsequent growth of the forest stands.     

Chronotype and its relationship with sleep disorders in children with attention deficit hyperactivity disorder

Chronotype can be classified as morningness types, people who prefer morning hours for their physical and mental activities; eveningness types, people who prefer the afternoon or evening hours; and intermediate types, those who show characteristics of both morningness and eveningness types. Attention deficit hyperactivity disorder (ADHD) has been linked with disturbances in chronotype, particularly increased eveningness. Despite the possibility of an association between chronotypes, sleep disturbances and ADHD symptoms, there is little evidence of this association considering the child population. The purpose of this study was to examine chronotype preferences in children aged between 7 and 12 years who were diagnosed as having ADHD in the context of sleep disturbances. The Schedule for Affective Disorders and Schizophrenia for School Age Children-Present and Lifetime Version, Conner’s Rating Scales, Children’s Sleep Habit Questionnaire and Children’s Chronotype Questionnaire were used for the evaluation of children with ADHD and healthy controls. The ADHD group was 73% combined-type, and the eveningness scores of the ADHD group (n = 52) were significantly higher than the control group (n = 52) (p < 0.01). There was a positive correlation between the higher scores of eveningness and total scores on resistance to sleep time (p < 0.09), respiratory problems during sleep and daytime sleepiness in the ADHD group. CSHQ total score was found to be a predictive factor for eveningness among children with ADHD (p < 0.01). These findings highlight possible reciprocal links between ADHD symptoms, sleep disturbances and chronotype in children aged 7–12 years, which might lead to individualized treatment options.