Predator Feeding Research Articles

Natural Enemies Associated with Brevipalpus sp. (Acari: Tenuipalpidae), Vector of Citrus Leprosis

Natural Enemies Associated with <i>Brevipalpus</i> sp. (Acari: Tenuipalpidae), Vector of Citrus Leprosis

Secondary predation constrains DNA-based diet reconstruction in two threatened shark species

Increasing fishing effort, including bycatch and discard practices, are impacting marine biodiversity, particularly among slow-to-reproduce taxa such as elasmobranchs, and specifically sharks. While some fisheries involving sharks are sustainably managed, collateral mortalities continue, contributing towards > 35% of species being threatened with extinction. To effectively manage shark stocks, life-history information, including resource use and feeding ecologies is pivotal, especially among those species with wide-ranging distributions. Two cosmopolitan sharks bycaught off eastern Australia are the common blacktip shark (Carcharhinus limbatus; globally classified as Near Threatened) and great hammerhead (Sphyrna mokarran; Critically Endangered). We opportunistically sampled the digestive tracts of these two species (and also any whole prey; termed the ‘Russian-doll’ approach), caught in bather-protection gillnets off northern New South Wales, to investigate the capacity for DNA metabarcoding to simultaneously determine predator and prey regional feeding ecologies. While sample sizes were small, S. mokkaran fed predominantly on stingrays and skates (Myliobatiformes and Rajiformes), but also teleosts, while C. limbatus mostly consumed teleosts. Metabarcoding assays showed extensive intermixing of taxa from the digestive tracts of predators and their whole prey, likely via the predator’s stomach chyme, negating the opportunity to distinguish between primary and secondary predation. This Russian-doll effect requires further investigation in DNA metabarcoding studies focussing on dietary preferences and implies that any outcomes will need to be interpreted concomitant with traditional visual approaches.

Correction to: Whale shark (Rhincodon typus) predatory flexible feeding behaviors on schooling fish

Correction to: Whale shark (Rhincodon typus) predatory flexible feeding behaviors on schooling fish

Ecology and Life History of Snook Species in Texas

AbstractIn recent years, the abundance and distribution of snook species (Centropomus spp.) have increased and expanded in Texas. As mobile predators, snook have the potential to alter marine communities as they expand; however, little is known about the functional impact of snook in Texas. Here, a long‐term (1982–2019) fishery‐independent data set was utilized to describe snook life history characteristics. Bag‐seine and gill‐net data were used to determine distribution, size, spawning, and recruitment seasonality for Common Snook C. undecimalis and Fat Snook C. parallelus in Texas. Snook collected from the lower Laguna Madre were used to describe diet, length–weight relationships, and sex ratios. Results indicated that both Common and Fat snook abundance and range increased in Texas with expansion primarily led by Common Snook. Common Snook were larger than Fat Snook based on the length frequency analysis, but the latter were heavier at a given length. Spawning season for both species occurred during summer and peaked in July and August for Fat and Common snook, respectively. Evidence for protandric hermaphroditism was observed in Common Snook with females being significantly larger than males and a 50:50 male‐to‐female ratio occurring at 670 mm total length (TL). Diet analyses indicated that Common and Fat snook are generalist predators feeding on a variety of prey species. An ontogenetic shift in diet was observed in Common Snook as individuals &lt;500 mm TL fed primarily on shrimp, and those ≥500 mm TL fed primarily on fish. Fat Snook and subadult Common Snook possessed a high degree of dietary overlap, with shrimp being the most common prey item identified for each. These findings provide managers with the foundational aspects of snook life history at a time when the potential effects of the snook range expansion in Texas remain largely undescribed.

Energetic and health effects of protein overconsumption constrain dietary adaptation in an apex predator

Studies of predator feeding ecology commonly focus on energy intake. However, captive predators have been documented to selectively feed to optimize macronutrient intake. As many apex predators experience environmental changes that affect prey availability, limitations on selective feeding can affect energetics and health. We estimated the protein:fat ratio of diets consumed by wild polar bears using a novel isotope-based approach, measured protein:fat ratios selected by zoo polar bears offered dietary choice and examined potential energetic and health consequences of overconsuming protein. Dietary protein levels selected by wild and zoo polar bears were low and similar to selection observed in omnivorous brown bears, which reduced energy intake requirements by 70% compared with lean meat diets. Higher-protein diets fed to zoo polar bears during normal care were concurrent with high rates of mortality from kidney disease and liver cancer. Our results suggest that polar bears have low protein requirements and that limitations on selective consumption of marine mammal blubber consequent to climate change could meaningfully increase their energetic costs. Although bear protein requirements appear lower than those of other carnivores, the energetic and health consequences of protein overconsumption identified in this study have the potential to affect a wide range of taxa.

Higher reproductive performance of a piscivorous avian predator feeding on lower trophic-level diets on ponds with shorter food chains

Variation in food-chain length may influence a predator’s trophic position. In aquatic food webs, the energy value of prey typically increases with its trophic rank; hence a higher trophic-level diet is often assumed to indicate better habitat quality. We related the body and health condition of pre-fledged Red-necked Grebes Podiceps grisegena to their dietary trophic level (estimated using stable nitrogen isotope signals of feathers) in two managed pond habitats with contrasting prey availability due to different fish population structures. Ponds stocked with young, small common carp Cyprinus carpio provided abundant fish and non-fish (insects and amphibians) resources for chicks. In ponds stocked with large carp, which also supported populations of small predatory fish, the breeding success of grebes was comparatively poor, because carp exceeded the size suitable for chicks and adversely affected non-fish prey. Pre-fledged grebes were in better condition (greater body mass, lower heterophil/lymphocyte ratio) in the food-rich small-fish ponds than in the food-poor ponds dominated by large fish. Values for δ15N suggested shorter food chains and a lower trophic-level diet for grebes in the food-rich ponds. Bayesian carbon and nitrogen isotope mixing models demonstrated the dietary prominence of small fish, both carp and predatory species. Between-habitat differences in food-chain length and grebe trophic position resulted from the higher trophic rank of small predatory fish in the food-poor ponds compared to the omnivorous carp in the food-rich ponds. Our results suggest that in aquatic food webs, feeding at higher trophic levels by strongly size-limited generalist avian predators can be associated with overall food scarcity due to the impact of fish, and thus trophic status cannot be used uncritically as a proxy for aquatic habitat quality.

Feeding habits of Lithobates megapoda (Anura: Ranidae), a threatened leopard frog used for human consumption, in Lake Chapala, Mexico

The Big-footed Leopard Frog (Lithobates megapoda) is a threatened and endemic species from western Mexico. This species has aquatic habits and it is distinguished by its large size, particularly by the length of its legs, reason for which it is captured for human consumption. Also, knowledge about its natural history is scarce and incomplete. In this study, we analyzed the composition of the diet of L. megapoda on the shore of Lake Chapala, the largest lake in Mexico. A total of 69 adult individuals were collected lifeless in fishing nets, during the rainy season (June-October), of which 48 had stomach contents. A total of 96 prey items were identified, which correspond to 13 prey categories. Fish constituted the most dominant prey category in the diet in terms of number, volume, frequency of occurrence, and relative importance. No significant differences were found in the consumption by prey type (aquatic or terrestrial). However, the aquatic preys had a greater relative importance and were more voluminous than the terrestrial ones. The diversity of prey categories, in terms of prey volume, indicates males may have a higher dietary diversity than females, but we not evaluated possible bias. In addition, a significant effect was found in the interaction of size (SVL) of frogs with the average of prey volume. Females (that are larger than males) consumed prey within a wide volume range and, the larger they are, more voluminous are prey. In this way it is possible that intraspecific competition for trophic resources in the environment is reduced. This study helps us understand the trophic ecology of L. megapoda, a frog species that plays an important role in the food web where it lives, as a predator feeding on aquatic and terrestrial organisms.

Quantifying the effects of intraspecific variation on predator feeding rates through nonlinear averaging

Abstract Theory suggests that intraspecific trait variation will alter species interaction strengths through nonlinear averaging when interaction strengths are nonlinear functions of individuals' traits. This effect is expected to be widespread, yet what factors mediate its magnitude in nature and hence its potential effects on ecosystems and communities are unclear. We sought to quantify how nonlinear predator functional responses, variation in prey densities and counteracting variation in attack rates and handling times among predator individuals of similar body size alter their population‐level feeding rates through nonlinear averaging in a natural system, and to determine the processes influencing the net magnitude of this effect. We used a field caging experiment in the rocky intertidal of Oregon, USA to quantify attack‐rate variation and feeding rates of the whelk Nucella ostrina on its barnacle and mussel prey. We also used empirically parameterized simulations to examine the effects of handling‐time variation among individuals on population‐level feeding rates. Within cages, individual attack‐rate variation reduced population‐level whelk feeding rates. However, the magnitude of this reduction differed among prey species and cages depending on cage‐specific magnitudes of attack‐rate variation and functional‐response nonlinearity. The inferred effects of handling‐time variation among individuals were of smaller magnitude than those of attack‐rate variation, yet counteracted them to cause a net weakening of the effect of individual attack‐rate variation on population‐level feeding rates. Across cages, attack‐rate and prey‐density variation had non‐additive effects that produced greater feeding‐rate reductions at the experiment scale relative to the cage scale. Our results indicate that the effects of trait variation via nonlinear averaging depend critically on the features of systems that determine the magnitudes of nonlinearities and trait variation. Because of counteracting trait variation, nonlinear‐averaging effects may be quite complex, involving both the variances and covariances of all traits and environmental variables influencing the ecological process of interest. A free Plain Language Summary can be found within the Supporting Information of this article.

Functional Pattern of Benthic Epifauna in the Chukchi Borderland, Arctic Deep Sea

Assessment of Arctic deep-sea ecosystem functioning is currently an urgent task considering that ongoing sea-ice reduction opens opportunities for resource exploitation of yet understudied deep-sea regions. We used Biological Trait Analysis to evaluate ecosystem functioning and test if common paradigms for deep-sea fauna apply to benthic epifauna of the deep-sea Arctic Chukchi Borderland (CBL). We also investigated the influence of environmental factors on the functional structure of the epifauna. The analysis was performed for 106 taxa collected with a beam trawl and a Remotely Operated Vehicle from 486 to 2610 m depth. The most common trait modalities were small-medium size, mobile, benthic direct and lecithotrophic larval development, and predatory feeding, which mostly supports the current view of epifauna in the global deep sea. Functional composition of epifauna differed between two depth strata (486–1059 m and 1882–2610 m), with depth and sediment carbon content explaining most of the functional variability. Proportional abundances of the modalities free-living, swimming, suspension feeders, opportunists/scavengers, internal fertilization and globulose were higher at deep stations. Functional redundancy (FR) was also higher there compared to the mid-depth stations, suggesting adaptation of fauna to the more homogeneous deep environment by fewer and shared traits. Mid-depth stations represented higher functional variability in terms of both trait modality composition and functional diversity, indicating more variable resource use in the more heterogeneous habitat. Food input correlated positively with the proportional abundance of the modalities tube-dwelling, sessile and deposit feeding. Areas with drop stones were associated with higher proportional abundance of the modalities attached, upright, and predators. Comparatively low FR may render the heterogeneous mid-depth area of the CBL vulnerable to disturbance through the risk of loss of functions. Across the study area, high occurrence of taxa with low dispersal ability among adult and larval life stages may prevent rapid adaptation to changes, reduce ability to recolonize and escape perturbation.

Dietary reconstruction and evidence of prey shifting in Pleistocene and recent gray wolves (Canis lupus) from Yukon Territory

We investigate if and how diets of gray wolves from the Yukon Territory, Canada, have changed from the Pleistocene (>52.8 ka BP to 26.5 ka BP [±170 y BP]) to the recent Holocene (1960s) using dental microwear analysis of carnassial teeth and stable isotope analyses of carbonates (δ13CCO3 and δ18OCO3) and collagen (δ13Ccol and δ15Ncol) from bone. We find that dental microwear patterns are similar between the Pleistocene and Holocene specimens, indicating that there has been no change in carcass utilization behaviours, where flesh, not bone, is primarily consumed. Based on minimal changes in δ13CCO3 and δ13Ccol values, we find that, over thousands of years, Yukon gray wolves have remained generalist predators feeding upon several large ungulate species. Interestingly, δ15Ncol values suggest that the extinction of megafaunal species at ~11.7 Ka induced a shift from a diet comprised primarily of horse (Equus sp.) to one based on cervids (i.e. moose and caribou). Survival of large-bodied cervids, such as caribou (Rangifer tarandus), was likely key to wolf survival. Although gray wolves survived the end Pleistocene megafauna extinction and demonstrate a degree of ecological flexibility, we suggest that failure to preserve major elements of their current niche (e.G. caribou) may result in continued population declines, especially in the face of increasing anthropogenic influences.

Estimating predator functional responses using the times between prey captures.

Predator functional responses describe predator feeding rates and are central to predator-prey theory. Ecologists have measured thousands of predator functional responses using the same basic experimental method. However, this design is ill-suited to address many current questions regarding functional responses. We derive a new experimental design and statistical analysis that quantifies functional responses using the times between a predators' feeding events requiring only one or a few trials. We examine the feasibility of the experimental method and analysis using simulations to assess the ability of the statistical model to estimate functional response parameters and perform a proof-of-concept experiment estimating the functional responses of two individual jumping spiders. Our simulations show that the statistical method reliably estimates functional response parameters. Our proof-of-concept experiment illustrates that the method provides reasonable estimates of functional response parameters. By virtue of the fewer number of trials required to measure a functional response, the method derived here promises to expand the questions that can be addressed using functional response experiments and the systems in which they can be measured. Thus, we hope that our method will refine our understanding of functional responses and predator-prey interactions more generally.

Bacterial Composition and Diversity of the Digestive Tract of Odontomachus monticola Emery and Ectomomyrmex javanus Mayr.

Simple SummaryBacteria are considered to be one of the compelling participants in ant dietary differentiation. The digestive tract of ants is characterized by a developed crop, an elaborate proventriculus, and an infrabuccal pocket, which is a special filtrating structure in the mouthparts, adapting to their special trophallaxis behavior. Ponerine ants are true predators and a primitive ant group; notably, their gut bacterial communities get less attention than herbivorous ants. In this study, we investigated the composition and diversity of bacterial communities in the digestive tract and the infrabuccal pockets of two widely distributed ponerine species (Odontomachus monticola Emery and Ectomomyrmex javanus Mayr) in northwestern China using high-throughput sequencing of the bacterial 16S rRNA gene. The results revealed that, not only do the gut bacterial communities display significant interspecies differences, but they also possess apparent intercolony characteristics. Within each colony, the bacterial communities were highly similar between each gut section (crops, midguts, and hindguts) of workers, but significantly different from their infrabuccal pockets, which were similar to bacterial communities in larvae of O. monticola. The relationship of the bacterial communities among the infrabuccal pockets, gut sections and larvae provide meaningful information to understand the social life and feeding behavior of ants.Ponerine ants are generalist predators feeding on a variety of small arthropods, annelids, and isopods; however, knowledge of their bacterial communities is rather limited. This study investigated the bacterial composition and diversity in the digestive tract (different gut sections and the infrabuccal pockets (IBPs)) of two ponerine ant species (Odontomachus monticola Emery and Ectomomyrmex javanus Mayr) distributed in northwestern China using high-throughput sequencing. We found that several dominant bacteria that exist in other predatory ants were also detected in these two ponerine ant species, including Wolbachia, Mesoplasma, and Spiroplasma. Bacterial communities of these two ant species were differed significantly from each other, and significant differences were also observed across their colonies, showing distinctive inter-colony characteristics. Moreover, bacterial communities between the gut sections (crops, midguts, and hindguts) of workers were highly similar within colony, but they were clearly different from those in IBPs. Further, bacterial communities in the larvae of O. monticola were similar to those in the IBPs of workers, but significantly different from those in gut sections. We presume that the bacterial composition and diversity in ponerine ants are related to their social behavior and feeding habits, and bacterial communities in the IBPs may play a potential role in their social life.

Allelopathy and micropredation paradigms reconcile with system stoichiometry

AbstractAllelopathy, a type of interference competition involving exuded chemicals, has been documented for several types of organisms including terrestrial plants, aquatic macrophytes, microbes, and planktonic algae. However, due to the dynamic nature of the aquatic environment it is unclear whether allelopathy is an evolutionarily stable competition mechanism in such a setting. In this research, we consider a cosmopolitan harmful algae species, Prymnesium parvum, for which multiple ecological roles of its produced deleterious chemicals have been suggested, including broadcast allelopathy (chemicals produced and exuded) and micropredation via cell–cell interactions (chemicals produced and held within the cell). To further investigate the ecological role of the deleterious chemicals, bioassays (with phytoplankton and zooplankton target organisms) were conducted using various fractions of a P. parvum culture grown under balanced N:P stoichiometry or imbalanced, P‐reduced stoichiometry. In addition, time‐series counts were generated with cell density enumerations and observations of behavior of a mixed species culture at intervals over a 24‐h period. Our results suggest that the apparent ecological role of the chemicals in a relatively high‐density population shifts depending on system stoichiometry in regard to nitrogen and phosphorus. We show that under balanced N:P conditions, deleterious chemical production is low and cell contact mediates mortality of prey. Differently, under imbalanced, P‐reduced conditions chemical effect is high and mass mortality occurs independent of cell contact. Thus, imbalanced N:P ratios shift the apparent ecological role of the deleterious chemicals from one of micropredation to one of broadcast allelopathy. These differences likely influence bloom dynamics and result in different ecological outcomes for systems affected by blooms. Further, we suggest that these differences indicate the importance of predatory mixotrophic feeding in the evolutionary maintenance of deleterious chemical production and the occurrence of allelopathic effects as a byproduct.

Deep learning classification of tooth scores made by different carnivores: achieving high accuracy when comparing African carnivore taxa and testing the hominin shift in the balance of power

The balance of power (that is the dominance on the predation arena between carnivore competitors and hominins) remains controversial. One reflection of this is the carnivore modification of hominin bones. During human evolution, hominins were first prey and then predators of other animals, including carnivores. Modifications reported on some hominin bones could result from primary predators feeding on them or post-depositional modifications by scavengers. Determining carnivore agency would be crucial to interpret such information. Here, a series of computer vision models based on convolutional neural networks is presented, comparing five different types of carnivores jointly and then pairwise. It is shown how such models contain different heuristics regarding specific carnivore taxa, which regarding tooth marks made by lions and spotted hyenas can be accurately classified by as much as 92% of the testing set. The present study also shows the potential of transfer knowledge in building accurate classification of images and for taphonomic interpretation. The application to tooth marking on a 500 ka hominin femoral shaft indicates that by that time, carnivore modifications of human remains may have resulted from post-depositional scavenging rather than by predation.

Asymptotic spreading speeds for a predator–prey system with two predators and one prey

This paper investigates the large time behaviour of a three species reaction–diffusion system, modelling the spatial invasion of two predators feeding on a single prey species. In addition to the competition for food, the two predators exhibit competitive interactions and, under some parameter condition, they can also be considered as two mutants. When mutations occur in the predator populations, the spatial spread of invasion takes place at a definite speed, identical for both mutants. When the two predators are not coupled through mutation, the spreading behaviour exhibits a more complex propagating pattern, including multiple layers with different speeds. In addition, some parameter conditions reveal situations where a nonlocal pulling phenomenon occurs and in particular where the spreading speed is not linearly determined.

Different combinations of serotonin receptors regulate predatory and bacterial feeding behaviors in the nematode Pristionchus pacificus.

Feeding behavior is one of the most fundamental behaviors in animals, and regulation of this behavior is critical for proper food intake. The nematode Pristionchus pacificus exhibits dimorphism in feeding behavior, bacterial feeding and predatory feeding on other nematodes, and the latter behavior is assumed to be an evolutionarily novel behavior. Both types of feeding behavior are modulated by serotonin; however, the downstream mechanism that modulates these behaviors is still to be clarified. Here, we focused on serotonin receptors and examined their expression patterns in P. pacificus. We also generated knockout mutants of the serotonin receptors using the CRISPR/Cas9 system and examined feeding behaviors. We found that Ppa-ser-5 mutants and the Ppa-ser-1; Ppa-ser-7 double mutant decreased predation. Detailed observation of the pharyngeal movement revealed that the Ppa-ser-1; Ppa-ser-7 double mutant reduces tooth movement, which is required for efficient predatory feeding. Conversely, Ppa-ser-7 and Ppa-mod-1 mutants decreased bacterial feeding. This study revealed that specific combinations of serotonin receptors are essential for the modulation of these distinct feeding behaviors, providing insight into the evolution of neural pathways to regulate novel feeding behavior.

Focus on Diverse Species

Birds are unique animals. They can fly, sing, and flaunt a rainbow of vivid colors. No other animals can make that claim. It’s not unusual for families to hang bird feeders around their property so that they can watch these feathered friends as they pause to check out the feasts being set out for them.One of the aims of this book is to encourage readers to set up bird feeders. Watching birds in your yard allows you to observe how they are adapted to their environment. Birds that have access to feeders have better overall fitness and a better chance of survival during very cold weather. About 10% of the diet of feeder-using birds actually comes from the feeders.Numerous suggestions are presented for types of seeds, as well as other foods such as suet, fruits, jellies, and mealworms, to put in feeders. Different types of feeders used for specific foods, ranging from tube and platform feeders to suet and nectar feeders, are described with colorful pictures and explanations. Illustrated ideas for clever do-it-yourself feeders include blueprints and provide schemes for fashioning your own creations. There is much advice about setting up these feeding stations, knowing how to determine seed freshness, how to store seeds, and when to discard them. Tips for arranging the yard to attract birds include kinds of plants from which birds might profit, how to provide for birds’ other needs (such as food, water, nesting materials, shelter, space), and how to deal with squirrels and cats.Enjoyable features of birdwatching include bird behavior, appearances, and adaptations. Suggested actions to look for include aggression, feather maintenance, threat displays, feeding, detection and avoidance of predators, and courtship and care of offspring. Notable adaptations and appearances to look for are similarities and differences in beak, foot, and wing shapes and unusual appearances and deformities.In addition to all of this valuable information, about half of the book is a dazzling section on the identification of birds that have been known to acquire meals at feeders. As the author points out, when you have a bird feeder, “you never know what species may show up.” But there are many features that can help identify the feeder feasters. Some are more complicated than others, but Earley provides helpful instructions for establishing bird body sizes and shapes, beak and tail characteristics, and kinds of movement. Field marks are considered the best traits to explore when first trying to identify a bird. These marks include head, eye, and facial characteristics; patches, streaks, and bars on the body; and many other clues.A convenient “Bird Quick-Find Guide” with 72 small pictures of birds is offered for use in attempting to identify an unknown bird at a feeder. Each picture suggests bird groups and page numbers in which an unknown bird might be found among the more than 150 additional pages describing characteristics that can help with identification. Many of these handy avian profiles incorporate maps showing where the birds are found, as well as suggestions on what to feed them. Since every possible feeder visitor is not necessarily included in this book, it is suggested that a complete field guide of North American birds may also be needed to help identify some of the feathered friends found at the feeder.Feed the Birds is a spectacular and lavishly illustrated volume that would be perfect for anyone who enjoys birds – their appearance, their behavior, and their presence on feeders. It is appropriate for middle school, high school, college, and adult readers. In addition to an index, Feed the Birds includes a fill-in chart for recording the reader’s bird experiences, a list of references, and suggestions for further reading. As you enjoy this book, remember that “the Earley bird gets the worm.”

Secondary production of macroinvertebrates as indicators of success in stream rehabilitation

AbstractHydromorphological rehabilitation is increasingly being used to reverse degradation of stream and river ecosystems. River rehabilitation projects have nevertheless been criticised for not meeting their goals or for not being monitored sufficiently well to assess whether their goals were met. There is therefore an urgent need to develop robust approaches to assessing treatment efficacy and to thus guide the increasing investment in rehabilitation. A headwater tributary of the River Welland in Leicestershire, UK was rehabilitated in summer 2014. Rehabilitation included removal of weirs and the creation of a distinct and meandered low‐flow channel with pool‐riffle sequences. Macroinvertebrates were collected in random sampling protocols stratified at in‐stream biotope level. The rehabilitated reach was compared with a semi‐natural upstream reach as a reference, and a similarly degraded reach as a control. This study demonstrated that rehabilitation of the River Welland had clear beneficial effects on ecological processes. It demonstrated that active re‐creation of lost biotope heterogeneity improved macroinvertebrate biodiversity and secondary production, which is the formation of heterotrophic biomass through time. The rehabilitated reach yielded higher production estimates for Gastropoda, Bivalvia, Malacostraca, Odonata, Arachnida and Ephemeroptera, Plecoptera and Trichoptera, and a lower estimate for Chironomidae relative to the control reach. The rehabilitated reach also had higher estimates of production for Shredder, Scraper, Filter‐feeder and Predator feeding groups relative to the control reach. Rehabilitation works transformed the reach from a condition more akin to the degraded reach to being more similar to the semi‐natural reach. These outcomes demonstrate recovery of the reach's entire macroinvertebrate community structure and function after rehabilitation. The results provide a clear message to river rehabilitation practitioners: rehabilitation of the function of a physically degraded river ecosystem is possible if the rehabilitation is planned to actively restore the lost in‐stream biotope diversity.

Spiders mimic the acoustic signalling of mutillid wasps to avoid predation: startle signalling or Batesian mimicry?

The importance of vision-reliant defensive traits (e.g. warning colours) in mimicry studies is well established, but their effectiveness is limited by visibility. In low light conditions, for instance, acoustic or tactile channels may be more effective. The juvenile and adult stages of the nocturnal hunting Palpimanus spiders audibly stridulate when harassed. Given this we hypothesized that the sound produced by Palpimanus has a defensive role against interspecific predators. Palpimanus though are poorly defended especially against something as large as a gecko. Hence we hypothesized that the stridulation is effective because the spider mimics co-occurring mutillid wasps. We staged predator feeding experiments in which mutillid wasps, sham-operated Palpimanus, silenced Palpimanus and a nonstridulating spider were offered to Eusparassus spiders and geckoes. Stridulating spiders had significantly greater survival against both predators than the nonstridulating treatments and comparable survival to the mutillid wasps. This result represents the first confirmed case of a spider using stridulation against an interspecific predator. Stridulation deterred Eusparasus spiders, while in geckoes stridulation acted postcapture as they dropped the prey instead of attempting to swallow them. For mutillid wasps this dropping response was typically more rapid than with Palpimanus but attempts to swallow silenced individuals were more frequent than sham-operated individuals, which were more likely to be dropped before any attempt to swallow. Analyses of stridulation characteristics of Palpimanus showed they were similar to acoustic signals of four of the co-occurring mutillid wasps and far more so than distress signals of control insects. Our study overall supports the notion that Palpimanus spiders are Batesian mimics of sympatrically occurring mutillids through the use of an aposematic acoustic signal and not just an example of a startle response.

Food availability, depth, and turbidity drive zooplankton functional diversity over time in a Neotropical floodplain

We evaluated temporal trends in zooplankton functional diversity (functional richness—FRic, evenness—FEve divergence—FDiv, and Community-Weighted Means—CWM) in 12 habitats of the Upper Parana River floodplain (Brazil) over 16 years (2000–2016) and their relationships with environmental predictors (chlorophyll-a, water depth, and turbidity). We hypothesized that different environmental drivers affect zooplankton's functional component in a distinct way. We predicted that: (i) FRic is positively related to increases in chlorophyll-a concentration and turbidity associated with impacts of damming on the floodplain and depth. (ii) FEve is negatively related to increases in chlorophyll-a concentration and turbidity, and positively related to depth. (iii) FDiv is negatively related to the increase in chlorophyll-a, depth, and turbidity. (iv) Finally, we asked how do each of the traits change the functional indexes and their relation to environmental predictors. FRic and FEve fluctuated oppositely and cyclically every five years. FDiv showed a trend similar to that of FRic. However, between 2005 and 2010 FDiv only decreased. All functional diversity indexes were explained by temporal variability, depth, and chlorophyll-a concentration. However, the influence of each variable was different for each component of functional diversity. For CWM, turbidity was negatively associated with life span and positively associated with predator escape, and type of reproduction, while predator escape and feeding type were negatively associated with depth. We highlight that, in order to maintain the drivers of zooplankton functional diversity (food availability, turbidity, and depth), it is extremely important to guarantee the floodplain ecosystem's original state of functionality.