Exploitative Competition Research Articles

Of wolves and bears: Seasonal drivers of interference and exploitation competition between apex predators

AbstractCompetition between apex predators can alter the strength of top‐down forcing, yet we know little about the behavioral mechanisms that drive competition in multipredator ecosystems. Interactions between predators can be synergistic (facilitative) or antagonistic (inhibitive), both of which are widespread in nature, vary in strength between species and across space and time, and affect predation patterns and predator–prey dynamics. Recent research has suggested that gray wolf (Canis lupus) kill rates decrease where they are sympatric with brown bears (Ursus arctos), however, the mechanisms behind this pattern remain unknown. We used data from two long‐term research projects in Scandinavia (Europe) and Yellowstone National Park (North America) to test the role of interference and exploitation competition from bears on wolf predatory behavior, where altered wolf handling and search time of prey in the presence of bears are indicative of interference and exploitation competition, respectively. Our results suggest the mechanisms driving competition between bears and wolves were dependent on the season and study system. During spring in Scandinavia, interference competition was the primary mechanism driving decreased kill rates for wolves sympatric with bears; handling time increased, but search time did not. In summer, however, when both bear and wolf predation focused on neonate moose, the behavioral mechanism switched to exploitation competition; search time increased, but handling time did not. Alternartively, interference competition did affect wolf predation dynamics in Yellowstone during summer, where wolves prey more evenly on neonate and adult ungulates. Here, bear presence at a carcass increased the amount of time wolves spent at carcasses of all sizes and wolf handling time for small prey, but decreased handling time for the largest prey. Wolves facilitate scavenging opportunities for bears, however, bears alter wolf predatory behavior via multiple pathways and are primarily antagonistic to wolves. Our study helps to clarify the behavioral mechanisms driving competition between apex predators, illustrating how interspecific interactions can manifest into population‐level predation patterns.

Interspecies Interactions of the 2,6-Dichlorobenzamide Degrading Aminobacter sp. MSH1 with Resident Sand Filter Bacteria: Indications for Mutual Cooperative Interactions That Improve BAM Mineralization Activity.

Bioaugmentation often involves an invasion process requiring the establishment and activity of a foreign microbe in the resident community of the target environment. Interactions with resident micro-organisms, either antagonistic or cooperative, are believed to impact invasion. However, few studies have examined the variability of interactions between an invader and resident species of its target environment, and none of them considered a bioremediation context. Aminobacter sp. MSH1 mineralizing the groundwater micropollutant 2,6-dichlorobenzamide (BAM), is proposed for bioaugmentation of sand filters used in drinking water production to avert BAM contamination. We examined the nature of the interactions between MSH1 and 13 sand filter resident bacteria in dual and triple species assemblies in sand microcosms. The residents affected MSH1-mediated BAM mineralization without always impacting MSH1 cell densities, indicating effects on cell physiology rather than on cell number. Exploitative competition explained most of the effects (70%), but indications of interference competition were also found. Two residents improved BAM mineralization in dual species assemblies, apparently in a mutual cooperation, and overruled negative effects by others in triple species systems. The results suggest that sand filter communities contain species that increase MSH1 fitness. This opens doors for assisting bioaugmentation through co-inoculation with "helper" bacteria originating from and adapted to the target environment.

Who’s afraid of the big, bad predator? Contrasting effects of apex predator presence on the behaviour of a mesopredator

Context Mesopredators experience top down pressure from apex predators, which may lead to behavioural changes such as spatial avoidance to reduce both interference and exploitative competition. However, apex predators may also facilitate mesopredators through the provision of carrion, so mesopredators should respond flexibly to the presence of apex predators. Aims We aimed to investigate the drivers of black-backed jackal (Canis mesomelas) space use and detection in areas with and without lions (Panthera leo). We predicted that jackal detection and space use will be greater if apex predators facilitate rather than suppress them. Additionally, we predicted that in the absence of lions, the relative abundance of small ungulate species may become important drivers of space use and detection, because jackals can switch from scavenging to hunting. Comparatively, in the presence of lions, larger ungulate species will become important drivers of space use and detection as these species become accessible to jackals through scavenging. Methods We used camera-trapping surveys, a single-species, single-season occupancy modelling approach, and the assessment of activity patterns to explore how apex predators influence the presence and probability of use of different sites in the Eastern Cape province of South Africa. Key results Apex predators both positively and negatively affected the detection of jackals, indicating that these mesopredators show behavioural flexibility at the individual site level. There was high overlap between jackal activity patterns in the presence and absence of lions; however, at one site with lions, jackal activity did not peak at night as observed at other sites. Conclusions Our results indicate that jackals demonstrate behavioural flexibility in the presence and absence of apex predators. Importantly, our results show that apex predators can both facilitate and suppress mesopredators, and that their behavioural responses are dependent on site-specific factors. Implications Our findings highlight that sympatric predator behaviours should be based on site-specific behaviours instead of the general patterns observed in more temperate systems.

Does the Sharing Economy Technology Disrupt Incumbents? Exploring the Influences of Mobile Digital Freight Matching Platforms on Road Freight Logistics Firms

In this paper, we study the disruptive power of the mobile digital sharing economy to the road freight logistics industry. New information technologies, such as the mobile internet, mobile payment methods, and GPS, have enabled platforms to match freight shippers’ demand with carriers’ supply by utilizing the convenience and mobility of smartphones. We empirically study the influence of the emergence of mobile digital freight matching platforms in the U.S. on the profitability and stock performance of two types of incumbent road freight logistics companies: freight arrangement companies (freight forwarders and brokers) and trucking companies (freight carriers). Since the mobile digital freight matching platforms mainly match small and mid‐sized trucking companies with shipping demand, we expect the platforms to introduce interference (direct) competition to traditional freight arrangement companies and exploitation (indirect) competition to large trucking companies, which potentially raises operational challenges for both types of incumbents. We use Difference‐in‐Differences (DID) analyses to study the incumbents’ profitability and the event study method to evaluate their stock performance. We find that after the advent of the mobile digital freight matching platforms in the U.S., the profitability of the traditional freight arrangement companies counter‐intuitively remained unchanged. In contrast, the profitability of the large trucking companies increased. Furthermore, we examine the changes in sales and costs behind these profitability changes. Our dynamic analyses suggest a time lag of the influence of the mobile digital freight matching platforms. Besides, we find that the stock value of the traditional freight arrangement companies received a significant negative shock, whereas the stock value of the large trucking companies showed no significant reaction. This study contributes to understanding the disruptive power of an emerging technology innovation of sharing economy to firm performances in an increasingly competitive and innovative business environment.

Varying degrees of spatio-temporal partitioning among large carnivores in a fenced reserve, South Africa

Context The spatio-temporal partitioning of large carnivores is influenced by interspecific competition and coexistence within small, enclosed reserves. Lions (Panthera leo), spotted hyaenas (Crocuta crocuta) and leopards (Panthera pardus) are the three largest African carnivores and have the greatest potential for intra-guild competition, particularly where space is limited. Aim To investigate the spatio-temporal partitioning between lions, spotted hyaenas and leopards in a small (~75 000 ha), enclosed nature reserve, Madikwe Game Reserve (Madikwe), South Africa. Methods We deployed 110 camera traps (baited n = 55 and unbaited n = 55) across Madikwe from 26 August 2019 until 6 May 2020. Von Mises kernel density plots were used to investigate daily temporal partitioning among the three species. A multiple-species, single-season occupancy model was used to investigate daily space use patterns. Key results We found both temporal and spatial exclusion between lions and spotted hyaenas on Madikwe. However, no evidence was found of spatio-temporal partitioning between lions and leopards, and spotted hyaenas and leopards. Conclusions Exploitative and interference competition on Madikwe might be high enough to warrant spatio-temporal partitioning between lions and spotted hyaenas to avoid the negative effects of intra-guild competition. Contrastingly, patterns observed between leopards and both lions and spotted hyaenas preclude the possibility of top-down control by superior carnivores. Implication These findings call for an adaptive management approach, where both carnivore and prey species compositions are constantly monitored. Management strategies such as these will allow for the conservation of valuable resources (i.e. prey species) to ensure the persistence of large carnivore populations across African ecosystems.

同域分布中华鬣羚与中华斑羚时空生态位特征

PDF HTML阅读 XML下载 导出引用 引用提醒 同域分布中华鬣羚与中华斑羚时空生态位特征 DOI: 10.5846/stxb202108022099 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: 中国博士后科学基金面上项目(2021M690484);国家自然科学基金(31801991);第二次青藏高原综合科学考察研究资助(2019QZKK0402);成都大熊猫繁育研究基地自立课题(2021CPB-B17) Spatio-temporal niche characteristics of sympatric Chinese serow and Chinese goral Author: Affiliation: Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:为了解同域分布有蹄类在环境复杂的山地森林生境中以何种方式维持种间关系以实现稳定共存,基于物种分布模型与日活动模式分析了四川省岷山、邛崃、大相岭、小相岭和凉山五大山系同域分布中华鬣羚(Capricornis milneedwardsii)与中华斑羚(Naemorhedus griseus)的时空生态位特征。结果显示:(1)在四川省五大山系,中华鬣羚的适宜栖息地面积为28006.07 km2,占研究区总面积的26.18%,其中高适宜栖息地面积为10015.90 km2,中华斑羚的适宜栖息地面积为21073.32 km2,占研究区总面积的19.71%,其中高适宜栖息地面积为8396.22 km2;(2)中华鬣羚与中华斑羚在生境因子选择上相似性高、栖息地重叠面积大,其空间生态位重叠度指数D=0.776,I=0.949,其适宜栖息地的主要重叠区域位于岷山和邛崃山系;(3)中华鬣羚与中华斑羚的日活动节律重叠指数为0.812;(4)中华鬣羚与中华斑羚属于同域分布的资源利用型竞争物种,中华鬣羚的存在会显著影响中华斑羚的日活动节律(P=0.016);二者同域分布时都会增加其昼间活动强度,并增加活动高峰期的强度及持续时间。本研究初步分析了中华鬣羚与中华斑羚的时空生态位特征,揭示了二者在空间、时间生态位上种群共存及种间竞争的耦合关系。研究有利于深入理解同域分布动物时空生态位特征、近缘物种的共存机制及种间竞争关系,为有蹄类等珍稀野生动物种群及栖息地的保护提供科学参考。 Abstract:In order to understand how the sympatric distribution of ungulates maintains interspecific relationships to achieve stable coexistence in a complex mountain forest habitat, this study analyzed the spatial and temporal ecological niche characteristics of sympatric distribution of the Chinese serow (Capricornis milneedwardsii) and the Chinese goral (Naemorhedus griseus) in the Minshan, Qionglai, Daxiangling, Xiaoxiangling and Liangshan mountain systems in Sichuan Province based on species distribution models and daily activity patterns. The results showed that:(1) in the five mountains of Sichuan Province, the suitable habitat area of the Chinese serow was 28006.07 km2, accounting for 26.18% of the total area of the study area, among which the highly suitable habitat area was 10015.90 km2. The suitable habitat area of the Chinese goral was 21073.32 km2, accounting for 19.71% of the total area of the study area, among which the highly suitable habitat area was 8396.22 km2. (2) Niche overlap indices, calculated by ENMTools, showed that the two species had high overlap (D=0.776, I=0.949). The Chinese serow and the Chinese goral had high selection similarity on environmental variables and large habitat overlap area. In terms of spatial distribution, the main overlapping areas of the Chinese serow and the Chinese goral suitable habitats are the Minshan Mountain and the Qionglai Mountain. And, the overlapping area of suitable habitats is 12967.50 km2, accounting for 46.30% and 61.54% of their total suitable habitat area, the overlapping area of highly suitable habitats was 5955.28 km2, accounting for 59.46% and 70.93% of their highly suitable habitats. (3) There was no significant difference in daily activity rhythm between the Chinese serow and the Chinese goral (P=0.534), and the overlap index was 0.812. (4) They were exploitation competition species, and the presence of the Chinese goral significantly affected the daily activity rhythm of the Chinese serow (P=0.016). They increased their diurnal activity intensity and enhanced the intensity and duration of their peak activity when they were sympatric distribution. In this study, the spatial and temporal niche characteristics of the Chinese serow and the Chinese goral were analyzed, and the coupling relationship of population coexistence and interspecific competition in spatial and temporal niche was revealed. This study, on the one hand, is helpful to deeply understand the spatial and temporal niche characteristics of sympatric distribution animals, the coexistence mechanism and interspecific competition of the related species. On the other hand, it provides a scientific reference for the conservation of rare wildlife populations and habitats, such as ungulates. 参考文献 相似文献 引证文献

Host-mediated, cross-generational intraspecific competition in a herbivore species

Conspecific insect herbivores co-occurring on the same host plant interact both directly through interference competition and indirectly through exploitative competition, plant-mediated interactions and enemy-mediated interactions. However, the situation is less clear when the interactions between conspecific insect herbivores are separated in time within the same growing season, as it is the case for multivoltine species. We hypothesized that early season herbivory would result in reduced egg laying and reduced performance of the next generation of herbivores on previously attacked plants. We tested this hypothesis in a choice experiment with box tree moth females (Cydalima perspectalis Walker, Lepidoptera: Crambidae). These females were exposed to box trees (Buxus sempervirens L., Buxaceae) that were either undamaged or attacked by conspecific larvae earlier in the season. We then compared the performance of the next generation larvae on previously damaged vs undamaged plants. Previous herbivory had no effect on oviposition behaviour, but the weight of next generation larvae was significantly lower in previously damaged plants. There was a negative correlation between the number of egg clutches laid on plants by the first generation and the performance of the next generation larvae. Overall, our findings reveal that early season herbivory reduces the performance of conspecific individuals on the same host plant later in the growing season, and that this time-lagged intraspecific competition results from a mismatch between the oviposition preference of females and the performance of its offspring.

In vitro interaction network of a synthetic gut bacterial community

A key challenge in microbiome research is to predict the functionality of microbial communities based on community membership and (meta)-genomic data. As central microbiota functions are determined by bacterial community networks, it is important to gain insight into the principles that govern bacteria-bacteria interactions. Here, we focused on the growth and metabolic interactions of the Oligo-Mouse-Microbiota (OMM12) synthetic bacterial community, which is increasingly used as a model system in gut microbiome research. Using a bottom-up approach, we uncovered the directionality of strain-strain interactions in mono- and pairwise co-culture experiments as well as in community batch culture. Metabolic network reconstruction in combination with metabolomics analysis of bacterial culture supernatants provided insights into the metabolic potential and activity of the individual community members. Thereby, we could show that the OMM12 interaction network is shaped by both exploitative and interference competition in vitro in nutrient-rich culture media and demonstrate how community structure can be shifted by changing the nutritional environment. In particular, Enterococcus faecalis KB1 was identified as an important driver of community composition by affecting the abundance of several other consortium members in vitro. As a result, this study gives fundamental insight into key drivers and mechanistic basis of the OMM12 interaction network in vitro, which serves as a knowledge base for future mechanistic in vivo studies.

Trophic niche overlap between coyotes and gray foxes in a temperate forest in Durango, Mexico.

Resource partitioning, and especially dietary partitioning, is a mechanism that has been studied for several canid species as a means to understand competitive relationships and the ability of these species to coexist. Coyotes (Canis latrans) and gray foxes (Urocyon cinereoargenteus) are two canid species that are widely distributed, in Mexico, and they are sympatric throughout most of their distribution range. However, trophic dynamic and overlap between them have not been thoroughly studied. In order to better understand their ecological relationship and potential competitive interactions, we studied the trophic niche overlap between both canids in a temperate forest of Durango, Mexico. The results are based on the analysis of 540 coyote and 307 gray fox feces collected in 2018. Both species consumed a similar range of food items, but the coyote consumed large species while the gray fox did not. For both species, the most frequently consumed food categories throughout the year and seasonally were fruit and wild mammals (mainly rodents and lagomorphs). Coyotes had higher trophic diversity in their annual diet (H' = 2.33) than gray foxes (H' = 1.80). When analyzing diets by season, trophic diversity of both species was higher in winter and spring and tended to decrease in summer and autumn. When comparing between species, this parameter differed significantly during all seasons except for summer. Trophic overlap throughout the year was high (R0 = 0.934), with seasonal variation between R0 = 0.821 (autumn) and R0 = 0.945 (spring). Both species based their diet on the most available food items throughout each season of the year, having high dietary overlap which likely can lead to intense exploitative competition processes. However, differences in trophic diversity caused by differential prey use can mitigate competitive interactions, allowing these different sized canid species to coexist in the study area.

Exploitative competition for floral resources reduces sugar intake but differently impacts the foraging behaviour of two non‐bee flower visitors

Identifying which behavioural strategies maximize individual fitness is a key objective in ecology. Organisms are known to adapt their foraging behaviour to their environment in response to abiotic and biotic constraints, such as the distribution of resources or the presence of competitors. For instance, bees are known to avoid recently visited flowers and thus focus their foraging on more rewarding patches. Whether other flower‐visiting insects adapt their foraging behaviour in response to exploitative competition for floral resources remains unknown. Here, we asked if a predatory hoverfly Episyrphus balteatus and a parasitoid Aphidius colemani 1) are physiologically impacted by flower resource limitation following exploitation of flowers by a competitor (either the bumblebee Bombus terrestris or E. balteatus); 2) have the ability to discriminate flowers that were previously exploited by a competitor; and 3) modify their foraging behaviour accordingly. Episyrphus balteatus and A. colemani individuals foraging on previously exploited flowers were found to be less concentrated in sugar compounds, especially in fructose and glucose, suggesting that previously exploited flowers contained less available sugars. Nevertheless, individuals did not avoid previously exploited patches in the choice experiment. On the contrary, E. balteatus females preferentially landed on inflorescences that had previously been exploited by conspecifics (but not by B. terrestris), while A. colemani did not show preferences between inflorescences. However, female hoverflies spent more time feeding on unexploited patches, suggesting that exploited patches were resource limited. To our knowledge, this study provides the first evidence of the use of social cues among E. balteatus individuals in food foraging strategies. It also shows that even insects with tiny nectar requirements, such as parasitoids, can suffer from heavy exploitative competition. Such results may have applied consequences for the understanding of natural enemy conservation, in particular in agroecosystems where competition with honeybees may be important.

Resource competition and technological diversity.

The work develops and investigates a mathematical model for evolution of the technological structure of an economic system where different technologies compete for the common essential resources. The model is represented by a system of consumer–resource rate equations. Consumers are technologies formalized as populations of weakly differentiated firms producing a similar commodity with like average output. Firms are characterized by the Leontief–Liebig production function in stock-flow representation. Firms self-replicate with a rate proportional to production output of the respective technology and dissolve with a constant rate of decay. The resources are supplied to the system from outside and consumed by concerned technologies; the unutilized resource amounts are removed elsewhere. The inverse of a per firm break-even resource availability is proposed to serve as a measure for competitiveness towards a given resource. The necessary conditions for coexistence of different technologies are derived, according to which each contender must be a superior competitor for one specific resource and an inferior competitor for the others. The model yields a version of the principle of competitive exclusion: in a steady state, the number of competing technologies cannot exceed the number of limiting resources. Competitive outcomes (either dominance or coexistence) in the general system of multiple technologies feeding on multiple essential resources are shown to be predictable from knowledge of the resource-dependent consumption and growth rates of each technological population taken alone. The proposed model of exploitative competition with explicit resource dynamics enables more profound insight into the patterns of technological change as opposed to conventional mainstream models of innovation diffusion.

Extrinsic Inter- and Intraspecific Competition in Parasitoid Wasps

The diverse ecology of parasitoids is shaped by extrinsic competition, i.e., exploitative or interference competition among adult females and males for hosts and mates. Adult females use an array of morphological, chemical, and behavioral mechanisms to engage in competition that may be either intra- or interspecific. Weaker competitors are often excluded or, if they persist, use alternate host habitats, host developmental stages, or host species. Competition among adult males for mates is almost exclusively intraspecific and involves visual displays, chemical signals, and even physical combat. Extrinsic competition influences community structure through its role in competitive displacement and apparent competition. Finally, anthropogenic changes such as habitat loss and fragmentation, invasive species, pollutants, and climate change result in phenological mismatches and range expansions within host-parasitoid communities with consequent changes to the strength of competitive interactions. Such changes have important ramifications not only for the success of managed agroecosystems, but also for natural ecosystem functioning.

Interaction between hunting strategy, habitat type and stratum drive intraguild predation and cannibalism

Intraguild predation (IGP) is a common interaction between generalist predators when they competitively exploit similar resources and prey on each other. Theoretical models predict limitations for intraguild predator coexistence unless some mechanisms, such as the utilization of alternative prey (i.e. trophic niche partitioning) and cannibalism, increase the relative intraspecific clustering and interspecific segregation. As hunting strategies determine trophic niches of predators and their own vulnerability to predation, the hunting strategies may also determine the relative importance of cannibalism, predation, and exploitative competition and consequently the intensity of IGP. The importance of hunting strategies on the potential outcome of IGP and how habitat properties modify the interaction between hunting strategies remain poorly understood. Using published data on spider prey of spider predators, we first investigated how predation of a top‐predator on a mesopredator is determined by the functional distance between both predators to understand how predation and exploitation are distributed in spider communities. Subsequently, we investigated the predation among spiders with particular hunting strategies to understand which strategies interact most frequently. We also investigated whether the interaction between hunting strategies was influenced by habitat type (forest, open (semi)natural habitat, agroecosystem) or by habitat stratum (ground versus vegetation). The hunting strategies of top‐predators and mesopredators interacted to determine the relative capture proportions of conspecifics and hetero‐specifics. This interaction was further modified by habitat type and stratum. Two mechanisms can reinforce coexistence in highly diverse spider communities. First, top‐predators preyed most frequently on functionally distinct mesopredators, which indicates the overall intensity of IGP may be relaxed by a balanced distribution between exploitative competition and predation. Second, cannibalism was common for top‐predators with a hunting strategy of frequently preying on functionally similar mesopredators. Cannibalism may lead to self‐limitation of top‐predator populations and may thereby facilitate coexistence between two predator species.

Multi‐infections, competitive interactions, and pathogen coexistence

AbstractMultiple infections, either simultaneous or sequential, affecting a single plant or crop are now recognized to be common in plant disease epidemics. These multiple infections thus generate a range of competitive interactions (exploitation competition, apparent competition, or interference competition) that directly impact competitors’ life history traits, and hence fitness. While a theoretical framework, based primarily on three ecological theories—niche exclusion, the “tragedy of the commons”, and the virulence–transmission trade‐off, provides insights into potential outcomes of multiple infections on pathogen evolution and virulence and on disease dynamics, experimental observations, although rather rare so far, strongly suggest that unexpected outputs can also occur. This review therefore attempts to provide a comprehensive overview of both theoretical and empirical knowledge about multiple infection in plants. It highlights the need for a detailed assessment of pathogen life history traits and their modulation according to competition types, host receptivity, and pathogen life strategies for a better understanding and prediction of the evolutionary and demographic outcomes of multiple infections, as well as research questions still open in this emerging field of plant pathology.

Exploitative Competition between Mountain Hare and Moose-Qualitative Effects on Hare Winter Forage?

Simple SummaryMountain hares in Scandinavia are classified as Near Threatened in the Norwegian and Swedish Redlists assessing the risk of species extinction. This is due to a possible population decline witnessed during the last decades in Scandinavia. Competition between large herbivores such as moose, red deer, roe deer on one hand and hares on the other, is one of several hypotheses that has been put forward to explain this decline. In a cafeteria trial (providing several types of forage to determine food preference) we investigate the effects of previous moose winter foraging on the food selection (i.e., amount consumed, bites per minute and bitediameter) of downy birch and goat willow by captive hares. We find that hares do not differentiate among levels of previous moose foraging on downy birch but have larger bite diameters of goat willow earlier eaten on by moose, compared to plants not fed on by moose. Thus, effects of moose on hare winter food quality seem to be limited. We highlight the need for studies focusing on (1) effects of previous moose foraging using wild hares in a natural experimental design, and (2) effects of moose foraging on available hare food at a landscape scale during winter.Mountain hares (Lepus timidus) in Scandinavia are classified as Near Threatened in the Norwegian and Swedish Redlists. This is due to a possible population decline witnessed during the last decades in Scandinavia. Competition between large herbivores and mountain hares is one of several hypotheses that has been put forward to explain this decline. In a cafeteria trial we investigate the effects of previous moose (Alces alces) winter browsing on the food selection (i.e., biomass consumed, bites per minute and bitediameter) of downy birch (Betula pubescens) and goat willow (Salix caprea) by captive mountain hares. We find that mountain hares do not differentiate among previous browsing levels of downy birch, but have larger bite diameters of goat willow earlier browsed by moose, compared to non-browsed plants. Thus, effects of moose on mountain hare winter food quality seem to be limited. We highlight the need for studies focusing on (1) qualitative effects of moose browsing using wild mountain hares in a natural experimental design, and (2) quantitative effects of moose browsing on available mountain hare forage at a landscape scale during winter.

T6SS secretes an LPS-binding effector to recruit OMVs for exploitative competition and horizontal gene transfer

Outer membrane vesicles (OMVs) can function as nanoscale vectors that mediate bacterial interactions in microbial communities. How bacteria recognize and recruit OMVs inter-specifically remains largely unknown, thus limiting our understanding of the complex physiological and ecological roles of OMVs. Here, we report a ligand-receptor interaction-based OMV recruitment mechanism, consisting of a type VI secretion system (T6SS)-secreted lipopolysaccharide (LPS)-binding effector TeoL and the outer membrane receptors CubA and CstR. We demonstrated that Cupriavidus necator T6SS1 secretes TeoL to preferentially associate with OMVs in the extracellular milieu through interactions with LPS, one of the most abundant components of OMVs. TeoL associated with OMVs can further bind outer membrane receptors CubA and CstR, which tethers OMVs to the recipient cells and allows cargo to be delivered. The LPS-mediated mechanism enables bacterial cells to recruit OMVs derived from different species, and confers advantages to bacterial cells in iron acquisition, interbacterial competition, and horizontal gene transfer (HGT). Moreover, our findings provide multiple new perspectives on T6SS functionality in the context of bacterial competition and HGT, through the recruitment of OMVs.

Small rodent cycles influence interactions among predators in a boreal forest ecosystem

Cyclic fluctuations of prey have profound effects on the functioning of ecosystems, for example, by changing the dynamics, behavior, and intraguild interactions of predators. The aim of this study was to assess the effect of rodent cyclic fluctuations in the interspecific interactions of a guild of small- and medium-sized predators: red fox (Vulpes vulpes), pine marten (Martes martes), and weasels (Mustela erminea and Mustela nivalis) in the boreal ecosystem. We analyzed eight years (2007–2014) of snow tracking data from southeastern Norway using structural equation models to assess hypothesized networks of causal relationships. Our results show that fluctuations in rodent abundance alter the strength of predator’s interactions, as well as the effect of determinant environmental variables. Pine marten and weasel abundances were positively associated with rodent population growth rate, but not red fox abundance. All predators were positively associated with each other; however, the association between red fox and the other predators weakened when rodents increased. Rodent fluctuations had variable effects on the habitat use of the predators. The presence of agricultural land was important for all predators, but this importance weakened for the mustelids as rodent abundance increased. We discuss the shifting role of interference and exploitative competition as possible mechanisms behind these patterns. Overall, we highlight the importance of accounting for the dynamics of prey resources when studying interspecific interactions among predators. Additionally, we demonstrate the importance of monitoring the predator populations in order to anticipate undesirable outcomes such as increased generalist predator abundances to the detriment of specialists.

A test of the use of gray wolf (Canis lupus) urine to reduce coyote (Canis latrans) depredation rates on loggerhead sea turtles (Caretta caretta) nests

Loggerhead sea turtles (Caretta caretta) are currently listed as vulnerable, with a decreasing population trend, by the International Union of Conservation of Nature. From 2015 to 2019, coyotes (Canis latrans) depredated 24.12% of loggerhead nests on the night they were laid on South Island beach at the Tom Yawkey Wildlife Center, near Georgetown, SC, resulting in an estimated 3816 eggs lost each year. Over that time, a South Carolina Department of Natural Resources Turtle Technician Team patrolled the beach at dawn every morning to cage and catalog loggerhead nests and eggs but were unable to cost-effectively protect the nests the night the eggs were laid. To test a new method to dissuade coyote depredation, we used dispensers filled with gray wolf (Canis lupus) urine to simulate wolf activity on seven sections of the beach and left seven sections untreated as controls. We observed a significant reduction in depredation rates where urine was present relative to control areas (G-test adjusted with the Williams correction, G = 5.749, df = 1, p = 0.0165). The results suggest this may be an example of exploitative competition in the absence of interference competition. With daily teams already patrolling the beaches, using wolf urine as a deterrent could be an inexpensive, non-invasive way to reduce coyote depredation on loggerhead and other sea turtle nests elsewhere.

Incongruent drivers of network, species and interaction persistence in food webs

Communities can be described by species, interactions and the network of interactions which emerge from these building blocks. Networks are often summarized by diverse metrics which capture key components of network topology, for example, number of trophic levels, number of interactions per species (i.e. degree) and frequency of apparent competition modules (i.e. motifs). Network metrics are often used to predict whole community responses following a perturbation. Understanding whether our predictive capabilities at the network level are maintained at other levels of organization such as species and interaction levels is critical but rarely studied. Our objective was to determine whether we can use different network metrics (e.g. modularity, species roles) to predict which networks, species and interactions will persist following a perturbation. Given the nested structure of interactions, species and networks, we hypothesized that those metrics which were correlated with network persistence would be the same metrics correlated with which species and interactions persist and that the direction of these correlations would be maintained across organizational levels (i.e. network, species and interactions). We used numerical simulations of a dynamic food web model and model selection to test the relationships between network metrics (e.g. degree, modularity, motif profiles) and network, species and interaction‐level persistence. We found that out degree and frequency of both apparent and exploitative competition were the best predictors of species persistence, however all metrics were weak predictors of species persistence. This demonstrates that metrics which predict network persistence are not always the best predictors of species and interaction level persistence. Additionally, metrics can work in opposition depending on the organizational scope examined; for example interaction strength is positively correlated with interaction persistence, but negatively correlated with species persistence. Multiscale analysis of network metrics such as this one, may provide critical insight for advancing network‐based environmental management in the Anthropocene.

Mechanisms Involved in Interspecific Communication between Wine Yeasts.

In parallel with the development of non-Saccharomyces starter cultures in oenology, a growing interest has developed around the interactions between the microorganisms involved in the transformation of grape must into wine. Nowadays, it is widely accepted that the outcome of a fermentation process involving two or more inoculated yeast species will be different from the weighted average of the corresponding individual cultures. Interspecific interactions between wine yeasts take place on several levels, including interference competition, exploitation competition, exchange of metabolic intermediates, and others. Some interactions could be a simple consequence of each yeast running its own metabolic programme in a context where metabolic intermediates and end products from other yeasts are present. However, there are clear indications, in some cases, of specific recognition between interacting yeasts. In this article we discuss the mechanisms that may be involved in the communication between wine yeasts during alcoholic fermentation.