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As reproduction phenologies shift with climate change, populations can experience intraspecific priority effects, wherein early hatching cohorts experience an advantage over late-hatching cohorts, resulting in altered demography. Our study objective was to identify how variation in egg hatching phenology alters intraspecific interactions in small-mouthed salamanders, Ambystoma texanum. We addressed two research questions: (Q1) How are demographic responses altered by variation in the temporal duration of hatching between cohorts, and (Q2) How does the seasonality of hatching delays affect demographic responses? We manipulated hatching phenologies of A. texanum eggs and reared larvae in outdoor mesocosms to metamorphosis. For Q1, hatching delay exhibited non-linear relationships with survival and body size, with the greatest asynchrony in cohort additions resulting in the highest mortality and largest body sizes. For Q2, hatching delay effects were stronger (i.e., survival was lower and body sizes larger) when they occurred later in the season, potentially due to temperature differences that larvae experienced. Overall, our results demonstrate that changes in intraspecific interactions due to phenological shifts can be context-dependent, depending on the strength (i.e., temporal duration) and seasonality of such processes. Identifying context-dependencies of phenological shifts will be critical for predicting changes in organismal demographics with climatic shifts. [ABSTRACT FROM AUTHOR]

Wetland hydroperiod affects the ecology and evolution of numerous freshwater organisms. Pond-breeding amphibians are particularly affected by hydroperiod, with their life histories and distributional patterns often resulting from how long ponds remain inundated. Substantial variability exists among species in their responsiveness to fluctuations in hydroperiod, making taxon-specific investigations needed to understand its general impacts. We tested whether two fall-breeding salamanders, Ambystoma annulatum and A. opacum, each of which have long (ᐳ 6 month) larval period durations, respond to variation in hydroperiod length. We manipulated hydroperiod in outdoor experimental mesocosms under three scenarios (short hydroperiod, medium hydroperiod, and constant water levels), focusing specifically on how hydroperiod affected their life history traits (survival, size, and time to metamorphosis). We found that in the shortened hydroperiod treatments, few individuals of either species completed metamorphosis and would have died, whereas nearly all surviving individuals underwent metamorphosis under longer hydroperiod treatments. After correcting for differences in survival, body size at metamorphosis was greater in constant hydroperiod treatments for only A. annulatum. Larval periods were on average longer in constant hydroperiods for both species. The relationship between size and time to metamorphosis was positive for both A. annulatum and A. opacum, with limited differences between hydroperiod treatments in this relationship for either species. Overall, these results indicate these fall-breeding species are indeed affected by hydroperiod variation, but in different ways, depending on the life history response. These diverse responses highlight the complexities of building generalized responses of amphibians to a shared stressor like hydroperiod variation, as taxon- and trait-specific responses appear to be common. Future work should consider other aspects of hydroperiod as a structuring abiotic force (e.g., onset of drying), or the life history traits of amphibians (e.g., their breeding phenology), to better understand the ecology and evolution of pondbreeding amphibians, as well as provide insights into management actions for their conservation. [ABSTRACT FROM AUTHOR]

Functional redundancy occurs when different predator species have similar effects on the diversity, abundance, and composition of a prey community. When multiple predators coexist, their interactions can alter prey survival and ultimately diversity through emergent multiple-predator effects (MPEs). MPEs can be exacerbated by differences in predator behavior; however, little is known about the magnitude of MPEs when predators compete for the same prey or have similar behavioral traits. To understand functional redundancy and the interactions of multiple predators in similar niches, as well as their impacts on the composition of a prey community, we conducted two experiments using two ambystomatid salamander predators (Ambystoma opacum and Ambystoma annulatum). We exposed a suite of tadpole prey (Anaxyrus americanus, Rana sphenocephala, Rana sylvatica, Pseudacris feriarum, and Pseudacris crucifer) to different experimental food webs in a mesocosm experiment, and a single prey species (R. sphenocephala) in microcosm experiment with substitutive and additive designs to test for MPEs. We found no evidence for functional redundancy between the two predators: A. annulatum selectively preyed on competitively dominant prey species (A. americanus) and did not alter community diversity. Ambystoma opacum decreased prey diversity relative to the control because of natural phenological mismatch with A. americanus. Interactions between the two predators (e.g., predator inference) were lacking, indicating that predation risk from each predator was independent for the one prey species we tested. A better understanding of community and ecosystem-level effects by A. annulatum can inform future conservation efforts and management decisions regarding this endemic species. [ABSTRACT FROM AUTHOR]

Phenology is a key driver of population and community dynamics. Phenological metrics (e.g., first date that an event occurred) often simplify information from the full phenological distribution, which may undermine efforts to determine the importance of life history events. Data regarding full phenological distributions are especially needed as many species are shifting phenology with climatic change which can alter life-history patterns and species dynamics. We tested whether skewness, kurtosis or maximum duration of breeding phenology affected juvenile emigration phenology and survival in natural populations of ringed (Ambystoma annulatum) and spotted salamanders (A. maculatum) spanning a 7-year period at two study locations. We evaluated the relative importance of different phenological metrics in breeding phenology and larval density dependence on emigration phenology and survival. We found that variability in emigration phenology differed by species, with ringed salamanders having a shorter duration and distributions that were more often right-skewed and leptokurtic compared to spotted salamanders. Emigration phenology was not linked to any measure of variability in breeding phenology, indicating phenological variability operates independently across life stages and may be subject to stage-specific influences. Emigration duration and skewness were partially explained by larval density, which demonstrates how phenological distributions may change with species interactions. Further tests that use the full phenological distribution to link variability in timing of life history events to demographic traits such as survival are needed to determine if and how phenological shifts will impact species persistence. [ABSTRACT FROM AUTHOR]

Body size differences among consumers often lead to asymmetric interactions, with larger individuals typically being stronger competitors and/or predators on small individuals. These types of interaction are particularly exemplified in freshwater pond communities, where substantial size variation exists both within and among species of top consumers. We investigated whether density dependence can modify the outcome of size‐structured interactions between larval stages of two pond‐breeding salamanders, Ambystoma annulatum and Ambystoma opacum. Size structure exists in populations of these species due to variation in the timing of breeding, which we hypothesised would amplify predation rates and competitive asymmetries from the early‐arriving species (A. annulatum) on the later‐arriving species (A. opacum).We manipulated the relative densities of both A. annulatum and A. opacum in outdoor mesocosms. We maintained the experiment through metamorphosis, and analysed size at metamorphosis, larval period length and survival of each species.Ambystoma annulatum imparted a strong density‐dependent effect on A. opacum through a combination of predation and competition. Survival of A. opacum was negatively related to the density of A. annulatum. For the A. opacum that survived, body size was reduced and larval period lengthened at higher A. annulatum densities, indicative of interspecific competition that was partly explained by resource pre‐emption. In contrast, A. annulatum was only affected by intraspecific density‐dependent competition.Our results suggest that density‐dependent effects reinforce asymmetric interactions among larval salamanders. However, the intensity of the asymmetric interactions is mediated by the arrival time and size of conspecifics. Specifically, earlier‐arriving species can negatively affect the later‐arriving species via size‐mediated predation and competition.The interactive effects of density dependence and arrival time of community members are probably a common mechanism generating size variability in ecological communities. Yet, most studies only evaluate one mechanism or the other. By interweaving these two processes, our work displays the importance of understanding context‐dependence in species interactions. [ABSTRACT FROM AUTHOR]

Population cycles are fundamentally linked with spatial synchrony, the prevailing paradigm being that populations with cyclic dynamics are easily synchronised. That is, population cycles help give rise to spatial synchrony. Here we demonstrate this process can work in reverse, with synchrony causing population cycles. We show that timescale‐specific environmental effects, by synchronising local population dynamics on certain timescales only, cause major population cycles over large areas in white‐tailed deer. An important aspect of the new mechanism is specificity of synchronising effects to certain timescales, which causes local dynamics to sum across space to a substantial cycle on those timescales. We also demonstrate, to our knowledge for the first time, that synchrony can be transmitted not only from environmental drivers to populations (deer), but also from there to human systems (deer‐vehicle collisions). Because synchrony of drivers may be altered by climate change, changes to population cycles may arise via our mechanism. [ABSTRACT FROM AUTHOR]

Direct and indirect effects both influence population and community dynamics. The relative strengths of these pathways are often compared using experimental approaches, but their evaluation in situ has been less frequent. We examined how individual and aggregate impacts of direct and indirect effects of species densities, proxies for competition and predation pressure, and habitat variables influenced patterns of larval density and body size of ringed (Ambystoma annulatum) and spotted salamanders (A. maculatum). We surveyed > 150 ponds in Missouri, USA, from 2012 to 2014 to measure the density and body size of each focal species, the density of co-occurring pond food web members, and select habitat features. We used structural equation modeling to quantify the relative importance of direct and indirect pathways on both body size and larval density. Overall, both responses were explained through a combination of direct and indirect effects. However, the magnitudes of direct effects were often greater than indirect effects. Some of the direct and indirect relationships with larval salamander size and density were also consistent with results from experimental studies. Finally, total direct and indirect effects were often weaker due to habitat and density variables negating each other's impacts. Overall, our study shows that direct effects were equivalent to, or more important than, indirect effects. We also demonstrate that the effects stemming from individual relationships can sum to produce net patterns that are negligible in magnitude. Further work on direct and indirect effects with observational data are needed to examine their magnitudes in natural communities. [ABSTRACT FROM AUTHOR]

Predation can have strong effects on the structure of pond-breeding amphibian communities. Many factors can influence the outcome of predator-prey interactions, including differences in densities, identities, and body sizes of both predator and prey. These different mediating factors can impart synergistic impacts on predation rates, though distinguishing such interactions among multiple factors are underexplored. We examined whether different body sizes of two predators, larval Marbled Salamanders (Ambystoma opacum) and adult Lesser Sirens (Siren intermedia), varied in their ability to forage on larval anurans across a range of prey densities. We specifically tested whether attack rates and handling times, the two main parameters of functional response models, varied across three size classes in both predator species. We found that larval Marbled Salamanders exhibited a Type II (saturating) functional response and that larger individuals had higher attack rates and shorter handling times, resulting in greater prey mortality at higher prey densities with larger predators. In contrast, Lesser Sirens were largely ineffective predators despite being an order of magnitude larger in body size than Marbled Salamanders; tadpole mortality was largely unrelated to their own density. Predator body size was a significant predictor of prey mortality for both predator species. Overall, our study shows that species identity could be as important as predator body size when predicting the outcomes of predator-prey interactions. [ABSTRACT FROM AUTHOR]

Understanding community interactions, such as predator–prey dynamics, is vital for determining species viability. Outside of larger macroinvertebrate predators, such as crayfish and dragonfly larvae, there is a paucity of information regarding the effectiveness of other macroinvertebrate predators in consuming larval amphibians, especially caudate larvae, during aquatic life-stages within pond communities. In this study, we tested the ability of a suite of macroinvertebrate predators to consume Spotted Salamander larvae (Ambystoma maculatum) at two points during larval development. We tested the ability of macroinvertebrate predators belonging to the genera Belostoma, Lestes, Notonecta, and Ranatra, the families Aeshnidae, Dytiscidae, Gomphidae, Gyrinidae, Hirudinae, Libellulidae, and Notonectidae, or order Trichoptera, as well as larvae of Rana clamitans, to consume A. maculatum immediately after hatching and several weeks into their larval period across four separate experiments. We tested for significant differences in percent survival of A. maculatum among predator treatments using ANOVA. Across all trials, we found a significant effect of predator treatment. Both hatchling and larval A. maculatum were susceptible to predation by Aeshnidae and Notonectidae. In all other treatments, we observed low or zero mortality of hatchlings of A. maculatum and 100% survival of larvae of A. maculatum. As Aeshnidae and Notonectidae are both gape unconstrained predators, the increase in larval size did not appear to increase survival of A. maculatum due to increased escape performance. Overall, rates of predation are low for A. maculatum for most macroinvertebrates during the tested life stages, suggesting that predation by only a handful of invertebrate taxa and vertebrates contribute to high mortality rates within this system. [ABSTRACT FROM AUTHOR]

Spatial synchrony is defined by related fluctuations through time in population abundances measured at different locations. The degree of relatedness typically declines with increasing distance between sampling locations. Standard approaches for assessing synchrony assume isotropy in space and uniformity across timescales of analysis, but it is now known that spatial variability and timescale structure in population dynamics are common features. We tested for spatial and timescale structure in the patterns of synchrony of freshwater plankton in Kentucky Lake, U.S.A. We also evaluated whether different mechanisms may drive synchrony and its spatial structure on different timescales. Using wavelet techniques and matrix regression, we analyzed phytoplankton biomass and abundances of seven zooplankton taxa at 16 locations sampled from 1990 to 2015. We found that zooplankton abundances and phytoplankton biomass exhibited synchrony at multiple timescales. Timescale structure in the potential mechanisms of synchrony was revealed primarily through networks of relationships among zooplankton taxa, which differed by timescale. We found substantial interspecific variability in geographic structures of synchrony and their causes: all mechanisms we considered strongly explained geographic structure in synchrony for at least one species, while Euclidean distance between sampling locations was generally less well supported than more mechanistic explanations. Geographic structure in synchrony and its underlying mechanisms also depended on timescale for a minority of the taxa tested. Overall, our results show substantial and complex but interpretable variation in structures of synchrony across three variables: space, timescale, and taxon. It seems likely these aspects of synchrony are important general features of freshwater systems. [ABSTRACT FROM AUTHOR]

ABSTRACT: Conservation and management activities are always constrained by finite resources. Therefore, decisions such as which sites to protect, whether existing habitat should be restored or whether new habitat should be created, and where on the landscape management efforts should be focused present difficult challenges. An overarching goal of many conservation or management plans is the long‐term persistence of populations, which is often dependent on functional connectivity and the maintenance of metapopulation dynamics. Graph theory and network approaches are frequently used tools for modeling functional connections between populations and between habitats. Less often, graph models are used to guide conservation or management decisions. We used spatial networks derived for an amphibian population to determine optimal locations to create new habitat, prioritize existing habitat for restoration, and determine the habitat most critical for maintaining connectivity within the existing metapopulation within Fort Leonard Wood, Missouri, USA, 2012–2014. Using data collected at 206 breeding ponds over 3 years, we constructed demographic networks representing the functional connectivity between ponds by dispersing ringed salamanders (Ambystoma annulatum). We incorporated uncertainty in key model parameters through Monte Carlo simulation, and used a graph‐theoretical parameterization of the metapopulation mean lifetime model to assess how changes in network structure affect persistence of the network. We conducted addition and removal experiments within our Monte Carlo simulations to rank and prioritize locations for pond creation, ponds for restoration, and ponds for preservation. Salamanders bred in 106 ponds in ≥1 year; 2.4% of ponds functioned predominantly as sources and 51% of occupied ponds functioned predominantly as sinks. The importance of a pond to the network was correlated with the number of emigrants dispersing from a pond, the number of ponds reached by these dispersers, and the frequency a pond functioned as a source. Creating new ponds at optimal locations increased the persistence of the network an average of 15.4% compared to randomly selected locations, whereas selective restoration of currently unoccupied ponds resulted in an average increase of 31.4% in network persistence, as compared to randomly selected unoccupied ponds. Through Monte Carlo simulation, we constructed biologically informed demographic connectivity networks for use as a spatial conservation or management planning tool. Although our approach was implemented with an amphibian and a breeding pond network, it is generalizable to any species occupying discrete habitat patches. © 2017 The Wildlife Society. [ABSTRACT FROM AUTHOR]

Spatial synchrony in population dynamics is a ubiquitous ecological phenomenon that can result from predator–prey interactions, synchronized environmental variation (Moran effects), or dispersal. Of these, dispersal historically has been the least well studied in natural systems, partly because of the difficulty in quantifying dispersal in situ. We hypothesized that dispersal routes of plankton were based on the major and consistent water current movements in Kentucky Lake, a large reservoir in western Kentucky, USA. Then, using 26‐year time series collected at 16 locations, we used matrix regression techniques to test whether spatial heterogeneity in strengths of hypothesized dispersal predicted spatial patterns of synchrony of phytoplankton and zooplankton, thereby testing for evidence of dispersal as a possible mechanism of synchrony in this system. Nearly all taxa showed significant spatial synchrony that did not decline with increasing linear distance between locations. All taxa also showed substantial geographic structure in synchrony that was not explained by linear distance. Matrix regression revealed that our hypothesized matrix of dispersal pathways, which differed substantially from linear distance, was a significant predictor of spatial variability in synchrony in phytoplankton biomass, and Bosmina longirostris and Daphnia lumholtzi densities. Thus dispersal was a likely mechanism of synchrony for these taxa. Our hypothesized dispersal matrix was a significant predictor of spatial patterns of synchrony for these taxa even after accounting for numerous alternative possible mechanisms, including possible Moran effects through any of ten physical/abiotic constraints. Our findings indicate that statistically comparing hypothesized or measured dispersal pathway information to synchrony data via matrix regressions can provide valuable evidence for the importance of dispersal as a mechanism of spatial synchrony. [ABSTRACT FROM AUTHOR]

Both abiotic and biotic factors influence population and community structure. However, the simultaneous assessment of the relative importance of both types of factors is rarely performed for multiple traits of a population, such as body size and abundance. Comparisons among different demographic rates are necessary for teasing apart the importance of species interactions and/or environmental conditions on both population and community structure. We tested whether biotic (e.g., larval competition) or abiotic factors influenced larval salamander density and body size in natural populations of two known salamander competitors, Ambystoma talpoideum and A. maculatum. Over six years, we surveyed 33 ponds where these species co-occur in western Kentucky, USA. We found that larval densities between species were positively correlated, and that habitat features had contrasting, species-specific effects. Larval sizes for each species showed negative intra- and interspecific relationships with larval densities of each species, but larval A. maculatum generally exerted the stronger relative interspecific effect. Overall, our study highlights that different characteristics of a population (i.e., body size or abundance) may be differentially affected by abiotic and biotic factors, even for ecologically similar, sympatric species. Understanding which traits are regulated by each component will advance our knowledge on how populations and communities are structured. [ABSTRACT FROM AUTHOR]

Ecological and evolutionary processes commonly result in morphological variation among larval amphibians. Variation in head shape plays a critical role in both food capture and predation risk in gape-limited salamanders, yet in situ studies of head shape variability are rare outside of cannibal morph assessments. We examined allometry differences in larval head width (HW) and snout-vent length (SVL) among three sympatric species of ambystomatid salamanders from 166 ponds in Missouri, USA: Ringed Salamander ( Ambystoma annulatum), Marbled Salamander ( A. opacum), and Spotted Salamander ( A. maculatum). We also tested whether several abiotic and biotic factors would predict HW after accounting for SVL. We found that larval HW and SVL were strongly correlated for all species but that the strength of this relationship varied among species. For early-stage larvae, Marbled Salamanders showed isometric scaling relationships, whereas both Spotted Salamanders and Ringed Salamanders were allometric. For late-stage larvae, all three species showed allometric patterns. At a small SVL, HW of small Ringed Salamanders was greater than the other species. As larvae increased in SVL, Marbled Salamander HW increased most rapidly and eventually exceeded both Ringed Salamanders and Spotted Salamanders of a similar size. We also found that both abiotic and biotic factors predicted significant differences in HW corrected for SVL among species, including predator density, competitor density, and hydroperiod. Overall, variability in scaling relationships may provide ecological advantages to each species at different points in ontogeny and different biotic and abiotic factors may induce such variation in asymmetric ways among species. [ABSTRACT FROM AUTHOR]

Comparisons of spatial and temporal variation in demographic rates are crucial to understanding population dynamics. Yet, even well-studied species are often lacking in comparisons of such variability in demographic data, making these contrasts imperative to conduct in population ecology research. We conducted a long-term monitoring study of Spotted Salamanders ( Ambystoma maculatum) at five ponds in Missouri, USA. We sampled populations using drift fences, and monitored breeding immigration dates, adult population sizes, sex ratio, juvenile recruitment, metamorph sizes, and metamorph emigration dates. Generally, we found that our study populations exhibited characteristics similar to other populations across their distribution. We also found spatial and temporal variation among populations in nearly all demographic parameters, however, indicating that multipopulation and multiyear studies will likely improve our inferential abilities in understanding population dynamics. We observed an overall positive relationship between metamorph size and date of metamorphosis, but this pattern was not consistent across ponds or years, indicating that different environmental pressures might influence selection on these traits. Finally, we identified rainfall amounts and frequency as the primary factors that influenced adult and metamorph movement patterns to and from ponds. Overall, the spatial and temporal variation in demographic data we provided can be useful for population modeling or conservation planning, in addition to furthering our understanding of population ecology of Spotted Salamanders. [ABSTRACT FROM AUTHOR]

Predator diversity and habitat complexity frequently influence species interactions at lower trophic levels, yet their joint investigation has been performed infrequently despite the demonstrated importance of each individual factor., We investigated how different top predators and varying habitat complexity influence the function of an intraguild predation module consisting of two larval salamanders, intraguild predator Ambystoma annulatum and intraguild prey A. maculatum., We manipulated predator food webs and habitat complexity in outdoor mesocosms., Top predators significantly influenced body condition and survival of A. annulatum, but habitat complexity had minimal effects on either response., A three-way interaction among the covariates top predator identity, habitat complexity and A. annulatum survival influenced body condition and survival of A. maculatum via a density-mediated indirect effect. Different top predator combinations had variable effects in different habitat complexity treatments on intraguild predator ( A. annulatum) survival that subsequently influenced intraguild prey ( A. maculatum) body condition and survival., Future work should consider how different top predators influence other food web components, which should vary due to predator attributes and the physical environments in which they co-occur. [ABSTRACT FROM AUTHOR]

In recent studies, habitat traits have emerged as stronger predictors of species occupancy, abundance, richness and diversity than competition. However, in many cases, it remains unclear whether habitat also mediates processes more subtle than competitive exclusion, such as growth, or whether intra- and interspecific interactions among individuals of different species may be better predictors of size., To test whether habitat traits are a stronger predictor of abundance and body size than intra- and interspecific interactions, we measured the density and body size of three species of larval salamanders in 192 ponds across a landscape., We found that the density of larvae was best predicted by models that included habitat features, while models incorporating interactions among individuals of different species best explained the body size of larvae. Additionally, we found a positive relationship between focal species density and congener density, while focal species body size was negatively related to congener density., We posit that salamander larvae may not experience competitive exclusion and thus reduced densities, but instead compensate for increased competition behaviourally (e.g. reduced foraging), resulting in decreased growth. The discrepancy between larval density and body size, a strong predictor of fitness in this system, also highlights a potential shortcoming in using density or abundance as a metric of habitat quality or population health. [ABSTRACT FROM AUTHOR]

A fundamental goal of evolutionary ecology is to understand how asymmetric competition influences phenotype expression, yet few studies have quantified the relative effects of intra- and interspecific competition on phenotypes. We examined the effects of intra- and interspecific larval competition on both discrete and continuous phenotype expression of the facultatively paedomorphic mole salamander (Ambystoma talpoideum). We manipulated the density and frequency of larval A. talpoideum and a common competitor, the spotted salamander (A. maculatum), in experimental mesocosms within a response surface design. The production of discrete ontogenetic morphs (metamorphs, paedomorphs, and overwintering larvae) was affected more by intraspecific than interspecific competition, but the effect varied between morphs. Paedomorph and metamorph production were more strongly affected by intraspecific than interspecific competition, while the production of overwintering larvae was affected by each type of competition approximately equally. Paedomorphs largely occurred only at low conspecific densities, overwintering larvae primarily occurred at high overall densities, and metamorph production peaked at intermediate densities of con- and heterospecifics. Density-dependent intraspecific competition had stronger effects on body size and growth rates than interspecific competition for both metamorphs and overwintering larvae, whereas interspecific competition more strongly affected paedomorph size. Overall, these results support the hypothesis that intraspecific competition influences both continuous and discrete phenotypic expression more strongly than interspecific competition. Fluctuating strengths of each type of competition can affect variation in life history strategies by influencing discrete ontogenetic pathways via individual body sizes, leading to differential morph production and fitness within and among morphs. [ABSTRACT FROM AUTHOR]

Assessment of the relative strengths of intra- and interspecific competition has increased in recent years and is critical to understanding the importance of competition. Yet, whether intra- and interspecific competition can have non-additive effects has rarely been tested. The resulting fitness consequences of such non-additive interactions are important to provide the context necessary to advance our understanding of competition theory., We compared the strength of additive and non-additive intra- and interspecific competition by manipulating densities of a pair of larval salamanders ( Ambystoma talpoideum and A. maculatum) in experimental mesocosms within a response surface design., Intraspecific density had the strongest effect on the strength of competition for both species, and few observed comparisons indicated interspecific competition was an important factor in predicting body size, growth or larval period length of either species., Non-additive effects of intra- and interspecific competition influenced some response variables, including size and mass at metamorphosis in A. maculatum, but at a reduced strength compared to intraspecific effects alone., Intraspecific competition was thus the dominant biotic interaction, but non-additive effects also impact the outcome of competition in these species, validating the importance of testing for and incorporating non-additive density effects into competition models. [ABSTRACT FROM AUTHOR]

Predation is a key determinant of pond community structure, yet not all predators are equally effective and not all life stages of potential prey are similarly susceptible. Understanding the effects of native and introduced species is essential to informing management strategies, especially for endemic and species of conservation concern. We examined the effects of five common predators (three native: Central Newts [ Notophthalmus viridescens louisianensis], aeshnid dragonfly naiads [Aeshnidae], and Southern Leopard Frog tadpoles [ Lithobates sphenocephalus]; and two introduced: Fathead Minnows [ Pimephales promelas] and Mosquitofish [ Gambusia affinis]) on survival of eggs and recently hatched larvae of Ringed Salamanders ( Ambystoma annulatum). We also examined the effect of supplemental food or cover availability on survival at each stage. Predators primarily showed a binary response to eggs, consuming all or none of them. Supplemental food did not influence whether eggs or larvae were consumed. Larvae were consumed by all predator species although the effect varied. The presence of cover did not reduce the impacts of the other predators on larval survival. Overall, the two introduced fish species had a greater impact on survival of the early stages of Ringed Salamanders than did the native predators. Further inquiries into the susceptibility of different life stages and survival will improve conservation strategies for rare and endemic species such as Ringed Salamanders. [ABSTRACT FROM AUTHOR]

Predation risk is an important contributor to community structure that varies in response to abiotic and biotic factors. In aquatic habitats, predation risk is often linked to hydroperiod as the latter directly influences predator identity within these ecosystems. For pond-breeding salamanders, intraguild predation (IGP) and cannibalism are prevalent interactions in larval communities, but the frequency of each type of agonistic interaction, as well as changes in their pervasiveness along hydroperiod gradients are not well understood. Size-structured populations of aquatic life stages (paedomorphic adults and overwintered larvae) of mole salamanders (Ambystoma talpoideum) have the potential to be dominant IG predators and cannibals in permanent ponds because of large size advantages over successive cohorts, but the species exists as only a single larval cohort in temporary ponds with reduced predatory abilities on guild members. Thus, both the potential for and intensity of predation by this species is linked to hydroperiod; yet, the predatory abilities of aquatic life stages of mole salamanders have not been evaluated. This study examined the extent to which larger size classes (paedomorphs and overwintered larvae) of mole salamanders preyed upon conspecifics and a congeneric competitor, the spotted salamander (Ambystoma maculatum). Predation trials occurred in indoor microcosms and were executed under two habitat treatments that included pseudo-natural conditions containing alternate prey and refugia, as well as simplified environments (no alternative food or cover). Embryos or hatchlings of mole and spotted salamanders were exposed either separately or concurrently to paedomorphic and overwintered larval mole salamanders in each habitat treatment. Additionally, overwintered larvae were offered as prey to paedomorphic adults. No significant differences in mortality were observed between habitat treatments (complex versus simple) for either embryo or hatchling predation experiments. Mortality of mole and spotted embryos did not differ when they were offered separately or together, but paedomorphs caused significantly higher mortality among mole embryos compared to spotted embryos. Hatchlings of both species were heavily preyed upon (nearly 100% in all trials), but overwintered larvae exhibited 100% survival with paedomorph predators, indicating size-thresholds of predation risk that were not species specific. Paedomorphs and overwintered larvae therefore are most likely generalist predators that feed equally and effectively on hatchlings of co-occurring species, but are more likely to consume egg masses that do not incur significant handling costs. When present, paedomorphs or overwintered larvae have the potential to alter population dynamics of both guild members and conspecifics by being dominant predators on early life stages. As the prevalence of overwintering and paedomorphosis varies along hydroperiod gradients, predation risk from this species is likely to occur discontinuously and thereby may be an important, yet variable, structuring force. [ABSTRACT FROM AUTHOR]

The article describes extreme cases of larval period length in Ambystoma annulatum (ringed salamander), a pond-breeding salamander that occurs in the Ozark and Ouachita Mountains of Missouri, Oklahoma, and Arkansas. It discusses two cattle tank mesocosm studies that were conducted at the university of Missouri in 2011-2013. Topics include the monitoring made on both individuals which were consolidated into one tank and most likely explanation for the atypical development of the salamander.

Variability in phenological shifts (seasonal changes in biological events) has become more common with climate change. As phenological variability increases due to climatic factors, species interactions within diverse communities can be affected. Shifts in hatching phenology can lead to body size variability that can alter species interactions, especially within and across trophic levels in complex food webs. To understand the effects of hatching phenology and food web complexity on prey communities, we conducted an experiment with ectotherms from ponds by manipulating hatching synchrony of a prey species across three dates and food web complexity. We hypothesized that predation on prey would be highest in the lowest synchrony treatment due to predator satiation effects in high synchrony additions. Food webs with top predators present had the lowest survival rates for prey compared to other food webs. Prey size at metamorphosis was also highest in the top predator food webs, suggesting a thinning effect. Hatching synchrony treatments did not have a significant impact on prey survival or size at metamorphosis except in treatments where intermediate and top predators were absent. Overall, our results show that top-down effects of predators may be enough to suppress the influence of phenological shifts in prey. [ABSTRACT FROM AUTHOR]

A tenet of ecology is that temporal variability in ecological structure and processes tends to decrease with increasing spatial scales (from locales to regions) and levels of biological organization (from populations to communities). However, patterns in temporal variability across trophic levels and the mechanisms that produce them remain poorly understood. Here we analyzed the abundance time series of spatially structured communities (i.e., metacommunities) spanning basal resources to top predators from 355 freshwater sites across three continents. Specifically, we used a hierarchical partitioning method to disentangle the propagation of temporal variability in abundance across spatial scales and trophic levels. We then used structural equation modeling to determine if the strength and direction of relationships between temporal variability, synchrony, biodiversity, and environmental and spatial settings depended on trophic level and spatial scale. We found that temporal variability in abundance decreased from producers to tertiary consumers but did so mainly at the local scale. Species population synchrony within sites increased with trophic level, whereas synchrony among communities decreased. At the local scale, temporal variability in precipitation and species diversity were associated with population variability (linear partial coefficient, β = 0.23) and population synchrony (β = −0.39) similarly across trophic levels, respectively. At the regional scale, community synchrony was not related to climatic or spatial predictors, but the strength of relationships between metacommunity variability and community synchrony decreased systematically from top predators (β = 0.73) to secondary consumers (β = 0.54), to primary consumers (β = 0.30) to producers (β = 0). Our results suggest that mobile predators may often stabilize metacommunities by buffering variability that originates at the base of food webs. This finding illustrates that the trophic structure of metacommunities, which integrates variation in organismal body size and its correlates, should be considered when investigating ecological stability in natural systems. More broadly, our work advances the notion that temporal stability is an emergent property of ecosystems that may be threatened in complex ways by biodiversity loss and habitat fragmentation. [ABSTRACT FROM AUTHOR]

Spatial synchrony, defined as correlated temporal fluctuations among populations, is a fundamental feature of population dynamics, but many aspects of synchrony remain poorly understood. Few studies have examined detailed geographical patterns of synchrony; instead most focus on how synchrony declines with increasing linear distance between locations, making the simplifying assumption that distance decay is isotropic. By synthesising and extending prior work, we show how geography of synchrony, a term which we use to refer to detailed spatial variation in patterns of synchrony, can be leveraged to understand ecological processes including identification of drivers of synchrony, a long-standing challenge. We focus on three main objectives: (1) showing conceptually and theoretically four mechanisms that can generate geographies of synchrony; (2) documenting complex and pronounced geographies of synchrony in two important study systems; and (3) demonstrating a variety of methods capable of revealing the geography of synchrony and, through it, underlying organism ecology. For example, we introduce a new type of network, the synchrony network, the structure of which provides ecological insight. By documenting the importance of geographies of synchrony, advancing conceptual frameworks, and demonstrating powerful methods, we aim to help elevate the geography of synchrony into a mainstream area of study and application. [ABSTRACT FROM AUTHOR]

This study was to examine the influences of manual acupuncture (MA) and electrical heat corresponding to reinforcing methods on nitric oxide (NO) release over the skin regions in humans. A device with collecting solution was taped to the skin surface along pericardium (PC) or lung (LU) meridian. Acupuncture needles were gently inserted into PC 4 with reinforcing stimulation (low force/rate) for 20 minutes in the MA group. LU11 on the finger was heated (43-44°C) by electrical heat for 20 minutes. Biocapture was consecutively conducted for two 20-minute intervals during and after each treatment. Total nitrite and nitrate (NOx-) in the collecting samples were quantified using chemiluminescence in blinded fashion. Baseline NOx- levels are higher and tended to be higher over PC and LU acupoints during the 1st biocapture. NOx- levels over PC regions were consistently increased by MA during both intervals. NOx- concentrations over LU acupoints were increased and tended to be increased by electrical heat in the 1st and 2nd biocapture. The results suggest that reinforcing MA and electrical heat induce NO released from the local skin regions with higher levels at acupoints, which improve local circulation and contribute to the beneficial effects of the therapies. [ABSTRACT FROM AUTHOR]

We present data on amphibian density, species richness, and diversity from a 7140-ha area consisting of 200 ponds in the Midwestern U.S. that represents most of the possible lentic aquatic breeding habitats common in this region. Our study includes all possible breeding sites with natural and anthropogenic disturbance processes that can be missing from studies where sampling intensity is low, sample area is small, or partial disturbance gradients are sampled. We tested whether pond area was a significant predictor of density, species richness, and diversity of amphibians and if values peaked at intermediate pond areas. We found that in all cases a quadratic model fit our data significantly better than a linear model. Because small ponds have a high probability of pond drying and large ponds have a high probability of fish colonization and accumulation of invertebrate predators, drying and predation may be two mechanisms driving the peak of density and diversity towards intermediate values of pond size. We also found that not all intermediate sized ponds produced many larvae; in fact, some had low amphibian density, richness, and diversity. Further analyses of the subset of ponds represented in the peak of the area distribution showed that fish, hydroperiod, invertebrate density, and canopy are additional factors that drive density, richness and diversity of ponds up or down, when extremely small or large ponds are eliminated. Our results indicate that fishless ponds at intermediate sizes are more diverse, produce more larvae, and have greater potential to recruit juveniles into adult populations of most species sampled. Further, hylid and chorus frogs are found predictably more often in ephemeral ponds whereas bullfrogs, green frogs, and cricket frogs are found most often in permanent ponds with fish. Our data increase understanding of what factors structure and maintain amphibian diversity across large landscapes. [ABSTRACT FROM AUTHOR]

Outcomes of predator–prey interactions depend on biotic and abiotic factors. Habitat complexity, for example, mediates predator functional response type and parameters (attack rate and handling time). However, the relationship between habitat complexity and functional response varies across ecosystems. We assessed interactions between the giant water bug, Belostoma sp., and its prey, rams-horn snails, Helisoma trivolvis, across four prey densities (N = 2, 4, 8, 16 snails) and three habitat complexity levels (No-complexity, Low-complexity, High-complexity) to understand how complexity affected the functional response. We also tested effects of predator and prey body size on number of prey killed. Belostoma exhibited a Type III functional response in all habitat complexity treatments. Attack rate tended to increase with increasing complexity. Handling time was different among treatments, being lowest in the No-complexity treatment and highest in the Low-complexity treatment. Belostoma body size was positively related, while Helisoma body size was inversely related, to the number of Helisoma killed. We show habitat complexity does not affect the shape of predator functional response but impacts response parameters in the Belostoma–Helisoma system. We reaffirm that attack rate, handling time, and mortality outcomes for prey within predator–prey interactions are affected by abiotic factors through habitat complexity. [ABSTRACT FROM AUTHOR]

Fluctuations in population abundances are often correlated through time across multiple locations, a phenomenon known as spatial synchrony. Spatial synchrony can exhibit complex spatial structures, termed 'geographies of synchrony', that can reveal mechanisms underlying population fluctuations. However, most studies have focused on spatial extents of 10s to 100s of kilometres, making it unclear how synchrony concepts and approaches should apply to dynamics at finer spatial scales.We used network analyses, multiple regression on similarity matrices, and wavelet coherence analyses to examine micro‐scale synchrony and geographies of synchrony, over distances up to 30 m, in a serpentine grassland plant community.We found that species' populations exhibited a geography of synchrony even over such short distances. Often, well‐synchronized populations were geographically separate, a spatial structure that was shaped mainly by gopher disturbance and dispersal limitation, and to a lesser extent by relationships with other plant species. Precipitation was a significant driver of site‐ and community‐wide temporal dynamics. Gopher disturbance appeared to drive synchrony on 2‐ to 6‐year timescales, and we detected coherent fluctuations among pairs of focal plant taxa.Synthesis. Micro‐geographies of synchrony are an intriguing phenomenon that may also help us better understand community dynamics. Additionally, the related geographies of synchrony and coherent temporal dynamics among some species pairs indicate that incorporating interspecific interactions can improve understanding of population spatial synchrony. [ABSTRACT FROM AUTHOR]

Understanding metapopulation dynamics requires knowledge about local population dynamics and movement in both space and time. Most genetic metapopulation studies use one or two study species across the same landscape to infer population dynamics; however, using multiple co-occurring species allows for testing of hypotheses related to different life history strategies. We used genetic data to study dispersal, as measured by gene flow, in three ambystomatid salamanders ( Ambystoma annulatum, A. maculatum, and A. opacum) and the Central Newt ( Notophthalmus viridescens louisianensis) on the same landscape in Missouri, USA. While all four salamander species are forest dependent organisms that require fishless ponds to reproduce, they differ in breeding phenology and spatial distribution on the landscape. We use these differences in life history and distribution to address the following questions: (1) Are there species-level differences in the observed patterns of genetic diversity and genetic structure? and (2) Is dispersal influenced by landscape resistance? We detected two genetic clusters in A. annulatum and A. opacum on our landscape; both species breed in the fall and larvae overwinter in ponds. In contrast, no structure was evident in A. maculatum and N. v. louisianensis, species that breed during the spring. Tests for isolation by distance were significant for the three ambystomatids but not for N. v. louisianensis. Landscape resistance also contributed to genetic differentiation for all four species. Our results suggest species-level differences in dispersal ability and breeding phenology are driving observed patterns of genetic differentiation. From an evolutionary standpoint, the observed differences in dispersal distances and genetic structure between fall breeding and spring breeding species may be a result of the trade-off between larval period length and size at metamorphosis which in turn may influence the long-term viability of the metapopulation. Thus, it is important to consider life history differences among closely related and ecologically similar species when making management decisions. [ABSTRACT FROM AUTHOR]

We examined pond-breeding amphibian community composition at 210 ponds in Missouri between 2002 and 2012 using drift fence, dipnet, and funnel trap data. We encountered a total of 20 pond-breeding amphibian species in the combined surveys. We also examined whether the presence of American Bullfrogs, Lithobates catesbeianus, and fish influenced these patterns of diversity. Our results indicate the presence of American Bullfrogs, fish, and their interaction influenced the community composition of amphibians at these sites but in opposite patterns. American Bullfrogs often had a positive relationship with the total number of species, total caudate species, and total anuran species, whereas fish presence was negatively associated overall with species diversity, and the presence of both American Bullfrogs and fish was negatively associated with anuran species diversity. It is important to have baseline community species composition data from wide geographical ranges so spatiotemporal changes in community structure can be noted and assessed. [ABSTRACT FROM AUTHOR]