The division of labor (DOL) and task allocation among groups of ants living in a colony is thought to be highly efficient, and key to the robust survival of a colony. A great deal of experimental and ...theoretical work has been done toward gaining a clear understanding of the evolution of, and underlying mechanisms of these phenomena. Much of this research has utilized mathematical modeling. Here we continue this tradition by developing a mathematical model for a particular aspect of task allocation, known as age-related repertoire expansion, that has been observed in the minor workers of the ant species \emph{Pheidole dentata}. In fact, we present a relatively broad mathematical modeling framework based on the dynamics of the frequency with which members of specific age groups carry out distinct tasks. We apply our modeling approach to a specific task allocation scenario, and compare our theoretical results with experimental data. It is observed that the model predicts perceived behavior, and provides a possible explanation for the aforementioned experimental results.
Plant diversity is an important driver of diversity at other trophic levels, suggesting that cascading extinctions could reduce overall biodiversity. Most evidence for positive effects of plant ...diversity comes from grasslands. Despite the fact that forests are hotspots of biodiversity, the importance of tree diversity, in particular its relative importance compared to other management related factors, in affecting forest‐associated taxa is not well known. To address this, we used data from 183 plots, located in different forest types, from Mediterranean to Boreal, and established along a climatic gradient across six European countries (FunDivEUROPE project). We tested the influence of tree diversity, tree functional composition (i.e. functional trait values), forest structure, climate and soil on the diversity and abundance/activity of nine taxa (bats, birds, spiders, microorganisms, earthworms, ungulates, foliar fungal pathogens, defoliating insects and understorey plants) and on their overall diversity and abundance/activity (multidiversity, multiabundance/activity). Tree diversity was a key driver of taxon‐level and overall forest‐associated biodiversity, along with tree functional composition, forest structure, climate and soil. Both tree species richness and functional diversity (variation in functional trait values) were important. The effects of tree diversity on the abundance/activity of forest‐associated taxa were less consistent. Nonetheless, spiders, ungulates and foliar fungal pathogens were all more abundant/active in diverse forests. Tree functional composition and structure were also important drivers of abundance/activity: conifer stands had lower overall multidiversity (although the effect was driven by defoliating insects), while stands with potentially tall trees had lower overall multiabundance/activity. We found more synergies than tradeoffs between diversity and abundance/activity of different taxa, suggesting that forest management can promote high diversity across taxa. Our results clearly show the high value of mixed forest stands for multiple forest‐associated taxa and indicate that multiple dimensions of tree diversity (taxonomic and functional) are important.
One of the current advances in functional biodiversity research is the move away from short-lived test systems towards the exploration of diversity-ecosystem functioning relationships in structurally ...more complex ecosystems. In forests, assumptions about the functional significance of tree species diversity have only recently produced a new generation of research on ecosystem processes and services. Novel experimental designs have now replaced traditional forestry trials, but these comparatively young experimental plots suffer from specific difficulties that are mainly related to the tree size and longevity. Tree species diversity experiments therefore need to be complemented with comparative observational studies in existing forests. Here we present the design and implementation of a new network of forest plots along tree species diversity gradients in six major European forest types: the FunDivEUROPE Exploratory Platform. Based on a review of the deficiencies of existing observational approaches and of unresolved research questions and hypotheses, we discuss the fundamental criteria that shaped the design of our platform. Key features include the extent of the species diversity gradient with mixtures up to five species, strict avoidance of a dilution gradient, special attention to community evenness and minimal covariation with other environmental factors. The new European research platform permits the most comprehensive assessment of tree species diversity effects on forest ecosystem functioning to date since it offers a common set of research plots to groups of researchers from very different disciplines and uses the same methodological approach in contrasting forest types along an extensive environmental gradient.
Aims
The aim of this study was to identify risk variants and haplotypes that impair dihydropyrimidine dehydrogenase (DPD) activity and are, therefore, candidate risk variants for severe toxicity to ...5‐fluorouracil (5‐FU) chemotherapy.
Methods
Plasma dihydrouracil/uracil (UH2/U) ratios were measured as a population marker for DPD activity in a total of 1382 subjects from 4 independent studies. Genotype and haplotype correlations with UH2/U ratios were assessed.
Results
Significantly lower UH2/U ratios (panova < 2 × 10−16) were observed in carriers of the 4 well‐studied 5‐FU toxicity risk variants with mean differences (MD) of −43.7% for DPYD c.1905 + 1G > A (rs3918290), −46.0% for DPYD c.1679T > G (rs55886062), −37.1%, for DPYD c.2846A > T (rs67376798), and −13.2% for DPYD c.1129‐5923C > G (rs75017182). An additional variant, DPYD c.496A > G (rs2297595), was also associated with lower UH2/U ratios (P < .0001, MD: −12.6%). A haplotype analysis was performed for variants in linkage disequilibrium with c.496A > G, which consisted of the common variant c.85T > C (rs1801265) and the risk variant c.1129‐5923C > G. Both haplotypes carrying c.496A > G were associated with decreased UH2/U ratios (H3, P = .003, MD: −9.6%; H5, P = .002, MD: −16.9%). A haplotype carrying only the variant c.85T > C (H2) was associated with elevated ratios (P = .004, MD: +8.6%).
Conclusions
Based on our data, DPYD‐c.496A > G is a strong candidate risk allele for 5‐FU toxicity. Our data suggest that DPYD‐c.85T > C might be protective; however, the deleterious impacts of the linked alleles c.496A > G and c.1129‐5923C > G likely limit this effect in patients. The possible protective effect of c.85T > C and linkage disequilibrium with c.496A > G and c.1129‐5923C > G may have hampered prior association studies and should be considered in future clinical studies.
Humans require multiple services from ecosystems, but it is largely unknown whether trade‐offs between ecosystem functions prevent the realisation of high ecosystem multifunctionality across spatial ...scales. Here, we combined a comprehensive dataset (28 ecosystem functions measured on 209 forest plots) with a forest inventory dataset (105,316 plots) to extrapolate and map relationships between various ecosystem multifunctionality measures across Europe. These multifunctionality measures reflected different management objectives, related to timber production, climate regulation and biodiversity conservation/recreation. We found that trade‐offs among them were rare across Europe, at both local and continental scales. This suggests a high potential for ‘win‐win’ forest management strategies, where overall multifunctionality is maximised. However, across sites, multifunctionality was on average 45.8‐49.8% below maximum levels and not necessarily highest in protected areas. Therefore, using one of the most comprehensive assessments so far, our study suggests a high but largely unrealised potential for management to promote multifunctional forests.
The Patient-Centered Outcomes Research Institute (PCORI) recently launched PCORnet to establish a single inter-operable multicenter data research network that will support observational research and ...randomized clinical trials. This paper provides an overview of the patient-powered research networks (PPRNs), networks of patient organizations focused on a particular health condition that are interested in sharing health information and engaging in research. PPRNs will build on their foundation of trust within the patient communities and draw on their expertise, working with participants to identify true patient-centered outcomes and direct a patient-centered research agenda. The PPRNs will overcome common challenges including enrolling a diverse and representative patient population; engaging patients in governance; designing the data infrastructure; sharing data securely while protecting privacy; prioritizing research questions; scaling small networks into a larger network; and identifying pathways to sustainability. PCORnet will be the first distributed research network to bring PCOR to national scale.
Ants, whose colonies have a tiered division of labor consisting of reproductive and sterile castes are among the most abundant, diverse and highly organized social organisms. Within the infertile ...worker caste, labor is divided through physical polymorphism (size-related behavioral specialization) and temporal polyethism (age-related division of labor). Although the nature and mechanisms of temporal polyethism have been intensely studied for 30 years, little is known about the underlying neural mechanisms that govern behavioral development and division of labor in ants. Using the ant Pheidole dentata as a model, I present a new paradigm and a novel neurobiological study of temporal polyethism in ants. My paradigm concerns repertoire expansion, a process of division of labor in which the number of tasks a worker performs increases with age through the addition and retention of behaviors. I found that repertoire size increased on average three-fold from the youngest to the oldest workers, a pattern not predicted by current models of temporal polyethism. I also examined the neurochemical and neuroanatomical correlates of behavioral maturation in minor workers of P. dentata. Serotonin and dopamine levels significantly increased during behavioral development and these neurochemicals were correlated with age-related increases in minor worker repertoire size. Although octopamine levels showed no age- or task-related patterns, the ratios of octopamine to serotonin and dopamine were greatest in the youngest minor workers and appeared to modulate inner-nest tasks. As minor workers aged so did their brains, which showed a significant remolding of the mushrooms bodies as revealed by ultrastructural imaging. Bouton size and the number of synapses on the projection interneurons increased significantly in older workers. Increased vesicle numbers within the boutons indicated an age-related enhancement of synaptic efficacy. The biogenic amine and synaptic ultrastructure markers indicate that significant neurophysiological changes accompany behavioral development in P. dentata and suggest that task allocation has a neural basis. My study presents an integrated socioneuroethological analysis of temporal polyethism that provides significant insight into the process and regulation of division of labor.
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