Predator Diversity Research Articles

Assessing effects of predator density and diversity on neophobia in Trinidadian guppies

Neophobic predator avoidance, where prey actively avoid novel stimuli, is thought to allow prey to cope with the inability to predict predation risk (i.e. uncertainty) while reducing the costs associated with learning. Recent studies suggest that neophobia is elicited as a response to unpredictable and elevated mean predation risk, and is linked to experience with diverse novel cues. However, no research has disentangled the effects of predator density and diversity on neophobia. We conditioned Trinidadian guppies (Poecilia reticulata) to high- or low-diversity predator model treatments paired with high, intermediate, or low concentrations of conspecific alarm cues as a proxy for predator density. We tested behavioural responses to a novel stimulus vs. a water control to determine differences in neophobia among treatments. We found that neophobic shoaling behaviour was shaped by mean risk (predator density). However both density and diversity shaped neophobic freezing, and to a weaker extent, neophobic area use. Our research suggests that predator diversity might elicit neophobic responses in guppies, but only when mean risk is high enough. The relationship between neophobia and components of predation risk is becoming increasingly relevant as ecological uncertainty becomes more prevalent with increasing climate change, anthropogenic impacts, and invasive species.

Predator Diversity Does Not Contribute to Increased Prey Risk: Evidence from a Mesocosm Study

Predation plays an important organisational role in structuring aquatic communities. Predator diversity can, however, lead to emergent effects in which the outcomes of predator–prey interactions are modified. The importance of predator diversity in regulating predator–prey interactions was investigated during a 9-day mesocosm study conducted in the middle reach of a temporarily open/closed, temperate, southern African estuary. The zooplankton community, comprising almost exclusively (>95% of total counts) calanoid and cyclopoid copepods of the genera Pseudodiaptomus, Paracartia and Oithona, was subject to three different juvenile fish predator treatments at natural densities: 1. predation by Gilchristella aestuaria, (Gilchrist, 1913; SL 15.3 ± 2.4 mm); 2. predation by Myxus capensis (Valenciennes, 1836; SL 12.8 ± 3.7 mm); and 3. a combination of the two predators. The presence of the predators contributed to a significant decline in the total zooplankton abundances, with a concurrent increase in total chlorophyll-a (Chl-a) concentrations, consistent with the expectations of a trophic cascade (ANCOVA; p < 0.05 in all cases). There were no significant differences in the total Chl-a concentration or total zooplankton abundances between the different predator treatments, suggesting that the increase in predator diversity did not contribute to increased prey risk or to the strength of the trophic cascade.

Improved crop protection and biodiversity of the agroecosystem by reduced tillage in rice paddy fields in southern China

Agricultural sustainability has benefited from the broad adoption of conservation agriculture (CA) practices for decades, in which the reduction of mechanical disturbances to soil (also known as reduced tillage, RT) is one of the most essential principles for CA implementation. Many studies have recommended the advantages of CA practices in the promotion of biodiversity, but the integrated impacts on crop productivity and biodiversity remain unclear. Since CA has been applied in rice production in the subtropical area of southern China for several years, the effects of CA, particularly the RT methods, need to be evaluated for the local and long-term adoption. In this study, we established an integrated network to illustrate how the reduction of tillage intensity influenced organisms including invertebrates (such as rice pests and their predators), pathogens and weeds, and then led to an impact on rice yield. The two-year study demonstrated that major rice pests, such as rice planthoppers, stem borers and apple snails, were effectively controlled by RT practice. Similarly, the occurrence of common diseases declined with less tillage. Compared to the conventional tillage (CT) treatment, the density of weeds in paddy fields deceased significantly in the RT treatment. In addition, the diversity and richness of pest predators increased remarkably in paddy fields where either reduced or no tillage was applied, which highlighted the significance of a CA strategy for the promotion of biodiversity in the agroecosystem. More importantly, the rice yield gradually increased after the two-year reduction of tillage. Taken together, our results suggest that the reduction of tillage intensity is beneficial for the protection of rice crops from various pests, and facilitates the sustainability of the agroecosystem and rice yield, which provides a solid basis and novel insights for the establishment of sustainable agroecosystems by CA-related practices in rice production in southern China.

Parasitoids and Predators of the Invasive Aphid Melanaphis sorghi Found in Sorghum and Non-Crop Vegetation of the Sorghum Agroecosystem.

Simple SummaryThe sorghum aphid is an invasive pest of grain sorghum in North America; their infestations when in high numbers can reduce grain sorghum yield. Fortunately, there are numerous beneficial insects such as parasitoid wasps, lady beetles, hoverfly and lacewing larvae that will feed on these aphids. These beneficial insects are naturally occurring in local habitats such as grasses and shrubs, Johnson grass, and cropland surrounding grain sorghum during and after sorghum production. The goal of this study was to estimate the relative effect of these habitats to serve as a source of natural enemies of the sorghum aphid in- and off-season of sorghum production. This study was conducted over two years and the results found that predators (lady beetles and their larvae, hoverfly and lacewing larvae) were most diverse in the habitat containing grasses and shrubs and most abundant during the sorghum-growing season. Parasitoid wasps were abundant across all habitat types during and outside of the sorghum-growing season. These results highlight the potential importance of persistence of natural enemies across vegetation types associated with their ability to manage sorghum aphid infestations. The natural enemies in these habitats are well positioned to play a role in suppressing sorghum aphid.Melanaphis sorghi (Theobald) (sorghum aphid), (=Melanaphis sacchari Zehntner) (Hemiptera: Aphididae), is an invasive pest of Sorghum bicolor (L.) in North America. Over 19 species of predators and parasitoids have been found to prey on M. sorghi. Natural enemies may reside in vegetation such as sorghum in cultivation (in-season) and persist after harvest (off-season), in Johnson grass (Sorghum halepense) (L.) and riparian areas consisting of shrubs and grasses, including Johnson grass. The objective was to assess the ability of these vegetation types to harbor M. sorghi natural enemies during and between annual grain sorghum production. Predator diversity was greatest in riparian vegetation in-season, with twelve species detected across seven families, and four orders of insects. Six lady beetle (Coleoptera: Coccinellidae) species were abundant in-season, and Cycloneda sanguinea (L.) persisted at relatively high abundance off-season. Parasitoid diversity was more limited (two primary parasitoids and one hyperparasitoid detected) with the primary parasitoids commonly detected. Aphelinus nigritus (Howard) (Hymenoptera: Aphelinidae), accounted for 85% and 57% of parasitoids in- and off-season, respectively. Aphelinus nigritus abundance was steady across the annual sorghum season in all vegetation types. Results from this study will inform land-management strategies on how diverse vegetations can play a role in the biological control of M. sorghi.

Following the track: accuracy and reproducibility of predation assessment on artificial caterpillars

AbstractExperimental studies of biotic interactions in real field conditions are essential to understand the structure and functioning of ecological networks. The use of artificial caterpillars to mimic actual prey availability is generally seen as a standard approach to compare the activity and diversity of predators along environmental gradients. Yet, even with standardized material and procedures, biases may still affect data from multiple observers with different expertise. We used pictures of artificial caterpillars with or without various predation marks, in an online survey that was targeted for the participants of the project, to evaluate the reliability of predation marks identification made by non‐scientists and by scientists with and without experience in predation mark identification. Pictures of artificial caterpillars displayed typical marks left by birds, mammals, and arthropods, as well as non‐predation marks (‘false positive’). In total 357 respondents scanned 7140 pictures of artificial caterpillars. Scientists were more confident and accurate in their observations than non‐scientists, but the differences in correct identifications among scientists and non‐scientists were low. Scientists with experience were also more accurate than scientists without experience, whereas there were no differences in self‐confidence among scientists with and without experience. Accuracy in predation mark identification did not differ among types of predators, but respondents were more keen to identify marks left by birds or mammals than marks left by arthropods. Our results have practical implications for the design of multi‐observer projects relying on artificial caterpillars as a proxy to assess predation intensity, in particular in the context of citizen science.

Escaping from predators: a review of Neotropical lizards defence traits

Lizards are commonly preyed by a great variety of predators, including vertebrates and invertebrates. Therefore, it is expected that lizards have developed a wide range of antipredator traits, increasing their chances of successful survival during agonistic events. Defence against predation involves two levels of behavioural strategies, commonly named primary and secondary defence traits. Primary defences relate to predator detection or interest and include as responses immobility, mimicry, aposematism, and cryptic colouration. Secondary defences occur after predator detection and attack, including traits that aim to prevent or interrupt predators. These defences encompass traits such as frightening (e.g., scratching or biting the predator), tail lashing, flouncing vigorously the body, cloacal discharge, agony vocalisations, and tail autotomy. In this review, we gathered information from 206 scientific publications, including peer-reviewed journals, short communications, scientific notes, and books. This compilation resulted in 22 defence traits, 23% passive and 77% active defences. Lizard species deal with a wide diversity of predators, but the number of field records, experiments, and antipredator studies remain scarce. We reviewed the defence traits presented by Neotropical lizards, using a phylogenetic approach in order to track evolutionary process behind these traits. Thanatosis, crypsis, and tail autotomy are symplesiomorphic for lizards, whereas venom and emetic substances are autapomorphic, and aposematism seems to be rare. We also present a novel case of defence trait where the dark colour helps lizards to be camouflaged in the burned vegetation. Our character mapping provides valuable information about the evolution of defensive traits in Neotropical lizards, combining natural history and phylogenetics. Trivial observations about any animal behaviour, including those provided by social networks and citizen science pages, might be important, and we strongly recommend that ethological observations describe the event in all possible details.

Abundance and Diversity of Coccinellid Predators in Rice Field Ecosystem in Payakumbuh District, Indonesia

Aims: The study aimed to study the abundance and biodiversity of Coccinellid predators in rice field Ecosystem in Payakumbuh District, Lima Puluh Kota Regency, West Sumatera, Indonesia.
 Study Design: Purposive random sampling.
 Place and Duration of Study: The research was conducted in rice field of Payakumbuh District, Lima Puluh Kota Regency, West Sumatera and Laboratory of Pest, Faculty of Agriculture, Riau University, Pekanbaru, Indonesia from January to April 2022.
 Methodology: Purposive random sampling was used in the research. Three rice fields in Payakumbuh District was chosen as sampling locations. Sweep net method was using to collect the coccinellid and the collected coccinellids were identified in Pest Laboratory, Faculty of Agriculture, Riau University, Pekanbaru, Indonesia. The data was analyzed by using Shannon-Winner diversity index to analyze biodiversity and evenness index.
 Results: 30 individuals of three species of coccinelid predators were found in rice field ecosystem in Payakumbuh district. The species were Micraspis lineata (20 individuals), Menochilus sexmaculatus (9 individuals) and Coleophora bisselata (1 individual). The species diversity index (H’) and species evenness index (E) were 0.73 and 0.66 respectively.
 Conclusion: The diversity of coccinellid predators in rice field in Payakumbuh district was quite stable and more stable.

Coping with antagonistic predation risks: Predator-dependent unique responses are dominant in Ceriodaphnia cornuta.

Inducible defences of prey are evolved under diverse and variable predation risks. However, during the co-evolution of prey and multiple predators, the responses of prey to antagonistic predation risks, which may put the prey into a dilemma of responding to predators, remain unclear. Based on antagonistic predation pressure from an invertebrate (Chaoborus larvae) and a vertebrate (Rhodeus ocellatus) predator, we studied the responses of multiple traits and transcriptomes of the freshwater crustacean Ceriodaphnia cornuta under multiple predation risks. Chaoborus predation risk altered the expression of genes encoding cuticle proteins and modulated the biosynthesis of steroid hormones, cutin, suberine, and wax, leading to the development of horns and increase in size at the late developmental stage. Meanwhile, fish predation risk primarily triggered genes encoding ribosomes and those involved in unsaturated fatty acid biosynthesis and cysteine and methionine metabolism, resulting in smaller individual size and earlier reproduction. Inducible responses of both transcriptome and individual traits revealed that predator-dependent unique responses were dominant and the dilemma of antagonistic responses was relatively limited. However, the unique individual traits in response to invertebrate predation could be significantly impaired by vertebrate predation risk, even though the unique responses to different predators were extremely weakly correlated and could be elicited simultaneously. These results indicate that diverse predator-dependent unique responses are favoured by Ceriodaphnia during its co-evolution with multiple predators. Nonetheless, Ceriodaphnia is not a generalist that can fully adopt all predator-dependent unique responses simultaneously under multiple predation risks.

Relative exposure to microplastics and prey for a pelagic forage fish

In the global ocean, more than 380 species are known to ingest microplastics (plastic particles less than 5 mm in size), including mid-trophic forage fishes central to pelagic food webs. Trophic pathways that bioaccumulate microplastics in marine food webs remain unclear. We assess the potential for the trophic transfer of microplastics through forage fishes, which are prey for diverse predators including commercial and protected species. Here, we quantify Northern Anchovy (Engraulis mordax) exposure to microplastics relative to their natural zooplankton prey, across their vertical habitat. Microplastic and zooplankton samples were collected from the California Current Ecosystem in 2006 and 2007. We estimated the abundance of microplastics beyond the sampled size range but within anchovy feeding size ranges using global microplastic size distributions. Depth-integrated microplastics (0–30 m depth) were estimated using a depth decay model, accounting for the effects of wind-driven vertical mixing on buoyant microplastics. In this coastal upwelling biome, the median relative exposure for an anchovy that consumed prey 0.287–5 mm in size was 1 microplastic particle for every 3399 zooplankton individuals. Microplastic exposure varied, peaking within offshore habitats, during the winter, and during the day. Maximum exposure to microplastic particles relative to zooplankton prey was higher for juvenile (1:23) than adult (1:33) anchovy due to growth-associated differences in anchovy feeding. Overall, microplastic particles constituted fewer than 5% of prey-sized items available to anchovy. Microplastic exposure is likely to increase for forage fishes in the global ocean alongside declines in primary productivity, and with increased water column stratification and microplastic pollution.

Characterizing the secret diets of siphonophores (Cnidaria: Hydrozoa) using DNA metabarcoding.

Siphonophores (Cnidaria: Hydrozoa) are abundant and diverse gelatinous predators in open-ocean ecosystems. Due to limited access to the midwater, little is known about the diets of most deep-dwelling gelatinous species, which constrains our understanding of food-web structure and nutrient flow in these vast ecosystems. Visual gut-content methods can rarely identify soft-bodied rapidly-digested prey, while observations from submersibles often overlook small prey items. These methods have been differentially applied to shallow and deep siphonophore taxa, confounding habitat and methodological biases. DNA metabarcoding can be used to assess both shallow and deep species’ diets under a common methodological framework, since it can detect both small and gelatinous prey. We (1) further characterized the diets of open-ocean siphonophores using DNA metabarcoding, (2) compared the prey detected by visual and molecular methods to evaluate their technical biases, and (3) evaluated tentacle-based predictions of diet. To do this, we performed DNA metabarcoding analyses on the gut contents of 39 siphonophore species across depths to describe their diets, using six barcode regions along the 18S gene. Taxonomic identifications were assigned using public databases combined with local zooplankton sequences. We identified 55 unique prey items, including crustaceans, gelatinous animals, and fish across 47 siphonophore specimens in 24 species. We reported 29 novel predator-prey interactions, among them the first insights into the diets of nine siphonophore species, many of which were congruent with the dietary predictions based on tentilla morphology. Our analyses detected both small and gelatinous prey taxa underrepresented by visual methods in species from both shallow and deep habitats, indicating that siphonophores play similar trophic roles across depth habitats. We also reveal hidden links between siphonophores and filter-feeders near the base of the food web. This study expands our understanding of the ecological roles of siphonophores in the open ocean, their trophic roles within the ‘jelly-web’, and the importance of their diversity for nutrient flow and ecosystem functioning. Understanding these inconspicuous yet ubiquitous predator-prey interactions is critical to predict the impacts of climate change, overfishing, and conservation policies on oceanic ecosystems.

Diversity of Microbial Eukaryotes Along the West Antarctic Peninsula in Austral Spring.

During a cruise from October to November 2019, along the West Antarctic Peninsula, between 64.32 and 68.37°S, we assessed the diversity and composition of the active microbial eukaryotic community within three size fractions: micro- (> 20 μm), nano- (20–5 μm), and pico-size fractions (5–0.2 μm). The communities and the environmental parameters displayed latitudinal gradients, and we observed a strong similarity in the microbial eukaryotic communities as well as the environmental parameters between the sub-surface and the deep chlorophyll maximum (DCM) depths. Chlorophyll concentrations were low, and the mixed layer was shallow for most of the 17 stations sampled. The richness of the microplankton was higher in Marguerite Bay (our southernmost stations), compared to more northern stations, while the diversity for the nano- and pico-plankton was relatively stable across latitude. The microplankton communities were dominated by autotrophs, mostly diatoms, while mixotrophs (phototrophs-consuming bacteria and kleptoplastidic ciliates, mostly alveolates, and cryptophytes) were the most abundant and active members of the nano- and picoplankton communities. While phototrophy was the dominant trophic mode, heterotrophy (mixotrophy, phagotrophy, and parasitism) tended to increase southward. The samples from Marguerite Bay showed a distinct community with a high diversity of nanoplankton predators, including spirotrich ciliates, and dinoflagellates, while cryptophytes were observed elsewhere. Some lineages were significantly related—either positively or negatively—to ice coverage (e.g., positive for Pelagophyceae, negative for Spirotrichea) and temperature (e.g., positive for Cryptophyceae, negative for Spirotrichea). This suggests that climate changes will have a strong impact on the microbial eukaryotic community.

Linking key human-environment theories to inform the sustainability of coral reefs

Effective solutions to the ongoing "coral reef crisis" will remain limited until the underlying drivers of coral reef degradation are better understood. Here, we conduct a global-scale study of how four key metrics of ecosystem states and processes on coral reefs (top predator presence, reef fish biomass, trait diversity, and parrotfish scraping potential) are explained by 11 indicators based on key human-environment theories from the social sciences. Our global analysis of >1,500 reefs reveals three key findings. First, the proximity of the nearest market has the strongest and most consistent relationships with these ecosystem metrics. This finding is in keeping with a body of terrestrial research on how market accessibility shapes agricultural practices, but the integration of these concepts in marine systems is nascent. Second, our global study shows that resource conditions tend to display a n-shaped relationship with socioeconomic development. Specifically, the probabilities of encountering a top predator, fish biomass, and fish trait diversity were highest where human development was moderate but lower where development was either high or low. This finding contrasts with previous regional-scale research demonstrating an environmental Kuznets curve hypothesis (which predicts a U-shaped relationship between socioeconomic development and resource conditions). Third, together, our ecosystem metrics are best explained by the integration of different human-environment theories. Our best model includes the interactions between indicators from different theoretical perspectives, revealing how marine reserves can have different outcomes depending on how far they are from markets and human settlements, as well as the size of the surrounding human population.

Strip intercropping of wheat and oilseed rape enhances biodiversity and biological pest control in a conventionally managed farm scenario

Abstract Conventional agriculture in the global north is typically characterized by large monocultures, commonly managed with high levels of pesticide or fertilizer input and mechanization. Strip intercropping, that is, diversifying cropland by growing strips of different crops using conventional machinery, may be a viable strategy to promote natural predator diversity and associated biological pest control in such conventional farming systems. We tested the influence of strip intercropping of conventionally managed winter wheat with oilseed rape, using common machinery with 27–36 m broad strips, on arthropod predator diversity and biological pest control. We characterized spider and carabid beetle communities, calculated pest aphid and pollen beetle densities and recorded parasitism rates for both crops (number of mummified aphids on wheat and number of parasitized pollen beetle larvae on oilseed rape). We observed a significant reduction in the densities of wheat aphids (50% decrease) and pollen beetle larvae (20% decrease) in strip intercropping areas compared to monocultures. Parasitism rates of wheat aphids increased significantly from 10% in monocultures to 25% in strip intercropping areas. The number of parasitized pollen beetle larvae did not show the same pattern but was higher towards the centre of the oilseed rape strip. Overall, the composition of predator communities benefited from the close neighbourhood of the two crop species in the strips, as carabid beetles were more abundant in oilseed rape and spiders were more abundant in wheat fields. Overall, strip intercropping reduced the dominance of one predator group and allowed for an equal representation of both spiders and carabid beetles in the mixture. Synthesis and applications. Our study presents evidence of the benefits of adopting strip intercropping with relatively large strips (adapted to existing machinery) for natural predator diversity and biological pest control in a large‐scale conventionally managed farm scenario. Wheat–oilseed rape strip intercropping reduced pest densities, increased parasitism of wheat aphids and promoted equal representation of natural predator groups well beyond the areas of monoculture. Overall, by reducing the area dedicated to only one crop, the implementation of strip intercropping adapted to mechanized agricultural scenarios can be used to increase crop heterogeneity at regional scales and enhance biodiversity and biological control, even in simplified landscapes dominated by large‐scale conventional agriculture.

Unconventional bird predators are relevant to vertebrate trophic relationships? A community science platform helps to answer this question.

Birds stand out among animal predators due their high species diversity and ecological flexibility. In a restrictive sense, bird predators include species that had vertebrate meat as main food item (conventional bird predators). However, insectivores, frugivores and omnivores birds occasionally include vertebrates in their diets (unconventional bird predators). Here, we use photographs posted in a community science platform (wikiaves) to examine the importance of conventional and unconventional bird predators to the trophic structure of Neotropical vertebrate assemblages. After detailed inspection of 71,285 photographs, we built a database of 6553 feeding events from 640 species distributed in 32 bird families. Vertebrates are part of the diet of 92 species of conventional and 91 species of unconventional bird predators. As expected, diets of conventional bird predators are predominantly composed of vertebrates (84% of feeding records, n = 1689), although invertebrates were also relevant for diets of owls, hawks and herons. In contrast, vertebrates comprised only 8% of feeding records (n = 358) among the unconventional bird predators. The contribution of vertebrates to diets of unconventional bird predators was relevant (> 10% of feeding records) in five of 24 analyzed bird families. Fishes, mammals and birds are the main preys of conventional predators, whereas unconventional predators focusing on ectothermic vertebrates (amphibians and reptiles). Unconventional predators expand the diversity of local vertebrate predators and consume distinct preys compared to conventional predators. Therefore, families of unconventional bird predators must be considered relevant to food web analysis of Neotropical vertebrate assemblages.

High morphological disparity in a bizarre Paleocene fauna of predatory freshwater reptiles

BackgroundThe consequences of the K-Pg mass extinction are reflected across present biodiversity, but many faunas that appeared immediately after the extinction event were very different from current ones. Choristodera is a clade of reptiles of uncertain phylogenetic placement that have an extremely poor fossil record throughout their 150-million-year history. Yet, choristoderes survived the K-Pg event and persisted until the Miocene.ResultsI describe the skulls and skeletons of two new choristoderes from a single Paleocene ecosystem in western North America that reveal the hidden Cenozoic diversity of this reptile clade. Despite their similar size, the new species deviate dramatically in morphology. Kosmodraco magnicornis gen. et sp. nov. possesses an extremely short snout and extensive cranial ornamentation. The sacrum of K. magnicornis bears enlarged muscle attachment sites and other modifications reminiscent of some giant crocodylians. In contrast, Champsosaurus norelli sp. nov. is a longirostrine species with an uninflated and ventrally divergent postorbital skull. Together with a North American choristodere previously classified in the European genus Simoedosaurus, K. magnicornis substantiates a new clade of giant, short-snouted taxa endemic to the Americas. C. norelli is found to be an early-diverging member of the genus Champsosaurus from the Cretaceous-Paleogene of the northern hemisphere. This suggests the presence of several ghost lineages of champsosaurid that crossed the K-Pg boundary.ConclusionsThe new taxa greatly increase Cenozoic choristodere richness and strengthen the evidence for the existence of distinctive freshwater faunas in Paleogene Eurasia and North America, where this clade diversified to exploit newly available macropredatory niches in the aftermath of the asteroid impact. The new choristoderes also reveal the distinct ecological context in which extant freshwater predators of the Americas like alligatoroids and gars have their origins: Paleocene fluviolacustrine ecosystems in North America displayed high large predator diversity and morphological disparity relative to modern ones.

Perennial flower strips in apple orchards promote natural enemies in their proximity

Apple production across Europe is experiencing major yield losses due to pest damage, and the need for alternative production methods are growing. Ecological infrastructures are important to create resilient production systems and increase functional biodiversity. This study investigated perennial flower strips as a means of promoting natural enemies, thereby reducing infestation by the rosy apple aphid, Dysaphis plantaginea, and fruit damage caused by it. In 2016 and 2017, effects of perennial flower strips were assessed in eight organic apple orchards with and without flower strips. In orchards with flower strips, assessments were done in tree rows at two distances: 1st and 3rd row from the flower strip. Assessments included field samples of arthropods, visual observations of D. plantaginea symptoms and observations of predators, observations of predators directly associated with aphid colonies, and fruit damage. In 2016, significantly more symptoms of D. plantaginea were observed in the 3rd row from the flower strip compared to the 1st row from the flower strip. Both years, more predators were observed in the 1st row from the flower strip than in the 3rd row from the flower strip. In 2017, more predators were observed in orchards with a flower strip than in orchards with no flower strip, and more predators were observed inside the aphid colonies in trees in the 1st row from the flower strip than in the 3rd row from the flower strip. Predator diversity in apple trees was also positively affected by proximity to a flower strip. In conclusion, perennial flower strips consistently promote the occurrence of natural enemies in their proximity, while the effect decreases with distance. The correlation between aphid abundance and predators was not always consistent, likely because the majority of the observed predators were generalists and therefore contributing to the natural regulation of the entire herbivore complex in the apple orchards.

Functional Responses and Additive Multiple Predator Effects of Two Common Wetland Fish

Understanding trophic interactions is essential for the prediction and measurement of structure and function in aquatic environments. Communities in these ecosystems may be shaped by variables such as predator diversity, prey density and emergent multiple predator effects (MPEs), which are likely to influence trophic dynamics. In this study, we examined the effect of key predatory fish in floodplain wetlands, namely Oreochromis mossambicus and Enteromius paludinosus, towards Chironomidae prey, using a comparative functional response (FR) approach. We used single predator species as well as intra- and interspecific paired species to contrast FRs under multiple predator scenarios. Attack rate and handling time estimates from single predator FRs were used to predict multiple predators’ feeding rates, which were compared to observe multiple predators’ feeding rates to quantify potential MPEs. From single fish trials, each species displayed a significant Type II FR, characterized by high feeding rates at low prey densities. Oreochromis mossambicus had a steeper (initial slope, i.e., higher attack rate) and higher (asymptote of curve, i.e., shorter handling time and higher maximum feeding rate) FR, whereas E. paludinosus exhibited lower-magnitude FRs (i.e., lower attack rate, longer handling time and lower feeding rate). In multiple predator scenarios, feeding rates were well-predicted by those of single predators, both in conspecific and interspecific pairs, and thus we did not find evidence for antagonistic or synergistic MPEs. Predator–prey interactions in wetland systems can have significant consequences on the structure and dynamics of ecological communities. In turn, this could have destabilizing effects on resources in tropical wetlands. These results, although experimental, help us understand how trophic interaction among conspecific or interspecific fish species in Austral tropical wetlands might influence their aquatic prey species. This will help us to understand food web dynamics better.

Aculeate Hymenopterans as Aposematic and Mimetic Models

Aposematism and mimicry are complex phenomena which have been studied extensively; however, much of our knowledge comes from just a few focal groups, especially butterflies. Aposematic species combine a warning signal with a secondary defense that reduces their profitability as prey. Aculeate hymenopterans are an extremely diverse lineage defined by the modification of the ovipositor into a stinger which represents a potent defense against predators. Aculeates are often brightly colored and broadly mimicked by members of other arthropod groups including Diptera, Lepidoptera, Coleoptera, and Araneae. However, aculeates are surprisingly understudied as aposematic and mimetic model organisms. Recent studies have described novel pigments contributing to warning coloration in insects and identified changes in cis-regulatory elements as potential drivers of color pattern evolution. Many biotic and abiotic factors contribute to the evolution and maintenance of conspicuous color patterns. Predator distribution and diversity seem to influence the phenotypic diversity of aposematic velvet ants while studies on bumble bees underscore the importance of intermediate mimetic phenotypes in transition zones between putative mimicry rings. Aculeate hymenopterans are attractive models for studying sex-based intraspecific mimicry as male aculeates lack the defense conferred by the females’ stinger. In some species, evolution of male and female color patterns appears to be decoupled. Future studies on aposematic aculeates and their associated mimics hold great promise for unraveling outstanding questions about the evolution of conspicuous color patterns and the factors which determine the composition and distribution of mimetic communities.

Hopf bifurcation and Bautin bifurcation in a prey–predator model with prey’s fear cost and variable predator search speed

This paper considers an extended predator–prey model, in which the fear of predators reduces prey reproduction and the search speed of predators depends on prey density. First, our mathematical analysis shows that high levels of fear can stabilize the coexistence steady state, while low levels would result in periodic oscillation. Comparing to the model ignoring fear where supercritical bifurcation occurs, Hopf bifurcation in our model can be both supercritical and subcritical, which leads to bi-stability and two limit cycles. Second, our analysis demonstrates that a relatively small search speed of predators can promote stability of the coexistence steady state, while a large speed would lead to periodic oscillation. Comparing to the model with invariant search speed where Hopf bifurcation takes place, Bautin bifurcation occurs in our model, which results in tri-stability and three limit cycles. While the paradox of enrichment always takes place in the Holling-type II predation model, it does not occur here when the search speed is small. Even when the speed is large, the prey species can adapt by enhancing their fear level and stabilize the system effectively. Third, our analysis shows that enhancing prey’s sensitivity to predation risk or slowing the predator search speed, can stabilize the coexistence steady state, while a low sensitivity and a high speed will lead to periodic oscillation. Numerical simulations confirm and extend our results.

Local Community Composition Drives Avian Borrelia burgdorferi Infection and Tick Infestation.

Globally, zoonotic vector-borne diseases are on the rise and understanding their complex transmission cycles is pertinent to mitigating disease risk. In North America, Lyme disease is the most commonly reported vector-borne disease and is caused by transmission of Borrelia burgdorferi sensu lato (s.l.) from Ixodes spp. ticks to a diverse group of vertebrate hosts. Small mammal reservoir hosts are primarily responsible for maintenance of B. burgdorferi s.l. across the United States. Nevertheless, birds can also be parasitized by ticks and are capable of infection with B. burgdorferi s.l. but their role in B. burgdorferi s.l. transmission dynamics is understudied. Birds could be important in both the maintenance and spread of B. burgdorferi s.l. and ticks because of their high mobility and shared habitat with important mammalian reservoir hosts. This study aims to better understand the role of avian hosts in tick-borne zoonotic disease transmission cycles in the western United States. We surveyed birds, mammals, and ticks at nine sites in northern California for B. burgdorferi s.l. infection and collected data on other metrics of host community composition such as abundance and diversity of birds, small mammals, lizards, predators, and ticks. We found 22.8% of birds infected with B. burgdorferi s.l. and that the likelihood of avian B. burgdorferi s.l. infection was significantly associated with local host community composition and pathogen prevalence in California. Additionally, we found an average tick burden of 0.22 ticks per bird across all species. Predator and lizard abundances were significant predictors of avian tick infestation. These results indicate that birds are relevant hosts in the local B. burgdorferi s.l. transmission cycle in the western United States and quantifying their role in the spread and maintenance of Lyme disease requires further research.