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Abstract Invasive species are a major threat to global biodiversity, yet also represent large‐scale unplanned ecological and evolutionary experiments to address fundamental questions in nature. Here we analyzed both native and invasive populations of predatory northern pike (Esox lucius) to characterize landscape genetic variation, determine the most likely origins of introduced populations, and investigate a presumably postglacial population from Southeast Alaska of unclear provenance. Using a set of 4329 SNPs from 351 individual Alaskan northern pike representing the most widespread geographic sampling to date, our results confirm low levels of genetic diversity in native populations (average 𝝅 of 3.18 × 10−4) and even less in invasive populations (average 𝝅 of 2.68 × 10−4) consistent with bottleneck effects. Our analyses indicate that invasive northern pike likely came from multiple introductions from different native Alaskan populations and subsequently dispersed from original introduction sites. At the broadest scale, invasive populations appear to have been founded from two distinct regions of Alaska, indicative of two independent introduction events. Genetic admixture resulting from introductions from multiple source populations may have mitigated the negative effects associated with genetic bottlenecks in this species with naturally low levels of genetic diversity. Genomic signatures strongly suggest an excess of rare, population‐specific alleles, pointing to a small number of founding individuals in both native and introduced populations consistent with a species' life history of limited dispersal and gene flow. Lastly, the results strongly suggest that a small isolated population of pike, located in Southeast Alaska, is native in origin rather than stemming from a contemporary introduction event. Although theory predicts that lack of genetic variation may limit colonization success of novel environments, we detected no evidence that a lack of standing variation limited the success of this genetically depauperate apex predator.

Invasive species are a major threat to global biodiversity, yet also represent large‐scale unplanned ecological and evolutionary experiments to address fundamental questions in nature. Here we analyzed both native and invasive populations of predatory northern pike (Esox lucius) to characterize landscape genetic variation, determine the most likely origins of introduced populations, and investigate a presumably postglacial population from Southeast Alaska of unclear provenance. Using a set of 4329 SNPs from 351 individual Alaskan northern pike representing the most widespread geographic sampling to date, our results confirm low levels of genetic diversity in native populations (average 흅 of 3.18 × 10−4) and even less in invasive populations (average 흅 of 2.68 × 10−4) consistent with bottleneck effects. Our analyses indicate that invasive northern pike likely came from multiple introductions from different native Alaskan populations and subsequently dispersed from original introduction sites. At the broadest scale, invasive populations appear to have been founded from two distinct regions of Alaska, indicative of two independent introduction events. Genetic admixture resulting from introductions from multiple source populations may have mitigated the negative effects associated with genetic bottlenecks in this species with naturally low levels of genetic diversity. Genomic signatures strongly suggest an excess of rare, population‐specific alleles, pointing to a small number of founding individuals in both native and introduced populations consistent with a species' life history of limited dispersal and gene flow. Lastly, the results strongly suggest that a small isolated population of pike, located in Southeast Alaska, is native in origin rather than stemming from a contemporary introduction event. Although theory predicts that lack of genetic variation may limit colonization success of novel environments, we detected no evidence that a lack of standing variation limited the success of this genetically depauperate apex predator. [ABSTRACT FROM AUTHOR]

© 2015 Elsevier Ltd. The biogeography of freshwater fish species during and after late-Pleistocene glaciations relate to how these species are genetically organized today, and the management of these often disjunct populations. Debate exists concerning the biogeography and routes of dispersal for Northern pike (Esox lucius) after the last glaciation. A hypothesis to account for the relatively low modern genetic diversity for E. lucius is post-glacial radiation from refugia, including lakes from within the un-glaciated portions of eastern Beringia. We report the remains of a Northern pike (E. cf. lucius) skull, including bones, teeth, bone collagen and ancient DNA. The remains were preserved at a depth of between 440 and 446cm in a 670cm long core of sediment from Quartz Lake, which initiated at ~11,200calyr BP in interior Alaska. A calibrated accelerator mass spectrometer (AMS) radiocarbon age of the collagen extracted from the preserved bones indicated that the organism was dated to 8820calyr BP and is bracketed by AMS values from analyses of terrestrial plant macrofossils, avoiding any potential aquatic reservoir effect that could have influenced the radiocarbon age of the bones. Scanning electron microscope images of the specimen show the hinged tooth anatomy typically of E.lucius. Molar C:N (3.5, 1σ=0.1) value of the collagen from the specimen indicated well-preserved collagen and its mean stable nitrogen isotope value is consistent with the known predatory feeding ecology of E.lucius. Ancient DNA in the bones showed that the specimen was identical to modern E.lucius. Our record of E.lucius from interior Alaska is consistent with a biogeographic scenario involving rapid dispersal of this species from glacial refugia in the northern hemisphere after the last glaciation.

© 2015 Elsevier Ltd. The biogeography of freshwater fish species during and after late-Pleistocene glaciations relate to how these species are genetically organized today, and the management of these often disjunct populations. Debate exists concerning the biogeography and routes of dispersal for Northern pike (Esox lucius) after the last glaciation. A hypothesis to account for the relatively low modern genetic diversity for E. lucius is post-glacial radiation from refugia, including lakes from within the un-glaciated portions of eastern Beringia. We report the remains of a Northern pike (E. cf. lucius) skull, including bones, teeth, bone collagen and ancient DNA. The remains were preserved at a depth of between 440 and 446cm in a 670cm long core of sediment from Quartz Lake, which initiated at ~11,200calyr BP in interior Alaska. A calibrated accelerator mass spectrometer (AMS) radiocarbon age of the collagen extracted from the preserved bones indicated that the organism was dated to 8820calyr BP and is bracketed by AMS values from analyses of terrestrial plant macrofossils, avoiding any potential aquatic reservoir effect that could have influenced the radiocarbon age of the bones. Scanning electron microscope images of the specimen show the hinged tooth anatomy typically of E.lucius. Molar C:N (3.5, 1σ=0.1) value of the collagen from the specimen indicated well-preserved collagen and its mean stable nitrogen isotope value is consistent with the known predatory feeding ecology of E.lucius. Ancient DNA in the bones showed that the specimen was identical to modern E.lucius. Our record of E.lucius from interior Alaska is consistent with a biogeographic scenario involving rapid dispersal of this species from glacial refugia in the northern hemisphere after the last glaciation.

Aim: The factors that set range limits for animal populations can inform management plans aimed at maintaining regional biodiversity. We examine abiotic and biotic drivers of the distribution of finescale dace (Chrosomus neogaeus) in two Great Plains basins to identify limiting factors for a threatened freshwater fish population at the edge of their range. Location: Great Plains, Nebraska, South Dakota and Wyoming, USA. Methods: We investigated abiotic and biotic factors influencing the contemporary distribution of finescale dace in the Belle Fourche and Niobrara River basins with Random Forests classification models using fish surveys from multiple agencies spanning 2008–2019 and GIS‐derived environmental data. Results: In both basins, finescale dace occurrence exhibited a nonlinear response to mean August water temperature. Abiotic covariates, including streamflow, water temperature and channel slope, were important limiting factors in the final model fit with Belle Fourche River basin surveys (n = 131). In contrast, a biotic covariate, native minnow richness, was the most important predictor of finescale dace occurrence in the Niobrara River basin model (n = 27). In the Niobrara River, native minnow richness was lower at sites with non‐native northern pike (Esox lucius). Main conclusions: Basin‐specific analyses revealed context dependencies for species–environment relationships, which can inform targeted restoration actions. Similar relationships between water temperature and finescale dace occurrence across both basins suggest summer thermal habitat as a regional limiting factor. The importance of biotic interactions in the Niobrara River highlights an emergent threat from invasive predators to a distinct assemblage of native prairie fishes. [ABSTRACT FROM AUTHOR]

A prerequisite to studying the physiological status of wild animals is the ability to obtain blood samples that reflect the condition prior to capture or handling. Based on research in avian taxa, it is recommended that such samples be obtained within 3 min of capture; however, this guideline has not been validated in wild teleosts. The present study addresses the time course of physiological changes in a number of blood metrics across six species of freshwater fish. Fishes were caught using a standardized angling protocol and held in a water-filled trough prior to the collection of a blood sample, via caudal phlebotomy, between 0.5 and 11 min after capture. Changes in whole-blood glucose and lactate concentrations, hematocrit, and plasma cortisol concentrations were assessed. Change-point analyses indicated that blood lactate concentrations and hematocrit did not deviate from baseline values until ∼2-5 min of handling for all species, whereas blood glucose concentrations generally did not deviate significantly from baseline over the 11 min test period. In all species, plasma cortisol concentrations began to increase above baseline between ∼4 and 8 min after capture. Thus, to ensure that blood samples are representative of baseline conditions across multiple metrics, we recommend that sampling be limited to less than 2 min in teleost fishes. [ABSTRACT FROM AUTHOR]

Morphological differentiation may allow individuals to cope with prevailing environmental conditions. Morphological differentiation in fish characterized by sagittiform shape and ambush predator behaviour, such as northern pike ( Esox lucius L., 1758), has rarely been addressed. Morphological differentiation was assessed in two rivers exhibiting contrasting flow regimes: a hydropeaking river characterized by large and frequent fluctuations in flow rates and an unregulated river. An increase in northern pike movement rate was observed in the hydropeaking river. Therefore, morphological features enhancing sustained and burst swimming, as well as manoeuvrability, were expected. Our objectives are to ( i) compare morphology between the two rivers and ( ii) assess morphological differentiation between sexes. Using geometric morphometrics, shape significantly diverged between rivers irrespective of sex and between sexes in the hydropeaking river. Individuals from the hydropeaking river had more elongated heads, deeper bodies and caudal peduncles, and longer dorsal fin insertions than individuals from the unregulated river. Caudal fin differences between rivers were not consistent between sexes. Morphological differentiation suggested a trade-off among adaptations for sustained and burst swimming, as well as manoeuvrability, to cope with variable flows in a hydropeaking river. Morphological differentiation may allow the exploitation of spatially and temporally variable environmental conditions, including those stemming from river flow regulation. [ABSTRACT FROM AUTHOR]

Understanding how individuals are distributed in space and time, as well as how they interact with dynamic environmental conditions, represent fundamental knowledge gaps for many fish species. Using acoustic telemetry tags, we monitored the temperatures and depths used by northern pike ( Esox lucius L., 1758) and largemouth bass ( Micropterus salmoides (Lacepède, 1802)) in Toronto Harbour (Lake Ontario). Northern pike and largemouth bass had similar thermal experiences throughout the year, except during summer, when northern pike were observed in cooler waters than largemouth bass. Both species used different depths throughout the year, with northern pike occupying deeper depths. Statistical modelling indicated that depth usage was influenced by all variables (season, species, and body size) and interactions between them, whereas thermal preferences were influenced by the main effects and interactions between species:season and species : body size. Both species were observed at temperatures warmer than those in the vicinity of nearby telemetry stations, but as station temperatures exceeded 20 °C, northern pike moved into cooler water, indicating active thermoregulation. These data will be useful for refining our understanding of the spatial ecology of fish and for informing fisheries and habitat management in this and other urban harbours of the Laurentian Great Lakes. [ABSTRACT FROM AUTHOR]

The biogeography of freshwater fish species during and after late-Pleistocene glaciations relate to how these species are genetically organized today, and the management of these often disjunct populations. Debate exists concerning the biogeography and routes of dispersal for Northern pike ( Esox lucius ) after the last glaciation. A hypothesis to account for the relatively low modern genetic diversity for E . lucius is post-glacial radiation from refugia, including lakes from within the un-glaciated portions of eastern Beringia. We report the remains of a Northern pike ( E. cf. lucius ) skull, including bones, teeth, bone collagen and ancient DNA. The remains were preserved at a depth of between 440 and 446 cm in a 670 cm long core of sediment from Quartz Lake, which initiated at ∼11,200 cal yr BP in interior Alaska. A calibrated accelerator mass spectrometer (AMS) radiocarbon age of the collagen extracted from the preserved bones indicated that the organism was dated to 8820 cal yr BP and is bracketed by AMS values from analyses of terrestrial plant macrofossils, avoiding any potential aquatic reservoir effect that could have influenced the radiocarbon age of the bones. Scanning electron microscope images of the specimen show the hinged tooth anatomy typically of E. lucius . Molar C:N (3.5, 1σ = 0.1) value of the collagen from the specimen indicated well-preserved collagen and its mean stable nitrogen isotope value is consistent with the known predatory feeding ecology of E. lucius . Ancient DNA in the bones showed that the specimen was identical to modern E. lucius . Our record of E. lucius from interior Alaska is consistent with a biogeographic scenario involving rapid dispersal of this species from glacial refugia in the northern hemisphere after the last glaciation. [ABSTRACT FROM AUTHOR]

We examined the long-term effects on prey fish communities of introducing Northern Pike (Esox lucius), a top predator fish, into small, Boreal Shield lakes lacking natural piscivore populations. During 1987-1994, Northern Pike were introduced into Lakes 110, 221, and 227 in the Experimental Lakes Area in northwestern Ontario, Canada. In Lake 227, prey fish were undetectable three years after the addition of Northern Pike. Although Northern Pike were removed from the lake by 1996, multiple independent visual and trapping surveys have yielded no evidence of any fish in Lake 227 since then. In 1994-1995, 85% of the Northern Pike were removed from Lake 221. In 2012, despite intensive sampling efforts using baited minnow traps, fyke nets, trap netting, gill netting, angling, and visual observation, no forage fish of any species was observed or caught in Lake 110 or 221. In all three lakes where Northern Pike were added, prey fish populations were extirpated or too small to detect. In Lake 221, we estimated the current population of Northern Pike to be 49 ± 37, a 59% decrease since 2000 when prey fish were still present. The mean total length and body condition of Northern Pike in Lake 221 had not changed since the prey community collapsed. Our findings suggest that the introduction of Northern Pike into lakes without natural piscivore populations has long-lasting effects on fish community structure, to the detriment of both Northern Pike and prey fish populations. [ABSTRACT FROM AUTHOR]

A pilot study of bioindicators of environmental health was performed in a non-industrial region of Poland in April 2008. Twenty wild-caught northern pike Esox lucius Linnaeus, 1758 were used. Established biomarkers of environmental stress were studied in these fish, including condition factor, macroscopic lesions, morphometry of hepatic melanomacrophage cells, follicular atresia, and histopathology of liver and gonads. Body weight, total body length, and gender were recorded; livers, gonads, and organs with macroscopic lesions were collected for histopathology. H&E-stained paraffin-embedded sections were studied by light microscopy. All fish appeared in good health and had no macroscopic lesions except for two fish with gut trematodes. Microscopic lesions were minimal and included peribiliary fibrosis and cholangitis, focal hepatic necrosis and vasculitis, biliary myxozoanosis, intestinal metazoan parasites, and post-spawning peritonitis. Very low levels of hepatic MMC and ovarian follicular atresia were found. The data constitute the first report of biomarkers of environmental stress in northern pike from northeastern Poland and can be used as a reference for future monitoring of fish health and aquatic pollution in this region. [ABSTRACT FROM AUTHOR]

Northern pike experience a global decline of populations and a better understanding of the species' population genetic diversity and structure is needed for proper conservation and management. We developed 17 novel microsatellite markers in North American northern pike, Esox lucius, and tested cross-amplification on European populations as well as all five other Esox species. One marker deviated significantly from Hardy-Weinberg equilibrium and no linkage disequilibrium among all loci pairs was observed. A mean of 6.88 alleles per locus was found (between 2 and 23 alleles) and mean expected heterozygozity was 0.49 (range 0.033-0.950). All loci were successfully amplified on E. lucius from North America and Europe and E. reichertii. Between eight and 11 loci were successfully amplified in other Esox species and four out of 17 loci were successfully cross-amplified on all species. [ABSTRACT FROM AUTHOR]

In recent decades, wetlands have been constructed or restored around the Baltic sea to counteract the eutrophication of its coastal waters. Some of these wetlands could also be suitable spawning and nursery areas for anadromous northern pike ( Esox lucius L.). We studied juvenile pike production in three coastal wetlands along the south-eastern coast of Sweden that were restored in different ways. Where terrestrial vegetation was temporarily flooded, pike larval/juvenile emigration increased from a few thousand individuals before restoration to over a hundred thousand afterwards. We suggest that vegetation was the key to this successful reproduction, as wetlands where vegetation was removed or reduced saw no similar increase in pike production. Flooded vegetation in shallow waters offers optimal spawning conditions, increased food resources, and refuge from predation. The growth and emigration of larvae and juveniles were followed over time, revealing that 80–95% of individuals left the wetlands within 1 month (at a size <6 cm). This emigration probably represents an adaption to seasonally decreasing water levels but may also be a way to avoid cannibalism. [ABSTRACT FROM AUTHOR]

Northern pike ( Esox lucius) are opportunistic predators that can switch to alternative prey species after preferred prey have declined. This trophic adaptability allows invasive pike to have negative effects on aquatic food webs. In Southcentral Alaska, invasive pike are a substantial concern because they have spread to important spawning and rearing habitat for salmonids and are hypothesised to be responsible for recent salmonid declines. We described the relative importance of salmonids and other prey species to pike diets in the Deshka River and Alexander Creek in Southcentral Alaska. Salmonids were once abundant in both rivers, but they are now rare in Alexander Creek. In the Deshka River, we found that juvenile Chinook salmon ( Oncorhynchus tshawytscha) and coho salmon ( O. kisutch) dominated pike diets and that small pike consumed more of these salmonids than large pike. In Alexander Creek, pike diets reflected the distribution of spawning salmonids, which decrease with distance upstream. Although salmonids dominated pike diets in the lowest reach of the stream, Arctic lamprey ( Lampetra camtschatica) and slimy sculpin ( Cottus cognatus) dominated pike diets in the middle and upper reaches. In both rivers, pike density did not influence diet and pike consumed smaller prey items than predicted by their gape-width. Our data suggest that (1) juvenile salmonids are a dominant prey item for pike, (2) small pike are the primary consumers of juvenile salmonids and (3) pike consume other native fish species when juvenile salmonids are less abundant. Implications of this trophic adaptability are that invasive pike can continue to increase while driving multiple species to low abundance. [ABSTRACT FROM AUTHOR]

Many species of fish display morphological divergence between individuals feeding on macroinvertebrates associated with littoral habitats (benthic morphotypes) and individuals feeding on zooplankton in the limnetic zone (limnetic morphotypes). Threespine stickleback ( Gasterosteus aculeatus L.) have diverged along the benthic-limnetic axis into allopatric morphotypes in thousands of populations and into sympatric species pairs in several lakes. However, only a few well known populations have been studied because identifying additional populations as either benthic or limnetic requires detailed dietary or observational studies. In the present study, we develop a Fisher's linear discriminant function based on the skull morphology of known benthic and limnetic stickleback populations from the Cook Inlet Basin of Alaska and test the feasibility of using this function to identify other morphologically divergent populations. Benthic and limnetic morphotypes were separable using this technique and, of 45 populations classified, three were identified as morphologically extreme (two benthic and one limnetic), nine as moderately divergent (three benthic and six limnetic), and the remaining 33 populations as morphologically intermediate. Classification scores were found to correlate with eye size, the depth profile of lakes, and the presence of invasive northern pike ( Esox lucius). This type of classification function provides a means of integrating the complex morphological differences between morphotypes into a single score that reflects the position of a population along the benthic-limnetic axis and can be used to relate that position to other aspects of stickleback biology. © 2010 The Linnean Society of London, Biological Journal of the Linnean Society, 2010, 101, 595-608. [ABSTRACT FROM AUTHOR]

Copyright of Canadian Field-Naturalist is the property of Ottawa Field Naturalists' Club and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Threespine stickleback ( Gasterosteus aculeatus) samples from Prator Lake in southcentral Alaska consist of the relatively rare form of weakly armoured individuals with few lateral plates and no pelvic spines. Prator Lake has been sampled for threespine stickleback since 1983. Exotic northern pike ( Esox lucius) were first observed in this lake in 1996. The appearance of pike corresponds with a dramatic decrease in stickleback numbers and apparent local extinction. The stickleback population may have been vulnerable to an exotic predator because Prator Lake lacks native piscivorous fishes, and this population had extreme armour reduction. [ABSTRACT FROM AUTHOR]

Abstract: Northern pike (Esox lucius) is not considered an endangered species in Italy, but since recent studies indicate the decline of this population, conservation and management strategies based on the genetic differentiation of natural northern pike populations are needed. In this paper, genetic diversity was analysed in 10 Italian and 2 East European northern pike populations by means of seven microsatellite loci. Data indicated an appreciable genetic differentiation, in spite of a low genetic variation, and agreed with the low level of genetic polymorphism already observed for this species in North America and North Europe. Results of statistical tests revealed genetic peculiarities of the Italian populations, even though signals of recent contact between populations were found and discussed in relation to anthropic impacts, particularly to the stocking practice. This investigation represents the first approach to the knowledge of the genetic variability of Italian pike populations using microsatellite markers, and reported results could be of interest for future management and conservation programmes of this species in Italy. [Copyright &y& Elsevier]

Copyright of Canadian Field-Naturalist is the property of Ottawa Field Naturalists' Club and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Griffiths RW, Newlands NK, Noakes DLG, Beamish FWH. Northern pike ( Esox lucius) growth and mortality in a northern Ontario river compared with that in lakes: influence of flow. Ecology of Freshwater Fish 2004: 13: 136–145. © Blackwell Munksgaard, 2004 We measured the growth and mortality characteristics of northern pike ( Esox lucius) in a northern Ontario river and examined the influence of flow on these characteristics by comparing our measurements with those estimated for a lake at the same latitude based on published studies. Pike ranged in total length from 229 to 784 mm, in mass from 70 to 4250 g, and in age from 1 to 10 years. The population showed a preponderance of 2–5-year olds, with few fish surviving beyond 7 years of age. Growth, in terms of length increase, was similar to that reported for circumpolar populations. Mean total length at 5 years of age was 577 mm, growth rate of young adults was 62.5 mm year−1, growth was isometric, longevity was 10 years of age, and the adult annual mortality rate was 49%. Growth and mortality characteristics of this riverine population were similar to those estimated for a lacustrine population at the same latitude. Flow thus had little measurable effect on the growth or mortality of pike possibly because of the overwhelming effect of other abiotic variables such as temperature, length of growing season and productivity. Consequently, growth characteristics of lacustrine populations can be used to assess the health and condition of riverine populations. [ABSTRACT FROM AUTHOR]

We developed and evaluated three qPCR assays for detecting environmental DNA from northern pike ( Esox lucius). The assays target the cytochrome oxidase 1 (EluCOI), control region (EluCR), and cytochrome b (EluCytB) genes of the mitochondrial DNA. Target specificity, assessed using the fluorescence signal (at 45 cycles) to noise (at 1 cycle) ratio (S/N), showed strong amplification in northern pike (mean S/N = 2.62, 3.52, 2.69 for EluCOI, EluCR, EluCytB). The mean S/N estimates from fifteen non-esocid freshwater fishes were about 1.0, as expected for no amplification. EluCR showed evidence of amplification (mean S/N = 3.16) in muskellunge ( Esox masquinongy). The sensitivity tests indicated EluCOI has a higher detection probability than EluCR and EluCytB at low (20 copies/reaction) copy number. The results favor using EluCOI although EluCytB and EluCR are viable assays for the detection of northern pike eDNA. [ABSTRACT FROM AUTHOR]

We studied two populations of damselfly larvae ( Enallagma boreale): one population cooccurred with a predatory fish (northern pike, Esox lucius); the other did not. Damselflies that cooccurred with pike adopted antipredator behavior (reduced activity) in response to chemical stimuli from injured conspecifics, and to chemical stimuli from pike, relative to a distilled water control. Damselflies from an area where pike do not occur responded only to chemical stimuli from injured conspecifics. In a second set of experiments, we conditioned pike-naive damselflies to recognize and respond to chemical stimuli from pike with antipredator behavior. Damselfly larvae that were previously unresponsive to pike stimuli learned to recognize pike stimuli after a single exposure to stimuli from pike and injured damselflies or pike and injured fathead minnows ( Pimephales promelas). The response to injured fathead minnows was not a general response to injured fish because damselfly larvae did not respond to chemical stimuli from injured swordtails ( Xiphophorus helleri), an allopatric fish. Taken together, these data suggest a flexible learning program that allows damselfly larvae to rapidly acquire the ability to recognize local predation risk based on chemical stimuli from predators, conspecifics, and heterospecific members of their prey guild. [ABSTRACT FROM AUTHOR]