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opencc-zeroOct 2019View details →

A meta-analysis of natural selection on plant functional traits

A common assumption in plant physiological ecology is that variation in functional traits reflects the adaptation of organisms to their abiotic environment. This assumption can be tested by estimating natural selection as the relationship between a functional trait and a fitness component (i.e. survival or reproduction) within a population. To understand how natural selection operates on plant functional traits, we compiled directional selection gradients (β), which estimate direct selection, and differentials (S), which estimate both direct and indirect selection, from studies conducted in manipulated and unmanipulated environments. We found that relative to manipulating biotic factors, manipulating abiotic factors had a ~5.7´ larger effect on β and a ~16´ larger effect on S, suggesting that functional traits primarily evolve in response to the abiotic environment. We found that the strength of selection on functional traits (β) did not vary with trait type, performance/fitness component, or measurement context (i.e. common garden vs. natural population). However, the direction of selection did differ between some trait types: β was positive for plant size traits, but negative for phenology traits. Lastly, we found that the absolute value of selection differentials (S) was ~2´ larger than the absolute value of selection gradients (β), indicating that there was indirect selection on functional traits. Overall, our meta-analysis illustrates that natural selection on plant functional traits is common, and that estimates of selection on these traits in experimentally manipulated environments can be used effectively to test hypotheses about the causes of adaptation.

Data from: Diabetes mellitus and the risk of fractures at specific sites: a meta-analysis

Objective: Diabetes mellitus (DM) is associated with an increased fracture risk; however, the impact of DM and subsequent fracture at different sites and the associations according to patient characteristics remain unknown. Design: Meta-analysis. Data Sources: The PubMed, EMBASE, and Cochrane Library databases were searched from inception to March 2018. Eligibility Criteria: We included prospective and retrospective cohort studies on the associations of DM and subsequent fracture risk at different sites. Data extraction and synthesis: Two authors independently extracted data and assessed the study quality. Relative risks (RRs) with 95% confidence intervals (CIs) were calculated using a random-effects model, and the heterogeneity across the included studies was evaluated using I2 and Q statistics. Results: Overall, DM was associated with an increased risk of total (RR: 1.32; 95% CI: 1.17–1.48; P<0.001), hip (RR: 1.77; 95% CI: 1.56–2.02; P<0.001), upper arm (RR: 1.47; 95% CI: 1.02–2.10; P=0.037), and ankle fractures (RR: 1.24; 95% CI: 1.10–1.40; P<0.001), whereas DM had no significant impact on the incidence of distal forearm (RR: 1.02; 95% CI: 0.88–1.19; P=0.809) and vertebral fractures (RR: 1.56; 95% CI: 0.78–3.12; P=0.209). RR ratios suggested that compared with type 2 DM (T2DM) patients, type 1 DM (T1DM) patients had greater risk of total (RR ratio: 1.24; 95% CI: 1.08–1.41; P=0.002), hip (RR ratio: 3.43; 95% CI: 2.27–5.17; P<0.001), and ankle fractures (RR ratio: 1.71; 95% CI: 1.06 –2.78; P=0.029). Although no other significant differences were observed between subgroups, the association of DM with upper arm or ankle, vertebrae, and total fracture differed according to sex, study design, and country, respectively. Conclusions: DM patients had greater risks of total, hip, upper arm, and ankle fractures, with T1DM having a more harmful effect than T2DM.

opencc-zeroDec 2011View details →

Data from: Do animals living in larger groups experience greater parasitism? A meta-analysis

Parasitism is widely viewed as the primary cost of sociality and a constraint on group size, yet studies report varied associations between group size and parasitism. Using the largest database of its kind, we performed a meta-analysis of 69 studies of the relationship between group size and parasite risk, as measured by parasitism and immune defenses. We predicted a positive correlation between group size and parasitism with organisms that show contagious and environmental transmission, and a negative correlation for searching parasites, parasitoids, and possibly vector-borne parasites (based on the encounter-dilution effect). Overall, we found a positive effect of group size (r=0.187) that varied in magnitude across transmission modes and measures of parasite risk, with only weak indications of publication bias. Among different groups of hosts, we found a stronger relationship between group size and parasite risk in birds than in mammals, which may be driven by ecological and social factors. A meta-regression showed that effect sizes increased with maximum group size. Phylogenetic meta-analyses revealed no evidence for phylogenetic signal in the strength of the group size-parasitism relationship. We conclude that group size is a weak predictor of parasite risk except in species that live in large aggregations, such as colonial birds, where effect sizes are larger.

opencc-zeroDec 2013View details →

Data from: The genetic basis of the fitness costs of antimicrobial resistance: a meta-analysis approach

The evolution of antibiotic resistance carries a fitness cost, expressed in terms of reduced competitive ability in the absence of antibiotics. This cost plays a key role in the dynamics of resistance by generating selection against resistance when bacteria encounter an antibiotic-free environment. Previous work has shown that the cost of resistance is highly variable, but the underlying causes remain poorly understood. Here, we use a meta-analysis of the published resistance literature to determine how the genetic basis of resistance influences its cost. We find that on average chromosomal resistance mutations carry a larger cost than acquiring resistance via a plasmid. This may explain why resistance often evolves by plasmid acquisition. Second, we find that the cost of plasmid acquisition increases with the breadth of its resistance range. This suggests a potentially important limit on the evolution of extensive multidrug resistance via plasmids. We also find that epistasis can significantly alter the cost of mutational resistance. Overall, our study shows that the cost of antimicrobial resistance can be partially explained by its genetic basis. It also highlights both the danger associated with plasmidborne resistance and the need to understand why resistance plasmids carry a relatively low cost.

opencc-zeroDec 2016View details →

Data from: Earthworms affect plant growth and resistance against herbivores: a meta-analysis

1. Subterranean detritivores such as earthworms can increase soil nutrient availability through their burrowing and casting activities. A number of recent studies have explored whether these changes caused by earthworms may in turn affect plant performance and resistance to herbivores, but no formal synthesis of this literature has been conducted to date. 2. We here formally tested for the effects of earthworms on plant growth, resistance and chemical defence against insect herbivores by performing a meta-analysis of the existing literature up to 2016. We also explored ecological factors that might explain among-studies variation in the magnitude of the earthworm effects on plant growth and resistance. 3. We found that earthworm presence increases plant growth (by 20 %) and nitrogen content (by 11 %). Overall, earthworms did not affect plant resistance against chewing herbivores (caterpillars, slugs and rootworms), and even led to a 22 % decrease in plant resistance against phloem-feeding herbivores (aphids). However, earthworm presence increased production of chemical defences by 31% when plants where attacked by cell-feeders (thrips), and resulted in an 81 % increase in resistance against thrips. The magnitude of earthworm effects was stronger when earthworm inoculations consisted of a mix of species and ecological types, and when densities of earthworms were high. 4. These results suggest that earthworm presence is an important factor underlying natural variation in plant defences against herbivores, and call for a better integration of the soil fauna in the studies of plant-herbivore interaction, both for applied and fundamental research.

Data from: Living in a high CO2 world: a global meta-analysis shows multiple trait-mediated responses of fish to ocean acidification

Understanding how marine organisms will be affected by global change is of primary importance to ensure ecosystem functioning and nature contributions to people. This study meets the call for addressing how life-history traits mediate effects of ocean acidification on fish. We built a database of overall and trait-mediated responses of teleost fish to future CO2 levels by searching the scientific literature. Using a meta-analytical approach, we investigated the effects of projected CO2 levels by IPCC for 2050-2070 and 2100 on fish eco-physiology and behavior from 320 contrasts on 42 species, stemming from polar to tropical regions. Moreover, since organisms may experience a mosaic of carbonate chemistry in coastal environments (e.g. in estuaries, upwelling zones and intertidal habitats), which may have higher pCO2 values than open ocean waters, we assessed responses from additional 103 contrasts on 21 fish species using pCO2 levels well above IPCC projections. Under mid- and end-of-century CO2 emission scenarios, we found multiple CO2-dose dependent effects on calcification, resting metabolic rate, yolk, behavioral performances, along with increased predation risk and decreased foraging, particularly for larvae. Importantly, many of the traits considered will not confer fish tolerance to elevated CO2 and far-reaching ecological consequences on fish population replenishment and community structure will likely occur. Extreme CO2 levels well above IPCC projections showed effects on fish mortality and calcification, while growth, metabolism and yolk were unaffected. CO2 exposures in short-term experiments increased fish mortality, which in turn decreased in longer-term exposures. Whatever the elevated CO2 levels considered, some key biological processes (e.g. reproduction, development, habitat choice) resulted critically understudied. Fish are an important resource for livelihoods in coastal communities and a key component for stability of marine ecosystems. Given the multiple trait-mediated effects evidenced here, we stress the need to fill the knowledge gap on important eco-physiological processes and to expand the number and duration of ocean acidification studies to multi-generational, multiple stressor (e.g. warming, hypoxia, fishing) and species interactions experiments to better elucidate complex ecosystem-level changes and how these changes might alter provisioning of ecosystem services.

Data from: The negative effects of pathogen-infected prey on predators: a meta-analysis

Intra-guild predation (IGP) – where a top predator (IGPred) consumes both a basal resource and a competitor for that resource (IGPrey) – has become a fundamental part of understanding species interactions and community dynamics. IGP communities composed of intraguild predators and prey have been well studied; however, we know less about IGP communities composed of predators, pathogens, and resources. Resource quality plays an important role in community dynamics and may influence IGP dynamics as well. We conducted a meta-analysis on predator–pathogen–resource communities to determine whether resource quality mediated by the pathogen affected predator life-history traits and if these effects met the theoretical constraints of IGP communities. To do this, we summarized results from studies that investigated the use of predators and pathogens to control insect pests. In these systems, the predators are the IGPred and pathogens are the IGPrey. We found that consumer longevity, fecundity, and survival decreased by 26%, 31% and 13% respectively, when predators consumed pathogen-infected prey, making the infected prey a low quality resource. Predators also significantly preferred healthy prey over infected prey. When we divided consumers by enemy type, strict predators (e.g. wolf spiders) had no preference while parasitoids preferred healthy prey. Our results suggest that communities containing parasitoids and pathogens may rarely exhibit intraguild predation; whereas, communities composed of strict predators and pathogens are more likely dominated by IGP dynamics. In these latter communities, the consumption of low and high quality resources suggests that IGP communities composed of strict predators, pathogens and prey should naturally persist, supporting IGP theory.

Data from: Patent foramen ovale closure, antiplatelet therapy or anticoagulation in patients with patent foramen ovale and cryptogenic stroke: a systematic review and network meta-analysis incorporating complementary external evidence

Objective: To examine the relative impact of three management options in patients less than 60 years old with cryptogenic stroke and a patent foramen ovale (PFO): PFO closure plus antiplatelet therapy, antiplatelet therapy alone, and anticoagulation alone. Design: Systematic review and network meta-analysis (NMA) supported by complementary external evidence Data sources: Medline, EMBASE, and Cochrane CENTRAL. Study selection: Randomised controlled trials (RCTs) addressing PFO closure and/or medical therapies in patients with PFO and cryptogenic stroke. Review methods: We conducted an NMA complemented with external evidence and rated certainty of evidence using the GRADE system. Results: Ten RCTs in eight studies proved eligible (n=4416). PFO closure versus antiplatelet therapy probably results in substantial reduction in ischaemic stroke recurrence (risk difference per 1000 patients over 5 years [RD]: -87, 95% credible interval [CrI] -100 to -33; moderate certainty). Compared with anticoagulation, PFO closure may confer little or no difference in ischaemic stroke recurrence (low certainty) but probably has a lower risk of major bleeding (RD -20, 95% Crl -27 to -2, moderate certainty). Relative to either medical therapy, PFO closure probably increases the risk of persistent atrial fibrillation (RD 18, CI +5 to +56, moderate certainty) and device-related adverse events (RD +36, 95% CI +23 to +50, high certainty). Anticoagulation, compared to antiplatelet therapy, may reduce the risk of ischaemic stroke recurrence (RD -71, 95% CrI -100 to +17, low certainty), but probably increases the risk of major bleeding (RD +12, CrI -5 to +65, moderate certainty). Conclusions: In patients less than 60 years old, PFO closure probably confers an important reduction in ischaemic stroke recurrence compared to antiplatelet therapy alone but may make no difference compared to anticoagulation. PFO closure incurs a risk of persistent atrial fibrillation and device-related adverse events. Compared to alternatives, anticoagulation probably increases major bleeding.

Data from: Ginkgo biloba extract for prevention of acute mountain sickness: a systematic review and meta-analysis of randomized controlled trials

Study objective: Trials of ginkgo biloba extract (GBE) for the prevention of acute mountain sickness (AMS) have been published since 1996. Because of their conflicting results, the efficacy of GBE remains unclear. We performed a systematic review and meta-analysis to assess whether GBE prevents acute mountain sickness. Methods: The Cochrane Library, EMBASE, Google Scholar, and PubMed databases were searched for articles published up to May 20, 2017. Only randomized controlled trials were included. AMS defined as acute mountain sickness–cerebral(AMS-C) score≧0.7 or Lake Louise Score (LLS)≧3 with headache. The main outcome measures were the relative risks of AMS in participants receiving GBE for prophylaxis. Meta-analyses were conducted using random-effects models. Sensitivity analyses, subgroup analyses and tests for publication bias were conducted. Results: Six published articles with a total of 451 participants met all eligibility criteria. In the primary meta-analysis of all 7 study groups, GBE showed trend of AMS prophylaxis, but it is not statistically significant (RR =0.68; 95% CI: 0.45 to 1.04; p-value=0.08) (Figure 2). The I2 statistic was 58.7% (p-value=0.02), indicating substantial heterogeneity. The results of subgroup analyses of studies with low risk of bias, low starting altitude (<2500 m), number of treatment days before ascending and dosage of GBE were similar. Conclusions: The currently available data suggest that although GBE may tend toward AMS prophylaxis, there are not enough data to show the statistically significant effect of GBE for preventing AMS. Further large randomized control studies are warranted.

opencc-zeroDec 2018View details →

Data from: One-shot dilation versus serial dilation technique for access in percutaneous nephrolithotomy: a systematic review and meta-analysis

Objective: The purpose of this study was to systematically review the outcomes of the use of one-shot dilation (OSD) and serial tract dilation for percutaneous nephrolithotomy (PCNL). Methods: A systematic review and meta-analysis was conducted. The randomized controlled trials (RCTs) included in the study were identified from EMBASE, MEDLINE, and the Cochrane Central Register of Controlled Trials. The last search was performed on April 30, 2018. Summary effects were calculated as risk ratios (RRs) with 95% confidence intervals (CIs) or mean differences (MDs) with 95% CIs. The endpoints included access time, fluoroscopy time, successful dilation rate, stone-free rate, postoperative decrease in hemoglobin levels, transfusion rate, complication rate, and length of postoperative hospital stay. Results: A total of 7 RCTs were included in the study, with clinical data reported for 697 patients. The overall access time was approximately 110 seconds shorter in the OSD group than in the serial dilation group (MD, -110.14; 95% CI, -161.99 to -58.30; P<0.0001). The fluoroscopy time was shorter with OSD in all RCTs. In addition, the decrease in postoperative hemoglobin levels was approximately 0.23 g/dl less in patients in the OSD group than in those in the serial dilation group (MD, -0.23; 95% CI, -0.39 to -0.07; P=0.004). No relationship was found between the successful dilation rate, stone-free rate, transfusion rate, or complication rate and the method of tract dilation. Conclusion: OSD is a safe and efficacious tract dilation technique that can reduce the access time, fluoroscopy time, and postoperative decrease in hemoglobin level. No difference was found in the successful dilation rate, stone-free rate, transfusion rate, or rate of complications between the OSD and serial dilation groups. The difference in the length of postoperative hospital stay was uncertain. OSD may be a better method of tract creation for PCNL.

Data from: On the link between functional traits and growth rate: meta-analysis shows effects change with plant size, as predicted

A plant's growth rate is seen as a central element of its ecological strategy, and as determined by its traits.Yet the literature is inconsistent about the empirical correlation between functional traits and growth, casting doubt on the capacity of some prominent traits to influence growth rate. We propose that traits should influence growth in a way that depends on the size of individual plants. We outline mechanisms and hypotheses based on new theoretical work, and test these predictions in tree species using a meta-analysis of 103 studies (> 500 correlations) for five traits (specific leaf area, wood density, maximum height, seed mass and maximum assimilation rate).We also recorded data for 14 other traits commonly used in the trait literature.To capture the effects of plant size, we tested for a shift in the direction of correlation between growth rates and each trait across three ontogenetic stages: seedling,sapling and adult. Results were consistent with predictions, although there were some limitations arising from unequal numbers of observation across ontogenetic stages.Specific leaf area was correlated with relative growth rate in seedlings but not in adult plants.Correlations of growth with wood density were not affected by ontogenetic stage. Seed mass, assimilation rate and maximum height were correlated with relative growth rate only in one ontogenetic stage category: seedlings,seedlings and adults,respectively. Although we were able to confirm several of our theoretical predictions,major knowledge gaps still exist in the trait literature.For example,for one third of the traits considered,the majority (> 75%) of reported correlations with growth came from the same ontogenetic stage. Synthesis: We show for some traits, how trait-growth correlations change in a predictable way with plant size.Our understanding of plant strategies should shift away from describing species as having a fixed growth strategy throughout their life (on a continuous axis from slow to fast growth), in favour of a size-dependent growth trajectories.

opencc-zeroDec 2013View details →

Data from: Placebo effects in trials evaluating 12 selected minimally invasive interventions: a systematic review and meta-analysis

Objectives: To analyse the impact of placebo effects on outcome in trials of selected minimally invasive procedures and to assess reported adverse events in both trial arms. Design: A systematic review and meta-analysis. Data sources and study selection: We searched MEDLINE and Cochrane library to identify systematic reviews of musculoskeletal, neurological and cardiac conditions published between January 2009 and January 2014 comparing selected minimally invasive with placebo (sham) procedures. We searched MEDLINE for additional randomised controlled trials published between January 2000 and January 2014. Data synthesis: Effect sizes (ES) in the active and placebo arms in the trials' primary and pooled secondary end points were calculated. Linear regression was used to analyse the association between end points in the active and sham groups. Reported adverse events in both trial arms were registered. Results: We included 21 trials involving 2519 adult participants. For primary end points, there was a large clinical effect (ES≥0.8) after active treatment in 12 trials and after sham procedures in 11 trials. For secondary end points, 7 and 5 trials showed a large clinical effect. Three trials showed a moderate difference in ES between active treatment and sham on primary end points (ES ≥0.5) but no trials reported a large difference. No trials showed large or moderate differences in ES on pooled secondary end points. Regression analysis of end points in active treatment and sham arms estimated an R2 of 0.78 for primary and 0.84 for secondary end points. Adverse events after sham were in most cases minor and of short duration. Conclusions: The generally small differences in ES between active treatment and sham suggest that non-specific mechanisms, including placebo, are major predictors of the observed effects. Adverse events related to sham procedures were mainly minor and short-lived. Ethical arguments frequently raised against sham-controlled trials were generally not substantiated.

Data from: Are heritability and selection related to population size in nature? Meta-analysis and conservation implications

It is widely thought that small populations should have less additive genetic variance and respond less efficiently to natural selection than large populations. Across taxa, we meta-analytically quantified the relationship between adult census population size (N) and additive genetic variance (proxy: h2) and found no reduction in h2 with decreasing N; surveyed populations ranged from four to one million individuals (1735 h2estimates, 146 populations, 83 species). In terms of adaptation, ecological conditions may systematically differ between populations of varying N; the magnitude of selection these populations experience may therefore also differ. We thus also meta-analytically tested whether selection changes with N, and found little evidence for systematic differences in the strength, direction, or form of selection with N across different trait types and taxa (7344 selection estimates, 172 populations, 80 species). Collectively, our results (i) indirectly suggest that genetic drift neither overwhelms selection more in small than in large natural populations, nor weakens adaptive potential/h2 in small populations, and (ii) imply that natural populations of varying sizes experience a variety of environmental conditions, without consistently differing habitat quality at small N. However, we caution that the data are currently insufficient to determine whether some small populations may retain adaptive potential definitively. Further study is required into (i) selection and genetic variation in completely isolated populations of known N, underrepresented taxonomic groups, and non-generalist species, (ii) adaptive potential using multidimensional approaches, and (iii) the nature of selective pressures for specific traits.

Data from: Impact of temperature and nutrients on carbon: nutrient tissue stoichiometry of submerged aquatic plants: an experiment and meta-analysis

Human activity is currently changing our environment rapidly, with predicted temperature increases of 1–5°C over the coming century and increased nitrogen and phosphorus inputs in aquatic ecosystems. In the shallow parts of these ecosystems, submerged aquatic plants enhance water clarity by resource competition with phytoplankton, provide habitat, and serve as a food source for other organisms. The carbon:nutrient stoichiometry of submerged aquatic plants can be affected by changes in both temperature and nutrient availability. We hypothesized that elevated temperature leads to higher carbon:nutrient ratios through enhanced nutrient-use efficiency, while nutrient addition leads to lower carbon:nutrient ratios by the luxurious uptake of nutrients. We addressed these hypotheses with an experimental and a meta-analytical approach. We performed a full-factorial microcosm experiment with the freshwater plant Elodea nuttallii grown at 10, 15, 20, and 25°C on sediment consisting of pond soil/sand mixtures with 100, 50, 25, and 12.5% pond soil. To address the effect of climatic warming and nutrient addition on the carbon:nutrient stoichiometry of submerged freshwater and marine plants we performed a meta-analysis on experimental studies that elevated temperature and/or added nutrients (nitrogen and phosphorus). In the microcosm experiment, C:N ratios of Elodea nuttallii decreased with increasing temperature, and this effect was most pronounced at intermediate nutrient availability. Furthermore, higher nutrient availability led to decreased aboveground C:P ratios. In the meta-analysis, nutrient addition led to a 25, 22, and 16% reduction in aboveground C:N and C:P ratios and belowground C:N ratios, accompanied with increased N content. No consistent effect of elevated temperature on plant stoichiometry could be observed, as very few studies were found on this topic and contrasting results were reported. We conclude that while nutrient addition consistently leads to decreased carbon:nutrient ratios, elevated temperature does not change submerged aquatic plant carbon:nutrient stoichiometry in a consistent manner. This effect is rather dependent on nutrient availability and may be species-specific. As changes in the carbon:nutrient stoichiometry of submerged aquatic plants can impact the transfer of energy to higher trophic levels, these results suggest that eutrophication may enhance plant consumption and decomposition, which could in turn have consequences for carbon sequestration.

opencc-zeroJun 2019View details →

Data from: The global prevalence of latent tuberculosis: a systematic review and meta-analysis

In 1999, the WHO estimated that one-third of the world"s population had latent tuberculosis infection (LTBI) which was recently updated to one-fourth. However, this is still based on controversial assumptions in combination with tuberculin skin test (TST) surveys. Interferon-gamma release assays (IGRAs) with a higher specificity than TST have since been widely implemented, but never used to estimate the global LTBI prevalence. We conducted a systematic review and meta-analysis of LTBI estimates based on both IGRA and TST results published between 2005 and 2018. Regional and global estimates of LTBI prevalence were calculated. Stratification was performed for low, intermediate and high TB incidence countries and a pooled estimate for each area was calculated using a random effects model. Among 3280 studies screened, we included 88 studies from 36 countries with 41 IGRA (n=67 167) and 67 TST estimates (n=284 644). The global prevalence of LTBI was 24.8% (95% CI: 19.7-30.0%) and 21.2% (95% CI: 17.9-24.4%) based on IGRA and a 10 mm TST cut-off respectively. The prevalence estimates correlated well to WHO incidence rates (Rs=0.70, p<0.001). In the first study of the global prevalence of LTBI derived from both IGRA and TST surveys, we found that one-fourth of the world"s population is infected. This is of relevance as both tests, although imperfect, are used to identify individuals eligible for preventive therapy. Enhanced efforts are needed targeting the large pool of latently infected as these individuals continuously constitutes an enormous source of potential active TB.

Data from: Determinants and co-expression of anti-predator responses in amphibian tadpoles: a meta-analysis

A wide range of taxa respond to perceived predation risk (PPR) through inducible defenses, and many prey are capable of responding both behaviorally and morphologically to the same risk event. In cases where multiple defenses confer protection by independent means (i.e., they are mechanistically independent) responses will either be co-expressed, or the expression of one defense will limit the capacity (or need) to respond along another axis. Our ability to generate a broad understanding of these patters has been limited, in part, by difficulties in comparing results across studies that employ distinct experimental protocols. Using the extensive literature on tadpole responses to PPR, we conducted a meta-analysis to identify the ecological and experimental determinants of inducible defence expression. We then assessed whether the magnitude of response to PPR along behavioural versus morphological response axes was positively, or negatively, correlated. The most commonly quantified responses to perceived risk in tadpoles included reductions in movement and swimming behaviour, and altered tail morphology. Our analyses reveal that tadpole behavioural responses are strongly influenced by prey family, predator taxon, evolutionary history with the predator (native vs. non-native), amount of prey consumed by the predator, and how perceived risk was manipulated (e.g., presence vs. absence of alarm cues). Tail morphology was similarly influenced by these factors, but also whether the target prey was palatable to predators. Thus, our results identify ecological and experimental features that critically influence the observed effect size in tadpole responses to PPR. A positive correlation between behavioural and morphological responses in studies where both were measured indicates that trait co-specialization is the predominant pattern of defense deployment in larval amphibians. This positive relationship suggests that survival tends to be maximized in tadpoles through equivalent coactivation of multiple independent axes of protection, opposed to maximal expression along any single axis.