Giving‐up densities and ideal pre‐emptive patch use in a predatory benthic stream fish

1. We used observational and experimental field studies together with an individual‐based simulation model to demonstrate that behaviours of mottled sculpin (Cottus bairdi) were broadly consistent with the expectations of Giving‐Up Density theory and an Ideal Pre‐emptive Distribution habitat selection model. 2. Specifically we found that: (i) adult mottled sculpin established territories within patches characterised by significantly higher prey densities and prey renewal rates than patches occupied by juveniles or randomly selected patches; (ii) patches abandoned by adult sculpin possessed significantly lower prey densities than newly occupied patches, although this was not true for juveniles; (iii) the observed giving‐up density (GUD) for adult sculpin (i.e. average prey density in patches recently abandoned) increased linearly with increasing fish size up to the average prey density measured in randomly selected patches (i.e. 350 prey items per 0.1 m²) and decreased with increasing sculpin density and (iv) juveniles rapidly shifted their distribution towards the highest quality patches following removal of competitively dominant adult sculpin. 3. These results provide the first evidence of the applicability of GUD theory to a stream‐dwelling organism, and they elucidate the underlying factors influencing juvenile and adult sculpin habitat selection and movement behaviours. Furthermore, optimal patch use, ideal pre‐emptive habitat selection and juvenile ‘floating’ provide behavioural mechanisms linking environmental heterogeneity in the stream benthos to density‐dependent regulation of mottled sculpin populations in this system.     

Morphological variation of the <Emphasis Type="Italic">Caloneis schumanniana</Emphasis> species complex (Bacillariophyceae) from different environmental conditions in North American streams

The aim of the present study is to test by molecular DNA data a hypothesis concerned to speciation by allopatry occurring in Mimagoniates microlepis, associated to the Serra do Mar mountain chain (Atlantic Rain Forest hotspot) in Southern Brazil. Overall genetic diversity and mean genetic distances were high, demonstrating both good conservation status and genetic differentiation. Neighbor-Joining (NJ) and parsimony analyses, together with population genetic parameters (Φ_ST, N_m, G_ST, and AMOVA), identified two main vicariant genetic/evolutionary stocks dividing the upper Iguaçu River samples from those of the coastal plains. Other well-supported intrinsic monophyletic clades were also identified, suggesting fast and remarkable speciation processes. In addition, the genetic, evolutionary, geographic, and phylogeographic evidences reinforced an occurring species complex. Moreover, these evolutionarily significant units (species complex) seem to be inside four natural biogeographic areas. Thus, the genesis and evolution of the Serra do Mar complex might be associated to diversification processes of M. microlepis. Such a consideration suggests that the areas including the upper Iguaçu River and the coastal plains of the states of São Paulo, Paraná, and Santa Catarina require distinct conservation policies involving one of the global biodiversity hotspots, namely, the Brazilian Atlantic Rain Forest.     

Long‐term effectiveness of oral second‐generation antipsychotics in patients with schizophrenia and related disorders: a systematic review and meta‐analysis of direct head‐to‐head comparisons

Second‐generation antipsychotics (SGAs) are recommended for maintenance treatment in schizophrenia. However, comparative long‐term effectiveness among SGAs is unclear. Here we provide a systematic review and meta‐analysis of randomized trials lasting ≥?6 months comparing SGAs head‐to‐head in schizophrenia and related disorders. The primary outcome was all‐cause discontinuation. Secondary outcomes included efficacy and tolerability, i.e., psychopathology, inefficacy‐related and intolerability‐related discontinuation, relapse, hospitalization, remission, functioning, quality of life, and adverse events. Pooled risk ratio and standardized mean difference were calculated using random‐effects models. Across 59 studies (N=45,787), lasting 47.4±32.1 weeks (range 24‐186), no consistent superiority of any SGA emerged across efficacy and tolerability outcomes. Regarding all‐cause discontinuation, clozapine, olanzapine and risperidone were significantly (p<0.05) superior to several other SGAs, while quetiapine was inferior to several other SGAs. As to psychopathology, clozapine and olanzapine were superior to several other SGAs, while quetiapine and ziprasidone were inferior to several other SGAs. Data for other efficacy outcomes were sparse. Regarding intolerability‐related discontinuation, risperidone was superior and clozapine was inferior to several other SGAs. Concerning weight gain, olanzapine was worse than all other compared non‐clozapine SGAs, and risperidone was significantly worse than several other SGAs. As to prolactin increase, risperidone and amisulpride were significantly worse than several other SGAs. Regarding parkinsonism, olanzapine was superior to risperidone, without significant differences pertaining to akathisia. Concerning sedation and somnolence, clozapine and quetiapine were significantly worse than some other SGAs. In summary, different long‐term SGA efficacy and tolerability patterns emerged. The long‐term risk‐benefit profiles of specific SGAs need to be tailored to individual patients to optimize maintenance treatment outcomes.     

Ontogenetic and spatial variation in size‐selective mortality of a marine fish

Although body size can affect individual fitness, ontogenetic and spatial variation in the ecology of an organism may determine the relative advantages of size and growth. During an 8‐year field study in the Bahamas, we examined selective mortality on size and growth throughout the entire reef‐associated life phase of a common coral‐reef fish, Stegastes partitus (the bicolour damselfish). On average, faster‐growing juveniles experienced greater mortality, though as adults, larger individuals had higher survival. Comparing patterns of selection observed at four separate populations revealed that greater population density was associated with stronger selection for larger adult size. Large adults may be favoured because they are superior competitors and less susceptible to gape‐limited predators. Laboratory experiments suggested that selective mortality of fast‐growing juveniles was likely because of risk‐prone foraging behaviour. These patterns suggest that variation in ecological interactions may lead to complex patterns of lifetime selection on body size.     

Habitat selection as a source of inter‐specific differences in recruitment of two diadromous fish species

• 1 For aquatic species with highly dispersive offspring, the addition of new individuals into an area (recruitment) is a key process in determining local population size so understanding the causes of recruitment variability is critical. While three general causative mechanisms have been identified (the supply of individuals, habitat selection and mortality), we have a limited understanding of how variation in each is generated, and the consequences this may have for the spatial and temporal distribution of recruits.
• 2 We examined whether active habitat selection during settlement could be the cause of variability in populations of two diadromous fish species using a field survey and laboratory‐based choice experiments. If larval behaviour is important, we predicted there would be inter‐specific differences in abundance between sites during the survey, and that larvae would prefer water collected from sites with higher conspecific abundances during the experiments.
• 3 During the field survey, significant differences were detected between two rivers (the Cumberland and Grey), with one species (Galaxias maculatus) found in higher abundances at one site (the Cumberland River) while comparable numbers of a closely related species (Galaxias brevipinnis) were caught at both sites. Laboratory choice experiments were conducted to determine whether larval preferences during settlement could be the cause of these differences. G. maculatus larvae showed a preference for freshwater over saltwater, indicating that the fish may be responding to reduced salinities around river mouths during settlement. The results of a second experiment were consistent with the notion that larval preferences could be the mechanism driving differences in the populations of the two rivers, with G. maculatus preferring water collected from the Cumberland River while G. brevipinnis did not prefer water from either river.
• 4 These results demonstrate that active habitat selection may be important in establishing spatial patterns of larvae at settlement, and that multiple cues are likely to be involved. This study also demonstrates that the behaviours exhibited by individuals can strongly influence the structure and dynamics of populations of aquatic species with complex life cycles.

     

Spatially variable response of native fish assemblages to discharge,predators and habitat characteristics in an arid‐land river

1. Fish assemblages and habitats were sampled annually at fixed sites in three tributaries of the Gila River catchment over a 21‐year span that included prolonged low‐ and high‐flow periods. Model selection was used to evaluate responses of seven native fishes with variable ecological traits (four small‐bodied cyprinids, one large‐bodied cyprinid, and two large‐bodied catostomids) to mean annual discharge and predacious non‐native fishes across the three sites. We also compared habitat use and overlap of native and non‐native fishes to identify potential for negative interactions among species. 2. Assemblage structure (species abundance and richness) and recruitment of native species was strongly and primarily affected by mean annual discharge and secondarily by location and densities of non‐native predators (mainly the centrarchid Micropterus dolomieui). 3. Densities of age‐0 catostomids and small‐bodied cyprinids were positively associated with discharge, and this pattern was strongest in the tributary with the lowest densities of non‐native predators. Absence or extreme low abundance of natives during low‐flow years was most pronounced at the sites where non‐native predators were comparatively common. Densities of adults of large‐bodied native species also varied by site, but often were positively associated with densities of non‐native predators. 4. Spatially variable responses of native fish assemblages indicated that the persistence of native fishes could be jeopardized if key habitats were lost or flow regimes unnaturally altered, particularly during low‐flow conditions when recruitment of native fishes is low and predation by non‐natives is high. Large‐bodied species may be less vulnerable to multiple years of poor conditions because adults are able to avoid predation by non‐natives and thus can rely on occasional high discharge years for successful recruitment. 5. As in other arid‐land streams, native fish assemblages of the Gila River Basin continue to decline. Our results indicate that conservation requires specific knowledge and consideration of physical influences as well as life‐history attributes of native and non‐native fishes.     

Thirty years of vegetation dynamics in response to a fluctuating rabbit population on sub‐Antarctic Macquarie Island

Australia's sub‐Antarctic Macquarie Island is presently undergoing one of the most ambitious vertebrate pest eradication programmes ever undertaken. The anticipated success of this programme will release the island's tundra‐like vegetation from well over a century of grazing and disturbance from House Mouse (Mus musculus), Ship Rat (Rattus rattus) and most significantly European Rabbit (Oryctolagus cuniculus). This study describes results from 30 years of vegetation quadrat monitoring (prior to the most recent and comprehensive pest eradication programme) when lower level pest animal control programmes were underway. Plant species were assigned to one of five distinct functional plant groups: Indigenous short‐lived perennials, Introduced short‐lived perennials, Indigenous perennials rarely grazed by rabbits, Indigenous perennials occasionally grazed by rabbits and Indigenous long‐lived perennials heavily grazed by rabbits, with one species, Agrostis magellanica, analysed as a sixth monospecific group. Results from monthly rabbit counts were used to compare changes in abundance of these six groups under different rabbit populations. It was found that there were three distinct phases of rabbit activity during the study period, indicated by (i) an initial very high count year in 1980–1981, followed by (ii) 20 years of low counts ending in 2001–2002 after which (iii) counts rose to medium/high until the commencement of the eradication programme in 2010–2011. Vegetation composition and progression were distinct for these three rabbit count phases. The first four of the plant functional groups decreased under lower count periods and increased in cover under higher rabbit count periods. Agrostis magellanica appears to respond primarily to interspecies competition and is disadvantaged under extended periods of low rabbit numbers. Indigenous long‐lived perennials heavily grazed by rabbits, which includes the large tussocks and megaherbs, is inversely related to rabbit numbers. During the study period, there has also been an overall decline in plant species richness with average species count per quadrat falling by between 0.6 and 2.7 taxa. This study attempts to address the observed vegetation change from this long‐term monitoring, to discuss other potential contributing factors and to use the results to predict likely future vegetation changes after eradication of vertebrate pests.     

The response of stream fish to local and reach‐scale variation in the occurrence of a benthic aquatic macrophyte

1. The aquatic macrophyte Podostemum ceratophyllum has been shown to increase stream productivity, abundance and biomass of benthic invertebrates, and local occurrences of some stream fishes. However, experimental evidence that fishes preferentially associate with Podostemum is lacking, and the value of Podostemum as a predictor of stream fish assemblage composition has not been studied. 2. We conducted two short‐term (2 week), small‐scale (36 m²) experimental manipulations of Podostemum cover in the Conasauga River (Georgia and Tennessee, U.S.), and found higher abundances of benthic insectivorous fishes in patches with augmented (>80%) compared to reduced (7%) Podostemum cover. In an observational study, we quantified associations among percent cover of Podostemum, fish species richness, land cover, shoal length and base‐flow turbidity at 20 randomly selected shoals from a 39‐km reach that spanned a gradient of decreasing forest land cover. 3. Richness of all fish species and of lotic fishes peaked in the centre of the study reach, and richness was weakly correlated with predictor variables. Occupancy models for individual species also indicated that longitudinal position was a strong covariate for 13 of 19 species examined, with little support that Podostemum cover influenced occupancy. 4. Local associations may reflect choices by benthic fishes to utilise Podostemum, whereas downstream decline in fish species richness and Podostemum cover may reflect altered capacity of the system to support native species.