Group Of Predators Research Articles

The effects of wheat‐pea mixed intercropping on biocontrol potential of generalist predators in a long‐term experimental trial

AbstractArthropod generalist predators can be effective natural control agents of pests and weeds in agroecosystems. Their activity and contribution to biocontrol may increase in response to more complex agricultural habitats. In this study, we investigated the effects of winter wheat‐pea mixed intercropping on the biocontrol potential of generalist predators compared with the respective mono‐crops. We evaluated not only the effects during the intercropping season but also the pre‐crop values of the mixture for the subsequent barley crop. Furthermore, we evaluated the influence of different long‐term soil organic carbon and fertility management regimes on activity and biocontrol potential of predators. Field work was conducted over two seasons in a field experiment located in Gembloux, Belgium. A set of proxies for ecosystem functions were measured using the Rapid Ecosystem Function Assessment approach. We measured attack and predation rates of sentinel prey and weed seeds artificially placed in the field. Furthermore, we assessed activity density of the main groups of generalist predators during the exposure of the baits. Our results showed that crop type affected activity and biocontrol potential of predators. Predation rates were much lower in wheat than pea and wheat‐pea. The mixture wheat‐pea had a positive effect on predator activity density compared to wheat mono‐crop, while pea supported an intermediate activity of epigeal predators. In the second season of the field work, we found the highest biocontrol potential by predators in barley plots cultivated after pea. Finally, our results failed to find any differences in biocontrol potential of predators between long‐term soil organic carbon and fertilisation management strategies. These results suggest that crop type has a major relevance in influencing the activity of generalist predators, and the mixed intercropping wheat‐pea may represent a valid strategy to enhance biological pest control in comparison to wheat cultivated as mono‐crop. Furthermore, we show that the cultivation of pea as mono‐crop may have an important pre‐crop value within the rotation increasing the provision of ecosystem services such as biocontrol.

Cattle dung in aquatic habitats alters mosquito predatory biocontrol dynamics

Anthropogenic land use changes influence ecosystem functioning and may alter trophic interactions. Intensification of free–range pastoral farming could promote degradation of aquatic habitats, with nutrient inputs adversely affecting water quality and resident communities. Reductions in natural enemies (and potentially efficacy thereof) and dampening of their interaction strength could promote the proliferation of vector mosquitoes, with consequences for disease transmission and nuisance biting. This study examined implications of a cattle dung eutrophication gradient (T0–T4: 0 g L−1, 1 g L−1, 2 g L−1, 4 g L−1 and 8 g L−1) on aquatic habitats for trophic and non–trophic interactions by two larval mosquito (Culex pipiens) natural enemies (notonectid: Anisops sardea; copepod: Lovenula falcifera) using comparative functional responses. Copepods generally exhibited lower interaction strength compared to notonectids, both as individuals and conspecific pairs. Effects of dung pollutants differed among predator groups, with high concentrations dampening interaction strengths being observed for single/paired copepods and paired notonectids, but not single notonectids or heterospecific pairs. Individual predators exhibited Type II functional responses, with feeding rates largely similar across dung concentrations within species. Non–trophic interactions were predominantly negative (i.e., antagonistic) between conspecific pairs and scaled unimodally with prey density. Dung pollution intensified negative non–trophic interactions in notonectid pairs, whereas heterospecific pairs exhibited positive (i.e., synergistic) non–trophic interactions at the highest dung concentration. Physico–chemical properties indicated that turbidity and pH increased with dung treatment concentrations, whereas conductivity and total dissolved solids both peaked at 1 g L−1 and 2 g L−1. These results improve understanding of mosquito regulation in degraded habitats, indicting effects of agricultural pollutants dampen trophic interaction strengths, depending on the taxon.

Mites and insects occurring on plants used as spices from South 24 Parganas district of West Bengal, India

The present paper reports occurrence of a total of 13 species of mites under 6 families, 9 genera, 2 orders and 9 species of insects under 9 genera, 6 families, 2 orders, occuring on spices plants in the Narendrapur campus of Ramakrishna Mission, collected during September 2021 to April 2022. Out of 13 species of mites, 6 and 7 species belonged to phytophagous and predatory groups, respectively. In case of insects, all were phytophagous in nature. Among the phytophagous and predatory mites, none of those occurred abundantly on any of the spice plants and in fact, in all cases, their occurrence was only occasional. Hence, from the present study neither any pest species nor any potential predatory species could be identified. Probably more intensive study in future may throw some light in this matter.

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.

Diversity of Spiders (Arachnida: Araneae) Recorded in Khasi Mandarin Ecosystem of Northeastern India

Background: Spiders are one of the most abundant predatory groups found in the Citrus orchards. They feed on insects as well as other arthropod pests. Keeping in view of their important role in the natural biological control, the current study was carried out to study the spider fauna of the Khasi Mandarin (Citrus reticulata) ecosystem present in the Northeastern parts of India. Methods: The field surveys were carried out during 2016-21 in the seven Northeastern states, namely, Assam, Arunachal Pradesh, Nagaland, Manipur, Mizoram and Tripura. The different localities were selected based on the pre dominance of Khasi Mandarin cultivation and the different geographical and climatic conditions. Result: During the course of the survey, spiders belonging to 19 species, 16 genus and 8 different families were recorded from the study areas. The predominant families were Salticidae (36.84%) and Araneidae (26.31%) along with the reported presence of Oxyopidae (10.52%), Hersiliidae (5.2%), Heteropodidae (5.2%), Pisauridae (5.2%), Tetragnathidae (5.2%) and Thomisidae (5.2%). The highest and least population of spiders belonged to the species, Oxyopes birmanicus Thorell (Family: Oxyopidae) and Neoscona spp. (Family: Araneidae) respectively. The rich faunal diversity of spiders found during the present investigation indicate that spiders could be utilized as potential biocontol agents in the management of Khasi Mandarin pest complex.

First Attempt to Infer Sound Hearing and Its Paleoenvironmental Implications in the Extinct Insular Canid Cynotherium sardous Studiati, 1857 (Sardinia, Italy).

Simple SummaryThe microtomographic approach allows nondestructive acquisition of anatomical details of the bone labyrinth that houses the inner ear. The petrosal bone can be a gold mine of information for a variety of questions in different research fields, including taxonomic, behavioral, and genetic studies. The semicircular canals provide information on head posture and locomotor ability, whereas the cochlea provides data on hearing ability. The petrosal bone is the hardest structure in the skeleton and could be well preserved in fossil specimens. As a result, it is becoming more and more popular in current archaeological and paleontological studies. In this study, petrosal microtomographic analysis was applied for the first time to Cynotherium sardous, a highly modified endemic canid that inhabited Sardinia during the Middle to Late Pleistocene. Indications about its hearing ability may provide interesting insights to better understand the new lifestyle and behavior this canid acquired during the long evolutionary process it underwent in the peculiar insular ecosystem with a depleted fauna. The poor hearing and echolocalization capabilities of Cynotherium sardous would have been the outcome of reduced competition pressure due to the absence of predators and the abundance of prey, such as the large ochotonid Prolagus sardus, while the high-frequency hearing could be interpreted as an adaptation to detect sounds emitted by its preferred prey.This is the first study on the bony labyrinth of Cynotherium sardous, an intriguing extinct canid that inhabited Sardinia in the late Middle and Late Pleistocene. The morphological features of the cochlea indicate that C. sardous had a lower number of cochlear turns (2.25) than all extant canids. This feature, as well as the reduced length of the spiral canal, the cochlear curvature rate, and the narrow basal membrane, indicates that C. sardous had poor hearing abilities limited to high-frequency sounds with a low limit of 250 Hz and poor echolocalization skills. From the data available, it is not possible to infer whether C. sardous was unable to echolocalize its prey and relied on other senses (e.g., smell and sight) to locate them or whether the acoustic range of C. sardous was specialized for identifying the sounds produced by its most common prey to transmit signals for predator warnings or group communication. All things considered, the results obtained confirm the utility of cochlea morphological studies in reconstructing the hearing abilities of this species and in providing some suggestions about its ethology, but they fall short of providing any new sound evidence regarding the ecological role of C. sardous in the Late Pleistocene Sardinian ecosystem.

Ecological Infrastructures May Enhance Lepidopterans Predation in Irrigated Mediterranean Farmland, Depending on Their Typology and the Predator Guild

Ecological infrastructures (EIs) are considered relevant components in agricultural landscapes to support biodiversity and ecosystem services. We used the predatory attacks on lepidopteran dummies as a proxy to assess predation rates in the agricultural matrix and different EIs types according to their location and vegetation structure. We aimed at comparing the effect of different types of EI on the predation intensity in two intensively irrigated agricultural areas located in the Sorraia and Tagus river valleys in central Portugal. We hypothesized that: (1) the predation rate would be higher near EIs compared with the agricultural matrix, (2) the positive effect of EIs on predation rate would differ with their typologies, and (3) the EIs’ proximity and proportion in the surrounding landscape would have a positive effect on the predation rate in agricultural fields. The EI typologies influenced differently the predator groups and the overall predation rate. Major differences were observed for bird predation, being higher in woody EIs. A positive correlation between predation rate and EIs area of the surrounding landscape, as well as a negative correlation with the distance to the nearest riparian and woody EIs, was observed for birds. The observed dissimilarities in the predators’ response may be related to habitat differences and its functional connectivity. The overall monthly low predation rates are possibly related to the intensive agricultural system and the small area occupied by EIs.

Stabilized Morphological Evolution of Spiders Despite Mosaic Changes in Foraging Ecology.

A prominent question in animal research is how the evolution of morphology and ecology interacts in the generation of phenotypic diversity. Spiders are some of the most abundant arthropod predators in terrestrial ecosystems and exhibit a diversity of foraging styles. It remains unclear how spider body size and proportions relate to foraging style, and if the use of webs as prey capture devices correlates with changes in body characteristics. Here, we present the most extensive data set to date of morphometric and ecological traits in spiders. We used this data set to estimate the change in spider body sizes and shapes over deep time and to test if and how spider phenotypes are correlated with their behavioral ecology. We found that phylogenetic variation of most traits best fitted an Ornstein-Uhlenbeck model, which is a model of stabilizing selection. A prominent exception was body length, whose evolutionary dynamics were best explained with a Brownian Motion (free trait diffusion) model. This was most expressed in the araneoid clade (ecribellate orb-weaving spiders and allies) that showed bimodal trends toward either miniaturization or gigantism. Only few traits differed significantly between ecological guilds, most prominently leg length and thickness, and although a multivariate framework found general differences in traits among ecological guilds, it was not possible to unequivocally associate a set of morphometric traits with the relative ecological mode. Long, thin legs have often evolved with aerial webs and a hanging (suspended) locomotion style, but this trend is not general. Eye size and fang length did not differ between ecological guilds, rejecting the hypothesis that webs reduce the need for visual cue recognition and prey immobilization. For the inference of the ecology of species with unknown behaviors, we propose not to use morphometric traits, but rather consult (micro-)morphological characters, such as the presence of certain podal structures. These results suggest that, in contrast to insects, the evolution of body proportions in spiders is unusually stabilized and ecological adaptations are dominantly realized by behavioral traits and extended phenotypes in this group of predators. This work demonstrates the power of combining recent advances in phylogenomics with trait-based approaches to better understand global functional diversity patterns through space and time. [Animal architecture; Arachnida; Araneae; extended phenotype; functional traits; macroevolution; stabilizing selection.].

Patterns in schizomid flagellum shape from elliptical Fourier analysis

The arachnid order Schizomida is a relatively understudied group of soil-dwelling predators found on all continents except Antarctica. While efforts to understand their biology are growing, there is still much to know about them. A curious aspect of their morphology is the male flagellum, a sexually dimorphic, tail-like structure which differs in shape across the order and functions in their courtship rituals. The flagellar shape is important for taxonomic classification, yet few efforts have been made to examine shape diversity across the group. Using elliptical Fourier analysis, a type of geometric morphometrics based on shape outline, we quantified shape differences across a combined nearly 550 outlines in the dorsal and lateral views, categorizing them based on genus, family, biogeographic realm, and habitat, with special emphasis on Caribbean and Cuban fauna. We tested for allometric relationships, differences in disparity based on locations and sizes in morphospace among these categories, and for clusters of shapes in morphospace. We found multiple differences in all categories despite apparent overlaps in morphospace, evolutionary allometry, and evidence for discrete clusters in some flagellum shapes. This study can serve as a foundation for further study on the evolution, diversification, and taxonomic utility of the male flagellum.

Emerging insights on effects of sharks and other top predators on coral reefs.

Predation is ubiquitous on coral reefs. Among the most charismatic group of reef predators are the top predatory fishes, including sharks and large-bodied bony fishes. Despite the threat presented by top predators, data describing their realized effects on reef community structure and functioning are challenging to produce. Many innovative studies have capitalized on natural experimental conditions to explore predator effects on reefs. Gradients in predator density have been created by spatial patterning of fisheries management. Evidence of prey release has been observed across some reefs, namely that potential prey increase in density when predator density is reduced. While such studies search for evidence of prey release among broad groups or guilds of potential prey, a subset of studies have sought evidence of release at finer population levels. We find that some groups of fishes are particularly vulnerable to the effects of predators and more able to capitalize demographically when predator density is reduced. For example, territorial damselfish appear to realize reliable population expansion with the reduction in predator density, likely because their aggressive, defensive behavior makes them distinctly vulnerable to predation. Relatedly, individual fishes that suffer from debilitating conditions, such as heavy parasite loads, appear to realize relatively stronger levels of prey release with reduced predator density. Studying the effects of predators on coral reefs remains a timely pursuit, and we argue that efforts to focus on the specifics of vulnerability to predation among potential prey and other context-specific dimensions of mortality hold promise to expand our knowledge.

Assessment of predatory activity in residential lawns and sod farms

The occurrence and abundance of predatory fauna in turfgrass systems have been reported; however, the activity of predators has rarely been described. The fall armyworm Spodoptera frugiperda (JE Smith) (Lepidoptera: Noctuidae) is a major pest of turfgrass in the United States for which arthropod predation is not considered a key pest management option, but the role of predation on S. frugiperda has not been assessed in turfgrass systems, which are managed at varying intensities. Thus, the objective of this study was to determine (1) the incidence and (2) the severity of predation in less intensively managed residential lawns and intensively managed sod farms. The percentage of predation on live S. frugiperda sentinel larvae and the percentage of predation and its severity on clay models were significantly greater in the residential lawns than in the sod farms. Among the seven impression types recorded on clay models, paired marks were the most abundant. Four new impression types, deep cut marks, stacked surface marks, scooped marks, and U-shaped marks, were observed on clay models in both turfgrass systems. Formicids were documented at significantly greater densities than were other predatory groups, such as carabids. Thus, the results show the need for enhanced predatory activity in sod farms by developing integrated pest management strategies and adopting measures to conserve natural enemies.

Understanding the trophic relationships amongst arthropods in olive grove by δN15and δC13stable isotope analysis

AbstractSo far the limited knowledge about the diet of omnivores and generalist predators in olive groves has not allowed the clarification of their role as natural enemies. Stable isotope (δN15and δC13) analysis is a useful tool for predicting the trophic position of a high number of species, the variety of basal resources and the flux of energy in the food web. We have explored the possible consumers of two important pests in the olive grove: adults ofPrays oleaeBern (Lepidoptera: Praydidae) during its anthophagous generation and the pupae ofBactrocera oleae(Rossi) (Diptera: Tephritidae). In addition, we have included in the study the adult instar of the secondary pestEuphyllura olivina(Costa) (Hemiptera: Psyllidae). These arthropods were clustered in isotopic groups according to their similarities in δN15and δC13content assuming that, in this case, they shared similar feeding habits. Using this criterion, we obtained eight isotopically different groups of predators and eleven groups of phytophagous insects. We have used Bayesian mixing models in order to identify the potential predators of the different pests included in our study and the proportion that each pest occupied in the diet of the identified predators. Different taxa of spiders andAnthocoris nemoralis(Fabricius) (Hemiptera: Anthocoridae) have emerged as potential predators ofB. oleae. Moreover, Gnaphosidae (Araneae) showed suitable isotopic characteristics to be identified as potential predator ofP. oleaeandA. nemoralishas been confirmed as a predator ofE. olivina. The presence ofE. olivinaas an abundant resource encourages the settlement of natural enemies in olive orchards which feed on this secondary pest, but are also ready to feed on any insect outbreak, for exampleP. oleae.

In the Shadow of Cormorants: Succession of Avian Colony Affects Selected Groups of Ground Dwelling Predatory Arthropods

(1) Nesting of the great cormorants strongly influences terrestrial ecosystems by physical destruction of vegetation and chemical changes in the soil and around the nesting colonies. (2) We investigated spider, harvestmen, and centipede assemblages in different influenced plots (starting colony, active dense colony, and partly abandoned colony) in the biggest Lithuanian cormorant colony in pine woods on the shore of the Baltic Sea in the Curonian Spit National Park in Lithuania. Selected groups of ground dwelling predatory arthropods were collected by pitfall traps in 2012–2014. (3) We recorded a total of 4299 spider specimens (102 species), 451 harvestmen specimens (9 species), and 1537 centipede specimens (7 species). The coverage of moss and herb vegetation, mean Ellenberg value for light, bare ground without vegetation, and number of nests significantly influenced the abundance, species richness, and ecological groups of arthropod predators. (4) Active ground hunters represented by spider Trochosa terricola and centipede Lithobius forficatus were positively influenced by bare ground without vegetation and a higher density of nests, and negatively influenced by an increasing coverage of moss and herbs. The opposite effect was found for web builder spiders and less movable species, represented by dominant spider species Diplostyla concolor and harvestmen Nemastoma lugubre and Oligolophus tridens. (5) The results show how cormorant influence the forest vegetation structure and affect the abundance and species diversity of ground dwelling predatory arthropods.

Soil macrofaunal communities develop a habitat-specific trophic structure dependent on the degree of degradation of alpine wetlands

The alpine wetlands in the Qinghai-Tibetan Plateau have degraded in recent decades. However, the response of the soil food web to the degradation is still unclear. Four habitats including a wet meadow (WM), a grassland meadow (GM), a moderately degraded meadow (MDM) and a severely degraded meadow (SDM) (sandy meadows) were selected along the degrees of degradation. The soil macrofaunal biomass and the environmental factors of vegetation and soil were investigated. The soil macrofaunal community biomass increased significantly from WM to MDM and decreased to a very small amount in SDM, with most taxa disappearing. The biomass of the trophic groups of detritivores, herbivores and predators exhibited similar responses to soil macrofaunal communities. The relative biomass of detritivores increased from WM to MDM, but herbivores responded in an opposite manner, resulting in the dominant trophic group and trophic structure varying progressively from WM to GM to MDM. Soil properties but not vegetation determined the changes in trophic groups and trophic structure. The results implied that the higher trophic levels (carnivores or omnivores) responded more sensitively than the lower trophic levels (herbivores) to alpine wetland degradation. Our results also suggested that soil macrofauna have a habitat-specific characteristic trophic structure and can be used as indicators of soil health conditions.

Predator-Pest Dynamics of Arthropods Residing in Louisiana Soybean Agroecosystems.

Simple SummarySoybean agroecosystems in the Midsouth support an assorted insect community. Louisiana soybean is heavily managed by growers, and the subsequent effect on residing arthropod populations is not well understood. For sustainable management of soybean, evaluations need not only focus on problematic pests, but also the resident natural enemies. This study addresses the compositional and temporal abundance of prominent insects in Louisiana soybean, both pest and beneficial. Pest and natural enemy populations were monitored to delineate potential associations. We found that the pest community was dominated by those that fed on soybean through piercing-sucking mouthparts. Predator populations were comprised mainly of spiders and big-eyed bugs. Pest and predator populations were similarly more abundant later in the soybean reproductive period. A moderate positive linear relationship was observed between pest and predator communities indicating a temporal correlation. Here we present essential information about the pest and natural enemy communities residing in Louisiana.Over the past two decades, management practices within Louisiana soybean production have shifted. Successful application of an integrated pest management (IPM) strategy requires an understanding of how these changes have affected predator-pest dynamics. Surveys monitoring foliage-foraging arthropod populations in soybean took place across six locations within Louisiana over six years (2012–2014 and 2015–2018). Temporal associations of pest groups, defoliating and piercing-sucking, and predator groups relating to soybean phenology were observed. Additionally, soybean maturity groups (III, IV, and V) were also evaluated to delineate potential differences. Results indicated higher abundances of piercing-sucking pests compared to defoliating pests across both datasets (2012–2014 and 2015–2018). Pest groups were more abundant in later soybean reproductive periods, mainly attributed to Chrysodeixis includens and Piezodorus guildinii. Predator populations were mainly comprised of Araneae and Geocoridae throughout the survey periods. From 2015 to 2018, soybean growth had a significant effect on total predator abundance with more predators present at the pod-fill and soybean maturity stage. Correlations between total pest abundance and total predators exhibited a moderate positive linear relationship. Soybean maturity groups only influenced piercing-sucking pest abundance, with later maturing groups (IV and V) having higher numbers. Thus, control tools and tactics aimed at controlling late season pests should be modified to avoid reducing predator populations.

LOCAL STABILITY ANALYSIS OF A PREDATOR-PREY DYNAMICS INCORPORATING BOTH SPECIES DENSITY INCREASING FUNCTIONAL RESPONSE

Most of the functional responses which have been incorporated to formulate mathematical biology consider individual contact or predator cooperation. In this study, we have introduced a different functional response that describes the prey-predator system when predators form a line and cooperatively attack a group of predators. We have also described the effect of prey on this system. Additionally, we find all the equilibrium points and their local stability behaviour.

High fitness areas drive the aggregation of the sea urchin Mesocentrotus nudus.

Sea urchin aggregation is a common phenomenon in coastlines. However, it remains controversial whether sea urchins form resource aggregations or behavioral aggregations in a non-spawning season. To clarify, we studied the aggregative responses to food and predators in the sea urchin Mesocentrotus nudus when high fitness areas (HFAs) were scarce versus sufficient. By taking the occupied area of each sea urchin (test diameter + spines = 4.5 cm) as a square (4.5 cm × 4.5 cm), we set scarce HFAs for the sea urchins in Experiment 1 (the squares of HFAs: the area occupied by experimental sea urchins = 1:1) and sufficient HFAs for the sea urchins in Experiment 2 (the squares of HFAs: the area occupied by experimental sea urchins = 2:1). If M. nudus form resource aggregations, they would aggregate passively under the scarce HFAs conditions, but not in the sufficient HFAs conditions. Conversely, if M. nudus form behavioral aggregation, aggregation would occur in both scarce and sufficient HFAs. The present results showed that in the scarce HFAs, M. nudus in the food and predator groups were significantly closer to the food and further from predators, and had significantly more aggregated numbers in HFAs than those in the control group. Sea urchins did not aggregate in response to food or predators under the sufficient HFAs, although significantly more sea urchins of the experimental group was found in HFAs than that of the control group. Sea urchins (at least M. nudus) form resource aggregations that are driven by the scarce HFAs. This provides valuable information into the mechanisms of the aggregation of sea urchins.

Predator Group Composition Indirectly Influences Food Web Dynamics through Predator Growth Rates.

AbstractConsiderable theoretical work predicts that intraspecific trait variation can have profound ecological consequences by altering species interactions. Because of their high flexibility, behavioral traits may be especially relevant in mediating how species respond to one another, thus affecting food web dynamics and ecosystem functioning. However, empirical evidence supporting this idea is limited. Here, we generated predator groups where we manipulated the composition of behavioral types within the groups to assess effects on predator growth rates, prey communities, basal resources, and ecosystem functioning in replicated outdoor ponds. Using European perch (Perca fluviatilis), we created three types of predator populations: two where all individuals expressed either bold or shy phenotypes and one that contained a mix of individuals of the two behavioral types. Bold perch grew faster in mixed populations, indicating that predator growth depends on each individual's behavioral type and that of its group members. However, there was no evidence that the behavioral composition of the perch population directly altered the dynamics of lower trophic levels. Instead, final perch biomass, not behavioral composition, had the strongest influence on lower trophic levels. Thus, the central question may not be whether predator behavior matters at all for trophic dynamics but rather when behavioral effects will predominate over effects of other influences, such as predator biomass variation.

Stairway to extinction? Influence of anthropogenic climate change on distribution patterns of montane Strigiformes in Mesoamerica

Although anthropogenic climate change (ACC) is a global phenomenon affecting all ecosystems, its effects are especially relevant in certain ecosystems, such as tropical montane forests. Responses of montane species to ACC in Mesoamerica remain unclear, limiting our ability to assess their vulnerability and the impacts on these ecosystems overall. To understand mechanisms underlying the distribution and vulnerability of montane faunas, we analyzed the influence of ACC on the geographic distribution of owls (order Strigiformes), which are a group of top avian predators distributed in montane forests. Using ecological niche models, we estimated the potential distributions of 35 species at present and under projected future climates (2050 and 2070) and analyzed changes in distributional patterns in terms of range size and altitudinal distribution for each species, as well as spatio-temporal patterns of species richness. Most of our projections (~86%) were consistent with the widely accepted hypothesis of species range shift to higher altitudes combined with reduction in distribution, as species try to track their climatic preferences. Interestingly, the mid-elevation species emerge as the most strongly affected by ACC, showing the highest rates of change. All climate scenarios produced a similar pattern of change in owl species richness, but they differed in the total number of species, a loss of 11 species and a maximum gain of seven species. Species richness remained relatively constant at mid elevations, whereas the greatest losses were in the highlands and the contiguous lowlands. Overall, our results suggest a severe impact of ACC in the coming decades for most owls of Mesoamerican montane forests.

Traveling wave solutions in predator–prey models with competition

This paper studies the minimal wave speed of traveling wave solutions in predator–prey models, in which there are several groups of predators that compete among different groups. We investigate the existence and nonexistence of traveling wave solutions modeling the invasion of predators and coexistence of these species. When the positive solution of the corresponding kinetic system converges to the unique positive steady state, a threshold that is the minimal wave speed of traveling wave solutions is obtained. To finish the proof, we construct contracting rectangles and upper–lower solutions and apply the asymptotic spreading theory of scalar equations. Moreover, multiple propagation thresholds in the corresponding initial value problem are presented by numerical examples, and one threshold may be the minimal wave speed of traveling wave solutions.