The evolution and maintenance of secondary sexual characteristics and behavior are heavily influenced by the variance in mating success among individuals in a population. The operational sex ratio ...(OSR) is often used as a predictor of the intensity of competition for mates, as it describes the relative number of males and females who are ready to mate. We investigate changes in aggression, courtship, mate guarding, and sperm release as a function of changes in the OSR using meta-analytic techniques. As the OSR becomes increasingly biased, aggression increases as competitors attempt to defend mates, but this aggression begins to decrease at an OSR of 1.99, presumably due to the increased costs of competition as rivals become more numerous. Sperm release follows a similar but not significant trend. By contrast, courtship rate decreases as the OSR becomes increasingly biased, whereas mate guarding and copulation duration increase. Overall, predictable behavioral changes occur in response to OSR, although the nature of the change is dependent on the type of mating behavior. These results suggest considerable flexibility of mating system structure within species, which can be predicted by OSR and likely results in variation in the strength of sexual selection.
In an attempt to restore the connectivity of fragmented river habitats, a variety of passage facilities have been installed at river barriers. Despite the cost of building these structures, there has ...been no quantitative evaluation of their overall success at restoring fish passage. We reviewed articles from 1960 to 2011, extracted data from 65 papers on fish passage efficiency, size and species of fish, and fishway characteristics to determine the best predictors of fishway efficiency. Because data were scarce for fishes other than salmonids (order Salmoniformes), we combined data for all non‐salmonids for our analysis. On average, downstream passage efficiency was 68.5%, slightly higher than upstream passage efficiency of 41.7%, and neither differed across the geographical regions of study. Salmonids were more successful than non‐salmonids in passing upstream (61.7 vs. 21.1%) and downstream (74.6 vs. 39.6%) through fish passage facilities. Passage efficiency differed significantly between types of fishways; pool and weir, pool and slot and natural fishways had the highest efficiencies, whereas Denil and fish locks/elevators had the lowest. Upstream passage efficiency decreased significantly with fishway slope, but increased with fishway length, and water velocity. An information‐theoretic analysis indicated that the best predictors of fish passage efficiency were order of fish (i.e. salmonids > non‐salmonids), type of fishway and length of fishway. Overall, the low efficiency of passage facilities indicated that most need to be improved to sufficiently mitigate habitat fragmentation for the complete fish community across a range of environmental conditions.
Competition from non-native salmonids is potentially impairing efforts to restore Atlantic salmon (Salmo salar) to parts of their historical range. In three separate meta-analyses, we collected 104 ...effect sizes from 25 published papers to quantify the effect of both native and non-native salmonids on the performance (i.e., behaviour, habitat use, growth and survival) of Atlantic salmon. The presence of other species had negative effects on the performance of Atlantic salmon; in particular, non-native species and brown trout (Salmo trutta), whether native or non-native, had the most negative effects. Contrary to our predictions, the negative effects of other species were not exacerbated in laboratory compared to field studies and did not increase with total salmonid abundance or the relative body size of the competitors. However, most studies in our analyses were conducted under laboratory conditions and at densities much higher than found in nature. Thus, a realistic assessment of the potential success of restoration programs when interspecific competitors are present should include more studies conducted under natural conditions.
Habitat degradation is one of the major reasons for freshwater species decline. Hydrogeomorphological processes (such as sediment transport, bank erosion, and flooding) operate at the catchment scale ...and determine habitat features in river reaches. However, habitat quality indices and restoration for freshwater fish species are often implemented at small spatial scales of a few hundred metres. The Morphological Quality Index (MQI) considers fluvial processes at larger scales as well as channel forms, human impacts, and historical changes, but few studies have assessed its relevance for ecosystem health. We investigated relationships between the MQI, habitat quality (using the Qualitative Habitat Evaluation Index, QHEI), land cover, and fish metrics (number of fish species, index of biotic integrity (IBI), and trout biomass) in 26 salmonid streams in Aotearoa New Zealand and Southern Ontario, Canada. We found a significant correlation between the MQI and QHEI, and both metrics were correlated with urban and native forest proportion in the catchment. However, we found no relation between the MQI and the proportion of agricultural land in the catchment, while the QHEI was correlated with agricultural land in the riparian zone, highlighting the importance of vegetated riparian buffers in providing fish habitat. Establishing a strong correlation with fish metrics remains challenging. Nevertheless, a modified MQI targeting ecological health could be used as an effective management tool for aquatic conservation.
Laser machining is a highly flexible non‐contact fabrication method used extensively across academia and industry. Whilst simulations based on fundamental understanding offer some insight into the ...processes, both the highly non‐linear interactions between laser light and matter and the variety of materials involved mean that theoretical modelling is not particularly applicable to practical experimentation. However, recent breakthroughs in machine learning have resulted in neural networks that are capable of accurate and rapid modelling of laser machining at a scale, speed, and precision well beyond those of existing theoretical approaches with applications including 3‐D surface visualisation and real‐time error correction. A perspective at the intersection of laser machining and machine learning is presented, followed by a discussion of future milestones and challenges for this field.
PurposeThe goal was emancipatory, to characterise and dislodge oppressive management practices, to allow for the possibility of seeking an alternative organisational construction free of ...postcolonial/subaltern subordination and discrimination in a local, well-documented narrative.Design/methodology/approachThe study was informed by a postcolonial/subaltern perspective and drew on the employment experience of an Aboriginal woman, Canada’s first Indigenous Dean of a law school. The researcher employed a combination of case study and critical discourse analysis with the aim of advancing rich analyses of the complex workings of power and privilege in sustaining Western, postcolonial relations.FindingsThe study made several conclusions: first, that the institution, a medium-sized Canadian university, carefully controlled the Indigenous subaltern to remake her to be palatable to Western sensibilities. Second, the effect of this control was to assimilate her, to subordinate her Indigeneity and to civilise in a manner analogous to the purpose of Indian residential schools. Third, that rather than management’s action being rational and neutral, focused on goal attainment, efficiency and effectiveness, it was an implicit moral judgement based on her race and an opportunity to exploit her value as a means for the university’s growth and status.Originality/valueThrough a postcolonial/subaltern perspective, this study demonstrated how management practices reproduced barriers to the participation of an Indigenous woman and the First Nations community that an organisation was intended to serve. The study demonstrated how a Western perspective – that of a university’s administration, faculty and staff – was privileged, or taken for granted, and the Indigenous perspective subordinated, as the university remained committed to the dispossession of Indigenous knowledge and values.
•We propose a continuum-armed bandit model of surveillance resource allocation.•Poisson process data is given as feedback, with filtering depending on the actions.•We derive an effective upper ...confidence bound approach with adaptive discretisation.•We show matching upper and lower bounds on the regret.
We consider a version of the continuum armed bandit where an action induces a filtered realisation of a non-homogeneous Poisson process. Point data in the filtered sample are then revealed to the decision-maker, whose reward is the total number of revealed points. Using knowledge of the function governing the filtering, but without knowledge of the Poisson intensity function, the decision-maker seeks to maximise the expected number of revealed points over T rounds. We propose an upper confidence bound algorithm for this problem utilising data-adaptive discretisation of the action space. This approach enjoys O˜(T2/3) regret under a Lipschitz assumption on the reward function. We provide lower bounds on the regret of any algorithm for the problem, via new lower bounds for related finite-armed bandits, and show that the orders of the upper and lower bounds match up to a logarithmic factor.
Despite the widespread use of stream restoration structures to improve fish habitat, few quantitative studies have evaluated their effectiveness. This study uses a meta-analysis approach to test the ...effectiveness of five types of in-stream restoration structures (weirs, deflectors, cover structures, boulder placement, and large woody debris) on both salmonid abundance and physical habitat characteristics. Compilation of data from 211 stream restoration projects showed a significant increase in pool area, average depth, large woody debris, and percent cover, as well as a decrease in riffle area, following the installation of in-stream structures. There was also a significant increase in salmonid density (mean effect size of 0.51, or 167%) and biomass (mean effect size of 0.48, or 162%) following the installation of structures. Large differences were observed between species, with rainbow trout (
Oncorhynchus mykiss
) showing the largest increases in density and biomass. This compilation highlights the potential of in-stream structures to create better habitat for and increase the abundance of salmonids, but the scarcity of long-term monitoring of the effectiveness of in-stream structures is problematic.
The future is not always open Grant, James D. E.; Kunzinger, Michael; Sämann, Clemens ...
Letters in mathematical physics,
01/2020, Letnik:
110, Številka:
1
Journal Article
Recenzirano
Odprti dostop
We demonstrate the breakdown of several fundamentals of Lorentzian causality theory in low regularity. Most notably, chronological futures (defined naturally using locally Lipschitz curves) may be ...non-open and may differ from the corresponding sets defined via piecewise
C
1
-curves. By refining the notion of a causal bubble from Chruściel and Grant (Class Quantum Gravity 29(14):145001, 2012), we characterize spacetimes for which such phenomena can occur, and also relate these to the possibility of deforming causal curves of positive length into timelike curves (
push-up
). The phenomena described here are, in particular, relevant for recent synthetic approaches to low-regularity Lorentzian geometry where, in the absence of a differentiable structure, causality has to be based on locally Lipschitz curves.
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