Stochastic Numerical Investigations for a Food Web System of Prey-Predation, Competition and Commensalism

Employing Levenberg-Marquardt backpropagation(LMB) neural network, the system of three species nonlinear equations are illuminated by designing an integrated numerical computing-based plot. The proposed dynamical system comprises of two competing species which are growing logistically in nature and, the third species is predating with Holling type II functional response mode on second species and also acts host for the first prey species. Besides, the prey species protect themselves to refuge high predation. The designed LMB neural network has been used to exhibits the solutions of the dynamical frame work. In each case of the species, a reference dataset of the planned LMB neural network is initiated in comparison of Adam numerical program. The approximate results of the food web system are displayed within the training, confirmation and testing strategies to redesign the neural network to minimize the mean square error (MSE) function employing the designed LMB. The investigations depend on the corresponding achievements and the examinations based on MSE out comes, correlation, regression and error histograms signify the proficiency, rightness as well as the potency of the suggested LMB neural network conspire.

Does the seed disperser matter? The influence of dispersal type on survival of Araucaria angustifolia seeds

Zoochoric dispersion is fundamental for the colonization of habitats by plants with large and heavy seeds such as the Paraná pine (Araucaria angustifolia). This is an endangered conifer from South America whose recruitment is heavily impacted by animals, but the way that different zoochoric dispersal modes and deposition sites can affect its successful establishment is not known yet. Thus, in this study, we aimed to evaluate the effect of dispersal mode (accordingly to the seed disperser), distance from adult conspecifics, and disposition site on long-term recruitment success. The experimental design included two environments (forest and open field) and each of them received 30 micro-habitat sampling stations (simulating deposition sites: 10 under conspecific; 10 far from conspecifics, next to a landmark; and 10 far from conspecifics, without a landmark), and each microhabitat had three levels of dispersal type simulating animal treatment (intact buried seed; intact seed over the ground; partially preyed seed over the ground), each with five seeds, totaling 900 seeds. In the forest environment, an experiment was also conducted to verify the fate of seeds using the spool and line technique. The environment and the micro-habitat alone did not explain seed survival, although the dispersal type given by the animal disperser was significant for survival and the buried seeds were the only ones that survived until the last survey. With the spool and line seed experiment, we attested that most of the Paraná pine seeds were preyed after removal (81.5%), and only buried seeds survived, reinforcing the role of scatter-hoarding animals as important agents in the Paraná pine dispersal. This way, our results showed that Paraná pine seeds suffer a very high predation rate, and that only a few seeds escape from predators and recruiting (only 1.1% of the all seeds used in the two experiments), indicating that the survival of seeds is a critical step in the life cycle of this plant, highlighting the role of dispersal mode in recruiting success.

Nutritional symbionts confer structural defence against predation and fungal infection in a grain pest beetle

Many insects benefit from bacterial symbionts that provide essential nutrients and thereby extend the hosts’ adaptive potential and their ability to cope with challenging environments. However, the implications of nutritional symbioses for the hosts’ defence against natural enemies remain largely unstudied. Here, we investigated if the cuticle-enhancing nutritional symbiosis of the saw-toothed grain beetle Oryzaephilus surinamensis confers protection against predation and fungal infection. We exposed age-defined symbiotic and symbiont-depleted (aposymbiotic) beetles to two antagonists that must actively penetrate the cuticle for a successful attack: wolf spiders (Lycosidae) and the fungal entomopathogen Beauveria bassiana. While young beetles suffered from high predation and fungal infection rates regardless of symbiont presence, symbiotic beetles were able to escape this period of vulnerability and reach high survival probabilities significantly faster than aposymbiotic beetles. To understand the mechanistic basis underlying these differences, we conducted a time-series analysis of cuticle development in symbiotic and aposymbiotic beetles by measuring cuticular melanisation and thickness. The results reveal that the symbionts accelerate their host's cuticle formation and thereby enable it to quickly reach a cuticle quality threshold that confers structural protection against predation and fungal infection. Considering the widespread occurrence of cuticle enhancement via symbiont-mediated tyrosine supplementation in beetles and other insects, our findings demonstrate how nutritional symbioses can have important ecological implications reaching beyond the immediate nutrient provisioning benefits.

Preliminary evaluation of the control effect of two predatory mite species on Eotetranychus sexmaculatus in rubber trees in Hainan Province, China

In this study, we aimed to clarify the effect of predatory mites on controlling the rubber tree pest mite Eotetranychus sexmaculatus (Riley) and explored basic application of the biocontrol technology “using predatory mites to control pest mites” to rubber trees. We selected two commercial species with high predation capacity from five species of predatory mites for further field-release tests. The results showed that among the five predatory mite species, Phytoseiulus persimilis (Athias‐Henriot) and Neoseiulus cucumeris (Oudemans) showed the highest and lowest daily average predation amounts on E. sexmaculatus, respectively, and that the commercial predatory mites Amblyseius swirskii (Athias‐Henriot) and Neoseiulus barkeri (Hughes) were demonstrated relatively high predation capacities on E. sexmaculatus and represent the ideal species for field release. Additionally, we found that field release by a hanging release sachet was suitable for a low field-population density of pest mites, and that predatory mites could be released at a dose of one sachet per tree and/or every other row or every other tree according to the actual situation of the pest mites. If the field population of E. sexmaculatus is at the peak egg-laying period, the release of A. swirskii should be top priority, which will lead to high control efficiency within 2 to 3 weeks. In case of low field-population density of E. sexmaculatus or a rainy season, top priority should be given to the release of N. barkeri, which might lead to high control efficiency within 3 to 4 weeks. The results showed that the release of A. swirskii had a more fast-acting effect with a higher control efficiency than N. barkeri at the early stage of release, whereas N. barkeri exhibited a better release effect with greater persistence than A. swirskii at the late stage of release.

Minicutting technique and IBA application in vegetational propagation of Schinus terebinthifolia Raddi

Vegetative propagation is an alternative for the production of seedlings of native tree species such as Schinus terebinthifolia that presents a high predation rate on its seeds. In order to develop vegetative propagation technology, different concentrations of indolebutyric acid (IBA) were tested in the rooting of apical and intermediate minicuttings of Schinus terebinthifolia. The 2x4 factorial experimental design involved two types of minicuttings (apical and intermediate) and four dosages of the hormone IBA (0, 1000, 2000, and 4000 mg. L-1). The percentages of survival and rooting were evaluated. The intermediate minicuttings (37% and 35%) showed significantly greater survival than the apical cuttings (22% and 9%) respectively at 30 and 60 days, regardless of the IBA concentration. Among the rooting averages at 60 days obtained in the different concentrations of IBA, the treatment of 4000 mg. L-1 generated the highest results (9% for apical and 35% for intermediate). The vegetative propagation by minicuttings of Schinus terebinthifolia demonstrated the viability of intermediate minicuttings with high rooting associated with the highest concentration of IBA.

Conspicuous animal signals avoid the cost of predation by being intermittent or novel: confirmation in the wild using hundreds of robotic prey

Social animals are expected to face a trade-off between producing a signal that is detectible by mates and rivals, but not obvious to predators. This trade-off is fundamental for understanding the design of many animal signals, and is often the lens through which the evolution of alternative communication strategies is viewed. We have a reasonable working knowledge of how conspecifics detect signals under different conditions, but how predators exploit conspicuous communication of prey is complex and hard to predict. We quantified predation on 1566 robotic lizard prey that performed a conspicuous visual display, possessed a conspicuous ornament or remained cryptic. Attacks by free-ranging predators were consistent across two contrasting ecosystems and showed robotic prey that performed a conspicuous display were equally likely to be attacked as those that remained cryptic. Furthermore, predators avoided attacking robotic prey with a fixed, highly visible ornament that was novel at both locations. These data show that it is prey familiarity—not conspicuousness—that determine predation risk. These findings replicated across different predator–prey communities not only reveal how conspicuous signals might evolve in high predation environments, but could help resolve the paradox of aposematism and why some exotic species avoid predation when invading new areas.

Functional Response and Predation Rate of Dicyphus cerastii Wagner (Hemiptera: Miridae)

Dicyphine mirids are important biological control agents (BCAs) in horticultural crops. Dicyphus cerastii Wagner can be found in protected tomato crops in Portugal, and has been observed feeding on several tomato pests. However, the predation capacity of this species is poorly studied. In order to investigate the predation capacity of D. cerastii, and how it is affected by prey size and mobility, we evaluated the functional response (FR) and predation rate of female predators on different densities of four prey species: Myzus persicae 1st instar nymphs (large mobile prey), Bemisia tabaci 4th instar nymphs, Ephestia kuehniella eggs (large immobile prey) and Tuta absoluta eggs (small immobile prey). Experiments were performed on tomato leaflets in Petri dish arenas for 24 h. Dicyphus cerastii exhibited type II FR for all prey tested. The predator effectively preyed upon all prey, consuming an average of 88.8 B. tabaci nymphs, 134.4 E. kuehniella eggs, 37.3 M. persicae nymphs and 172.3 T. absoluta eggs. Differences in the FR parameters, attack rate and handling time, suggested that prey size and mobility affected predation capacity. Considering the very high predation rates found for all prey species, D. cerastii proved to be an interesting candidate BCA for tomato crops.

Molecular phyloecology suggests a trophic shift concurrent with the evolution of the first birds

Birds are characterized by evolutionary specializations of both locomotion (e.g., flapping flight) and digestive system (toothless, crop, and gizzard), while the potential selection pressures responsible for these evolutionary specializations remain unclear. Here we used a recently developed molecular phyloecological method to reconstruct the diets of the ancestral archosaur and of the common ancestor of living birds (CALB). Our results suggest a trophic shift from carnivory to herbivory (fruit, seed, and/or nut eater) at the archosaur-to-bird transition. The evolutionary shift of the CALB to herbivory may have essentially made them become a low-level consumer and, consequently, subject to relatively high predation risk from potential predators such as gliding non-avian maniraptorans, from which birds descended. Under the relatively high predation pressure, ancestral birds with gliding capability may have then evolved not only flapping flight as a possible anti-predator strategy against gliding predatory non-avian maniraptorans but also the specialized digestive system as an evolutionary tradeoff of maximizing foraging efficiency and minimizing predation risk. Our results suggest that the powered flight and specialized digestive system of birds may have evolved as a result of their tropic shift-associated predation pressure.

Predation and Resource Availability Interact to Drive Life-History Evolution in an Adaptive Radiation of Livebearing Fish

Predation risk and resource availability are two primary factors predicted by theory to drive the evolution of life histories. Yet, disentangling their roles in life-history evolution in the wild is challenging because (1) the two factors often co-vary across environments, and (2) environmental effects on phenotypes can mask patterns of genotypic evolution. Here, we use the model system of the post-Pleistocene radiation of Bahamas mosquitofish (Gambusia hubbsi) inhabiting blue holes to provide a strong test of the roles of predation and resources in life-history evolution, as the two factors do not co-vary in this system and we attempted to minimize environmental effects by raising eight populations under common laboratory conditions. We tested a priori predictions of predation- and resource-driven evolution in five life-history traits. We found that life-history evolution in Bahamas mosquitofish largely reflected complex interactions in the effects of predation and resource availability. High predation risk has driven the evolution of higher fecundity, smaller offspring size, more frequent reproduction, and slower growth rate—but this predation-driven divergence primarily occurred in environments with relatively high resource availability, and the effects of resources on life-history evolution was generally greater within environments having high predation risk. This implies that resource-driven selection on life histories overrides selection from predators when resources are particularly scarce. While several results matched a priori predictions, with the added nuance of interdependence among selective agents, some did not. For instance, only resource levels, not predation risk, explained evolutionary change in male age at maturity, with more rapid sexual maturation in higher-resource environments. We also found faster (not slower) juvenile growth rates within low-resource and low-predation environments, probably caused by selection in these high-competition scenarios favoring greater growth efficiency. Our approach, using common-garden experiments with a natural system of low- and high-predation populations that span a continuum of resource availability, provides a powerful way to deepen our understanding of life-history evolution. Overall, it appears that life-history evolution in this adaptive radiation has resulted from a complex interplay between predation and resources, underscoring the need for increased attention on more sophisticated interactions among selective agents in driving phenotypic diversification.

Ecomorphology of Ostrea edulis (Linnaeus, 1758) in Kuala Gigieng Waters, Aceh Besar District

Ostrea edulis is one of the most common types of meat oysters and is commonly consumed by people in Kuala Gigieng, but until now there is not much scientific information about this species. The purpose of this study was to describe the ecomorphology of Ostrea edulis in Kuala Gigieng waters. This research was conducted from August to September 2013 in Kuala Gigieng Waters, Aceh Besar District. The method used in this research is purposive sampling. Identification of samples based on shell morphological characteristics including the exterior and interior of the shell using a magnifier lamp. The results showed that Ostrea edulis found in Kuala Gigieng waters had round, rough, hard, thick and uneven shells. The two valves are also not the same size, where the left valve is more concave than the right valve which tends to be flat. This is a form of the adaptation pattern of Ostrea edulis in Kuala Gigieng which tends to have a medium sand and clay sand substrate with a fairly high predation from both natural and human predation.