Climate‐induced changes in the distribution of freshwater fish: observed and predicted trends

1. Climate change could be one of the main threats faced by aquatic ecosystems and freshwater biodiversity. Improved understanding, monitoring and forecasting of its effects are thus crucial for researchers, policy makers and biodiversity managers. 2. Here, we provide a review and some meta‐analyses of the literature reporting both observed and predicted climate‐induced effects on the distribution of freshwater fish. After reviewing three decades of research, we summarise how methods in assessing the effects of climate change have evolved, and whether current knowledge is geographically or taxonomically biased. We conducted multispecies qualitative and quantitative analyses to find out whether the observed responses of freshwater fish to recent changes in climate are consistent with those predicted under future climate scenarios. 3. We highlight the fact that, in recent years, freshwater fish distributions have already been affected by contemporary climate change in ways consistent with anticipated responses under future climate change scenarios: the range of most cold‐water species could be reduced or shift to higher altitude or latitude, whereas that of cool‐ and warm‐water species could expand or contract. 4. Most evidence about the effects of climate change is underpinned by the large number of studies devoted to cold‐water fish species (mainly salmonids). Our knowledge is still incomplete, however, particularly due to taxonomic and geographic biases. 5. Observed and expected responses are well correlated among families, suggesting that model predictions are supported by empirical evidence. The observed effects are of greater magnitude and show higher variability than the predicted effects, however, indicating that other drivers of changes may be interacting with climate and seriously affecting freshwater fish. 6. Finally, we suggest avenues of research required to address current gaps in what we know about the climate‐induced effects on freshwater fish distribution, including (i) the need for more long‐term data analyses, (ii) the assessment of climate‐induced effects at higher levels of organisation (e.g. assemblages), (iii) methodological improvements (e.g. accounting for uncertainty among projections and species’ dispersal abilities, combining both distributional and empirical approaches and including multiple non‐climatic stressors) and (iv) systematic confrontation of observed versus predicted effects across multi‐species assemblages and at several levels of biological organisation (i.e. populations and assemblages).     

Dramatic phenotypic plasticity within species of Siphomutabilus n. g. (Digenea: Cryptogonimidae) from Indo-Pacific caesionines (Perciformes: Lutjanidae)

A survey of Indo-Pacific lutjanids of the subfamily Caesioninae revealed the presence of Siphodera gurukun Machida, 1910 and two new cryptogonimid taxa from off Heron and Lizard Islands on the Great Barrier Reef, Australia, Ningaloo Reef, Western Australia and Rasdhoo Atoll, Maldives. A combined morphological and genetic characterisation of these species shows that they form a clade distinct from the type-species of Siphodera Linton, 1910, S. vinaledwardsii (Linton, 1901), and warrants the proposal of a new genus. Here we propose Siphomutabilus n. g. and transfer Siphodera gurukun Machida, 1986 as the type-species, Siphomutabilus gurukun (Machida, 1986) n. comb. Siphodera aegyptensis Hassanine & Gibson, 2005 is transferred to Siphomutabilus as S. aegyptensis (Hassanine & Gibson, 2005) n. comb. based on morphological and ecological similarities. Siphomutabilus raritas n. sp. is described from Caesio cuning (Bloch) off Lizard Island and S. bitesticulatus n. sp. is described from Pterocaesio marri Schultz off Heron Island. The two new species are unique in that they have two testes, making their morphology broadly consistent with that of Metadena Linton, 1910, yet the molecular analyses conducted here indicates that they are unequivocally united with Siphomutabilus gurukun (which has multiple testes) to the exclusion of Metadena lutiani (Yamaguti, 1942), which was sequenced here. The dramatic phenotypic plasticity observed among such closely related species of Siphomutabilus suggests a secondary modification of what is generally considered a robust generic diagnostic character within this and other digenean families, highlighting the need for a combined morphological and molecular diagnostic approach when characterising these taxa. Siphodera Linton, 1910 is amended to include just two species, the type-species S. vinaledwardsii (Linton, 1901) Linton, 1910 and S. cirrhiti Yamaguti, 1970, which are distinguished by their lack of oral spines and multiple testes that are primarily extracaecal. Siphodera ghanensis Fischthal & Thomas, 1968 is considered a species incertae sedis here based on significant morphological and ecological differences compared with species of Siphodera and Siphomutabilus n. g.     

Identification of Pauses during Formation of HIV-1 Virus Like Particles

HIV Gag polymerizes on the plasma membrane to form virus like particles (VLPs) that have similar diameters to wild-type viruses. We use multicolor, dual-penetration depth, total internal reflection fluorescence microscopy, which corrects for azimuthal movement, to image the assembly of individual VLPs from the time of nucleation to the recruitment of VPS4 (a component of the endosomal sorting complexes required for transport, and which marks the final stage of VLP assembly). Using a mathematical model for assembly and maximum-likelihood comparison of fits both with and without pauses, we detect pauses during Gag polymerization in 60% of VLPs. Pauses range from 2 to 20 min, with an exponentially distributed duration that is independent of cytosolic Gag concentration. VLPs assembled with late domain mutants of Gag (which do not recruit the key endosomal sorting complexes required for transport proteins Alix or TSG101) exhibit similar pause distributions. These pauses indicate that a single rate-limiting event is required for continuation of assembly. We suggest that pauses are either related to incorporation of defects in the hexagonal Gag lattice during VLP assembly or are caused by shortcomings in interactions of Gag with essential and still undefined cellular components during formation of curvature on the plasma membrane.     

A ten-year comparative study of the population dynamics and parasitoidism in the native paper wasp Polistes fuscatus and the invasive P. dominulus

The invasive success of Polistes dominulus in North America has been attributed to its greater productivity relative to native Polistes. Liberation from parasites and parasitoids are thought to be major factors contributing to the high productivity of P. dominulus. We analyzed historical records of colony relative abundance and productivity of P. dominulus and the sympatric, native Polistes fuscatus from 1995 to 2010 using historical data from our Michigan Polistes study site. We also analyzed evidence of parasitoids from 294 P. fuscatus and 507 P. dominulus archived combs from 2001 to 2010. Additionally, we examined field and laboratory colonies from outside of our study site for parasites and parasitoids in 2009 and 2010. We documented one parasite and three parasitoids exploiting Polistes in our Michigan study sites. Our historical records document that P. dominulus initially displaced P. fuscatus rapidly, then slowed, and finally the two populations stabilized. Furthermore, the historical pattern of decreasing displacement of P. fuscatus by P. dominulus corresponded temporally with a significant decline in the productivity and a significant increase in Dibrachys cavus infestation of P. dominulus. Our evidence indicates that the parasitoid, D. cavus, is a major factor in stabilizing the populations of the sympatric P. dominulus and P. fuscatus.     

Pharmacological properties and predicted binding mode of arylmethylene quinuclidine-like derivatives at the α3β4 nicotinic acetylcholine receptor (nAChR)

We have carried out a pharmacological evaluation of arylmethylene quinuclidine derivatives interactions with human α3β4 nAChRs subtype, using cell-based receptor binding, calcium-influx, electrophysiological patch-clamp assays and molecular modeling techniques. We have found that the compounds bind competitively to the α3β4 receptor with micromolar affinities and some of the compounds behave as non-competitive antagonists (compounds 1, 2 and 3), displaying submicromolar IC₅₀ values. These evidences suggest a mixed mode of action for these compounds, having interactions at the orthosteric site and more pronounced interactions at an allosteric site to block agonist effects. One of the compounds, 1-benzyl-3-(diphenylmethylene)-1-azoniabicyclo[2.2.2]octane chloride (compound 3), exhibited poorly reversible use-dependent block of α3β4 channels. We also found that removal of a phenyl group from compound 1 confers a partial agonism to the derived analog (compound 6). Introducing a hydrogen-bond acceptor into the 3-benzylidene quinuclidine derivative (compound 7) increases agonism potency at the α3β4 receptor subtype. Docking into the orthosteric binding site of a α3β4 protein structure derived by comparative modeling accurately predicted the experimentally-observed trend in binding affinity. Results supported the notion that binding requires a hydrogen bond formation between the ligand basic nitrogen and the backbone carbonyl oxygen atom of the conserved Trp-149.     

Patterns of diversity and adaptation in Glomeromycota from three prairie grasslands

Arbuscular mycorrhizal (AM) fungi are widespread root symbionts that often improve the fitness of their plant hosts. We tested whether local adaptation in mycorrhizal symbioses would shape the community structure of these root symbionts in a way that maximizes their symbiotic functioning. We grew a native prairie grass (Andropogon gerardii) with all possible combinations of soils and AM fungal inocula from three different prairies that varied in soil characteristics and disturbance history (two native prairie remnants and one recently restored). We identified the AM fungi colonizing A. gerardii roots using PCR amplification and cloning of the small subunit rRNA gene. We observed 13 operational taxonomic units (OTUs) belonging to six genera in three families. Taxonomic richness was higher in the restored than the native prairies with one member of the Gigaspora dominating the roots of plants grown with inocula from native prairies. Inoculum source and the soil environment influenced the composition of AM fungi that colonized plant roots. Correspondingly, host plants and AM fungi responded significantly to the soil–inoculum combinations such that home fungi often had the highest fitness and provided the greatest benefit to A. gerardii. Similar patterns were observed within the soil–inoculum combinations originating from two native prairies, where five sequence types of a single Gigaspora OTU were virtually the only root colonizers. Our results indicate that indigenous assemblages of AM fungi were adapted to the local soil environment and that this process occurred both at a community scale and at the scale of fungal sequence types within a dominant OTU.     

Human cytochromes P450 in health and disease

There are 18 mammalian cytochrome P450 (CYP) families, which encode 57 genes in the human genome. CYP2, CYP3 and CYP4 families contain far more genes than the other 15 families; these three families are also the ones that are dramatically larger in rodent genomes. Most (if not all) genes in the CYP1, CYP2, CYP3 and CYP4 families encode enzymes involved in eicosanoid metabolism and are inducible by various environmental stimuli (i.e. diet, chemical inducers, drugs, pheromones, etc.), whereas the other 14 gene families often have only a single member, and are rarely if ever inducible or redundant. Although the CYP2 and CYP3 families can be regarded as largely redundant and promiscuous, mutations or other defects in one or more genes of the remaining 16 gene families are primarily the ones responsible for P450-specific diseases—confirming these genes are not superfluous or promiscuous but rather are more directly involved in critical life functions. P450-mediated diseases comprise those caused by: aberrant steroidogenesis; defects in fatty acid, cholesterol and bile acid pathways; vitamin D dysregulation and retinoid (as well as putative eicosanoid) dysregulation during fertilization, implantation, embryogenesis, foetogenesis and neonatal development.