Scientific Diaspora from an Emerging Economy: Inclination to Return and Connections to the Home Country

To better inform policies on talent flow in emerging countries, this article evaluates the determinants of return migration among Brazilian researchers and post-graduate students in Britain, as well as, their personal and professional ties to Brazil. Most participants were inclined to engage in return migration (67%). The perception of the job market and career values were associated to their willingness to return, particularly, to receive job advertisements from EU institutions (OR=0.32, p=0.03) and to identify high income as professional success (OR=0.35, p=0.05). Personal ties to Brazil were both more frequent and influential in return migration plans than professional ties. Only 19% of participants were actively involved in research partnerships between the two countries. A series of policy implications were discussed at the institutional, national and international level. Evidence-based policies to engage with the scientific diaspora and to foster international partnerships are both critical to maximize social benefits and to secure equitable development worldwide. Keywords: scientific diaspora, international mobility of researchers, brain drain, migration, international research partnerships

New P-glycoprotein inhibitors: potential tools to reduce Multidrug Resistance

One of the classical protection mechanism of cancer cells involves an increased expression of drug efflux transport proteins like P-glycoprotein (P-gP). P-gP is an ABC drug efflux transporter which is fisiologically express in many tissues such as the blood-brain-barrier (BBB) where it is involved in the protection of the CNS from potentially toxic agents. This protein is able to transport a wild structural different substrates, including many drugs used for a wild range of therapeutic applications. Therefore, the research of safe and effective P-gP inhibitors endowed of high selectivity and potency represent a great challenge in medicinal chemistry. In particular, the possibility to have selective molecules able to inhibit this protein could be useful to modulate the pharmacological behaviour of drugs including those used for chemo-therapy-resistant tumors. Up to now many agents modulating P-gP have been characterized including channel blockers, calmodulin antagonists, immunosuppressant and protein kinase inhibitors but all these compounds produced disappointing results in vivo because the use of high dose resulting in unacceptable toxicity. Some new drugs such as biricodar, tariquidar and elacridar have satisfactory inhibitory effects on P-gP. This latter displayed a high potency for P-gP transporter but it also inhibited breast cancer resistance protein (BCPR). On the basis of computational studies which suggested a general pharmacophore of a substrate/inhibitor of P-gP transporter, in which both a planar aromatic domain and a presence of a basic nitrogen atom within an extended side chain are described, we designed and synthesised new compounds. These molecules possessed a benzylethereal side chain substituted by aliphatic spacer of 2, 3, or 4 methylenes linked to an arylpiperazine nucleus. All the synthesized compounds have been tested in vitro to evaluated the inhibitor activity on Caco2 cells in which P-gP is overexpressed and the best results have been obtained for compounds having a four methylene chain. Unfortunatelly, as expected, all arylpiperazine classes displayed hight serotoninergic 5-HT1A and dopaminergic D2 receptor affinities. In order to improve P-gP affinity and eliminate serotoninergic and dopaminergic activities some structural manipulations on these derivatives have been carried out such as the substitution of the aryl and arylpiperazine moieties with a methylic and tetrahydroisoquinoline nucleuses respectively. Besides new ligand series arylmethyloxyphenyl1,2,3 were prepared by removing the alkylpiperazinic ring and linking arylmethyl groups directly to the phenoxyalkyl nucleous. Moreover the replacemant of the oxygen atom with a nitrogen one led to arylmethylaminophenyl2 derivatives more potent than the oxygen-analogues, which behaved as elacridar but displayed a more simple structure. However, in N-methylpiperazine series the spacer length poorly influenced the P-gP inhibitory activity. On other hand, analogously to the arylpiperazine-derivatives, also within the tetrahydroisoquinoline-derivatives, the spacer elongation improved P-gP inhibitory activity. Since the limit of P-gP inhibitors such as elacridar is the poor selectivity toward other ABC transporters, in particular the BCRP pump, all the active compounds were tested for their ability to inhibit [3H]-mitoxantrone, a specific BCRP substrate. The results showed that only arylmethylaminephenyl derivatives displayed a good BCRP inhibition activity. These results led us to consider the 2-[(3-methoxyphenylethyl)phenoxy]- fragment, present in the more selective P-gP inhibitors, the pivotal molecular basis to design novel P-gP inhibitors. All the synthesized compounds have been tested in vitro to evaluated the inhibitor activity on Caco2 cells in which P-gP is overexpressed and the best results have been obtained for compounds having a four methylene chain. Unfortunatelly, as expected, all arylpiperazine classes displayed hight serotoninergic 5-HT1A and dopaminergic D2 receptor affinities. In order to improve P-gP affinity and eliminate serotoninergic and dopaminergic activities some structural manipulations on these derivatives have been carried out such as the substitution of the aryl and arylpiperazine moieties with a methylic and tetrahydroisoquinoline nucleuses respectively. Besides new ligand series arylmethyloxyphenyl1,2,3 were prepared by removing the alkylpiperazinic ring and linking arylmethyl groups directly to the phenoxyalkyl nucleous. Moreover the replacemant of the oxygen atom with a nitrogen one led to arylmethylaminophenyl2 derivatives more potent than the oxygen-analogues, which behaved as elacridar but displayed a more simple structure. However, in N-methylpiperazine series the spacer length poorly influenced the P-gP inhibitory activity. On other hand, analogously to the arylpiperazine-derivatives, also within the tetrahydroisoquinoline-derivatives, the spacer elongation improved P-gP inhibitory activity. Since the limit of P-gP inhibitors such as elacridar is the poor selectivity toward other ABC transporters, in particular the BCRP pump, all the active compounds were tested for their ability to inhibit [3H]-mitoxantrone, a specific BCRP substrate. The results showed that only arylmethylaminephenyl derivatives displayed a good BCRP inhibition activity. These results led us to consider the 2-[(3-methoxyphenylethyl)phenoxy]- fragment, present in the more selective P-gP inhibitors, the pivotal molecular basis to design novel P-gP inhibitors. All the synthesized compounds have been tested in vitro to evaluated the inhibitor activity on Caco2 cells in which P-gP is overexpressed and the best results have been obtained for compounds having a four methylene chain. Unfortunatelly, as expected, all arylpiperazine classes displayed hight serotoninergic 5-HT1A and dopaminergic D2 receptor affinities. In order to improve P-gP affinity and eliminate serotoninergic and dopaminergic activities some structural manipulations on these derivatives have been carried out such as the substitution of the aryl and arylpiperazine moieties with a methylic and tetrahydroisoquinoline nucleuses respectively. Besides new ligand series arylmethyloxyphenyl1,2,3 were prepared by removing the alkylpiperazinic ring and linking arylmethyl groups directly to the phenoxyalkyl nucleous. Moreover the replacemant of the oxygen atom with a nitrogen one led to arylmethylaminophenyl2 derivatives more potent than the oxygen-analogues, which behaved as elacridar but displayed a more simple structure. However, in N-methylpiperazine series the spacer length poorly influenced the P-gP inhibitory activity. On other hand, analogously to the arylpiperazine-derivatives, also within the tetrahydroisoquinoline-derivatives, the spacer elongation improved P-gP inhibitory activity. Since the limit of P-gP inhibitors such as elacridar is the poor selectivity toward other ABC transporters, in particular the BCRP pump, all the active compounds were tested for their ability to inhibit [3H]-mitoxantrone, a specific BCRP substrate. The results showed that only arylmethylaminephenyl derivatives displayed a good BCRP inhibition activity. These results led us to consider the 2-[(3-methoxyphenylethyl)phenoxy]- fragment, present in the more selective P-gP inhibitors, the pivotal molecular basis to design novel P-gP inhibitors. All the synthesized compounds have been tested in vitro to evaluated the inhibitor activity on Caco2 cells in which P-gP is overexpressed and the best results have been obtained for compounds having a four methylene chain. Unfortunatelly, as expected, all arylpiperazine classes displayed hight serotoninergic 5-HT1A and dopaminergic D2 receptor affinities. In order to improve P-gP affinity and eliminate serotoninergic and dopaminergic activities some structural manipulations on these derivatives have been carried out such as the substitution of the aryl and arylpiperazine moieties with a methylic and tetrahydroisoquinoline nucleuses respectively. Besides new ligand series arylmethyloxyphenyl1,2,3 were prepared by removing the alkylpiperazinic ring and linking arylmethyl groups directly to the phenoxyalkyl nucleous. Moreover the replacemant of the oxygen atom with a nitrogen one led to arylmethylaminophenyl2 derivatives more potent than the oxygen-analogues, which behaved as elacridar but displayed a more simple structure. However, in N-methylpiperazine series the spacer length poorly influenced the P-gP inhibitory activity. On other hand, analogously to the arylpiperazine-derivatives, also within the tetrahydroisoquinoline-derivatives, the spacer elongation improved P-gP inhibitory activity. Since the limit of P-gP inhibitors such as elacridar is the poor selectivity toward other ABC transporters, in particular the BCRP pump, all the active compounds were tested for their ability to inhibit [3H]-mitoxantrone, a specific BCRP substrate. The results showed that only arylmethylaminephenyl derivatives displayed a good BCRP inhibition activity. These results led us to consider the 2-[(3-methoxyphenylethyl)phenoxy]- fragment, present in the more selective P-gP inhibitors, the pivotal molecular basis to design novel P-gP inhibitors. All the synthesized compounds have been tested in vitro to evaluated the inhibitor activity on Caco2 cells in which P-gP is overexpressed and the best results have been obtained for compounds having a four methylene chain. Unfortunatelly, as expected, all arylpiperazine classes displayed hight serotoninergic 5-HT1A and dopaminergic D2 receptor affinities. In order to improve P-gP affinity and eliminate serotoninergic and dopaminergic activities some structural manipulations on these derivatives have been carried out such as the substitution of the aryl and arylpiperazine moieties with a methylic and tetrahydroisoquinoline nucleuses respectively. Besides new ligand series arylmethyloxyphenyl1,2,3 were prepared by removing the alkylpiperazinic ring and linking arylmethyl groups directly to the phenoxyalkyl nucleous. Moreover the replacemant of the oxygen atom with a nitrogen one led to arylmethylaminophenyl2 derivatives more potent than the oxygen-analogues, which behaved as elacridar but displayed a more simple structure. However, in N-methylpiperazine series the spacer length poorly influenced the P-gP inhibitory activity. On other hand, analogously to the arylpiperazine-derivatives, also within the tetrahydroisoquinoline-derivatives, the spacer elongation improved P-gP inhibitory activity. Since the limit of P-gP inhibitors such as elacridar is the poor selectivity toward other ABC transporters, in particular the BCRP pump, all the active compounds were tested for their ability to inhibit [3H]-mitoxantrone, a specific BCRP substrate. The results showed that only arylmethylaminephenyl derivatives displayed a good BCRP inhibition activity. These results led us to consider the 2-[(3-methoxyphenylethyl)phenoxy]- fragment, present in the more selective P-gP inhibitors, the pivotal molecular basis to design novel P-gP inhibitors. All the synthesized compounds have been tested in vitro to evaluated the inhibitor activity on Caco2 cells in which P-gP is overexpressed and the best results have been obtained for compounds having a four methylene chain. Unfortunatelly, as expected, all arylpiperazine classes displayed hight serotoninergic 5-HT1A and dopaminergic D2 receptor affinities. In order to improve P-gP affinity and eliminate serotoninergic and dopaminergic activities some structural manipulations on these derivatives have been carried out such as the substitution of the aryl and arylpiperazine moieties with a methylic and tetrahydroisoquinoline nucleuses respectively. Besides new ligand series arylmethyloxyphenyl1,2,3 were prepared by removing the alkylpiperazinic ring and linking arylmethyl groups directly to the phenoxyalkyl nucleous. Moreover the replacemant of the oxygen atom with a nitrogen one led to arylmethylaminophenyl2 derivatives more potent than the oxygen-analogues, which behaved as elacridar but displayed a more simple structure. However, in N-methylpiperazine series the spacer length poorly influenced the P-gP inhibitory activity. On other hand, analogously to the arylpiperazine-derivatives, also within the tetrahydroisoquinoline-derivatives, the spacer elongation improved P-gP inhibitory activity. Since the limit of P-gP inhibitors such as elacridar is the poor selectivity toward other ABC transporters, in particular the BCRP pump, all the active compounds were tested for their ability to inhibit [3H]-mitoxantrone, a specific BCRP substrate. The results showed that only arylmethylaminephenyl derivatives displayed a good BCRP inhibition activity. These results led us to consider the 2-[(3-methoxyphenylethyl)phenoxy]- fragment, present in the more selective P-gP inhibitors, the pivotal molecular basis to design novel P-gP inhibitors. All the synthesized compounds have been tested in vitro to evaluated the inhibitor activity on Caco2 cells in which P-gP is overexpressed and the best results have been obtained for compounds having a four methylene chain. Unfortunatelly, as expected, all arylpiperazine classes displayed hight serotoninergic 5-HT1A and dopaminergic D2 receptor affinities. In order to improve P-gP affinity and eliminate serotoninergic and dopaminergic activities some structural manipulations on these derivatives have been carried out such as the substitution of the aryl and arylpiperazine moieties with a methylic and tetrahydroisoquinoline nucleuses respectively. Besides new ligand series arylmethyloxyphenyl1,2,3 were prepared by removing the alkylpiperazinic ring and linking arylmethyl groups directly to the phenoxyalkyl nucleous. Moreover the replacemant of the oxygen atom with a nitrogen one led to arylmethylaminophenyl2 derivatives more potent than the oxygen-analogues, which behaved as elacridar but displayed a more simple structure. However, in N-methylpiperazine series the spacer length poorly influenced the P-gP inhibitory activity. On other hand, analogously to the arylpiperazine-derivatives, also within the tetrahydroisoquinoline-derivatives, the spacer elongation improved P-gP inhibitory activity. Since the limit of P-gP inhibitors such as elacridar is the poor selectivity toward other ABC transporters, in particular the BCRP pump, all the active compounds were tested for their ability to inhibit [3H]-mitoxantrone, a specific BCRP substrate. The results showed that only arylmethylaminephenyl derivatives displayed a good BCRP inhibition activity. These results led us to consider the 2-[(3-methoxyphenylethyl)phenoxy]- fragment, present in the more selective P-gP inhibitors, the pivotal molecular basis to design novel P-gP inhibitors. All the synthesized compounds have been tested in vitro to evaluated the inhibitor activity on Caco2 cells in which P-gP is overexpressed and the best results have been obtained for compounds having a four methylene chain. Unfortunatelly, as expected, all arylpiperazine classes displayed hight serotoninergic 5-HT1A and dopaminergic D2 receptor affinities. In order to improve P-gP affinity and eliminate serotoninergic and dopaminergic activities some structural manipulations on these derivatives have been carried out such as the substitution of the aryl and arylpiperazine moieties with a methylic and tetrahydroisoquinoline nucleuses respectively. Besides new ligand series arylmethyloxyphenyl1,2,3 were prepared by removing the alkylpiperazinic ring and linking arylmethyl groups directly to the phenoxyalkyl nucleous. Moreover the replacemant of the oxygen atom with a nitrogen one led to arylmethylaminophenyl2 derivatives more potent than the oxygen-analogues, which behaved as elacridar but displayed a more simple structure. However, in N-methylpiperazine series the spacer length poorly influenced the P-gP inhibitory activity. On other hand, analogously to the arylpiperazine-derivatives, also within the tetrahydroisoquinoline-derivatives, the spacer elongation improved P-gP inhibitory activity. Since the limit of P-gP inhibitors such as elacridar is the poor selectivity toward other ABC transporters, in particular the BCRP pump, all the active compounds were tested for their ability to inhibit [3H]-mitoxantrone, a specific BCRP substrate. The results showed that only arylmethylaminephenyl derivatives displayed a good BCRP inhibition activity. These results led us to consider the 2-[(3-methoxyphenylethyl)phenoxy]- fragment, present in the more selective P-gP inhibitors, the pivotal molecular basis to design novel P-gP inhibitors. All the synthesized compounds have been tested in vitro to evaluated the inhibitor activity on Caco2 cells in which P-gP is overexpressed and the best results have been obtained for compounds having a four methylene chain. Unfortunatelly, as expected, all arylpiperazine classes displayed hight serotoninergic 5-HT1A and dopaminergic D2 receptor affinities. In order to improve P-gP affinity and eliminate serotoninergic and dopaminergic activities some structural manipulations on these derivatives have been carried out such as the substitution of the aryl and arylpiperazine moieties with a methylic and tetrahydroisoquinoline nucleuses respectively. Besides new ligand series arylmethyloxyphenyl1,2,3 were prepared by removing the alkylpiperazinic ring and linking arylmethyl groups directly to the phenoxyalkyl nucleous. Moreover the replacemant of the oxygen atom with a nitrogen one led to arylmethylaminophenyl2 derivatives more potent than the oxygen-analogues, which behaved as elacridar but displayed a more simple structure. However, in N-methylpiperazine series the spacer length poorly influenced the P-gP inhibitory activity. On other hand, analogously to the arylpiperazine-derivatives, also within the tetrahydroisoquinoline-derivatives, the spacer elongation improved P-gP inhibitory activity. Since the limit of P-gP inhibitors such as elacridar is the poor selectivity toward other ABC transporters, in particular the BCRP pump, all the active compounds were tested for their ability to inhibit [3H]-mitoxantrone, a specific BCRP substrate. The results showed that only arylmethylaminephenyl derivatives displayed a good BCRP inhibition activity. These results led us to consider the 2-[(3-methoxyphenylethyl)phenoxy]- fragment, present in the more selective P-gP inhibitors, the pivotal molecular basis to design novel P-gP inhibitors. All the synthesized compounds have been tested in vitro to evaluated the inhibitor activity on Caco2 cells in which P-gP is overexpressed and the best results have been obtained for compounds having a four methylene chain. Unfortunatelly, as expected, all arylpiperazine classes displayed hight serotoninergic 5-HT1A and dopaminergic D2 receptor affinities. In order to improve P-gP affinity and eliminate serotoninergic and dopaminergic activities some structural manipulations on these derivatives have been carried out such as the substitution of the aryl and arylpiperazine moieties with a methylic and tetrahydroisoquinoline nucleuses respectively. Besides new ligand series arylmethyloxyphenyl1,2,3 were prepared by removing the alkylpiperazinic ring and linking arylmethyl groups directly to the phenoxyalkyl nucleous. Moreover the replacemant of the oxygen atom with a nitrogen one led to arylmethylaminophenyl2 derivatives more potent than the oxygen-analogues, which behaved as elacridar but displayed a more simple structure. However, in N-methylpiperazine series the spacer length poorly influenced the P-gP inhibitory activity. On other hand, analogously to the arylpiperazine-derivatives, also within the tetrahydroisoquinoline-derivatives, the spacer elongation improved P-gP inhibitory activity. Since the limit of P-gP inhibitors such as elacridar is the poor selectivity toward other ABC transporters, in particular the BCRP pump, all the active compounds were tested for their ability to inhibit [3H]-mitoxantrone, a specific BCRP substrate. The results showed that only arylmethylaminephenyl derivatives displayed a good BCRP inhibition activity. These results led us to consider the 2-[(3-methoxyphenylethyl)phenoxy]- fragment, present in the more selective P-gP inhibitors, the pivotal molecular basis to design novel P-gP inhibitors. All the synthesized compounds have been tested in vitro to evaluated the inhibitor activity on Caco2 cells in which P-gP is overexpressed and the best results have been obtained for compounds having a four methylene chain. Unfortunatelly, as expected, all arylpiperazine classes displayed hight serotoninergic 5-HT1A and dopaminergic D2 receptor affinities. In order to improve P-gP affinity and eliminate serotoninergic and dopaminergic activities some structural manipulations on these derivatives have been carried out such as the substitution of the aryl and arylpiperazine moieties with a methylic and tetrahydroisoquinoline nucleuses respectively. Besides new ligand series arylmethyloxyphenyl1,2,3 were prepared by removing the alkylpiperazinic ring and linking arylmethyl groups directly to the phenoxyalkyl nucleous. Moreover the replacemant of the oxygen atom with a nitrogen one led to arylmethylaminophenyl2 derivatives more potent than the oxygen-analogues, which behaved as elacridar but displayed a more simple structure. However, in N-methylpiperazine series the spacer length poorly influenced the P-gP inhibitory activity. On other hand, analogously to the arylpiperazine-derivatives, also within the tetrahydroisoquinoline-derivatives, the spacer elongation improved P-gP inhibitory activity. Since the limit of P-gP inhibitors such as elacridar is the poor selectivity toward other ABC transporters, in particular the BCRP pump

When are fish sources versus sinks of nutrients in lake ecosystems?

Animals can be important in nutrient cycling through a variety of direct and indirect pathways. A high biomass of animals often represents a large pool of nutrients, leading some ecologists to argue that animal assemblages can represent nutrient sinks within ecosystems. The role of animals as sources vs. sinks of nutrients has been debated particularly extensively for freshwater fishes. We argue that a large pool size does not equate to a nutrient sink; rather, animals can be nutrient sinks when their biomass increases, when emigration rates are high, and/or when nutrients in animal carcasses are not remineralized. To further explore these ideas, we use a simple model to evaluate the conditions under which fish are phosphorus (P) sources or sinks at the ecosystem (lake) level, and at the habitat level (benthic and water column habitats). Our simulations suggest that, under most conditions, fish are sinks for benthic P but are net P sources to the water column. However, P source and sink strengths depend on fish feeding habits (proportion of P consumed from the benthos and water column), migration patterns, and especially the fate of carcass P. Of particular importance is the rate at which carcasses are mineralized and the relative importance of benthic vs. pelagic primary producers in taking up mineralized P (and excreted P). Higher proportional uptake of P by benthic primary producers increases the likelihood that fish are sinks for water column P. Carcass bones and scales are relatively recalcitrant and can represent a P sink even if fish biomass does not change over time. Thus, there is a need for better documentation of the fraction of carcass P that is remineralized, and the fate of this P, under natural conditions. We urge a more holistic perspective regarding the role of animals in nutrient cycling, with a focus on quantifying the rates at which animals consume, store, release, and transport nutrients under various conditions

Allometric and stoichiometric traits predict nutrient excretion rates by benthic consumers

Benthic consumers profoundly impact nutrient regeneration in coastal marine ecosystems. The concurrent nutrient imbalance and warming of our coastal seas will change the nutritional requirements and metabolic demands of these consumers, which may affect their ability to recycle nitrogen and phosphorous. Here we explore whether nutrient excretion rates of two benthic consumers, the Baltic clam (Macoma balthica) and the invasive spionid polychaete (Marenzelleria spp.) can be quantified with basic biological traits across seasons using allometric and stoichiometric relationships. We found species-specific N and P excretion rates that positively link to allometric traits, i.e., per individual rates increased with body mass and temperature; thus, high mass-specific excretion rates characterized small relative to large macrofaunal individuals. Interestingly, our body size scaling coefficients diverge from predictions by the metabolic theory of ecology (MTE) and the universal model of excretion. Furthermore, stoichiometric traits and stable isotope signatures (delta C-13 and delta N-15) explained a minor additional proportion of variability in excretion rates among species. The excretion rates also varied strongly seasonally, with the highest nutrient recycling rates during summer months, when community NH4-N and PO4-P excretion clearly exceeded net sediment efflux. The seasonal pattern emphasized that changes in temperature and food availability drove metabolic processes and thus excretion rates of the benthic consumers, and indicated that these effects could outweigh the importance of animal biomass. Our results highlight the benefits of using allometric and stoichiometric traits when quantifying species-specific contributions to nutrient recycling in coastal marine environments, and in predicting alteration of function in response to environmental change.Peer reviewe

High-throughput screening, next generation sequencing and machine learning: advanced methods in enzyme engineering

Enzyme engineering is an important biotechnological process capable of generating tailored biocatalysts for applications in industrial chemical conversion and biopharma. Typical enhancements sought in enzyme engineering and in vitro evolution campaigns include improved folding stability, catalytic activity, and/or substrate specificity. Despite significant progress in recent years in the areas of high-throughput screening and DNA sequencing, our ability to explore the vast space of functional enzyme sequences remains severely limited. Here, we review the currently available suite of modern methods for enzyme engineering, with a focus on novel readout systems based on enzyme cascades, and new approaches to reaction compartmentalization including single-cell hydrogel encapsulation techniques to achieve a genotype–phenotype link. We further summarize systematic scanning mutagenesis approaches and their merger with deep mutational scanning and massively parallel next-generation DNA sequencing technologies to generate mutability landscapes. Finally, we discuss the implementation of machine learning models for computational prediction of enzyme phenotypic fitness from sequence. This broad overview of current state-of-the-art approaches for enzyme engineering and evolution will aid newcomers and experienced researchers alike in identifying the important challenges that should be addressed to move the field forward

Fish Distributions and Nutrient Cycling in Streams: Can Fish Create Biogeochemical Hotspots?

Rates of biogeochemical processes often vary widely in space and time, and characterizing this variation is critical for understanding ecosystem functioning. In streams, spatial hotspots of nutrient transformations are generally attributed to physical and microbial processes. Here we examine the potential for heterogeneous distributions of fish to generate hotspots of nutrient recycling. We measured nitrogen (N) and phosphorus (P) excretion rates of 47 species of fish in an N-limited Neotropical stream, and we combined these data with population densities in each of 49 stream channel units to estimate unit- and reach-scale nutrient recycling. Species varied widely in rates of N and P excretion as well as excreted N:P ratios (6–176 molar). At the reach scale, fish excretion could meet \u3e75% of ecosystem demand for dissolved inorganic N and turn over the ambient NH4 pool i

Male aggression varies with consortship rate and habitat in a dolphin social network

Coalitions and alliances exemplify the core elements of conflict and cooperation in animal societies. Ecological influences on alliance formation are more readily attributed to within-species variation where phylogenetic signals are muted. Remarkably, male Indo-Pacific bottlenose dolphins in Shark Bay, Western Australia, exhibit systematic spatial variation in alliance behavior, not simply within a species or population, but within a single social network. Moving SE-NW along Peron Peninsula in Shark Bay, males ally more often in trios than pairs, consort females more often, and exhibit greater seasonal movements. Ecological models predict more male-male conflict in the north, but sufficient observations of aggression are lacking. However, dolphins often incur marks, in the form of tooth rakes, during conflicts. Here we report that the incidence of new tooth rake marks varies systematically in the predicted pattern, with greater marking in the north, where males form more trios and consort females at a higher rate. While our previous work demonstrated that alliance complexity has an ecological component, we can now infer that ecological variation impacts the level of alliance-related conflict in Shark Bay