Predation Regimes Research Articles

Combined effects of turbulence and different predation regimes on zooplankton in highly colored water-implications for environmental change in lakes.

In aquatic ecosystems, predation is affected both by turbulence and visibility, but the combined effects are poorly known. Both factors are changing in lakes in the Northern Hemisphere; the average levels of turbulence are predicted to increase due to increasing wind activities, while water transparency is decreasing, e.g., due to variations in precipitation, and sediment resuspension. We explored experimentally how turbulence influenced the effects of planktivorous fish and invertebrate predators on zooplankton when it was combined with low visibility caused by high levels of water color. The study was conducted as a factorial design in 24 outdoor ponds, using the natural zooplankton community as a prey population. Perch and roach were used as vertebrate predators and Chaoborus flavicans larvae as invertebrate predators. In addition to calm conditions, the turbulent dissipation rate used in the experiments was 10−6 m2 s−3, and the water color was 140 mg Pt L−1. The results demonstrated that in a system dominated by invertebrates, predation pressure on cladocerans increased considerably under intermediate turbulence. Under calm conditions, chaoborids caused only a minor reduction in the crustacean biomass. The effect of fish predation on cladocerans was slightly reduced by turbulence, while predation on cyclopoids was strongly enhanced. Surprisingly, under turbulent conditions fish reduced cyclopoid biomass, whereas in calm water it increased in the presence of fish. We thus concluded that turbulence affects fish selectivity. The results suggested that in dystrophic invertebrate-dominated lakes, turbulence may severely affect the abundance of cladocerans. In fish-dominated dystrophic lakes, on the other hand, turbulence-induced changes in planktivory may considerably affect copepods instead of cladocerans. In lakes inhabited by both invertebrates and fish, the response of top-down regulation to turbulence resembles that in fish-dominated systems, due to intraguild predation. The changes in planktivorous predation induced by abiotic factors may possibly cascade to primary producers.

Stress and success: Individual differences in the glucocorticoid stress response predict behavior and reproductive success under high predation risk

A fundamental element of how vertebrates respond to stressors is by rapidly elevating circulating glucocorticoid hormones. Individual variation in the magnitude of the glucocorticoid stress response has been linked with reproductive success and survival. But while the adaptive value of this response is believed to stem in part from changes in the expression of hormone-mediated behaviors, it is not clear how the behavior of stronger and weaker glucocorticoid responders differs during reproduction, or during exposure to ecologically relevant stressors. Here we report that in a population of barn swallows (Hirundo rustica erythrogaster) experiencing high rates of nest predation, circulating levels of corticosterone (the primary avian glucocorticoid) during exposure to a standardized stressor predict aspects of subsequent behavior and fitness. Individuals that mounted a stronger corticosterone stress response during the early reproductive period did not differ in clutch size, but fledged fewer offspring. Parents with higher stress-induced corticosterone during the early reproductive period later provisioned their nestlings at lower rates. Additionally, in the presence of a model predator stress-induced corticosterone was positively associated with the latency to return to the nest, but only among birds that were observed to return. Model comparisons revealed that stress-induced hormones were better predictors of the behavioral and fitness effects of exposure to transient, ecologically relevant stressors than baseline corticosterone. These findings are consistent with functional links between individual variation in the hormonal and behavioral response to stressors. If such links occur, then selection on the heritable components of the corticosterone stress response could promote adaptation to novel environments or predation regimes.

Predator-induced phenotypic plasticity of laterality

Lateralized brain function, or partitioning of tasks to separate hemispheres of the brain, directly impacts behaviour and fitness. Highly lateralized individuals tend to outperform nonlateralized individuals in many survival-related behaviours, such as the ability to learn, escape predators and multitask. Despite these benefits to lateralization, there is a great deal of observed variation in this trait within and between populations that is likely determined by the balance between costs and benefits of laterality in a given environment. Laterality appears to be heritable, but it can also vary with the environment experienced during development. We investigated the role of evolutionary history and developmental plasticity in determining the degree of laterality in the Trinidadian guppy, Poecilia reticulata, a freshwater fish that experiences variable predation pressure in its native range. We compared pairs of closely related populations that experience either high or low levels of predation in the wild, and manipulated the perceived predation risk in the rearing environment using a common garden split-brood design. We assayed laterality in mature male guppies using a detour test. Fish reared with exposure to chemical predator cues were more lateralized than their brothers reared without predator cues. This plastic response is in the direction we would predict if lateralization is favoured in environments with high predation risk. However, unlike findings in related species, we did not detect repeatable differences in degree of laterality associated with historical predation regime, suggesting that predation risk experienced over evolutionary history does not shape laterality patterns in guppies. Thus, although it is currently underemphasized in the literature, plasticity is likely an important contributor to variation in laterality.

Gastropod shell repair tracks predator abundance

AbstractPredator‐prey interactions can shape biological communities and drive evolutionary change. The assessment of predation rates in modern and ancient ecosystems presents many challenges. We examined the utility of one common predation metric, shell repair frequency, as a proxy for crushing predation on marine gastropod populations. Our six localities near Bamfield, British Columbia, represented two contrasting predation regimes: three high‐wave‐energy (exposed) environments have low predation rates, while three low‐wave‐energy (protected) environments exhibit high predation rates. We measured the occurrence of repair scars for local populations of the gastropod Chlorostoma funebrale, and recorded multiple independent variables (shell measurements, water velocity, predatory crab abundance) at each locality. Fisher's exact test established that the repair frequencies observed in the protected localities were significantly greater than those of the exposed environments. Factors important in predicting the likelihood of an individual having a repair scar were examined using binomial logistic regression. A model containing the main effects of crab abundance, shell height, shell thickness and water velocity provided the best fit in predicting the presence of repair scars, with crab abundance having the largest contribution. The strong relationship between the presence of repair scars and predator abundance indicates that repair frequency is a valid tool for assessing predation intensity in gastropod populations.

Prey-induced vertical migration in Chaoborus larvae under different predator and light regimes

For freshwater prey like Daphnia and larvae of Chaoborus, it is well documented that they adjust their residence depth in the water column in response to predator kairomones in order to decrease encounter probability with the respective predator. Despite the importance of infochemicals in predator–prey interactions, it has not been tested if predators adjust their residence depth in response to infochemicals released by prey. Here, we use an indoor system with a stratified water column and show that the predatory phantom midge Chaoborus prefers strata with Daphnia incubation water over strata with control water. Further, the chemically mediated effect of a top predator (fish) on this system was shown to be light dependent with Chaoborus avoiding prey-conditioned water when it also contained fish kairomone in brighter surface water, but not in deeper and thus darker water layers. The foraging kairomone released by Daphnia can be extracted from incubation water via C18-based solid-phase extraction. These results add another dimension to the steering role of infochemicals in predator–prey interactions in zooplankton.

Predation Life History Responses to Increased Temperature Variability

The evolution of life history traits is regulated by energy expenditure, which is, in turn, governed by temperature. The forecasted increase in temperature variability is expected to impose greater stress to organisms, in turn influencing the balance of energy expenditure and consequently life history responses. Here we examine how increased temperature variability affects life history responses to predation. Individuals reared under constant temperatures responded to different levels of predation risk as appropriate: namely, by producing greater number of neonates of smaller sizes and reducing the time to first brood. In contrast, we detected no response to predation regime when temperature was more variable. In addition, population growth rate was slowest among individuals reared under variable temperatures. Increased temperature variability also affected the development of inducible defenses. The combined effects of failing to respond to predation risk, slower growth rate and the miss-match development of morphological defenses supports suggestions that increased variability in temperature poses a greater risk for species adaptation than that posed by a mean shift in temperature.

Co-evolution of offspring antipredator competence and parental brood defense in convict cichlids

Convict cichlids are Neotropical freshwater fish with biparental brood defense of their free-swimming young. In this study, we correlate ontogenetic changes in swimming performance measured by maximum velocity and burst speeds with skeletal ossification of larvae and consider how these data provide insights into the proximate mechanisms for the evolution of parental care. In lab tests, swimming velocity and acceleration of the young increased nonlinearly with body length with a rapid improvement at 7 mm in standard length (SL). The timing of abrupt improvement in swimming velocity and acceleration coincided with the timing of skeletal ossification from cartilage to bone. Radii of defended broods in the field reflected the interaction of parental defense competence and offspring antipredator competence. In the Rio Cabuyo, Costa Rica, brood radii increased steadily until the young were 6.45 mm SL, and then plateaued. Taken together, these data indicate interdependent and co-evolved traits that encompass larval ontogenetic development, antipredator performance, habitat-specific predation regime, and parental care.

Predation risk in tadpole populations shapes behavioural responses of prey but not strength of trait-mediated indirect interactions

Prey animals often respond to predators by reducing activity levels. This can produce a trait-mediated indirect interaction (TMII) between predators and prey resources, whereby reduced foraging by prey in the presence of a predator causes an increase in prey resources. TMIIs play important roles in structuring communities, and it is important to understand factors that determine their strength. One such influence may be behavioural variation in the prey species, with indirect effects of predators being stronger within populations that are more responsive to the presence of a predator. We tested 1) whether the behavioural responsiveness of populations of wood frog tadpoles to predator cues was related to the predation risk in their native ponds, and 2) whether more responsive tadpoles yielded stronger TMIIs. To do this, we 1) measured the activity of tadpoles from 18 populations in mesocosms with and without caged predators, and 2) measured changes in the biomass of periphyton (the tadpoles’ diet) between predator treatments for each population. We found that tadpoles from higher predation risk ponds reduced their time outside refuges more in the presence of predators and tended to move less when visible, suggesting possible local adaptation to predation regimes. Though the presence of predators generally resulted in higher periphyton biomass – a TMII – there was no evidence that the strength of this TMII was affected by variation in tadpole behaviour. Foraging activity and general activity may be decoupled to some extent, enabling high predation risk-adapted tadpoles to limit the fitness costs of reduced foraging when predators are present.

Large-scale climate variability and rodent abundance modulates recruitment rates in Willow Ptarmigan (Lagopus lagopus)

AbstractRecruitment of juveniles is important for the size of the next year’s breeding population in many bird species. Climate variability and predation may affect recruitment rates, and when these factors are spatially correlated, recruitment rates in spatially separated populations of a species may be synchronized. We used production data from an extensive survey of Willow Ptarmigan from 2000 to 2011 to investigate spatial synchrony in recruitment of juveniles within and among mountain region populations. In addition, we assessed the effects of predation and large—as well as local—scale climate on recruitment of juveniles. Recruitment was synchronized both within and among mountain regions, but the mean spatial correlation was strongest among mountain regions. This may be caused by small-scale factors such as predation or habitat structure, or be a result of sampling variation, which may be large at small spatial scales. The strong synchrony suggests that populations are subject to similar environmental forces. We used mixed effect models at the survey area and mountain region scales to assess the effect of rodent abundance (a proxy for predation rates) and local and regional climate during the breeding season on the recruitment of juvenile birds. Model selection based on AICc revealed that the most parsimonious models at both spatial scales included positive effects of rodent abundance and the North Atlantic oscillation during May, June and July (NAOMJJ). The NAOMJJ index was positively related to temperature and precipitation during the pre-incubation period; temperature during the incubation period and positive NAOMJJ values accelerate plant growth. A comparison of the relative effects of NAOMJJ and rodent abundance showed that variation in NAOMJJ had greatest impact on the recruitment of juveniles. This suggests that the climate effect was stronger than the effect of rodent abundance in our study populations. This is in contrast to previous studies on Willow Ptarmigan, but may be explained by the collapse in rodent cycles since the 1990s. If Willow Ptarmigan dynamics in the past were linked to the rodent cycle through a shared predator regime, this link may have been weakened when rodent cycles became more irregular, resulting in a more pronounced effect of environmental perturbation on the dynamics of ptarmigan.

Effect of prey personality depends on predator species

The ability of prey to respond to predators is especially important in human-altered habitats, where prey are faced with changing predator regimes. A growing body of research has shown the important ecological impacts of intraspecific, individual differences in behavior, but few studies have shown direct fitness consequences of behavioral types in a predation context. We examined behavioral syndromes in the endemic Largespring mosquitofish (Gambusia geiseri) and how the behavioral type of individual G. geiseri affected their behavior and survival when exposed to 3 different species of predators. We measured latency to emerge from a container, time spent moving, and tank area used for individual G. geiseri in the presence and absence of predators. We then measured behavior and survival of these same individuals in one-on-one predation trials. We found that behavioral types and correlations between latency to emerge, time spent moving, and area used were consistent regardless of predator presence. Behavioral type did not predict survival of the predation trial. However, higher behavioral scores correlated with more escapes from predatory Fundulus grandis. We argue that this result indicates that active/exploratory fish have a greater ability than their conspecifics to escape this species, which is a novel predator. Our results illustrate the potential importance of considering individual differences in behavior in studying the impacts of introduced predator species.

Proteomic analysis of Daphnia magna hints at molecular pathways involved in defensive plastic responses.

BackgroundPhenotypic plasticity in defensive traits occurs in many species when facing heterogeneous predator regimes. The waterflea Daphnia is well-known for showing a variety of these so called inducible defences. However, molecular mechanisms underlying this plasticity are poorly understood so far. We performed proteomic analysis on Daphnia magna exposed to chemical cues of the predator Triops cancriformis. D. magna develops an array of morphological changes in the presence of Triops including changes of carapace morphology and cuticle hardening.ResultsUsing the 2D-DIGE technique, 1500 protein spots could be matched and quantified. We discovered 179 protein spots with altered intensity when comparing Triops exposed animals to a control group, and 69 spots were identified using nano-LC MS/MS. Kairomone exposure increased the intensity of spots containing muscle proteins, cuticle proteins and chitin-modifying enzymes as well as enzymes of carbohydrate and energy metabolism. The yolk precursor protein vitellogenin decreased in abundance in 41 of 43 spots.ConclusionIdentified proteins may be either directly involved in carapace stability or reflect changes in energy demand and allocation costs in animals exposed to predator kairomones. Our results present promising candidate proteins involved in the expression of inducible defences in Daphnia and enable further in depth analysis of this phenomenon.

Using adaptive traits to consider potential consequences of temporal variation in selection: male guppy colour through time and space

Temporal variation in selection is typically evaluated by estimating and comparing selection coefficients in natural populations. Meta-analyses of these coefficients have yielded important insights, but selection coefficients are limited in several respects, including low statistical power, imperfect fitness surrogates, and uncertainty regarding consequences for trait change. A complementary approach without these limitations is to examine temporal variation in adaptive traits themselves, which is mechanistically easier and more directly relevant to evolutionary consequences. We illustrate this approach by analyzing the colour patterns of male guppies, Poecilia reticulata, from each of six sites in Trinidad in each of 6 years. This system is particularly appropriate for our study because key aspects of colour variation are genetically-based and responsive to selection. However, although spatial patterns of colour variation have been extensively considered in this system, no study has yet formally assessed annual temporal variation in non-manipulated populations. Matching previous conclusions for the guppy system, we find that guppies from different sites manifest different colour patterns in association with different predation regimes. We here add the new finding that, although some temporal variation is present, spatial patterns of colour variation are generally consistent across years. These results suggest that, when considering adaptive traits, spatial variation is more important than temporal variation, although our study system might be exceptional in this regard. Additional studies examining spatiotemporal variation in adaptive traits could help to improve our understanding of the role that spatiotemporal variation in selection plays in the evolutionary process. © 2014 The Linnean Society of London, Biological Journal of the Linnean Society, 2014, 112, 108–122.

Predator-driven intra-species variation in locomotion, metabolism and water velocity preference in pale chub (Zacco platypus) along a river

Fish inhabit environments that vary greatly in terms of predation intensity, and these predation regimes are generally expected to be a major driver of divergent natural selection. To test whether there is predator-driven intra-species variation in the locomotion, metabolism and water velocity preference of pale chub (Zacco platypus) along a river, we measured unsteady and steady swimming and water velocity preference among fish collected from both high- and low-predation habitats in the Wujiang River. We also measured the routine metabolic rate (RMR), maximum metabolic rate (MMR) and cost of transport (COT) and calculated the optimal swimming speed (Uopt). The fish from the high-predation populations showed a shorter response latency, elevated routine metabolism, lower swimming efficiency at low swimming speed and lower water velocity preference compared with those from the low-predation populations. Neither of the kinematic parameters fast-start and critical swimming speed (Ucrit) showed a significant difference between the high- and low-predation populations. The fish from the high-predation populations may improve their predator avoidance capacity primarily through an elevated routine metabolism and shorter response latency to achieve advanced warning and escape, rather than an improved fast-start swimming speed or acceleration. Thus, the cost of this strategy is an elevated RMR, and no trade-off between unsteady and steady swimming performance was observed in the pale chub population under various predation stresses. It was interesting to find that the high-predation fish showed an unexpected lower velocity preference, which might represent a compromise between predation avoidance, foraging and energy saving.

Natural selection in novel environments: predation selects for background matching in the body colour of a land fish

antipredator camouflage colonization colour crypsis invasion success Pacific leaping blenny The invasion of a novel habitat often results in a variety of new selective pressures on an individual. One pressure that can severely impact population establishment is predation. The strategies that animals use to minimize predation, especially the extent to which those strategies are habitat or predator specific, will subsequently affect individuals’ dispersal abilities. The invasion of land by a fish, the Pacific leaping blenny, Alticus arnoldorum, offers a unique opportunity to study natural selection following the colonization of a novel habitat. Various studies have examined adaptations in respiration and locomotion, but how these fish have responded to the predation regime on land was unknown. We studied five replicate populations of this fish around the island of Guam and found their body coloration converged on the terrestrial rocky backgrounds on which the fish were most often found. Subsequent experiments confirmed that this background matching significantly reduced predation. Natural selection has therefore selected for background matching in the body coloration of the Pacific leaping blenny to minimize predation, but it is a strategy that is habitat specific. A subsequent comparative study of closely related blenny species suggested that the evolutionary ancestor of the Pacific leaping blenny might have resembled the rocky backgrounds on land prior to invasion. The ancestors of the Pacific leaping blenny may therefore have already been ideally suited for the predator regime on land. More generally our results imply that animals must either already possess antipredator strategies that will be effective in new environments, or must adapt very quickly to new predation pressures if successful establishment is to occur.

EVOLUTION OF MALE COLORATION DURING A POST-PLEISTOCENE RADIATION OF BAHAMAS MOSQUITOFISH (GAMBUSIA HUBBSI)

Sexual signal evolution can be complex because multiple factors influence the production, transmission, and reception of sexual signals, as well as receivers' responses to them. To grasp the relative importance of these factors in generating signal diversity, we must simultaneously investigate multiple selective agents and signaling traits within a natural system. We use the model system of the radiation of Bahamas mosquitofish (Gambusia hubbsi) inhabiting blue holes to test the effects of resource availability, male body size and other life-history traits, key aspects of the transmission environment, sex ratio, and predation risk on variation in multiple male color traits. Consistent with previous work examining other traits in this system, several color traits have repeatedly diverged between predation regimes, exhibiting greater elaboration in the absence of predators. However, other factors proved influential as well, with variation in resource levels, body size, relative testes size, and background water color being especially important for several color traits. For one prominent signaling trait, orange dorsal fins, we further confirmed a genetic basis underlying population differences using a laboratory common-garden experiment. We illustrate a promising approach for gaining a detailed understanding of the many contributing factors in the evolution of multivariate sexual signals.

Predation‐associated divergence of male genital morphology in a livebearing fish

Male genital morphology is remarkably diverse across internally fertilizing animals, a phenomenon largely attributed to sexual selection. Ecological differences across environments can alter the context of sexual selection, yet little research has addressed how this may influence the rapid, divergent evolution of male genitalia. Using the model system of Bahamas mosquitofish (Gambusia hubbsi) undergoing ecological speciation across blue holes, we used geometric morphometric methods to test (i) whether male genital shape (the small, approximately 1mm long, distal tip of the sperm-transfer organ, the gonopodium) has diverged between populations with and without predatory fish and (ii) whether any observed divergence has a genetic basis. We additionally examined the effects of genetic relatedness and employed model selection to investigate other environmental factors (i.e. interspecific competition, adult sex ratio and resource availability) that could potentially influence genital shape via changes in sexual selection. Predation regime comprised the most important factor associated with male genital divergence in this system, although sex ratio and some aspects of resource availability had suggestive effects. We found consistent, heritable differences in male genital morphology between predation regimes: Bahamas mosquitofish coexisting with predatory fish possessed more elongate genital tips with reduced soft tissue compared with counterparts inhabiting blue holes without predatory fish. We suggest this may reflect selection for greater efficiency of sperm transfer and fertilization during rapid and often forced copulations in high-predation populations or differences in sexual conflict between predation regimes. Our study highlights the potential importance of ecological variation, particularly predation risk, in indirectly generating genital diversity.

The effects of low levels of light at night upon the endocrine physiology of western scrub‐jays (Aphelocoma californica)

Florida scrub-jays (Aphelocoma coerulescens) in the suburbs breed earlier than jays in native habitat. Amongst the possible factors that influence this advance (e.g., food availability, microclimate, predator regime, etc.), is exposure to artificial lights at night (LAN). LAN could stimulate the reproductive axis of the suburban jays. Alternatively, LAN could inhibit pineal melatonin (MEL), thus removing its inhibitory influence on the reproductive axis. Because Florida scrub-jays are a threatened species, we used western scrub-jays (Aphelocoma californica) to investigate the effects of LAN upon reproductive hormones and melatonin. Jays were held under conditions in which the dark-phase of the light:dark cycle was without illumination and then under low levels of LAN. Under both conditions, birds were exposed first to short-days (9.5L:14.5D) that were gradually increased to long-days (14.5L:9.5D). At various times, blood samples were collected during the light part of the cycle to measure reproductive hormones (luteinizing hormone, LH; testosterone, T; and estradiol, E2 ). Similarly, samples to assess melatonin were collected during the dark. In males, LAN caused a depression in LH levels and levels were ∼4× greater under long- than short-days. In females, there was no effect of LAN or photoperiod upon LH. LAN resulted in depressed T levels in females, although there was no effect on T in males. E2 levels in both sexes were lower under LAN than under an unlighted dark-phase. Paradoxically, MEL was higher in jays under LAN, and under long-days. MEL did not differ by sex. LAN disrupted the extraordinarily strong correlation between T and E2 that existed under unlighted nocturnal conditions. Overall, our findings fail to support the hypothesis that LAN stimulates the reproductive axis. Rather, the data demonstrate that LAN tends to inhibit reproductive hormone secretion, although not in a consistent fashion between the sexes.

Predator density and timing of arrival affect reef fish community assembly

Most empirical studies of predation use simple experimental approaches to quantify the effects of predators on prey (e.g., using constant densities of predators, such as ambient vs. zero). However, predator densities vary in time, and these effects may not be well represented by studies that use constant predator densities. Although studies have independently examined the importance of predator density, temporal variability, and timing of arrival (i.e., early or late relative to prey), the relative contribution of these different predator regimes on prey abundance, diversity, and composition remains poorly understood. The hawkfish (Paracirrhites arcatus), a carnivorous coral reef fish, exhibits substantial variability in patch occupancy, density, and timing of arrival to natural reefs. Our field experiments demonstrated that effects of hawkfish on prey abundance depended on both hawkfish density and the timing of their arrival, but not on variability in hawkfish density. Relative to treatments without hawkfish, hawkfish presence reduced prey abundance by 50%. This effect increased with a doubling of hawkfish density (an additional 33% reduction), and when hawkfish arrived later during community development (a 34% reduction). Hawkfish did not affect within-patch diversity (species richness), but they increased between-patch diversity (beta) based on species incidence (22%), and caused shifts in species composition. Our results suggest that the timing of predator arrival can be as important as predator density in modifying prey abundance and community composition.

Predator avoidance in extremophile fish.

Extreme habitats are often characterized by reduced predation pressures, thus representing refuges for the inhabiting species. The present study was designed to investigate predator avoidance of extremophile populations of Poecilia mexicana and P. sulphuraria that either live in hydrogen sulfide-rich (sulfidic) springs or cave habitats, both of which are known to have impoverished piscine predator regimes. Focal fishes that inhabited sulfidic springs showed slightly weaker avoidance reactions when presented with several naturally occurring predatory cichlids, but strongest differences to populations from non-sulfidic habitats were found in a decreased shoaling tendency with non-predatory swordtail (Xiphophorus hellerii) females. When comparing avoidance reactions between P. mexicana from a sulfidic cave (Cueva del Azufre) and the adjacent sulfidic surface creek (El Azufre), we found only slight differences in predator avoidance, but surface fish reacted much more strongly to the non-predatory cichlid Vieja bifasciata. Our third experiment was designed to disentangle learned from innate effects of predator recognition. We compared laboratory-reared (i.e., predator-naïve) and wild-caught (i.e., predator-experienced) individuals of P. mexicana from a non-sulfidic river and found no differences in their reaction towards the presented predators. Overall, our results indicate (1) that predator avoidance is still functional in extremophile Poecilia spp. and (2) that predator recognition and avoidance reactions have a strong genetic basis.

A review on utilizing Bosmina size structure archived in lake sediments to infer historic shifts in predation regimes

Zooplankton are considered excellent indicators of aquatic food web structure, due to their role as grazers on primary producers and their sensitivity to predation by both planktivorous fish and invertebrates. Several key zooplankton taxa also leave identifiable remains that are often well-preserved in lake sediments, providing an opportunity to track changes in predation pressure over timescales of decades to thousands of years. For example, the small-bodied cladoceran zooplankter Bosmina (Branchiopoda, Crustacea) is often highly abundant in lake sediments, and because Bosmina often undergoes cyclomorphosis in response to fish and invertebrate predation, measurements of subfossil Bosmina features can be indicative of predation regime shifts. This review focuses on Bosmina cyclomorphic responses to varying predation regimes and the application of these principles to Bosmina subfossil remains to better understand long-term ecological changes occurring in lakes. We conclude that subfossil Bosmina size structure is a promising indicator of historic changes in predation pressure in response to fish introductions/extirpations/population