Search

Growth–survival tradeoffs may be a generalizable mechanism influencing trajectories of prey evolution. Here, we investigate evolutionary contributions to growth and survival in western mosquitofish (Gambusia affinis) from 10 populations from high- and low-predation ancestral environments. We assess (i) the degree to which evolutionary components of growth and survival are consistent or inconsistent across populations within ancestral predation environments, and (ii) whether growth and survival trade off at the population level. We measure growth and survival on groups of common-reared mosquitofish in pond mesocosms. We find that evolution of growth is consistent, with fish from low-predation ancestral environments showing higher growth, while the evolution of survival is inconsistent, with significant population-level divergence unrelated to ancestral predation environment. Such inconsistency prevents a growth–survival tradeoff across populations. Thus, the generalizability of contemporary evolution probably depends on local context of evolutionary tradeoffs, and a continued focus on singular selective agents (e.g. predators) without such local context will impede insights into generalizable evolutionary patterns.

Humans are dominant global drivers of ecological and evolutionary change, rearranging ecosystems and natural selection. In the present article, we show increasing evidence that human activity also plays a disproportionate role in shaping the eco-evolutionary potential of systems—the likelihood of ecological change generating evolutionary change and vice versa. We suggest that the net outcome of human influences on trait change, ecology, and the feedback loops that link them will often (but not always) be to increase eco-evolutionary potential, with important consequences for stability and resilience of populations, communities, and ecosystems. We also integrate existing ecological and evolutionary metrics to predict and manage the eco-evolutionary dynamics of human-affected systems. To support this framework, we use a simple eco–evo feedback model to show that factors affecting eco-evolutionary potential are major determinants of eco-evolutionary dynamics. Our framework suggests that proper management of anthropogenic effects requires a science of human effects on eco-evolutionary potential.

Trophic cascades have become a dominant paradigm in ecology, yet considerable debate remains about the relative strength of density- (consumptive) and trait-mediated (non-consumptive) effects in trophic cascades. This debate may, in part, be resolved by considering prey experience, which shapes prey traits (through genetic and plastic change) and influences prey survival (and therefore density). Here, we investigate the cascading role of prey experience through the addition of mosquitofish (Gambusia affinis) from predator-experienced or predator-naive sources to mesocosms containing piscivorous largemouth bass (Micropterus salmoides), zooplankton, and phytoplankton. These two sources were positioned along a competition-defense tradeoff. Results show that predator-naive mosquitofish suffered higher depredation rates, which drove a density-mediated cascade, whereas predator-experienced mosquitofish exhibited higher survival but fed less, which drove a trait-mediated cascade. Both cascades were similar in strength, leading to indistinguishable top-down effects on lower trophic levels. Therefore, the accumulation of prey experience with predators can cryptically shift cascade mechanisms from density- to trait-mediated.

Designing eDNA tools to detect and quantify rare species includes inherent assumptions about the spatial distribution of the organism, spatial nature of eDNA dynamics, and the real‐world performance of alternate assays under field conditions. Here, we use cage experiments with small numbers of Atlantic salmon (Salmo salar), to reveal that eDNA detection rates and eDNA quantities follow a predictable, but nonlinear relationship with distance from a point source. In contrast to the common assumption of consistent eDNA degradation moving away from a source, eDNA detections and concentrations increased up to roughly 70 m downstream before declining steadily. We apply our eDNA distance functions to selection of stream sampling intervals for detecting fish without known locations and find that even a single juvenile salmon can be reliably detected with intervals up to 400 m spacing. Finally, we show that two different qPCR eDNA assays provide very different detection probabilities in nature despite similar efficiency in laboratory testing, demonstrating the importance of experimentally assessing assay efficiencies in the wild as well as the capacity for multiplexing as a strategy to ensure high detection efficiency when monitoring rare species.

Phenotypic trait differences among populations can shape ecological outcomes for communities and ecosystems. However, few studies have mechanistically linked heritable and plastic components of trait variation to generalizable processes of ecology, such as trophic cascades. Here, we assess morphological and behavioral trait variation in nine populations of common garden-reared western mosquitofish (

Growth–survival tradeoffs may be a generalizable mechanism influencing trajectories of prey evolution. Here, we investigate evolutionary contributions to growth and survival in western mosquitofish ( Gambusia affinis ) from 10 populations from high- and low-predation ancestral environments. We assess (i) the degree to which evolutionary components of growth and survival are consistent or inconsistent across populations within ancestral predation environments, and (ii) whether growth and survival trade off at the population level. We measure growth and survival on groups of common-reared mosquitofish in pond mesocosms. We find that evolution of growth is consistent, with fish from low-predation ancestral environments showing higher growth, while the evolution of survival is inconsistent, with significant population-level divergence unrelated to ancestral predation environment. Such inconsistency prevents a growth–survival tradeoff across populations. Thus, the generalizability of contemporary evolution probably depends on local context of evolutionary tradeoffs, and a continued focus on singular selective agents (e.g. predators) without such local context will impede insights into generalizable evolutionary patterns.

Wild populations must continuously respond to environmental changes or they risk extinction. Those responses can be measured as phenotypic rates of change, which can allow us to predict contemporary adaptive responses, some of which are evolutionary. About two decades ago, a database of phenotypic rates of change in wild populations was compiled. Since then, researchers have used (and expanded) this database to examine phenotypic responses to specific types of human disturbance. Here, we update the database by adding 5675 new estimates of phenotypic change. Using this newer version of the data base, now containing 7338 estimates of phenotypic change, we revisit the conclusions of four published articles. We then synthesize the expanded database to compare rates of change across different types of human disturbance. Analyses of this expanded database suggest that: (i) a small absolute difference in rates of change exists between human disturbed and natural populations, (ii) harvesting by humans results in higher rates of change than other types of disturbance, (iii) introduced populations have increased rates of change, and (iv) body size does not increase through time. Thus, findings from earlier analyses have largely held-up in analyses of our new database that encompass a much larger breadth of species, traits, and human disturbances. Lastly, we use new analyses to explore how various types of human disturbances affect rates of phenotypic change, and we call for this database to serve as a steppingstone for further analyses to understand patterns of contemporary phenotypic change.

The COVID-19 pandemic and its related human activity shutdowns provide unique opportunities for biodiversity monitoring through what has been termed the ?anthropause? or the ?great human confinement experiment.? The pandemic caused immense disruption to human activity in the northeastern United States in the spring of 2020, with notable reductions in traffic levels. These shutdowns coincided with the seasonal migration of adult amphibians, which are typically subject to intense vehicle-impact mortality. Using data collected as part of an annual community science monitoring program in Maine from 2018 to 2021, we examined how amphibian mortality probabilities responded to reductions in traffic during the pandemic. While we detected a 50% decline for all amphibians, this was driven entirely by reductions in frog mortality. Wildlife collision data from the Maine Department of Transportation on other wildlife species support our finding of drastic declines in wildlife road mortality in spring 2020 when compared with immediately previous and subsequent years. Additionally, we find that frogs suffer significantly higher road mortality than salamanders, particularly when conditions are warmer and wetter.

Wild populations must continuously adapt to environmental changes or they risk extinction. Such adaptations can be measured as phenotypic rates of change and can allow us to predict patterns of contemporary evolutionary change. About two decades ago, a dataset of phenotypic rates of change in wild populations was compiled. Since then, researchers have used (and expanded) this dataset to look at microevolutionary processes in relation to specific types of human disturbances. Here, we have updated the dataset adding 5675 estimates of phenotypic changes and used it to revisit established patterns of contemporary evolutionary change. Using this newer version, containing 7338 estimates of phenotypic changes, we revisit the conclusions of four published articles. We then synthesize the expanded dataset to compare rates of change across different types of human disturbance. Analyses of this expanded dataset suggests that: I. a small absolute difference in rates of change exists between human disturbed and natural populations, II. harvesting by humans results in larger rates of change than other types of disturbances, III. introduced populations have increased rates of change, and IV. body size does not increase through time. Overall, findings from earlier analyses have largely held-up in analyses of our new dataset that encompass a much larger breadth of species, traits, and human disturbances. Lastly, we found that types of human disturbances affect rates of phenotypic change, and we call for this database to serve as a steppingstone for further analyses to understand patterns of contemporary evolution.

While many species distributions are shifting poleward or up in elevation in response to a changing climate, others are shifting their habitats along localized gradients in environmental conditions as abiotic conditions become more stressful. Whether species are moving across regional or local environmental gradients in response to climate change, range-shifting species become embedded in established communities of competitors and predators. The consequences of these shifts for both resident and shifting species are often unknown, as it can be difficult to isolate the effects of multiple species interactions. Using a model system of insects in high-elevation ponds in the Rocky Mountains of Colorado, we sought to disentangle the effects of predation and intraguild interactions on the survival and development of a semi-permanent pond resident caddisfly Limnephilus externus and the habitat-shifting caddis Asynarchus nigriculus that is being forced into semi-permanent ponds as temporary ponds dry too quickly to complete development. We conducted a manipulative in-situ pond cage experiment in which L. externus and A. nigriculus caddisfly larvae in single-species treatments and together were exposed to the presence/absence of predatory Dytiscus diving beetle larvae. This approach allowed us to isolate the effects of intraguild interactions and predation on the survival and development of both the resident and habitat-shifting species. We found that intraguild interactions had strong negative effects on the resident and habitat-shifting species. Intraguild interactions reduced the survival of the resident L. externus and increased the variation in survival of the shifting A. nigriculus. However, Dytiscus predators reduced these negative effects, stabilizing the community by increasing L. externus survival and reducing variation in A. nigriculus survival. We also found that intraguild interactions reduced L. externus biomass but resulted in increased A. nigriculus development. A. nigriculus development was also increased by predation. Our results show that strong intraguild interactions between resident and shifting species are likely to have negative consequences for both species. However, the presence of predators reduces these negative consequences of the habitat shift on both the resident and the shifting.

It has been suggested that the human species may be undergoing an evolutionary transition in individuality (ETI). But there is disagreement about how to apply the ETI framework to our species, and whether culture is implicated as either cause or consequence. Long-term gene–culture coevolution (GCC) is also poorly understood. Some have argued that culture steers human evolution, while others proposed that genes hold culture on a leash. We review the literature and evidence on long-term GCC in humans and find a set of common themes. First, culture appears to hold greater adaptive potential than genetic inheritance and is probably driving human evolution. The evolutionary impact of culture occurs mainly through culturally organized groups, which have come to dominate human affairs in recent millennia. Second, the role of culture appears to be growing, increasingly bypassing genetic evolution and weakening genetic adaptive potential. Taken together, these findings suggest that human long-term GCC is characterized by an evolutionary transition in inheritance (from genes to culture) which entails a transition in individuality (from genetic individual to cultural group). Thus, research on GCC should focus on the possibility of an ongoing transition in the human inheritance system.

Many invasive species may be constrained in their ability to invade high latitude or elevation habitats due to limits of cold tolerance. However, isolated populations at the edge of these species' geographic ranges may face a combination of strong selection and lack of maladaptive gene flow that allows them to adapt to the cold and invade further. Here we show that an isolated population of Gambusia affinis (on Cape Cod, MA, USA), one of the most invasive fish in the world, can survive temperatures lower than any reported tolerances for other populations, with large, long-lived females showing more tolerance than males. Indeed, male acute cold tolerance appears insufficient, suggesting the population may persist through winters mainly via the ability of mated females to delay offspring production until spring. This combination of female cold tolerance and life history may open the door for further expansion of this invasive species into high latitude freshwater habitats.

Evolution in harvested species has become a major concern for its potential to affect yield, sustainability, and recovery. However, the current singular focus on harvest-mediated evolution in target species overlooks the potential for evolution in non-target members of communities. Here we use an individual-based model to explore the scope and pattern of harvest-mediated evolution at non-target trophic levels and its potential feedbacks on abundance and yield of the harvested species. The model reveals an eco-evolutionary trophic cascade, in which harvest at top trophic levels drives evolution of greater defense or competitiveness at subsequently lower trophic levels, resulting in alternating feedbacks on the abundance and yield of the harvested species. The net abundance and yield effects of these feedbacks depends on the intensity of harvest and attributes of non-target species. Our results provide an impetus and framework to evaluate the role of non-target species evolution in determining fisheries yield and sustainability.

Eco-evolutionary feedbacks may determine the outcome of predator–prey interactions in nature, but little work has been done to quantify the feedback effect of short-term prey adaptation on predator performance. We tested the effects of prey availability and recent (less than 100 years) prey adaptation on the feeding and growth rate of largemouth bass ( Micropterus salmoides ), foraging on western mosquitofish ( Gambusia affinis ). Field surveys showed higher densities and larger average body sizes of mosquitofish in recently introduced populations without bass. Over a six-week mesocosm experiment, bass were presented with either a high or low availability of mosquitofish prey from recently established populations either naive or experienced with bass. Naive mosquitofish were larger, less cryptic and more vulnerable to bass predation compared to their experienced counterparts. Bass consumed more naive prey, grew more quickly with naive prey, and grew more quickly per unit biomass of naive prey consumed. The effect of mosquitofish history with the bass on bass growth was similar in magnitude to the effect of mosquitofish availability. In showing that recently derived predation-related prey phenotypes strongly affect predator performance, this study supports the presence of reciprocal predator–prey trait feedbacks in nature.

Trophic cascades have become a dominant paradigm in ecology, yet considerable debate remains about the relative strength of density- (consumptive) and trait-mediated (non-consumptive) effects in trophic cascades. This debate may, in part, be resolved by considering prey experience, which shapes prey traits (through genetic and plastic change) and influences prey survival (and therefore density). Here, we investigate the cascading role of prey experience through the addition of mosquitofish (Gambusia affinis) from predator-experienced or predator-naïve sources to mesocosms containing piscivorous largemouth bass (Micropterus salmoides), zooplankton, and phytoplankton. These two sources were positioned along a competition-defense tradeoff. Results show that predator-naïve mosquitofish suffered higher depredation rates, which drove a density-mediated cascade, whereas predator-experienced mosquitofish exhibited higher survival but fed less, which drove a trait-mediated cascade. Both cascades were similar in strength, leading to indistinguishable top-down effects on lower trophic levels. Therefore, the accumulation of prey experience with predators can cryptically shift cascade mechanisms from density- to trait-mediated.

Summary There is a lack of consensus in theoretical and empirical literature on whether height–diameter (H:D) relationships of canopy trees are asymptotic. To investigate H:D allometry, particularly in the transition to the canopy, we focused on shade-tolerant Abies balsamea, across steep physical gradients associated with elevation, and correlated biotically generated gradients of stem density, canopy height and canopy species composition. We addressed these questions: A. What is the relation between H:D allometric form and emergence into the canopy? B. Is H:D allometry asymptotic? C. What aspects of the H:D relationship are most sensitive to environmental conditions? Using maximum likelihood, we compared the performance of alternative H:D forms (linear, power function, non-sigmoid asymptotic and sigmoid asymptotic), incorporating elevation and local canopy height as covariates. Abies balsamea H:D allometric form was clearly sigmoid asymptotic, by a wide AIC margin, across all gradients, to an asymptote slightly above canopy height. The commonly used power function had essentially no empirical support (ΔAIC >> 10). Canopy height decreased with elevation, but with much variation, so elevation was a poor predictor of the asymptote. Across environmental gradients, H:D allometries overlapped for trees far below the canopy, but diverged strongly for trees approaching different canopy heights. Changes in resource allocation and modification of growth form that could generate asymptotic H:D allometries are consistent with known physical forces and diverse research findings in tree developmental biology and physiology. Synthesis. The H:D asymptote and its tight relation to canopy height, unapparent in aggregated H:D data, became clear only when canopy height and elevation were included explicitly in allometric models. Asymptotic H:D allometries may be the norm, though often undetected, in unmanaged forests without recent catastrophic disturbance. Appropriate asymptotic H:D models may reduce error in forest carbon and biomass estimation and promote theoretical and empirical integration in the ecology and evolution of tree allometry.

Cyanobacteria and their toxins have received significant attention in eutrophic temperate and tropical systems where conspicuous blooms of certain planktonic taxa release toxins into fresh water, threatening its potability and safe use for recreation. Although toxigenic cyanobacteria are not confined to high nutrient environments, bloom-forming species, or planktonic taxa, these other situations are studied les often studied. For example, toxin production in picoplankton and benthic cyanobacteria-the predominant photoautotrophs found in polar lakes-is poorly understood. We quantified the occurrence of microcystin (MC, a hepatotoxic cyanotoxin) across 18 Arctic lakes in southwestern Greenland. All of the focal lakes contained detectable levels of MC, with concentrations ranging from 5 ng·L(-1) to400 ng·L(-1) during summer, 2013-2015. These concentrations are orders of magnitude lower than many eutrophic systems, yet the median lake MC concentration in Greenland (57 ng·L(-1)) was still 6.5 times higher than the median summer MC toxicity observed across 50 New Hampshire lakes between 1998 and 2008 (8.7 ng·L(-1)). The presence of cyanotoxins in these Greenlandic lakes demonstrates that high latitude lakes can support toxigenic cyanobacteria, and suggests that we may be underestimating the potential for these systems to develop high levels of cyanotoxins in the future.