Ontogenetic trait variation influences tree community assembly across environmental gradients

Intraspecific trait variation is hypothesized to influence the relative importance of community assembly mechanisms. However, few studies have explicitly considered how intraspecific trait variation among ontogenetic stages influences community assembly across environmental gradients. Because the relative importance of abiotic and biotic assembly mechanisms can differ among ontogenetic stages within and across environments, ontogenetic trait variation may have an important influence on patterns of functional diversity and inferred assembly mechanisms. We tested the hypothesis that variation in functional diversity across a topo-edaphic gradient differs among ontogenetic stages and that these patterns reflect a shift in the relative importance of different assembly mechanisms. In a temperate forest in the Missouri Ozarks, USA, we compared functional diversity of leaf size and specific leaf area (SLA) of 34 woody plant species at two ontogenetic stages (adults and saplings) to test predictions about how the relative importance of abiotic and biotic filtering changes among adult and sapling communities. Local communities of adults had lower mean SLA and lower functional dispersion of SLA than expected by chance, particularly at the resource-limited end of the topo-edaphic gradient, suggesting an important role for abiotic filtering among co-occurring adults. In contrast, local communities of saplings often had higher functional dispersion of leaf size and SLA than expected by chance regardless of their location along the topo-edaphic gradient, suggesting an important role for biotic filtering among co-occurring saplings. Moreover, the overall strength of trait-environment relationships varied between saplings and adults for both leaf traits, generally resulting in stronger environmental shifts in mean trait values and trait dispersion for adults relative to saplings. Our results illustrate how community assembly mechanisms may shift in their relative importance during ontogeny, leading to variable patterns of functional diversity across environmental gradients. Moreover, our results highlight the importance of integrating ontogeny, an important axis of intraspecific trait variability, into approaches that use plant functional traits to understand community assembly and species coexistence

The role of the lissencephaly protein Pac1 during nuclear migration in budding yeast

During mitosis in Saccharomyces cerevisiae, the mitotic spindle moves into the mother–bud neck via dynein-dependent sliding of cytoplasmic microtubules along the cortex of the bud. Here we show that Pac1, the yeast homologue of the human lissencephaly protein LIS1, plays a key role in this process. First, genetic interactions placed Pac1 in the dynein/dynactin pathway. Second, cells lacking Pac1 failed to display microtubule sliding in the bud, resulting in defective mitotic spindle movement and nuclear segregation. Third, Pac1 localized to the plus ends (distal tips) of cytoplasmic microtubules in the bud. This localization did not depend on the dynein heavy chain Dyn1. Moreover, the Pac1 fluorescence intensity at the microtubule end was enhanced in cells lacking dynactin or the cortical attachment molecule Num1. Fourth, dynein heavy chain Dyn1 also localized to the tips of cytoplasmic microtubules in wild-type cells. Dynein localization required Pac1 and, like Pac1, was enhanced in cells lacking the dynactin component Arp1 or the cortical attachment molecule Num1. Our results suggest that Pac1 targets dynein to microtubule tips, which is necessary for sliding of microtubules along the bud cortex. Dynein must remain inactive until microtubule ends interact with the bud cortex, at which time dynein and Pac1 appear to be offloaded from the microtubule to the cortex

Letter to the Editor (Human immunodeficiency virus in Costa Rica)

Recent reports of 12 confirmed cases of acquired immunodeficiency syndrome (AIDS) in Costa Rica have generated interest in the extent of spread of human T-lymphotropic virus type III/LAV (HTLV-III) in Latin America (1). To date, all cases of AIDS in Costa Rica have occurred in members of previously identified, high-risk groups, chiefly hemophiliacs. To examine the possibility of heterosexual transmission in Costa Rica, we utilized sera collected in a population-based case-control study of cervical cancer, conducted by the Costa Rican Demographic Association and other institution

Decomposition of coarse woody debris in a long-term litter manipulation experiment: A focus on nutrient availability

The majority of above-ground carbon in tropical forests is stored in wood, which is returned to the atmosphere during decomposition of coarse woody debris. However, the factors controlling wood decomposition have not been experimentally manipulated over time scales comparable to the length of this process.We hypothesized that wood decomposition is limited by nutrient availability and tested this hypothesis in a long-term litter addition and removal experiment in a lowland tropical forest in Panama. Specifically, we quantified decomposition using a 15-year chronosequence of decaying boles, and measured respiration rates and nutrient limitation of wood decomposer communities.The long-term probability that a dead tree completely decomposed was decreased in plots where litter was removed, but did not differ between litter addition and control treatments. Similarly, respiration rates of wood decomposer communities were greater in control treatments relative to litter removal plots; litter addition treatments did not differ from either of the other treatments. Respiration rates increased in response to nutrient addition (nitrogen, phosphorus, and potassium) in the litter removal and addition treatments, but not in the controls.Established decreases in concentrations of soil nutrients in litter removal plots and increased respiration rates in response to nutrient addition suggest that reduced rates of wood decomposition after litter removal were caused by decreased nutrient availability. The effects of litter manipulations differed directionally from a previous short-term decomposition study in the same plots, and reduced rates of bole decomposition in litter removal plots did not emerge until after more than 6 years of decomposition. These differences suggest that litter-mediated effects on nutrient dynamics have complex interactions with decomposition over time

Towards a Sustainable Development Licence to Operate for the extractive sector: Consultation paper from the International Resource Panel Working Group on mineral resource governance for sustainable development

Mineral resources are a foundation of social and economic development. The 17 Goals and 169 Targets in the 2030 Agenda for Sustainable Development recognise the importance of these resources, and depend on infrastructure and technologies that use them in vast quantities. Mineral resources present major governance challenges for many countries, in particular for developing countries. The governance architecture of the extractive sector currently suffers from a range of well-documented shortcomings, which undermine its ability to deliver social, economic, environmental and governance benefits. This consultation paper introduces—and seeks feedback concerning—the International Resource Panel's efforts to formulate a new multi-level governance framework for the extractive sector, entitled the Sustainable Development Licence to Operate or SDLO. The SDLO builds on the achievements of the social licence to operate, and is not intended to function as a licence in the regulatory sense. It will instead set out clear principles, policy options and best practice that are intended to function as a common reference point, enabling all public, private and other relevant actors in the extractive sector to make decisions compatible with the 2030 Agenda's vision of sustainable development

Flood-risk mapping: contributions towards an enhanced assessment of extreme events and associated risks

Currently, a shift from classical flood protection as engineering task towards integrated flood risk management concepts can be observed. In this context, a more consequent consideration of extreme events which exceed the design event of flood protection structures and failure scenarios such as dike breaches have to be investigated. Therefore, this study aims to enhance existing methods for hazard and risk assessment for extreme events and is divided into three parts. In the first part, a regionalization approach for flood peak discharges was further developed and substantiated, especially regarding recurrence intervals of 200 to 10 000 years and a large number of small ungauged catchments. Model comparisons show that more confidence in such flood estimates for ungauged areas and very long recurrence intervals may be given as implied by statistical analysis alone. The hydraulic simulation in the second part is oriented towards hazard mapping and risk analyses covering the whole spectrum of relevant flood events. As the hydrodynamic simulation is directly coupled with a GIS, the results can be easily processed as local inundation depths for spatial risk analyses. For this, a new GIS-based software tool was developed, being presented in the third part, which enables estimations of the direct flood damage to single buildings or areas based on different established stage-damage functions. Furthermore, a new multifactorial approach for damage estimation is presented, aiming at the improvement of damage estimation on local scale by considering factors like building quality, contamination and precautionary measures. The methods and results from this study form the base for comprehensive risk analyses and flood management strategies

Herpes Simplex Virus Type 2 Antibodies: High Prevalence in Monogamous Women in Costa Rica

We studied the prevalence of antibody to Herpes simplex virus types I and 2 (HSV-I and HSV-2) in 766 randomly selected Costa Rican women 25-59 years of age in a national household survey in 1984-1985. Overall, 97.1% were seropositive for HSV-l and 39.4% for HSV -2. Only 1.1% of HSV -2 seropositive women gave a history of symptomatic genital herpes. HSV-2 virus antibody increased with age and with the number of lifetime sexual partners. HSV -2 seroprevalence among women who reported only 1 lifetime sexual partner was almost twice as high as the prevalence among women who denied sexual experience (30.5% vs. 17.7%) and reached 79.2% among women with \u3c 4 partners. HSV-2 seroprevalence was lower among women whose partners used condoms: 28.9% for those who had used condoms for at least 2 years vs. 44.3% for those who never used condoms