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Supplemental data from: Intraspecific facial bite marks in tyrannosaurids provide insight into sexual maturity and evolution of bird-like intersexual display
— 2021-09-10 <p>Intraspecific aggression, or agonism, is a widespread intrasexual selective behavior important to understanding animal behavioral ecology and reproductive systems. Such behavior can be studied either by direct observation or inferred from wound/scar frequency in extant species, but is difficult to document in extinct taxa, limiting understanding of its evolution. Among extant archosaurs, crocodylians display extensive intrasexual aggression, whereas birds show extreme visual/vocal intersexual display. The evolutionary origin of this behavioral divergence, and pattern in non-avian dinosaurs, is unknown. Here we document the morphology, frequency, and ontogeny of intraspecific facial bite lesions (324 lesions) in a large sample of tyrannosaurids (202 specimens, 528 elements) to infer patterns of intraspecific aggression in non-avian theropods. Facial scars are consistent in position and orientation across tyrannosaurid species, suggesting bites were inflicted due to repeated/postured behavior. Facial scars are absent in young tyrannosaurids, first appear in immature animals (~50% adult skull length), are present in ~60% of the adult-sized specimens, and show aggressor:victim size isometry. The ontogenetic distribution of bite scars suggests agonistic behavior is associated with the onset of sexual maturity, and scar presence in approximately half the specimens may relate to a sexual pattern. Considered in a phylogenetic context, intraspecific bite marks are consistent and widely distributed in fossil and extant crocodyliforms and non-maniraptoriform theropods, suggesting a potential plesiomorphic behavior in archosaurs. Their absence in maniraptoriform theropods, including birds, may reflect a transition from boney cranial ornamentation and crocodylian-like intrasexual aggression to avian-like intersexual display with the evolution of pennaceous feathers.</p> https://creativecommons.org/publicdomain/zero/1.0/
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Hematoma expansion shift analysis to assess acute intracerebral hemorrhage treatments
— 2021-06-04 <p style="margin-bottom:11px;"><b>Objective:</b> Hematoma expansion (HE) is commonly analyzed as a dichotomous outcome in intracerebral hemorrhage (ICH) trials.  In this proof-of-concept study, we propose a “HE shift” analysis model as a method to improve the evaluation of candidate ICH therapies.</p> <p style="margin-bottom:11px;"><b>Methods</b>: Using data from the Antihypertensive Treatment of Acute Cerebral Hemorrhage II (ATACH-2) trial, we performed HE shift analysis in response to intensive blood pressure lowering by generating polychotomous strata based on a) previously established HE definitions, b) percentile/absolute quartiles of hematoma volume change, and c) quartiles of 24-hour follow-up hematoma volumes. The relationship between blood pressure treatment and HE shift was explored using proportional odds models.</p> <p style="margin-bottom:11px;"><b>Results</b>: The primary analysis population included 863 patients. In both treatment groups, approximately one-third of patients exhibited no HE. Using a trichotomous HE stratification, the highest strata of ≥33% revealed a 5.8% reduction in hematoma growth for those randomized to intensive therapy (aOR: 0.77 [95% CI: 0.60-0.99]). Using percentile quartiles of hematoma volume change, we observed a favorable shift to reduce growth in patients treated with intensive therapy: aOR: 0.73 (0.57-0.93). Similarly, in a tetrachotomous analysis of 24-hour follow-up hematoma volumes, shifts in the highest stratum (&gt; 21.9 mL) was most notable.</p> <p><b>Conclusions</b>: Our findings suggest that intensive blood pressure reduction may preferentially mitigate growth in patients at risk of high volume HE. A shift analysis model of HE provides additional insights into the biological effects of a given therapy and may be an additional way to assess hemostatic agents in future studies.</p> <p><b>Registration</b>: ClinicalTrials.gov Identifier: NCT01176565</p> https://creativecommons.org/publicdomain/zero/1.0/
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Model output data for "Negative density-dependent dispersal emerges from the joint evolution of density- and body condition-dependent dispersal strategies"
— 2020-08-18 <p>Empirical studies have documented both positive and negative density-dependent dispersal, yet most theoretical models predict positive density dependence as a mechanism to avoid competition. Several hypotheses have been proposed to explain the occurrence of negative density-dependent dispersal, but few of these have been formally modeled. Here, we developed an individual based model of the evolution of density-dependent dispersal. This model is novel in that it considers the effects of density on dispersal directly, and indirectly through effects on individual condition. Body condition is determined mechanistically, by having juveniles compete for resources in their natal patch. We found that the evolved dispersal strategy was a steep, increasing function of both density and condition. Interestingly, although populations evolved a positive density-dependent dispersal strategy, the simulated metapopulations exhibited negative density-dependent dispersal. This occurred because of the negative relationship between density and body condition: high density sites produced low condition individuals that lacked the resources required for dispersal. Our model therefore generates the novel hypothesis that observed negative density-dependent dispersal can occur when high density limits the ability of organisms to disperse. We suggest that future studies consider how phenotype is linked to the environment when investigating the evolution of dispersal.</p> https://creativecommons.org/publicdomain/zero/1.0/
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Data from: Genetic architecture and genomic patterns of gene flow between hybridizing species of Picea
— 2015-02-23 Hybrid zones provide an opportunity to study the effects of selection and gene flow in natural settings. We employed nuclear microsatellites (single sequence repeat (SSR)) and candidate gene single-nucleotide polymorphism markers (SNPs) to characterize the genetic architecture and patterns of interspecific gene flow in the Picea glauca × P. engelmannii hybrid zone across a broad latitudinal (40–60 degrees) and elevational (350–3500 m) range in western North America. Our results revealed a wide and complex hybrid zone with broad ancestry levels and low interspecific heterozygosity, shaped by asymmetric advanced-generation introgression, and low reproductive barriers between parental species. The clinal variation based on geographic variables, lack of concordance in clines among loci and the width of the hybrid zone points towards the maintenance of species integrity through environmental selection. Congruency between geographic and genomic clines suggests that loci with narrow clines are under strong selection, favoring either one parental species (directional selection) or their hybrids (overdominance) as a result of strong associations with climatic variables such as precipitation as snow and mean annual temperature. Cline movement due to past demographic events (evidenced by allelic richness and heterozygosity shifts from the average cline center) may explain the asymmetry in introgression and predominance of P. engelmannii found in this study. These results provide insights into the genetic architecture and fine-scale patterns of admixture, and identify loci that may be involved in reproductive barriers between the species. https://creativecommons.org/publicdomain/zero/1.0/
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Data from: Parallel and nonparallel genome-wide divergence among replicate population pairs of freshwater and anadromous Atlantic salmon
— 2017-09-20 Little is known about the genetic basis differentiating resident and anadromous forms found in many salmonid species. Using a medium-density SNP array, we documented genomic diversity and divergence at 2336 genetically mapped loci among three pairs of North American anadromous and freshwater Atlantic salmon populations. Our results show that across the genome, freshwater populations have lower diversity and a smaller proportion of private polymorphism relative to anadromous populations. Moreover, differentiation was more pronounced among freshwater than among anadromous populations at multiple spatial scales, suggesting a large effect of genetic drift in these isolated freshwater populations. Using nonhierarchical and hierarchical genome scans, we identified hundreds of markers spread across the genome that are potentially under divergent selection between anadromous and freshwater populations, but few outlier loci were repeatedly found in all three freshwater–anadromous comparisons. Similarly, a sliding window analysis revealed numerous regions of high divergence that were nonparallel among the three comparisons. These last results show little evidence for the parallel evolution of alleles selected for in freshwater populations, but suggest nonparallel adaptive divergence at many loci of small effects distributed through the genome. Overall, this study emphasizes the important role of genetic drift in driving genome-wide reduction in diversity and divergence in freshwater Atlantic salmon populations and suggests a complex multigenic basis of adaptation to resident and anadromous strategies with little parallelism. https://creativecommons.org/publicdomain/zero/1.0/
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Data from: Host specificity in subarctic aphids
— 2018-10-11 The specificity of parasitic interaction depends on the adaptations of both the host and the parasite. Over time, these interactions evolve and change as a result of an “arms race” between host and parasite, and the resulting species-specific adaptations may be maintained, perpetuating these interactions across speciation events. With speciation and species sorting over time, complex systems of interactions evolve. Here, we elucidate some of these interactions using the aphids (Hemiptera: Aphididae) of Churchill as a model system. We analyzed these interactions by testing for two patterns in host-specificity: monophagy and phylogenetic clustering. We defined monophagy as one species feeding upon a single host plant species, an association which is driven by arms races in morphology, chemical resistance/tolerance, and camouflage; this pattern was observed in 7 of 22 aphid species. Secondly, we observed three separate cases where groups of closely related aphid species fed upon individual plant species (examples of phylogenetic clustering). One explanation for uncovering species-specific interactions in a recently deglaciated, sub-arctic locality is that the species involved in the associations moved north together. Testing different levels of specificity in species interactions allows us to accurately elucidate these patterns and gives us insight into where to direct future research. https://creativecommons.org/publicdomain/zero/1.0/
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Predicting the effects of reservoir water level management on the reproductive output of a riparian songbird
— 2021-02-25 <p>Yellow warblers were monitored in Revelstoke, British Columbia, Canada for 12 breeding seasons spanning 2005 to 2017. Data on the breeding biology of individually marked warblers was used to construct an individual-based model describing the effects of reservoir operations on the reproductive output of yellow warblers. This model was parameterised using data on the breeding biology of approximately 30 breeding pairs per year that a provided data on nest sites (ground elevation and nest height), breeding phenology (date of first egg for each clutch initiated), clutch size, brood parasitism by brown-headed cowbirds, nest fate and whether females re-nested following nest failure or success. The raw data was filtered, excluding nests that failed due to abandonment following brood parasitism and flooding, and formatted to allow estimation of nest survival rates using Program MARK. </p> https://creativecommons.org/publicdomain/zero/1.0/
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Data from: Molecular analysis of parasitoid linkages (MAPL): gut contents of adult parasitoid wasps reveal larval host
— 2010-11-08 Metamorphosing insects often have complex and poorly known life-histories. In particular, what they feed on during their larval stages remains unknown for the vast majority of species and its documentation only results from difficult and time-intensive field observations, rearing or dissections. Through the application of a DNA analysis of gut contents in adult parasitoid wasps, we were able to selectively sequence a diagnostic DNA marker that permitted the identification of the host used by these wasps during their larval stages. By reproducing these results in species with different life-histories, we excluded other potential sources of host DNA, confirming that after ingestion by the parasitoid larva the host DNA can persist through metamorphosis in the abdominal contents of the adult wasp. Our discovery considerably extends the applicability of molecular analysis of gut contents by enabling documentation of the food used by insects during their larval stages and thus increasing the accuracy and precision of food web-studies. The 24% success rate of our approach is surprisingly high considering the challenging context for host DNA preservation, and we discuss the factors possibly affecting this rate. We propose Molecular Analysis of Parasitoid Linkages (MAPL) as a new method to document host-parasitoid associations at a faster pace and with unrivalled precision. Because of the key regulatory role of parasitoid wasps in ecosystems, which makes them the most commonly used biological control agents, MAPL will have immediate applications in both basic and applied biological sciences. https://creativecommons.org/publicdomain/zero/1.0/
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Data from: Use of environmental sites by mule deer: a proxy for relative risk of chronic wasting disease exposure and transmission
— 2018-11-21 Prions that cause chronic wasting disease (CWD) in cervids can remain infective for years outside the host. Infectious cervids shed prions for a long time, consequently depositing prions in frequently used areas. These environmental prions are important in CWD epidemiology. Unfortunately, effective tools for quantifying CWD prions in soil, water, and other environmental sources are not currently available. Our goal was to investigate relative differences in visits by mule deer (Odocoileus hemionus hemionus) to various environmental site types as an indicator of the relative risk of prion contamination and disease transmission. For this, we deployed a system of triggered-by-movement cameras at eight site types in a CWD-endemic area in Saskatchewan, Canada. We first assessed whether the relative differences among site types in the frequency of visits by mule deer of any sex-and-age class, males, and females varied by season and site type. We then assessed whether the rate of behaviors with a high risk of environmental prion transmission (either contamination or acquisition) differed by season and site type. Finally, we assessed whether the intensity of visitation, based on the number of animals per picture, differed by season and site type. We found that grain sources and beds were key attractants for mule deer: (1) The greatest number of pictures with mule deer per camera-day occurred at grain sources across all seasons, except in fawning, when beds were the most visited sites; (2) during pre-rut and early gestation, mule deer visited grain sources at least twice as often as most other sites; (3) females were more likely to visit beds and grain sources, but there was no significant site preferences for males after accounting for season; (4) mule deer were most likely to be pictured contacting the environment at grain sources in early gestation; and (5) beds and grain sources were the most intensively visited sites. We also found that environmental contacts at waterholes were more frequent during spring. We discuss the potential importance of various sites in the transmission of CWD and how their modification could potentially reduce the risk of prion environmental exposure among mule deer. https://creativecommons.org/publicdomain/zero/1.0/
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Data from: Testing for latitudinal gradients in defense at the macroevolutionary scale
— 2018-08-24 Plant defences against herbivores are predicted to evolve to be greater in warmer climates, such as lower latitudes where herbivore pressure is also thought to be higher. Instead, recent findings are often inconsistent with this expectation, suggesting alternative hypotheses are needed. We tested for latitudinal gradients in plant defence evolution at the macroevolutionary scale by characterizing plant chemical defences across 80 species of the evening primroses, spanning both North and South America. We quantified phenolics in leaves, flowers and fruits, using advanced analytical chemistry techniques. Dominant individual ellagitannin compounds, total concentrations of ellagitannins, flavonoids, total phenolics, and compound diversity were quantified. Variation in these compounds were predicted with latitude, temperature, precipitation, and continent using phylogenetic generalized least squares multiple regression models. Latitude did not strongly explain patterns for the chemical defences. Instead, fruit total ellagitannins, oenothein A and total phenolics were greater in species inhabiting regions with colder climates. Using analytical chemistry and 80 species in two continents, we show that contrary to classic predictions, concentrations of secondary metabolites are not greater at lower latitudes or in warmer regions. We propose higher herbivore pressure in colder climates and gradients in resource availability as potential drivers of the observed patterns. https://creativecommons.org/publicdomain/zero/1.0/
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Data from: Turning down the heat: vegetation feedbacks limit fire regime responses to global warming
— 2019-05-16 Climate change is projected to dramatically increase boreal wildfire activity, with broad ecological and socio-economic consequences. As global temperatures rise, periods with elevated fire weather are expected to increase in frequency and duration, which would be expected to increase the number and size of fires. Statistical forecasts or simulations of future fire activity often account for direct climatic effects only, neglecting other controls of importance, such as biotic feedbacks. This could result in overestimating the effects of climate change on fire activity, if the future distribution of vegetation or fuels were to change. We incorporated sensitivity to climate or fire weather and vegetation in a fire simulation model, and represented explicitly two key biotic feedbacks linked to succession and regeneration processes. We used this model to forecast annual fire activity from 2011 to 2099 over a large region of boreal forest in Québec, Canada, dominated by balsam fir (Abies balsamea (L.) Mill) and yellow birch (Betula alleghaniensis Britt.) or paper birch (Betula papyrifera Marsh.), with and without the biotic feedbacks. Our simulations show that vegetation changes triggered by fire disturbance altered future fire activity, and may even be as important a driver as climate change itself. Indeed, over the course of the century, vegetation changes were projected to offset much of the increase in fire activity that would be expected due to global warming as such. It follows that if biotic feedbacks are not included in statistical or simulation-based forecasts, the resultant projections of future fire activity could be biased upwards to a very considerable degree. For the case of end-of-century mean annual burn rate, we estimated this positive bias to be as high as 400%. Accounting for biotic feedbacks in simulation models is therefore necessary for accurate projection of future wildfire activity and associated vegetation changes. Purely statistical forecasts based on current vegetation cannot be relied upon, in the presence of biotic feedbacks. Our results further suggest that vegetation management could reduce fire risk in some systems by altering the abundance and distribution of the most highly flammable fuels, and thus mitigate the impact of climate change on fire activity. https://creativecommons.org/publicdomain/zero/1.0/
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Data from: Is biasing offspring sex ratio adaptive? a test of Fisher’s principle across multiple generations of a wild mammal in a fluctuating environment
— 2018-10-30 Fisher’s principle explains that population sex ratio in sexually reproducing organisms is maintained at 1:1 due to negative frequency-dependent selection, such that individuals of the rare sex realize greater reproductive opportunity than individuals of the more common sex until equilibrium is reached. If biasing offspring sex ratio towards the rare sex is adaptive, individuals that do so should have a higher number of grandoffspring. In a wild population of North American red squirrels (Tamiasciurus hudsonicus) that experiences fluctuations in resource abundance and population density, we show that overall across 26 years, the secondary sex ratio was 1:1; however, stretches of years during which adult sex ratio was biased did not yield offspring sex ratios biased towards the rare sex. Females that had litters biased towards the rare sex did not have more grandoffspring. Critically, adult sex ratio was not temporally autocorrelated across years, thus the population sex ratio experienced by parents was independent of the population sex ratio experienced by their offspring by the time of their primiparity. Expected fitness benefits of biasing offspring sex ratio may be masked or negated by fluctuating environments across years, which limit the predictive value of the current sex ratio. https://creativecommons.org/publicdomain/zero/1.0/
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Data from: The evolution of hominoid cranial diversity: a quantitative genetic approach
— 2017-09-21 Hominoid cranial evolution is characterized by substantial phenotypic diversity, yet the cause of this variability has rarely been explored. Quantitative genetic techniques for investigating evolutionary processes underlying morphological divergence are dependent on the availability of good ancestral models, a problem in hominoids where the fossil record is fragmentary and poorly understood. Here, we use a maximum likelihood approach based on a Brownian motion model of evolutionary change to estimate nested hypothetical ancestral forms from 15 extant hominoid taxa. These ancestors were then used to calculate rates of evolution along each branch of a phylogenetic tree using Lande’s generalized genetic distance. Our results show that hominoid cranial evolution is characterized by strong stabilizing selection. Only two instances of directional selection were detected; the divergence of Homo from its last common ancestor with Pan, and the divergence of the lesser apes from their last common ancestor with the great apes. In these two cases, selection gradients reconstructed to identify the specific traits undergoing selection indicated that selection on basicranial flexion, cranial vault expansion and facial retraction characterizes the divergence of Homo, whereas the divergence of the lesser apes was defined by selection on neurocranial size reduction. https://creativecommons.org/publicdomain/zero/1.0/
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Data from: The ‘filtering’ metaphor revisited: competition and environment jointly structure invasibility and coexistence
— 2018-07-30 ‘Filtering’, or the reduction in species diversity that occurs because not all species can persist in all locations, is thought to unfold hierarchically, controlled by the environment at large scales and competition at small scales. However, the ecological effects of competition and the environment are not independent, and observational approaches preclude investigation into their interplay. We use a demographic approach with 30 plant species to experimentally test (i) the effect of competition on species persistence in two soil moisture environments, and (ii) the effect of environmental conditions on mechanisms underlying competitive coexistence. We find that competitors cause differential species persistence across environments even when effects are lacking in the absence of competition, and that the traits that determine persistence depend on the competitive environment. If our study had been observational and trait-based, we would have erroneously concluded that the environment filters species with low biomass, shallow roots, and small seeds. Changing environmental conditions generated idiosyncratic effects on coexistence outcomes, increasing competitive exclusion of some species while promoting coexistence of others. Our results highlight the importance of considering environmental filtering in light of, rather than in isolation from, competition, and challenge community assembly models and approaches to projecting future species distributions. https://creativecommons.org/publicdomain/zero/1.0/
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Habitat area and environmental filters determine avian richness along an elevation gradient in mountain peatlands
— 2021-11-26 <p>Globally, relationships between avian richness and elevation in mountain ecosystems typically reflect one of four well-documented patterns, but the mechanisms responsible for these patterns are poorly understood. We investigated which pattern best described bird species richness in peatlands of the Upper Bow Basin of the Canadian Rocky Mountains (1300 to 2000 m a.s.l.) and used a model competition framework to investigate possible mechanisms. Avian richness displayed a plateauing (cubic) relationship in response to increasing elevation (AICc weight = 0.48). Log richness was significantly positively related to log peatland area (R<sup>2</sup> = 0.42, p = 0.001); however, once we accounted for the richness-area relationship (area was not related to elevation (R<sup>2</sup> = 0.13, p = 0.083)), the richness-elevation relationship was best described by a negative linear model rather than a cubic model (AICc weight = 0.69, R<sup>2</sup> = 0.39). Consequently, we reject the neutral model of the mid-domain effect and conclude that peatland area and one or more environmental filters are simultaneously driving relationships between avian richness and elevation in Rocky Mountain peatlands. Multi-causality likely explains why researchers in different geographies observe inconsistent patterns between richness and elevation: drivers and interactions among drivers may vary spatially. Importantly, Natural Subregion was a stronger predictor of avian species richness than elevation per se (AICc weight = 0.96), suggesting that the responsible environmental filter(s) is relatively homogenous within ecological land classes (e.g., primary productivity) rather than directly variable with elevation (e.g., temperature). The results also lend insight into priorities for future research on richness-elevation patterns in mountain birds.</p> https://creativecommons.org/publicdomain/zero/1.0/
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Reversal learning in FTD (fMRI)
— 2021-07-07 <p class="MsoNoSpacing"><b>Objective</b>: Frontotemporal Dementia (FTD) is a neurodegenerative disorder that results in disinhibition and difficulty with flexible responding when provided feedback. Inflexible responding is observed early in the course of the illness and contributes to the financial and social morbidities of FTD. Reversal learning is an established cognitive paradigm that indexes flexible responding in the face of feedback signaling a change in reinforcement contingencies, with components of reversal learning associated with specific neurotransmitter systems. The objective of the study was to evaluate the neural mechanisms underlying impaired flexible behavioural responding in FTD using a reversal learning paradigm combined with fMRI.</p> <p class="MsoNoSpacing"><b>Methods</b>: Twenty-two patients meeting the diagnostic criteria for FTD and twenty-one healthy controls completed the study. Participants completed an fMRI-adapted reversal learning task that indexes behavioural flexibility when provided positive and negative feedback.</p> <p class="MsoNoSpacing"><b>Results</b>: Patients with FTD demonstrated poorer behavioural flexibility relative to controls and abnormal BOLD responses within the left ventrolateral prefrontal cortex to incorrect responses made during the learning phase, and during correct responses when reward contingencies were reversed. As well, patients showed decreased activity within the left dorsal lateral prefrontal cortex to incorrect responses compared to controls.</p> <p class="MsoNoSpacing"><b>Conclusions</b>: These findings suggest that reversal learning impairments in patients with FTD, in particular those with frontal predominant atrophy, may be related to impaired flexible motor responding when selecting among several choices and deficient attention to relevant stimuli during instances of conflict (i.e. receiving negative feedback). These results and the associated neurotransmitter systems mediating these regions may provide targets for future pharmacological or behavioural interventions mediating these cognitive deficits.</p> https://creativecommons.org/publicdomain/zero/1.0/
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Dispersal without drivers: Intrinsic and extrinsic variables have no impact on movement distances in a terrestrial amphibian
— 2022-09-26 <p>Dispersive movements are often thought to be multicausal and driven by individual body size, sex, conspecific density, environmental variation, personality and/or other variables. Yet such variables often do not account for most of the variation among dispersive movements in nature, leaving open the possibility that dispersion may be indeterministic. We assessed the amount of variation in 24 h movement distances that could be accounted for by potential drivers of displacement with a large empirical dataset of movement distances performed by Fowler’s Toads (<em>Anaxyrus fowleri</em>) on the northern shore of Lake Erie at Long Point, Ontario (2002–2021, incl.). These toads are easy to sample repeatedly, can be identified individually and move parallel to the shoreline as they forage at night, potentially dispersing to new refuge sites. Using a linear mixed-effect model that incorporated random effect terms to account for sampling variance and inter-annual variation, we found that all potential intrinsic and extrinsic drivers of movement accounted for virtually none of the variation observed among 24 h distances moved by these animals, whether over short or large spatial scales. We examined the idea of movement personality by testing variance per individual toad and found no evidence of individuality in movement distances. We conclude that deterministic variables, whether intrinsic or extrinsic, neither can be shown to nor are necessary to drive movements in this population over all spatial scales. Stochastic, short-timescale movements, such as daily foraging movements, can instead accumulate over time to produce large spatial-scale movements that are dispersive in nature.</p> https://creativecommons.org/publicdomain/zero/1.0/
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Which physicochemical variables should zooplankton ecologists measure when they conduct field studies?
— 2021-05-10 <p><span lang="EN-CA" style="background:white;">Over the last century, a rich literature has developed describing how the physical and chemical environment influences zooplankton communities, but there is little guidance on the suite of limnological variables that should be measured by zooplankton ecologists. We performed a literature review to assess: 1) Which variables were measured most often by zooplankton ecologists; 2) Which of these variables were consistently related to zooplankton abundance and richness; and 3) Whether key variables were overlooked by investigators. Our results show that there is a core group of nine limnological variables that are measured most frequently, including lake surface area, pH, phosphorus, nitrogen, dissolved oxygen, conductivity, chlorophyll-<i>a</i>, maximum depth, and temperature. These variables were among those most often associated with </span>variation in zooplankton, but several others, including dissolved organic carbon, alkalinity, and nitrate were sampled infrequently, despite showing promise as important explanatory variables<span style="background:white;">. The selection of variables in past studies did not correlate with how often those variables were significant in the literature, but instead, might have been related to their ease of measurement. Neglecting to measure important variables could have implications for fundamental and applied studies that aim to understand the factors structuring zooplankton communities and their response to environmental change.</span></p> https://creativecommons.org/publicdomain/zero/1.0/
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Data from: Heavily hunted wolves have higher stress and reproductive steroids than wolves with lower hunting pressure
— 2015-08-18 1. Human-caused harassment and mortality (e.g. hunting) affects many aspects of wildlife population dynamics and social structure. Little is known, however, about the social and physiological effects of hunting, which might provide valuable insights into the mechanisms by which wildlife respond to human-caused mortality. To investigate physiological consequences of hunting, we measured stress and reproductive hormones in hair, which reflect endocrine activity during hair growth. Applying this novel approach, we compared steroid hormone levels in hair of wolves (Canis lupus) living in Canada's tundra–taiga (n = 103) that experience heavy rates of hunting with those in the northern boreal forest (n = 45) where hunting pressure is substantially lower. The hair samples revealed that progesterone was higher in tundra–taiga wolves, possibly reflecting increased reproductive effort and social disruption in response to human-related mortality. Tundra–taiga wolves also had higher testosterone and cortisol levels, which may reflect social instability. To control for habitat differences, we also measured cortisol in an out-group of boreal forest wolves (n = 30) that were killed as part of a control programme. Cortisol was higher in the boreal out-group than in our study population from the northern boreal forest. Overall, our findings support the social and physiological consequences of human-caused mortality. Long-term implications of altered physiological responses should be considered in management and conservations strategies. https://creativecommons.org/publicdomain/zero/1.0/
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Density dependence mediates the ecological impact of an invasive fish
— 2021-04-15 <p>Aim:</p> <p>The way in which habitat heterogeneity and predator density affect predator-prey dynamics, space use, and prey risk are understudied aspects of foraging ecology, particularly for invasive species. Likewise, how an invasive species’ impact scales with its abundance is poorly understood. We used a model invasive species, lionfish (Pterois volitans), to understand effects of multiple predators on consumption rate and prey mortality risk, foraging among multiple patches. Location Florida, USA Methods We considered effects of both predator and prey abundance on density-dependent impact. We used functional response methodology to quantify the per-capita effect of P. volitans, assessing concomitant influences of prey refuge (3 levels) and predator density (3 levels) on predator-prey space use and predation efficiency across increasing prey densities (7 levels). We then assessed intraspecific interaction outcomes by comparing observed per-capita effects with predicted estimates based on consumption rates of individual predators. This allowed us to detect the presence of emergent multiple predator effects (MPEs) and tease apart density-dependent impacts. Results Lionfish predatory impact was mediated by predator and prey density but unaffected by refugia. We detected non-linear scaling of impact with increasing predator abundance. Pairs of lionfish had the greatest per-capita effect, whose cumulative impact on prey matched that expected of independently foraging predators. At the highest predator density (four fish) antagonistic multiple predator effects precipitated prey risk reduction, in which we observed the lowest per-capita effect. Across predator abundance, prey mortality rates were inversely density-dependent. Despite incongruent patch preferences between predators and their prey, predator impacts were context-independent. Main conclusions Quantifying non-independent consumptive effects of multiple conspecific predators across levels of prey abundance can inform better prediction and understanding of invasive species' density-dependent effects. Additionally, consideration of heterogeneity-mediated FRs and predator-prey spatial distributions may facilitate more precise and realistic predictions of invader impact across their invaded range.</p> https://creativecommons.org/publicdomain/zero/1.0/

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