Ionotropic Receptors as a Driving Force behind Human Synapse Establishment

The origin of nervous systems is a main theme in biology and its mechanisms are largely underlied by synaptic neurotransmission. One problem to explain synapse establishment is that synaptic orthologs are present in multiple aneural organisms. We questioned how the interactions among these elements evolved and to what extent it relates to our understanding of the nervous systems complexity. We identified the human neurotransmission gene network based on genes present in GABAergic, glutamatergic, serotonergic, dopaminergic, and cholinergic systems. The network comprises 321 human genes, 83 of which act exclusively in the nervous system. We reconstructed the evolutionary scenario of synapse emergence by looking for synaptic orthologs in 476 eukaryotes. The Human–Cnidaria common ancestor displayed a massive emergence of neuroexclusive genes, mainly ionotropic receptors, which might have been crucial to the evolution of synapses. Very few synaptic genes had their origin after the Human–Cnidaria common ancestor. We also identified a higher abundance of synaptic proteins in vertebrates, which suggests an increase in the synaptic network complexity of those organisms.     

Environment versus dispersal in the assembly of western Amazonian palm communities

Aim It is a central issue in ecology and biogeography to understand what governs community assembly and the maintenance of biodiversity in tropical rain forest ecosystems. A key question is the relative importance of environmental species sorting (niche assembly) and dispersal limitation (dispersal assembly), which we investigate using a large dataset from diverse palm communities. Location Lowland rain forest, western Amazon River Basin, Peru. Methods We inventoried palm communities, registering all palm individuals and recording environmental conditions in 149 transects of 5 m × 500 m. We used ordination, Mantel tests and indicator species analysis (ISA) to assess compositional patterns, species responses to geographical location and environmental factors. Mantel tests were used to assess the relative importance of geographical distance (as a proxy for dispersal limitation) and environmental differences as possible drivers of dissimilarity in palm species composition. We repeated the Mantel tests for subsets of species that differ in traits of likely importance for habitat specialization and dispersal (height and range size). Results We found a strong relationship between compositional dissimilarity and environmental distance and a weaker but also significant relationship between compositional dissimilarity and geographical distance. Consistent with expectations, relationships with environmental and geographical distance were stronger for understorey species than for canopy species. Geographical distance had a higher correlation with compositional dissimilarity for small‐ranged species compared with large‐ranged species, whereas the opposite was true for environmental distance. The main environmental correlates were inundation and soil nutrient levels. Main conclusions The assembly of palm communities in the western Amazon appears to be driven primarily by species sorting according to hydrology and soil, but with dispersal limitation also playing an important role. The importance of environmental characteristics and geographical distance varies depending on plant height and geographical range size in agreement with functional predictions, increasing our confidence in the inferred assembly mechanisms.     

The seasonal dynamics of Copidodiaptomus numidicus (Gurney, 1909) and Thermocyclops dybowskii (Lande, 1890) in Castelo-do-Bode Reservoir

We investigated the population dynamics of Copidodiaptomus numidicus (Copepoda: Calanoida) and Thermocyclops dybowskii (Copepoda: Cyclopoida) in Castelo-do-Bode Reservoir (Portugal). Both species in the reservoir were regulated mainly by food availability during the summers of 1993 and 1994. C. numidicus was always more abundant than T. dybowskii in the reservoir. C. numidicus produced two generations during the sampling period of both years whereas T. dybowskii produced two and three generations in 1993 and 1994, respectively. Because of high temperatures and low rainfall in 1994, the reservoir was more eutrophic than in 1993. Higher clutch size and a higher percentage of ovigerous females suggest that both species were benefiting from better feeding conditions in 1994. Despite this, population growth was reduced in 1994 relatively to 1993. Vertebrate predation and predation by copepods seem to have been minor factors in explaining this decline. However, the presence of Mesostoma sp. in the reservoir may have contributed to the reduction of both copepod populations during specific periods in 1994 although the calanoid was more affected than the cyclopoid by this predation.     

Midsummer heat wave effects on lacustrine plankton: Variation of assemblage structure and fatty acid composition

The effects of the 2003 European heat wave on a freshwater plankton assemblage and its fatty acid (FA) composition were investigated. Composition and FA profiles of four size categories of planktonic organisms collected in 2003 were compared to those of the colder year 2002.     

Sex differences in the electrocommunication signals of the electric fish Apteronotus bonapartii

The South American weakly-electric knifefish (Apteronotidae) produce highly diverse and readily quantifiable electrocommunication signals. The electric organ discharge frequency (EODf), and EOD modulations (chirps and gradual frequency rises (GFRs)), vary dramatically across sexes and species, presenting an ideal opportunity to examine the proximate and ultimate bases of sexually dimorphic behavior. We complemented previous studies on the sexual dimorphism of apteronotid communication signals by investigating electric signal features and their hormonal correlates in Apteronotus bonapartii, a species which exhibits strong sexual dimorphism in snout morphology. Electrocommunication signals were evoked and recorded using a playback paradigm, and were analyzed for signal features including EOD frequency and the structure of EOD modulations. To investigate the androgenic correlates of sexually dimorphic EOD signals, we measured plasma concentrations of testosterone and 11-ketotestosterone. A. bonapartii responded robustly to stimulus playbacks. EODf was sexually monomorphic, and males and females produced chirps with similar durations and amounts of frequency modulation. However, males were more likely than females to produce chirps with multiple frequency peaks. Sexual dimorphism in apteronotid electrocommunication signals appears to be highly evolutionarily labile. Extensive interspecific variation in the magnitude and direction of sex differences in EODf and in different aspects of chirp structure suggest that chirp signals may be an important locus of evolutionary change within the clade. The weakly-electric fish represent a rich source of data for understanding the selective pressures that shape, and the neuroendocrine mechanisms that underlie, diversity in the sexual dimorphism of behavior.     

Potential new areas for conservation of key botanical families in the subtropical Atlantic Forest

Myrtaceae, Lauraceae and Fabaceae are regarded as essential floristic elements of Atlantic forests due to their outstanding species richness, endemism levels, and ecological functions. Nonetheless, Atlantic forests are being subjected to multiple human disturbances that compromise the conservation of their flora. This study, therefore, intended to address whether there exist potential areas for conservation with great richness of tree/shrub species of the aforementioned families in different forest types within the subtropical Atlantic Forest. For this, data collected systematically across?~?23% of the subtropical Brazilian Atlantic Forest were employed. The univariate Local Moran I statistic was used to search for clusters of sample plots with great richness of species of the studied families. Six clusters were found throughout the evergreen rainforest (ERF) and Araucaria forest (AF), and most of them contained more than half of all species of these families observed on the sample plots, besides many others belonging to different families. A cluster of Myrtaceae and a cluster of Lauraceae in the ERF were the only ones that overlapped protected areas. The clusters of Lauraceae in the AF, located in ecotone zones with the ERF, had?~?50% of native forest cover, whereas the clusters of Myrtaceae and Fabaceae had?~?10% of forest cover. Inasmuch as forests in the study area have been heavily exploited, the clusters have relevant conservation value. Protected areas could be expanded or converted into more restrictive conservation categories to enhance the conservation of populations of key elements of the Atlantic Forest. Yet, non-protected areas deserve attention regarding the management of forest resources and conservation-by-use strategies.

     

MacStylet, software to analyse electrical penetration graph data on the Macintosh

Conclusion Since the EPG method is increasingly utilized in the investigation of plant-Homoptera interactions, this software has been developed to enable fast processing of abundant data. The objective seems to have been achieved and, with a little practice, a 2-hour experiment may be analysed in about 10–15 minutes. Mac-Stylet is stand-alone shareware, freely distributed to all persons interested (request to G. Febvay, email: febvay@jouy.inra.fr).