Predicting the similarity of parasite communities in freshwater fishes using the phylogeny,ecology and proximity of hosts

Parasite communities tend to be dissimilar in hosts that are geographically, phylogenetically, ecologically and developmentally distant from one another. The decay of community similarity is a powerful and increasingly common method of studying parasite beta diversity, but most studies have examined only a single type of distance. Here, we evaluate distances based on the phylogeny, ecology, spatial proximity and size of hosts, as predictors of the similarity of parasite communities in individual hosts, host populations and host species. We surveyed parasites in six species of fish collected simultaneously from six localities in the St. Lawrence River, Canada, and species in a common group of larval parasites were discriminated using DNA sequences from barcode region of cytochrome c oxidase I. Distances based on the habitat use patterns of host species were good predictors of short‐term, ecological similarity of parasite communities, such as that operating at the scale of the individual host. The genetic distance between host species was associated with almost all types of similarity at all scales, particularly qualitative and phylogenetic similarity of parasite communities at the level of populations and meta‐populations of hosts. The trophic level, diet, spatial proximity and size of hosts were poor predictors of parasite community similarity. The increased taxonomic resolution provided by molecular data increased the explanatory power of regression models, and different factors were implicated when parasite species were distinguished with DNA barcodes than when larval parasites were lumped into morphospecies, as is commonly practiced.     

Estimating diet in individual pumpkinseed sunfish Lepomis gibbosus using stomach contents,stable isotopes and parasites

The diets of 99 pumpkinseed sunfish Lepomis gibbosus from a pair of small, adjacent lakes in Ontario, Canada, were estimated from their stomach contents, trophically transmitted parasites and stable isotopes of carbon and nitrogen in fish tissue. The three methods provided virtually unrelated information. There was no significant correlation in the importance of any prey item across all three methods. Fish with similar diets according to one method of estimating diet showed no tendency to be similar according to other methods. Although there was limited variation in fish size and the spatial scale of the study was small, both fish size and spatial origin showed comparatively strong associations with diet data obtained with all three methods. These results suggest that a multidisciplinary approach that accounts for fish size and spatial origins is necessary to accurately characterize diets of individual fish.     

Submarine Communications Cables and Law of the Sea: Problems in Law and Practice

Submarine communications cables laid on the seabed of the ocean are the foundation of the world's international telecommunications network. International law, in particular, the law of the sea, has recognized the freedom to lay submarine cables and perform associated operations and has placed certain obligations on states related to the protection of submarine cables. This article examines the international law with respect to submarine cables and discusses the various problems with both the law and state practice on submarine cables. It argues that these problems are illustrations of the traditional challenges that face the law of the sea; that is, the balancing and accommodation of competing uses of ocean space. It concludes that an important step toward resolving these problems is enhanced consultation and cooperation between cable companies and governments and that efforts should focus on creating such mechanisms.     

Nonconsumptive effects in a multiple predator system reduce the foraging efficiency of a keystone predator

Many studies have demonstrated that the nonconsumptive effect (NCE) of predators on prey traits can alter prey demographics in ways that are just as strong as the consumptive effect (CE) of predators. Less well studied, however, is how the CE and NCE of multiple predator species can interact to influence the combined effect of multiple predators on prey mortality. We examined the extent to which the NCE of one predator altered the CE of another predator on a shared prey and evaluated whether we can better predict the combined impact of multiple predators on prey when accounting for this influence. We conducted a set of experiments with larval dragonflies, adult newts (a known keystone predator), and their tadpole prey. We quantified the CE and NCE of each predator, the extent to which NCEs from one predator alters the CE of the second predator, and the combined effect of both predators on prey mortality. We then compared the combined effect of both predators on prey mortality to four predictive models. Dragonflies caused more tadpoles to hide under leaf litter (a NCE), where newts spend less time foraging, which reduced the foraging success (CE) of newts. Newts altered tadpole behavior but not in a way that altered the foraging success of dragonflies. Our study suggests that we can better predict the combined effect of multiple predators on prey when we incorporate the influence of interactions between the CE and NCE of multiple predators into a predictive model. In our case, the threat of predation to prey by one predator reduced the foraging efficiency of a keystone predator. Consequently, the ability of a predator to fill a keystone role could be compromised by the presence of other predators.     

Taxonomic Classification of Bacterial 16S rRNA Genes Using Short Sequencing Reads: Evaluation of Effective Study Designs

Massively parallel high throughput sequencing technologies allow us to interrogate the microbial composition of biological samples at unprecedented resolution. The typical approach is to perform high-throughout sequencing of 16S rRNA genes, which are then taxonomically classified based on similarity to known sequences in existing databases. Current technologies cause a predicament though, because although they enable deep coverage of samples, they are limited in the length of sequence they can produce. As a result, high-throughout studies of microbial communities often do not sequence the entire 16S rRNA gene. The challenge is to obtain reliable representation of bacterial communities through taxonomic classification of short 16S rRNA gene sequences. In this study we explored properties of different study designs and developed specific recommendations for effective use of short-read sequencing technologies for the purpose of interrogating bacterial communities, with a focus on classification using naïve Bayesian classifiers. To assess precision and coverage of each design, we used a collection of ∼8,500 manually curated 16S rRNA gene sequences from cultured bacteria and a set of over one million bacterial 16S rRNA gene sequences retrieved from environmental samples, respectively. We also tested different configurations of taxonomic classification approaches using short read sequencing data, and provide recommendations for optimal choice of the relevant parameters. We conclude that with a judicious selection of the sequenced region and the corresponding choice of a suitable training set for taxonomic classification, it is possible to explore bacterial communities at great depth using current technologies, with only a minimal loss of taxonomic resolution.     

Behavioural responses of shallow-water benthic marine scavengers to fish carrion: a preliminary study

Observations of the behavioural responses of near-shore marine scavengers to fish carrion were made at two depths (1–2 m, 16–18 m). Gobies and juvenile whelks were the most numerous scavengers, but appeared to consume little biomass. The first scavengers to appear at carrion (seconds/minutes) were swimming forms, later (minutes) joined by fast-moving, crawling portunid crabs. Large scavengers (crabs/starfish/catsharks) arrived after tens of minutes/hours. Scavengers were ‘direct feeders’ on the bait (crabs and some fish) or ‘indirect feeders’ (gobies and whelks) on scraps generated by direct feeders. Scavengers spent little time in aggression. While fish spent relatively low proportions of their time feeding (e.g. Lipophrys pholis: 2.2–15.8%), crabs fed almost continuously (e.g. Carcinus maenas: 97.8–99.3%) before leaving baits. Crab presence depressed fish feeding. Crabs were wasteful feeders that macerated the baits, generating scraps for indirect feeders and attracting more scavengers. Large scavengers consumed most bait.     

Regulation of TORC2 function and localization by Rab5 GTPases in Saccharomyces cerevisiae

The evolutionarily conserved Target of Rapamycin (TOR) complex-2 (TORC2) is an essential regulator of plasma membrane homeostasis in budding yeast (Saccharomyces cerevisiae). In this yeast, TORC2 phosphorylates and activates the effector protein kinase Ypk1 and its paralog Ypk2. These protein kinases, in turn, carry out all the crucial functions of TORC2 by phosphorylating and thereby controlling the activity of at least a dozen downstream substrates. A previously uncharacterized interplay between the Rab5 GTPases and TORC2 signaling was uncovered through analysis of a newly suspected Ypk1 target. Muk1, one of two guanine nucleotide exchange factors for the Rab5 GTPases, was found to be a physiologically relevant Ypk1 substrate; and, genetic analysis indicates that Ypk1-mediated phosphorylation activates the guanine nucleotide exchange activity of Muk1. Second, it was demonstrated both in vivo and in vitro that the GTP-bound state of the Rab5 GTPase Vps21/Ypt51 physically associates with TORC2 and acts as a direct positive effector required for full TORC2 activity. These interrelationships provide a self-reinforcing control circuit for sustained up-regulation of TORC2-Ypk1 signaling. In this overview, we summarize the experimental basis of these findings, their implications, and speculate as to the molecular basis for Rab5-mediated TORC2 activation.     

Visual-Olfactory Integration in the Human Disease Vector Mosquito Aedes aegypti

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A distance–performance trade‐off in the phenotypic basis of dispersal

Across taxa, individuals vary in how far they disperse, with most individuals staying close to their origin and fewer dispersing long distances. Costs associated with dispersal (e.g., energy, risk) are widely believed to trade off with benefits (e.g., reduced competition, increased reproductive success) to influence dispersal propensity. However, this framework has not been applied to understand variation in dispersal distance, which is instead generally attributed to extrinsic environmental factors. We alternatively hypothesized that variation in dispersal distances results from trade‐offs associated with other aspects of locomotor performance. We tested this hypothesis in the stream salamander Gyrinophilus porphyriticus and found that salamanders that dispersed farther in the field had longer forelimbs but swam at slower velocities under experimental conditions. The reduced swimming performance of long‐distance dispersers likely results from drag imposed by longer forelimbs. Longer forelimbs may facilitate moving longer distances, but the proximate costs associated with reduced swimming performance may help to explain the rarity of long‐distance dispersal. The historical focus on environmental drivers of dispersal distances misses the importance of individual traits and associated trade‐offs among traits affecting locomotion.