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Recent work has revealed the importance of contemporary evolution in shaping ecological outcomes. In particular, rapid evolutionary divergence between populations has been shown to impact the ecology of populations, communities, and ecosystems. While studies have focused largely on the role of adaptive divergence in generating ecologically important variation among populations, much less is known about the role of gene flow in shaping ecological outcomes. After divergence, populations may continue to interact through gene flow, which may influence evolutionary and ecological processes. Here, we investigate the role of gene flow in shaping the contemporary evolution and ecology of recently diverged populations of anadromous steelhead and resident rainbow trout (Oncorhynchus mykiss). Results show that resident rainbow trout introduced above waterfalls have diverged evolutionarily from downstream anadromous steelhead, which were the source of introductions. However, the movement of fish from above to below the waterfalls has facilitated gene flow, which has reshaped genetic and phenotypic variation in the anadromous source population. In particular, gene flow has led to an increased frequency of residency, which in turn has altered population density, size structure, and sex ratio. This result establishes gene flow as a contemporary evolutionary process that can have important ecological outcomes. From a management perspective, anadromous steelhead are generally regarded as a higher conservation priority than resident rainbow trout, even when found within the same watershed. Our results show that anadromous and resident O. mykiss populations may be connected via gene flow, with important ecological consequences. Such eco-evolutionary processes should be considered when managing recently diverged populations connected by gene flow.

Abstract: Natural selection shapes the evolution of antipredator traits in prey. However, selection in the wild depends on ecological context, including features of predator and prey populations, making field studies of selection critical to understanding how predators shape selection on prey defences. Threespine stickleback (Gasterosteus aculeatus) is a classic system to study the effects of predators on the natural selection of prey. In lakes and rivers, fish predators have been shown to impose selection against low plated adult stickleback phenotypes and genotypes. We directly measured selection by predatory salmonids on the Ectodysplasin‐A (Eda) gene in estuary stickleback from California. Despite previous studies showing a positive correlation between predator presence and frequency of the Eda “complete” allele in estuary populations, we found that Eda “low” genotypes were not significantly more frequent in salmonid predator diets. Further, we found no evidence of changes in Eda genotype frequencies across generations that would suggest directional selection driven by predators. Prior selection studies have examined the effects of large resident trout on adult stickleback. In contrast, predators in this study were juvenile anadromous salmonids, which only ate juvenile stickleback whose plate phenotypes had not fully developed. Thus, in this case, predator life history and stickleback ontogeny may preclude strong selection on stickleback armour. Our results underscore the importance of selection studies in the wild for understanding the context‐dependent nature of selection in natural populations.

The portfolio effect plays a critical role in population productivity and stability. Age structure of spawning salmon represents an example of portfolio effects such that the risks of experiencing unfavorable conditions are spread across time. However, the distribution of maturation ages for Pacific salmon (Oncorhynchus spp.) is increasingly concentrated into fewer and younger ages, which may impact population resilience to climate change. We explored the population dynamics of Sacramento River fall- run Chinook salmon (O. tshawytscha) under different age structure scenarios using a life-cycle model and compared two mechanisms that can underlie these changes--mortality and maturation. In addition, we tested whether age structure promotes resilience to drought. We found that high age structure diversity increased the stability of population size and harvest compared with low diversity. However, mean population size responded differently depending on the underlying mechanism. Reduced mortality of adult fish ages 4-5 increased escapement, whereas delayed maturation decreased escapement. Overall, high age structure diversity was able to buffer against the adverse effects of droughts by reducing the variability of population size and harvest compared with low diversity. Our results suggest that age structure promotes stability of salmon in an increasingly variable climate. Key words: Age structure, portfolio effects, climate change, salmon, population dynamics, Introduction Intraspecific variation drives eco-evolutionary processes and plays a critical role in species and ecosystem resilience to climate change (Bolnick et al. 2011; Pauls et al. 2013; Des Roches et [...]

Ecological forecasts are potentially of great value for managing fisheries and for stakeholders dependent on their long-term sustainability. Yet, most forecasting approaches are data-intensive, requiring information not just on the focal species but also on ecological interactions and the physical environment. Empirical dynamic modeling (EDM) is an equation-free approach to forecasting species' abundance using only data on past abundance, but the time series required for this approach must be long enough to reconstruct the dynamics of the system. This requirement is rarely met, especially for long-lived species. Here we used simulations and empirical data to demonstrate that incorporating time series from multiple age classes can improve our ability to forecast abundance compared to a single age class or index of total abundance. Including data from multiple age classes produced the greatest gains in forecast accuracy when time series were the shortest. Overall, our results show that the incorporation of age structure could allow EDM to be applied to many species for which relatively short time series would have previously been a limiting factor. Key words: forecast, age structure, ecology, population dynamics, empirical dynamic modeling, Introduction Predicting population changes is a critical component of sustainable fisheries management and conservation biology (Clark et al. 2001; Hobday et al. 2016; Payne et al. 2017; Jacox et al. [...]

Anadromous river herring (alewife and blueback herring) persist at historically low abundances and are caught as bycatch in commercial fisheries, potentially preventing recovery despite conservation efforts. We used newly established single- nucleotide polymorphism genetic baselines for alewife and blueback herring to define fine-scale reporting groups for each species. We then determined the occurrence of fish from these reporting groups in bycatch samples from a Northwest Atlantic fishery over four years. Within sampled bycatch events, the highest proportions of alewife were from the Block Island (34%) and Long Island Sound (22%) reporting groups, while for blueback herring the highest proportions were from the Mid- Atlantic (47%) and Northern New England (24%) reporting groups. We then quantified stock-specific mortality in a focal geographic area (~3500 [km.sup.2], including Block Island Sound) of high bycatch incidence and sampling effort, where the most accurate estimates of mortality could be made. During this period, we estimate that bycatch took about 4.6 million alewife and 1.2 million blueback herring, highlighting the need to reduce bycatch mortality for the most depleted river herring stocks. Key words: Alosa pseudoharengus, A. aestivalis, bycatch, genetic stock identification (GSI), mixing proportion estimates, mortality estimates, 1. Introduction Anadromous fish populations represent unique sources of biological diversity (Fraser et al. 2011) but are impacted by anthropogenic activities in both their marine and freshwater environments (Limburg and [...]

Cities are uniquely complex systems regulated by interactions and feedbacks between nature and human society. Characteristics of human society-including culture, economics, technology and politics-underlie social patterns and activity, creating a heterogeneous environment that can influence and be influenced by both ecological and evolutionary processes. Increasing research on urban ecology and evolutionary biology has coincided with growing interest in eco-evolutionary dynamics, which encompasses the interactions and reciprocal feedbacks between evolution and ecology. Research on both urban evolutionary biology and eco-evolutionary dynamics frequently focuses on contemporary evolution of species that have potentially substantial ecological-and even social-significance. Still, little work fully integrates urban evolutionary biology and eco-evolutionary dynamics, and rarely do researchers in either of these fields fully consider the role of human social patterns and processes. Because cities are fundamentally regulated by human activities, are inherently interconnected and are frequently undergoing social and economic transformation, they represent an opportunity for ecologists and evolutionary biologists to study urban "socio-eco-evolutionary dynamics." Through this new framework, we encourage researchers of urban ecology and evolution to fully integrate human social drivers and feedbacks to increase understanding and conservation of ecosystems, their functions and their contributions to people within and outside cities.

Ecological traps can be caused when partial restoration leads organisms to make maladaptive habitat choices. One example of this is fishways (e.g., fish ladders) that provide upstream passage at dams but are not paired with adequate downstream passage. We tested the hypothesis that attracting anadromous fishes to spawn above a dam, but blocking downstream passage of their offspring leads to an ecological trap. Using passive integrated transponder (PIT) tags, we monitored the movements of steelhead (Oncorhynchus mykiss) at a dam and fishway on the central California coast. We found that downstream passage for juveniles and kelts was limited by four factors: migration delay, loss in the reservoir, avoidance of the downstream bypass, and water depths on the spillway. Based on the spillway-passage depth thresholds, we estimated that the ability for fish to pass downstream was limited to only half of the migration season in 55% of the past 20 years (2002-2021). Our results support the ecological trap hypothesis, which may explain why restoration using fishways has failed to produce recovery gains in this population and elsewhere. Key words: ecological trap, fish passage, fishway, downstream passage, restoration, steelhead, dam Des pieges ecologiques peuvent survenir quand une restauration partielle mene des organismes a faire des choix d'habitat mal adaptes. Des passes migratoires (p. ex., echelles a poissons) qui permettent le franchissement de barrages vers l'amont, mais qui ne sont pas jumelees a un passage adequat vers l'aval en constituent un exemple. Nous avons valide l'hypothese voulant que le fait d'attirer des poissons anadromes pour qu'ils fraient en amont d'un barrage tout en bloquant le passage vers l'aval de leur progeniture produise un piege ecologique. Nous avons utilise des etiquettes a transpondeur passif integre (PIT) pour suivre les deplacements de saumons arc-en-ciel (Oncorhynchus mykiss) a travers un barrage et une passe migratoire dans le centre de la cote californienne. Nous avons constate que le passage vers l'aval pour les juveniles et les saumons vides est limite par quatre facteurs, soit les retards dans la migration, les pertes dans le reservoir, l'evitement du contournement vers l'aval et la profondeur de l'eau dans l'evacuateur. A la lumiere des seuils de profondeur du passage dans l'evacuateur, nous estimons que, pour 55 % des 20 dernieres annees (2002-2021), les poissons ne pouvaient passer vers l'aval que durant la moitie de la periode de migration. Nos resultats appuient l'hypothese du piege ecologique, ce qui pourrait expliquer pourquoi la restauration faisant appel a des passes migratoires n'a pas produit de gains dans le retablissement de cette population et dans d'autres regions. [Traduit par la Redaction] Mots-cles : piege ecologique, passage de poissons, passe migratoire, passage vers l'aval, restauration, saumon arc-en-ciel, barrage, Introduction Ecological restoration is frequently undertaken with the goal of increasing abundances of target species by restoring the habitats in which those species live or reproduce (Palmer et al. 1997). [...]

Experiments have revealed much about top-down and bottom-up control in ecosystems, but manipulative experiments are limited in spatial and temporal scale. To obtain a more nuanced understanding of trophic control over large scales, we explored long-term time-series data from 13 globally distributed lakes and used empirical dynamic modelling to quantify interaction strengths between zooplankton and phytoplankton over time within and across lakes. Across all lakes, top-down effects were associated with nutrients, switching from negative in mesotrophic lakes to positive in oligotrophic lakes. This result suggests that zooplankton nutrient recycling exceeds grazing pressure in nutrient-limited systems. Within individual lakes, results were consistent with a 'seasonal reset' hypothesis in which top-down and bottom-up interactions varied seasonally and were both strongest at the beginning of the growing season. Thus, trophic control is not static, but varies with abiotic conditions - dynamics that only become evident when observing changes over large spatial and temporal scales.

Historically, many biologists assumed that evolution and ecology acted independently because evolution occurred over distances too great to influence most ecological patterns. Today, evidence indicates that evolution can operate over a range of spatial scales, including fine spatial scales. Thus, evolutionary divergence across space might frequently interact with the mechanisms that also determine spatial ecological patterns. Here, we synthesize insights from 500 eco-evolutionary studies and develop a predictive framework that seeks to understand whether and when evolution amplifies, dampens, or creates ecological patterns. We demonstrate that local adaptation can alter everything from spatial variation in population abundances to ecosystem properties. We uncover 14 mechanisms that can mediate the outcome of evolution on spatial ecological patterns. Sometimes, evolution amplifies environmental variation, especially when selection enhances resource uptake or patch selection. The local evolution of foundation or keystone species can create ecological patterns where none existed originally. However, most often, we find that evolution dampens existing environmental gradients, because local adaptation evens out fitness across environments and thus counteracts the variation in associated ecological patterns. Consequently, evolution generally smooths out the underlying heterogeneity in nature, making the world appear less ragged than it would be in the absence of evolution. We end by highlighting the future research needed to inform a fully integrated and predictive biology that accounts for eco-evolutionary interactions in both space and time.

Intraspecific biodiversity is vital for species persistence in an increasingly volatile world. By embracing methods that integrate information at different spatiotemporal scales, we can directly monitor and reconstruct changes in intraspecific biodiversity. Here we combined genetics and otolith biochronologies to describe the genotypic and phenotypic diversity of Chinook salmon (Oncorhynchus tshawytscha) in the Yuba River, California, comparing cohorts that experienced a range of hydroclimatic conditions. Yuba River salmon have been heavily impacted by habitat loss and degradation, and large influxes of unmarked hatchery fish each year have led to concern about introgression and uncertainty around the viability of its wild populations, particularly the rarer spring‐run salmon. Otolith strontium isotopes showed that Yuba River origin fish represented, on average, 42% (range 7%–73%) of spawners across six return years (2009–2011, 2018–2020), with large interannual variability. The remainder of adult Chinook salmon in the river were primarily strays from the nearby Feather River hatchery, and since 2018 from the Mokelumne River hatchery. Among the Yuba‐origin spawners, on average, 30% (range 14%–50%) exhibited the spring‐run genotype. The Yuba‐origin fish also displayed a variety of outmigration phenotypes that differed in the timing and size at which they left the Yuba river. Early‐migrating fry dominated the returns (mean 59%, range 33%–89%), and their contribution rates were negatively correlated with freshwater flows. It is unlikely that fry survival rates are elevated during droughts, suggesting that this trend reflects disproportionately low survival of larger later migrating parr, smolts, and yearlings along the migratory corridor in drier years. Otolith daily increments indicated generally faster growth rates in non‐natal habitats, emphasizing the importance of continuing upstream restoration efforts to improve in‐river growing conditions. Together, these findings show that, despite a long history of habitat degradation and hatchery introgression, the Yuba River maintains intraspecific biodiversity that should be taken into account in future management, restoration, and reintroduction plans. The finding that genotypic spring‐run are reproducing, surviving, and returning to the Yuba River every year suggests that re‐establishment of an independent population is possible, although hatchery‐wild interactions would need to be carefully considered. Integrating methods is critical to monitor changes in key genetic, physiological, and behavioral traits to assess population viability and resilience. [ABSTRACT FROM AUTHOR]

Anadromous fishes exhibit diverse life history and functional traits. Spawning anadromous fishes bring nutrients to fresh waters, and their life history and functional traits can influence nutrient loading patterns. We asked how nutrient inputs varied across 12 species of North American anadromous fishes and how these patterns affected river-wide trends in nutrient loading. We used portfolio effect analyses to assess whether diversity stabilized or destabilized nutrient inputs to freshwater ecosystems over time. Recent decreases in body size reduced per individual nutrient loading for several key species, which in turn decreased cumulative loading. Invasion also altered nutrient loading; non-native American shad (Alosa sapidissima) now provide nearly half of the annual marine-derived nutrient inputs to the Columbia River. Counter to expectations, species diversity (richness and evenness) did not significantly increase the stability of nutrient inputs to fresh waters. Species loss in the Connecticut River increased stability, while species gain in the Columbia River decreased stability. Les poissons anadromes presentent des cycles biologiques et des caracteres fonctionnels varies. Les poissons anadromes reproducteurs apportent des elements nutritifs dans les milieux d'eau douce, et leur cycle biologique et leurs caracteres fonctionnels peuvent influencer la repartition de la charge en elements nutritifs. Nous avons examine les variations des apports en elements nutritifs entre 12 especes de poissons anadromes nord-americains et l'incidence de ces variations sur l'evolution de la charge en elements nutritifs a l'echelle de la riviere. Nous avons utilise des analyses de l'effet de portefeuille pour determiner si la diversite stabilisait ou destabilisait les apports en elements nutritifs dans les ecosystemes d'eau douce au fil du temps. Des diminutions recentes de la taille du corps ont entraine une baisse de la charge en elements nutritifs par individu pour plusieurs especes cles, ce qui s'est traduit par une baisse des charges cumulatives. Les invasions ont egalement modifie la charge en elements nutritifs; l'alose savoureuse (Alosa sapidissima), une espece non indigene, represente aujourd'hui pres de la moitie des apports annuels en elements nutritifs d'origine marine dans le fleuve Columbia. Contrairement aux attentes, la diversite specifique (richesse et uniformite) n'a pas entraine une augmentation significative de la stabilite des apports en elements nutritifs dans les milieux d'eau douce. La disparition d'especes dans le fleuve Connecticut a accru la stabilite, alors que l'apparition d'especes dans le fleuve Columbia a reduit la stabilite. [Traduit par la Redaction], Introduction Interest in spatial linkages among ecosystems has expanded over the past two decades with the recognition that migratory animals provide resource subsidies that effect the strength and form of [...]

Intraspecific variation is an important form of biodiversity that can alter community and ecosystem properties. Recent work demonstrates the community effects of intraspecific variation in predators via altering prey communities and in foundation species via shaping habitat attributes. However, tests of the community effects of intraspecific trait variation in predators acting on foundation species are lacking despite the fact that consumption of foundation species can have strong community effects by shaping habitat structure. Here, we tested the hypothesis that intraspecific foraging differences among populations of mussel‐drilling dogwhelk predators (Nucella) differentially alter intertidal communities through effects on foundational mussels. We conducted a 9‐month field experiment where we exposed intertidal mussel bed communities to predation from three Nucella populations that exhibit differences in size‐selectivity and consumption time for mussel prey. At the end of the experiment, we measured mussel bed structure, species diversity, and community composition. While exposure to Nucella originating from different populations did not significantly alter overall community diversity, we found that differences in Nucella mussel selectivity significantly altered foundational mussel bed structure, which in turn altered the biomass of shore crabs and periwinkle snails. Our study extends the emerging paradigm of the ecological importance of intraspecific variation to include the effects of intraspecific variation on predators of foundation species. [ABSTRACT FROM AUTHOR]

Bycatch of mid-trophic-level anadromous fishes that connect marine and freshwater ecosystems is a growing conservation concern. Anadromous alewife (Alosa pseudoharengus) and blueback herring (Alosa aestivalis) are important components of coastal freshwater and marine food webs, but have experienced dramatic declines in the abundances of spawning adults. Freshwater-focused restoration efforts have yielded few consistent signs of recovery, raising concerns that bycatch in Northwest Atlantic commercial fisheries may be negating these conservation actions. Using data from 15 microsatellites genotyped for baseline populations and bycatch, we conducted genetic stock identification to understand how bycatch was partitioned among previously identified regional genetic stocks. We then combined this information with fishery observer data to estimate genetic stock-specific bycatch mortality for the southern New England Atlantic herring fishery (2012-2013). Bycatch overall, but especially in the Atlantic herring fishery, was disproportionately assigned to the most severely depleted genetic stocks (alewife southern New England stock--70% of assignments; blueback herring mid-Atlantic stock--78% of assignments). These genetic stocks overlap in the region surrounding Long Island Sound, suggesting that bycatch taken from this area in recent years may be negatively impacting recovery efforts in this region. Our study suggests that mitigating bycatch on the southern New England fishing grounds may benefit recovery efforts for alewife and blueback herring genetic stocks that have experienced the greatest declines in spawning adult abundances. Les prises accessoires de poissons anadromes de niveaux trophiques intermediaires qui relient les ecosystemes marins aux ecosystemes d'eau douce sont de plus en plus preoccupantes en ce qui concerne la conservation. Si le gaspareau (Alosa pseudoharengus) anadrome et l'alose d'ete (Alosa aestivalis) sont des elements importants des reseaux trophiques marins et d'eau douce littoraux, ils ont connu des baisses considerables de l'abondance d'adultes reproducteurs. Les efforts de restauration axes sur les milieux d'eau douce ont produit peu d'indices de retablissement coherents, donnant a penser que ces efforts de conservation pourraient etre contrecarres par les prises accessoires dans les peches commerciales du nord-ouest de l'Atlantique. En utilisant les donnees de 15 microsatellites genotypes pour des populations de reference et des prises accessoires, nous avons identifie les stocks pour comprendre la repartition des prises accessoires parmi differents stocks genetiques regionaux deja identifies. Nous avons ensuite combine cette information a des donnees d'observation des peches pour estimer la mortalite des prises accessoires propre aux differents stocks genetiques pour la peche au hareng du sud de la Nouvelle-Angleterre (2012-2013). Les prises accessoires en general, mais particulierement dans la peche au hareng, etaient demesurement affectees aux stocks genetiques les plus decimes (70 % des affectations au stock de gaspareaux du sud de la Nouvelle-Angleterre; 78 % des affectations au stock medio-atlantique d'aloses d'ete). Ces stocks genetiques se chevauchent dans la region entourant le detroit de Long Island, donnant a penser que les prises accessoires prelevees dans cette region aucours des dernieres annees pourraient avoir un impact negatif sur les efforts de retablissement dans cette region. L'etude donne a penser que la reduction des prises accessoires dans les zones de peche du sud de la Nouvelle-Angleterre pourrait etre benefique pour les efforts de retablissement des stocks genetiques de gaspareaux et d'aloses d'ete ayant connu les baisses les plus importantes d'abondance d'adultes reproducteurs. [Traduit par la Redaction], Introduction The incidental catch of nontarget species in commercial fisheries (i.e., bycatch) represents a major threat to the health of marine ecosystems (Crowder and Murawski 1998; Chuenpagdee et al. 2003). [...]

We compared the accuracy of different combinations of natural markers, specifically otolith elemental (Sr:Ca and Ba:Ca) and isotopic ratios ([sup.87:86]Sr) with and without genetic stock constraints to evaluate their ability to distinguish among anadromous river herring (i.e., alewife, Alosa pseudoharengus, and blueback herring, Alosa aestivalis) populations from their US ranges. Model accuracy increased when constrained to a regional level by genetic stocks. Both species were misclassified to sites up to 1000 km from their collection location when only otolith chemistry was used. The inclusion of genetic constraints improved reclassification rates, and the longer time scale of genetic variation makes this method less sensitive to interannual variation. We recommend the combined approach of otolith chemistry and genetics as a means to trace river herring in marine bycatch back to river of origin. Resume : Nous avons compare l'exactitude de differentes combinaisons de marqueurs naturels, plus precisement des rapports elementaires (Sr:Caet Ba:Ca) et isotopiques ([sup.87:86]Sr) d'otolites avec et sans information relative au stock genetique, afin d'evaluer leur pertinence pour distinguer differentes populations d'aloses (gaspareau, Alosa pseudoharengus, et alose d'ete, Alosa aestivalis) anadromes dans leurs aires de repartition aux Etats-Unis. L'exactitude du modele augmentait quand de l'information sur le stock genetique permettait de contraindre le modele au niveau regional. Les deux especes etaient erronement affectees a des sites distants de jusqu'a 1000 km du lieu de leur prelevement quand seule la chimie des otolites etait utilisee. L'inclusion de contraintes genetiques ameliore les taux de reclassification, et l'echelle temporelle plus grande des variations genetiques rend ce modele moins sensible aux variations interannuelles. Nous recommandons une approche combinee comprenant la chimie des otolites et la genetique pour retracer la riviere d'origine des aloses dans les prises accessoires en mer. [Traduit par la Redaction], Introduction Alewife (Alosa pseudoharengus) and blueback herring (Alosa aestivalis) are two closely related species of iteroparous, anadromous fishes, collectively referred to as river herring (Fay et al. 1983). Both species [...]