Phage therapy is drawing more interest as antibiotic resistance becomes an ever more serious threat to public health. Bacterial biofilms represent a major obstacle in the fight against bacterial ...infections as they are inherently refractory to many types of antibiotics. Treating biofilms with phage has shown promise in a handful of experimental and case studies. However, quantification of the effect of phage combined with antibiotics is needed to pave the way for larger clinical trials. Here we explore the effect of using phage in combination with a total of nine antibiotics, applied simultaneously or as a pretreatment before antibiotics are applied to in vitro biofilms of Staphylococcus aureus. Most antibiotics alone were ineffective at low concentration (2×MIC), but the addition of phage to treatment regimens led to substantial improvements in efficacy. At high concentration (10×MIC), antibiotics alone were effective, and in most cases the addition of phage to treatment regimens did not improve efficacy. Using phage with rifampin was also very effective at reducing the outgrowth of resistant strains during the course of treatment.
Animal behaviour is increasingly recognised as critical to the prediction of non-native species success and impacts. Rainbow trout and brown trout have been introduced globally, but there appear to ...be differences in their patterns of invasiveness and ecological impact. Here, we investigated whether diploid rainbow trout and diploid and triploid brown trout differ among several key behavioural measures linked to invasiveness and impact. We assessed activity, boldness, aggression, and feeding, using open field, novel object, shelter, mirror, feeding, and functional response experiments. We also tested within each fish type for behavioural syndromes comprising correlations among activity, boldness and aggression. Rainbow trout were more active and aggressive but less bold than diploid and triploid brown trout. In small groups, however, rainbow trout were bolder than both types of brown trout. Diploid brown trout were more active and bolder than triploids when tested individually, and had a higher functional response than both rainbow trout and triploid brown trout. In terms of behavioural syndromes, there was no association between activity and boldness in rainbow trout, however, there was in both brown trout types. The increased activity and aggression of rainbow trout may reflect an increased stress response to novel situations, with this response reduced in a group. These results suggest that rainbow trout do not manage their energy budgets effectively, and may explain why they have limited survival as invaders. In addition, the lower functional response of rainbow trout may explain why they are implicated in fewer ecological impacts, and the triploidy treatment also appears to lower the potential impact of brown trout. Comparative analyses of multiple behaviours of invasive species and genetic variants may thus be key to understanding and predicting invader success and ecological impacts.
The influence of climate change on the ecological impacts of invasive alien species (IAS) remains understudied, with deoxygenation of aquatic environments often-overlooked as a consequence of climate ...change. Here, we therefore assessed how oxygen saturation affects the ecological impact of a predatory invasive fish, the Ponto-Caspian round goby (
Neogobius melanostomus
), relative to a co-occurring endangered European native analogue, the bullhead (
Cottus gobio
) experiencing decline in the presence of the IAS. In individual trials and mesocosms, we assessed the effect of high, medium and low (90%, 60% and 30%) oxygen saturation on: (1) functional responses (FRs) of the IAS and native, i.e. per capita feeding rates; (2) the impact on prey populations exerted; and (3) how combined impacts of both fishes change over invasion stages (Pre-invasion, Arrival, Replacement, Proliferation). Both species showed Type II potentially destabilising FRs, but at low oxygen saturation, the invader had a significantly higher feeding rate than the native. Relative Impact Potential, combining fish per capita effects and population abundances, revealed that low oxygen saturation exacerbates the high relative impact of the invader. The Relative Total Impact Potential (RTIP), modelling both consumer species’ impacts on prey populations in a system, was consistently higher at low oxygen saturation and especially high during invader Proliferation. In the mesocosm experiment, low oxygen lowered RTIP where both species were present, but again the IAS retained high relative impact during Replacement and Proliferation stages at low oxygen. We also found evidence of multiple predator effects, principally antagonism. We highlight the threat posed to native communities by IAS alongside climate-related stressors, but note that solutions may be available to remedy hypoxia and potentially mitigate impacts across invasion stages.
Investigate the effect of cumulative head impacts on saccade latency and errors, measured across two successive football seasons.
Participants were acquired from a sample of convenience-one Canadian ...university football team. Head impacts were collected during training camp, practices, eight regular season games, and four playoff games in each season. Saccade measurements were collected at five time points-before and after training camp, at midseason, after regular season, and after playoffs.
Two seasons following players from a single USports football team during practices and games.
Players who completed a baseline saccade measurement and a minimum of one follow-up measurement were included in the study. A total of 127 players were monitored across two competitive seasons, including 61 players who participated in both seasons.
Head impact measurements were collected using helmet-mounted sensors.
Saccade latency and number of errors were measured using high-speed video or electro-oculography.
On average, each head impact increased prosaccade latency by 5.16 × 10 -3 ms (95% confidence interval CI, 2.26 × 10 -4 -1.00 × 10 -2 , P = 0.03) and antisaccade latency by 5.74 × 10 -3 ms (95% CI, 7.18 × 10 -4 -1.06 × 10 -2 , P = 0.02). These latency increases did not decrease between the two seasons; in fact, prosaccade latencies were 23.20 ms longer (95% CI, 19.40-27.14, P < 0.001) at the second season's baseline measurement than the first. The number of saccade errors was not affected by cumulative head impacts.
Repetitive head impacts in Canadian university football result in cumulative declines in brain function as measured by saccade performance.
Football organizations should consider implementing policies focused on reducing head impacts to improve player safety.
•Relative Control Potential is a new metric developed to compare biocontrol agents.•M. albidus and M. viridis both effectively prey upon larvae of C. pipiens.•M. albidus was deemed more efficacious ...for the control of C. pipiens.•Increased temperatures drive higher magnitude functional responses on target prey.•Applying abundance and fecundity improves Relative Control Potential predictions.
We currently lack the capacity to rapidly and reliably predict the efficacy of biological control agents due to inadequate consistency in derivations of functional and numerical responses and potential effects of context-dependencies. Here, we propose and apply a novel metric, Relative Control Potential (RCP), which combines the functional response (FR, per capita effect) with proxies for the numerical response (NR, agent population response) to compare agent efficacies, where RCP = FR × abundance (or other proxies e.g. fecundity). The RCP metric is a comparative ratio between potential biocontrol agents, where values > 1 indicate higher relative control efficacy. Further, RCP can compare the efficacy of agents under environmental contexts, such as temperature change. We thus derived the RCP for two predatory cyclopoid copepods, Macrocyclops albidus (Cyclopoida: Cyclopidae) and Megacyclops viridis (Cyclopoida: Cyclopidae), towards larvae of the mosquito Culex pipiens (Diptera: Culicidae) under temperatures representative of current and future climate. Both copepods exhibited potentially population destabilising Type II FRs, with increasing temperatures inducing greater magnitude FRs through increased attack rates and decreased handling times. Attack rates by M. albidus were higher than M. viridis, yet handling times and maximum feeding rates were similar between the species across all temperatures. The inclusion of abundance data drives an elevated RCP of M. albidus and the integration of fecundity drives greater RCP of M. albidus at peak temperatures. Q10 values are indicative of increased feeding activity by both copepods with temperature increases, however relative feeding level increases of M. viridis slowed towards the peak temperature. We present RCP calculations and biplots that represent the comparative efficacies of the two biological control agents across temperatures. The Relative Control Potential (RCP) metric thus provides a new tool for practitioners to better assess the potential efficacy of biocontrol agents before their integration into management approaches for pests, vectors and invasive species.
The Functional Response (FR) has been identified as a powerful predictive tool to forecast the ecological impacts of existing, emerging and future invasive alien species. In particular, the ...parameters of attack rate
a
and handling time
h
may be predictive of the ecological impacts of invaders when utilised in comparison with trophically analogous natives. However, researchers in many cases face somewhat contradictory impact predictions based on the use of one parameter or the other. Here, we thus propose a new metric, the Functional Response Ratio (FRR), which is simply
a
divided by
h
: that is, FRR =
a
/
h
. Given that high values of
a
and low values of
h
should associate with high impact, and vice versa, the FRR metric balances the information from both parameters. This also resolves contradictions when one parameter gives opposite predictions to the other. Using multiple examples obtained from the literature, we find that the FRR indeed resolves such contradictions and that values of FRR of invaders are consistently higher than those of natives, irrespective of experimental or environmental context. Accordingly, the use of FRR provides a novel and reliable metric for scientists, stakeholders and practitioners to predict the ecological impacts of existing, emerging and future invasive alien species across taxa and trophic groups.
Biodiversity is declining on a global scale and the spread of invasive alien species (IAS) is a major driver, particularly through predatory impacts. Thus, effective means of assessing and predicting ...the consequences of IAS predation on native prey population stability remains a vital goal for conservation. Here, we applied two classic ecological concepts, consumer functional response (FR) and prey switching, to predict and understand the ecological impacts of juveniles of the lionfish (
Pterois volitans
), a notorious and widespread marine invader. Functional responses and prey switching propensities were quantified towards three representative prey species:
Artemia salina
,
Palaemonetes varians
, and
Gammarus oceanicus
. Lionfish exhibited potentially destabilising Type II FRs towards individual prey species, owing to high consumption rates at low prey densities, whilst FR magnitudes differed among prey species. Functional response attack rates (
a
) were highest, and handling times (
h
) lowest, towards
A. salina
, followed by
P. varians
and then
G. oceanic
us. Maximum feeding rates (1/
h
) and functional response ratios (FRR;
a
/
h
) also followed this impact gradient for the three prey species. Lionfish, however, displayed a potentially population stabilising prey switching propensity (i.e. frequency-dependent predation) when multiple prey species were presented simultaneously, where disproportionately less of rare prey, and more of abundant prey, were consumed. Whilst FR and FRR magnitudes indicate marked
per capita
lionfish predatory impacts towards prey species, a strong prey switching propensity may reduce in-field impacts by offering low density prey refuge in biodiverse communities. Our results thus corroborate field patterns documenting variable impacts of lionfish, with prey extirpations less likely in diverse communities owing to frequency-dependent predation.
Interactions between multiple invasive alien species (IAS) might increase their ecological impacts, yet relatively few studies have attempted to quantify the effects of facilitative interactions on ...the success and impact of aquatic IAS. Further, the effect of abiotic factors, such as habitat structure, have lacked consideration in ecological impact prediction for many high-profile IAS, with most data acquired through simplified assessments that do not account for real environmental complexities. In the present study, we assessed a potential facilitative interaction between a predatory invasive fish, the Ponto-Caspian round goby (Neogobius melanostomus), and an invasive bivalve, the Asian clam (Corbicula fluminea). We compared N. melanostomus functional responses (feeding-rates under different prey densities) to a co-occurring endangered European native analogue fish, the bullhead (Cottus gobio), in the presence of increased levels of habitat complexity driven by the accumulation of dead C. fluminea biomass that persists within the environment (i.e. 0, 10, 20 empty bivalve shells). Habitat complexity significantly influenced predation, with consumption in the absence of shells being greater than where 10 or 20 shells were present. However, at the highest shell density, invasive N. melanostomus maximum feeding-rates and functional response ratios were substantially higher than those of native C. gobio. Further, the Relative Impact Potential metric, by combining per capita effects and population abundances, indicated that higher shell densities exacerbate the relative impact of the invader. It therefore appears that N. melanostomus can better tolerate higher IAS shell abundances when foraging at high prey densities, suggesting the occurrence of an important facilitative interaction. Our data are thus fully congruent with field data that link establishment success of N. melanostomus with the presence of C. fluminea. Overall, we show that invader-driven benthic habitat complexity can alter the feeding-rates and thus impacts of predatory fishes, and highlight the importance of inclusion of abiotic factors in impact prediction assessments for IAS.
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•Invasive Corbicula clam shells significantly influenced predation by fish.•Invader-driven benthic habitat complexity can stabilise fish feeding rates.•Invasive goby, N. melanostomus, better tolerated shell-driven habitat complexity.•Higher shell densities exacerbated the invader impact relative to native C. gobio.•Invader-driven abiotic factors can underpin facilitative interactions.
Aim
The spread of invasive non‐native species (INNS) will pose major threats to global biodiversity over the coming decades. However, predicting how key effects of climate change will influence the ...abilities of INNS to establish and exert ecological impact is a major challenge. One overlooked aspect of global change is the expected freshening of certain marine systems, which may interact with INNS and lead to drastic effects on community structure and stability.
Location
Baltic Sea, Europe.
Methods
Here, using three predatory amphipod crustaceans, we experimentally assessed how salinity reduction may affect the impacts of the emerging INNS, Pontogammarus maeoticus, relative to an existing INNS, Gammarus tigrinus and a trophically analogous native, Gammarus salinus. We quantified per capita impacts of the three species via the comparative functional response method (prey consumption over a range of prey densities) under a predicted seawater freshening scenario. We then combined amphipod functional responses with their life history traits to compare population‐level relative impact potential (RIP) on prey of the three amphipod species across salinities.
Results
Freshening substantially altered the predicted relative ecological impacts of both the INNS compared with the native. First, the functional responses of invasive P. maeoticus and G. tigrinus increased under freshening, while that of the native G. salinus decreased. Second, RIP became consistently higher for both the INNS compared to the native with increased freshening.
Main conclusions
Our methods thus reveal potential for climate change via seawater freshening to drive large shifts in dominance and ecological impacts of INNS compared with natives. With the number of INNS introductions unlikely to saturate in the near future, we highlight the need to assess the impacts of potential future INNS, alongside established non‐natives and native species, in combination with abiotic changes associated with climate change.
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