Effects Of Interspecific Interactions Research Articles

Species interactions amplify functional group responses to elevated CO2 and N enrichment in a 24-year grassland experiment.

Plant functional groups (FGs) differ in their response to global changes, although species within those groups also vary in such responses. Both species and FG responses to global change are likely influenced by species interactions such as inter-specific competition and facilitation, which are prevalent in species mixtures but not monocultures. As most studies focus on responses of plants growing in either monocultures or mixtures, but rarely both, it remains unclear how interspecific interactions in diverse ecological communities, especially among species in different FGs, modify FG responses to global changes. To address these issues, we leveraged data from a 16-species, 24-year perennial grassland experiment to examine plant FG biomass responses to atmospheric CO2, and N inputs at different planted diversity. FGs differed in their responses to N and CO2 treatments in monocultures. Such differences were amplified in mixtures, where N enrichment strongly increased C3 grass success at ambient CO2 and C4 grass success at elevated CO2. Legumes declined with N enrichment in mixtures at both CO2 levels and increased with elevated CO2 in the initial years of the experiment. Our results suggest that previous studies that considered responses to global changes in monocultures may underestimate biomass changes in diverse communities where interspecific interactions can amplify responses. Such effects of interspecific interactions on responses of FGs to global change may impact community composition over time and consequently influence ecosystem functions.

Core Species Derived from Multispecies Interactions Facilitate the Immobilization of Cadmium

Microbial consortia have opened new avenues for heavy-metal remediation. However, the limited understanding of the overall effect of interspecific interactions on remediation efficacy hinders its application. Here, the effects of multispecies growth and biofilm formation on Cd immobilization were explored from direct and multiple interactions through random combinations of two or three rhizosphere bacteria. In monocultures, Cd stress resulted in an average decrease in planktonic biomass of 26%, but through cooperation, the decrease was attenuated in dual (21%) and triple cultures (13%), possibly involving an increase in surface polysaccharides. More than 65% of the co-cultures exhibited induction of biofilm formation under Cd stress, which further enhanced the role of biofilms in Cd immobilization. Notably, excellent biofilm-forming ability or extensive social induction makes Pseudomonas putida and Brevundimonas diminuta stand out in multispecies biofilm formation and Cd immobilization. These two core species significantly increase the colonization of soil microorganisms on rice roots compared to the control, resulting in a 40% decrease in Cd uptake by rice. Our study enhances the understanding of bacterial interactions under Cd stress and provides a novel strategy for adjusting beneficial soil consortia for heavy-metal remediation.

Impacts of Interspecific Interactions on Crop Growth and Yield in Wheat (Triticum aestivum L.)/Maize (Zea mays L.) Strip Intercropping under Different Water and Nitrogen Levels

Interspecific interactions and recovery growth play an important role in crop growth, development and ultimately yield in intercropping systems. However, the impact of different water and nitrogen levels on intercropping production, interspecific interactions between intercrops, and the recovery growth of late-maturing crops is still unclear. A two-year field experiment was conducted in Yangling, Shaanxi province, to investigate the dynamics of interspecific interactions, and the effects of interspecific interactions on crop growth and yield. The experiment consisted of three factors, including three cropping systems (wheat/maize intercropping, sole wheat, sole maize), three nitrogen (N) levels and two water applications (supplementary irrigation and rainfed). The results demonstrated that, during the co-growth period, intercropped wheat was more competitive than intercropped maize; so, intercropped wheat showed a yield advantage. Intercropping increased maize yield under irrigated conditions, and this was attributed to the full recovery growth of intercropped maize after wheat harvest. However, rainfed and nil nitrogen aggravated the interspecific competition, and water deficit under maize rows, in turn, limited the recovery growth of intercropped maize, leading to yield reduction. However, compared with sole maize, the yield of intercropped maize decreased, indicating nitrogen deficiency limited the recovery growth of intercropped maize. Among all treatments, the intercropping of medium nitrogen fertilizer with irrigation had the best yield improvement and land use advantages, the total yield of intercropping was 14.8% higher than that of sole cropping, and the land use efficiency increased 16%. These results confirmed that supplementary irrigation and optimal nitrogen application alleviated the interspecific competition, promoted the recovery growth of intercropped maize and improved the yield of wheat/maize intercropping system.

Interactions between species change the uptake of ammonium and nitrate in Abies faxoniana and Picea asperata.

Plant nitrogen (N) uptake is affected by plant-plant interactions, but the mechanisms remain unknown. A 15N-labeled technique was used in a pot experiment to analyze the uptake rate of ammonium (NH4+) and nitrate (NO3-) by Abies faxoniana Rehd. et Wils and Picea asperata Mast. in single-plant mode, intraspecific and interspecific interactions. The results indicated that the effects of plant-plant interactions on N uptake rate depended on plant species and N forms. Picea asperata had a higher N uptake rate of both N forms than A. faxoniana, and both species preferred NO3-. Compared with single-plant mode, intraspecific interaction increased NH4+ uptake for A. faxoniana but reduced that for P. asperata, while it did not change NO3- uptake for the two species. The interspecific interaction enhanced N uptake of both N forms for A. faxoniana but did not affect the P. asperata compared with single-plant mode. NH4+ and NO3- uptake rates for the two species were regulated by root N concentration, root nitrate reductase activity, root vigor, soil pH and soil N availability under plant-plant interactions. Decreased NH4+ uptake rate for P. asperata under intraspecific interaction was induced by lower root N concentration and nitrate reductase activity. The positive effects of interspecific interaction on N uptake for A. faxoniana could be determined mainly by positive rhizosphere effects, such as high soil pH. From the perspective of root-soil interactions, our study provides insight into how plant-plant interactions affect N uptake, which can help to understand species coexistence and biodiversity maintenance in forest ecosystems.

An In Vitro Mixed Infection Model With Commensal and Pathogenic Staphylococci for the Exploration of Interspecific Interactions and Their Impacts on Skin Physiology.

The skin microbiota has been recognized to play an integral role in the physiology and pathology of the skin. The crosstalk between skin and the resident microbes has been extensively investigated using two-dimensional (2D) and three-dimensional (3D) cell cultures in vitro; however, skin colonization by multiple species and the effects of interspecific interactions on the structure and function of skin remains to be elucidated. This study reports the establishment of a mixed infection model, incorporating both commensal (Staphylococcus epidermidis) and pathogenic (Staphylococcus aureus) bacteria, based on a 3D human epidermal model. We observed that co-infecting the 3D epidermal model with S. aureus and S. epidermidis restricted the growth of S. aureus. In addition, S. aureus induced epidermal cytotoxicity, and the release of proinflammatory cytokines was attenuated by the S. aureus-S. epidermidis mixed infection model. S. epidermidis also inhibited the invasion of the deeper epidermis by S. aureus, eliciting protective effects on the integrity of the epidermal barrier. This 3D culture-based mixed infection model would be an effective replacement for existing animal models and 2D cell culture approaches for the evaluation of diverse biotic and abiotic factors involved in maintaining skin health.

Effects of Interspecific Interactions on Infracommunities of Helminths Parasitizing Creek Chub (Semotilus atromaculatus)

Natural infections of Allocreadium lobatum Wallin, 1909 (Trematoda), Proteocephalus sp. (Cestoda), Rhabdochona canadensis Moravec and Arai, 1971 (Nematoda), Paulisentis missouriensis Keppner, 1974 (Acanthocephala), and Schyzocotyle acheilognathi (Yamaguti, 1934) (Cestoda) in the intestine of creek chub (Semotilus atromaculatus) were analyzed to determine whether patterns of interspecific competition were evident. Data from nearly 2 decades of sampling from the same system were analyzed for patterns of co-occurrence and abundance consistent with negative interactions. Co-occurrence analyses (null models and logistic regression) did not detect negative associations among parasite species. Positive associations among species were more common in null model comparisons. Correlation analyses demonstrated some significant negative correlations between the abundances of pairs of parasite species in some samples, but the overwhelming majority of correlations were insignificant or positive. Previous work did not detect negative microhabitat interactions among the most common helminths studied herein, and together, these results suggest the parasite communities of creek chub in the study area are absent any substantial effect of antagonistic or other negative interspecific interactions. Differences in transmission rate, mode, and spatiotemporal variation are likely dominant processes explaining the patterns observed in the present investigation.

Yeast facilitates the multiplication of Drosophila bacterial symbionts but has no effect on the form or parameters of Taylor's law.

Interactions between microbial symbionts influence their demography and that of their hosts. Taylor's power law (TL)-a well-established relationship between population size mean and variance across space and time-may help to unveil the factors and processes that determine symbiont multiplications. Recent studies suggest pervasive interactions between symbionts in Drosophila melanogaster. We used this system to investigate theoretical predictions regarding the effects of interspecific interactions on TL parameters. We assayed twenty natural strains of bacteria in the presence and absence of a strain of yeast using an ecologically realistic set-up with D. melanogaster larvae reared in natural fruit. Yeast presence led to a small increase in bacterial cell numbers; bacterial strain identity largely affected yeast multiplication. The spatial version of TL held among bacterial and yeast populations with slopes of 2. However, contrary to theoretical prediction, the facilitation of bacterial symbionts by yeast had no detectable effect on TL's parameters. These results shed new light on the nature of D. melanogaster's symbiosis with yeast and bacteria. They further reveal the complexity of investigating TL with microorganisms.

Competition among juvenile brown trout, grayling, and landlocked Atlantic salmon in flumes — predicting effects of interspecific interactions on salmon reintroduction success

Worldwide declines in salmonid populations have generated major interest in conservation and restoration of wild populations and riverine habitats. Species reintroductions to previous habitats raise questions about their potential impact on these systems. In River Klarälven, landlocked Atlantic salmon (Salmo salar) have been extinct from upper reaches for over 50 years due to hydropower dams. Here we study competitive interactions among juvenile salmon, grayling (Thymallus thymallus), and brown trout (Salmo trutta) that occur in the upper reaches of the river. We examine foraging rates, aggression, and activity of juvenile fish in allopatry at three different densities and in sympatry with one or both potential competitors in laboratory flumes. Salmon captured prey less frequently in the presence of brown trout and grayling, whereas grayling and brown trout were unaffected by salmon, but affected each other. Grayling was the most aggressive and active species, whereas salmon the least. Consequently, reintroduction of salmon probably will have little impact on grayling and brown trout, whereas grayling and brown trout could affect the success of reintroducing salmon.

БAЛЕТНА ТA ЦИРКОВA НЕОКЛАСИКА: ПРОЦЕСИ ІНТЕГРАЦІЇ, СИНТЕЗУ ТА ТРАНСФОРМАЦІЇ

Метa дослiдження полягає в системному розгляді особливостей хореогрaфiчної культури циркових хореогрaфiчних тa aкробaтичних мiнiaтюр нa корд-де-пaрель із позицiй клaсичного бaлетного мистецтвa. Простежено iсторичний процес iнтегрaцiї бaлетних форм у циркове мистецтво тa нaпрями їх стильової трaнсформaцiї в особливих сценiчних умовaх цирку сучaсного етaпу.
 Методологiя дослiдження ґрунтується нa зaстосувaннi комплексного пiдходу до вивчення хореогрaфiчної культури сумiжних видiв мистецтв. Крiм того, використовуються емпiричнi, описовi тa зaгaльнонaуковi методи компaрaтивного aнaлiзу i синтезу. Нaуковa новизнa полягaє у виявленнi стильової тотожностi тa спорiдненостi основних художньо-технологiчних принципiв бaлетної неоклaсики тa циркового жaнру повiтряної гiмнaстики нa корд-де-пaрель. Хореогрaфiчнa культурa у процесi еволюцiї збaгaчувaлaсь нaслiдкaми мiжвидової взaємодiї мистецтв: вiд укорiнення трюкових елементiв у бaлетi – до сучaсного етaпу розквiту бaлетної культури у цирковому мистецтвi, що впливaло нa її стильову особливiсть у чaсопросторовiй динaмiцi. Нaпрями синтезу циркового мистецтвa тa бaлету спостерiгaються в основних пaрaметрaх стилю тa зaсобiв вирaзностi жaнру повiтряної гiмнaстики нa корд-де-пaрель. Aрхiтектонiкa подiбних дуетних номерiв укрaїнських циркових aртистiв ґрунтується нa неокласичних бaлетних принципaх Pas-de-deux: пiдйом нa кaнaт нaближений до неоклaсичного entree; aкробaтичнi фiгури «прaпорець», кружляння, провиси тa «стрiлa» – вaрiaцiї солiстiв, особливий вертикaльний обертовий спуск нa полотнi – фуете. Плaстичнiсть, ритмiчнiсть, експресiя обумовленa музичним супроводом i знaходиться нa перетинi двох векторiв – сучасної хореогрaфiї тa циркової гімнастики, вирaженої у трюкaх. Технiкa їх повiтряного виконaння у вертикaльнiй площинi (нa вiдмiну вiд горизонтaльної – у бaлетi) демонструє нову оптику сприйняття.
 Ключовi словa: бaлет, цирк, aкробaтикa, корд-де-пaрель, тaнець, культурa, хореогрaфiя, синтез.

Effects of Interspecific Interactions on Microhabitat Use of Three Helminths Parasitizing Creek Chub (Semotilus atromaculatus) in Southeastern Nebraska

Natural infections of Paulisentis missouriensis (Acanthocephala), Rhabdochona canadensis (Nematoda), and Allocreadium lobatum (Trematoda) in the intestine of creek chub (Semotilus atromaculatus) were studied to determine whether microhabitat use of these helminths was affected by interspecific interactions. Comparison of mean relative positions and intestinal segment use of all 3 helminths revealed no negative interactions among the 3 species. Paulisentis missouriensis appeared entirely unaffected by the presence of either R. canadensis or A. lobatum. Each of the latter 2 species, however, appeared to exhibit some shift toward, rather than away from, the location of P. missouriensis in co-infected hosts. However, the effect size in both cases was small and therefore could be spurious. At higher intensities of co-infecting P. missouriensis, worms of A. lobatum were either distributed far to the anterior or far to the posterior of the intestinal locations occupied by P. missouriensis. This constituted the only evidence in the present investigation for negative interspecific interactions among these 3 frequently co-occurring helminths in this system.

Research progress in effects of interspecific interaction on medicinal plants in intercropping system

Intercropping farming system is one of the essence of traditional agriculture in China and one of the most common and basic patterns of modern ecological planting. Intercropping system uses the principle of species diversity to create reasonable interspecific interaction conditions with obvious productivity advantages. In this paper, the interspecies interaction is divided into aboveground and underground parts from the space view, and its influence and mechanism on the yield and secondary metabolites of medicinal plants are elaborated.The interspecific interaction in the aboveground part mainly introduces the distribution and utilization of space resources among plants. The interspecific interaction in the underground part mainly introduces the soil rhizosphere effect and related mediating factors, root exudates, soil microorganisms, root space structure and soil environmental factors. On the basis of understanding the mechanism of interspecific interaction, this paper further discusses the application of intercropping in traditional Chinese medicine ecological agriculture, taking the effective control of diseases and insect pests, the increase of medicinal material yield and the improvement of medicinal material quality as the benefit index, so as to seek better advantages of intercropping and provide ideas for the utilization of intercropping production mode in traditional Chinese medicine ecological agriculture.

Effects of interspecific interactions on seed germination between dominant species in the Yangtze River Estuary

Seed germination is the key stage of population recruitment. Competition between native and invasive species can greatly influence the seed germination and the stability of the affected populations and communities, which in turn will affect the stability of native ecosystems. In this paper, we studied the interactions between dominant species in Chongming Dongtan wetland at seed germination stage using a germination experiment. We found that both salinity and interspecific interaction significantly affected the seed germination process of dominant marsh plants, but the effects were not consistent among different species. Generally, germination rate of Scirpus mariqueter was inhibited by high salinity, whereas that of Suaeda glauca was promoted by salt. Almost all the species germinated more slowly in salt water than in fresh water. Invasive Spartina alterniflora seeds significantly promoted the germination rate of Scirpus mariqueter in salt water despite of its heavy competitive effects on this native sedge in the adult stage. Besides, the germination rate of Spartina alterniflora was significantly inhibited by Phragmites australis and Suaeda glauca seeds in salt water, whereas its germination speed was significantly inhibited by Phragmites australis in fresh water. Our study revealed the pattern of interspecific interactions in the early life stages of plants, which may improve our understanding of population and community dynamics and provide some guidance to invasive species control and wetland management.

Modeling interactions and dynamics of Aphidius matricariae and Praon volucre (Hymenoptera: Braconidae) on two major aphid species in a greenhouse

Interspecific interactions between parasitoid wasps affect the selection of effective biological control agents. In this study, we investigated the effects of extrinsic interspecific interactions between Aphidius matricariae Halifay and Praon volucre (Haliday) (Hymenoptera: Braconidae) on the population sizes of each parasitoid on Myzus persicae (Sulzer) on sweet pepper and Aphis gossypii Glover on cucumber, at 25 ± 2 °C, 60 ± 5% RH and a 14:10 h L:D photoperiod. The population dynamics of these parasitoids were also analyzed numerically using the Lotka–Volterra competition model. Interspecific interaction between the two parasitoids had reduced the population size of each parasitoid on both host aphids. The effect of this interspecific interaction b was more pronounced for P. volucre. Without interspecific interactions, the mean population size of P. volucre varied from 85.2 ± 10.70 to 107.1 ± 12.40 numbers on M. persicae and from 187.8 ± 18.4 to 249.8 ± 24.7 numbers on A. gossypii. Under conditions of coexistence with A. matricariae, however, the abundance of P. volucre significantly decreased to 8.92 ± 2.65–17 ± 5.16 numbers on M. persicae and 53.6 ± 19–65.3 ± 25.2 numbers on A. gossypii. Phase diagrams and time trajectories showed that coexistence of these two parasitoids on M. persicae and A. gossypii lasted for just a short period after which the inferior parasitoid population, P. volucre, declined to zero.

The Effects of Interspecific Interactions Between Bloom Forming Cyanobacteria and Scenedesmus quadricauda (Chlorophyta) on Their Photophysiology

Eutrophication and enhanced external nutrient loading of lakes and seas are most clearly reflected by increased cyanobacterial blooms, which are often toxic. Freshwater cyanobacteria produce a number of bioactive secondary metabolites, some of which have allelopathic properties, significantly influencing the biological processes of other algae, thereby affecting species composition and succession of the phytoplankton. The goal of this work was to investigate the influence of bloom-forming cyanobacterial exudates on the photophysiology of the green alga Scenedesmus quadricauda by chlorophyll fluorescence analysis. We were able to prove the effect of algal cell-free fltrates on the performance of S. quadricauda and demonstrate for the first time that the freshwater picocyanobacterium Cyanobium gracile has strong negative impact on the coexisting green alga. Neither the cyanotoxin (MYC, CYN and ATX) producing, nor the non-toxic strains showed any systematic effect on the production of S. quadricauda. Various strains of the cyanobacterium Cylindrospermopsis raciborskii inhibited the performance of the green alga independently of their origin. Our results urge further studies for a better understanding of the factors affecting the release of allelopathic compounds and the mechanisms of their effects on target organisms.

Interactions among competing nematode species affect population growth rates.

Investigations of the interplay of organisms in an ecological community are a prerequisite to understanding the processes that shape the structures of those communities. Among several types of interactions, interest in the positive interactions of species that compete for the same resource has grown, as they may provide a mechanism enabling coexistence. In the laboratory experiment described herein, the effects of interspecific interaction on the population growth of two bacterial-feeding nematode species, Panagrolaimus cf. thienemanni and Poikilolaimus cf. regenfussi, were investigated. Specifically, we asked: (1) whether there is an interspecific interaction between organisms competing for a mutual resource and (2) whether these interactions are altered by the competitors' initial densities and (3) their variable growth rates (induced by different food supplies). Each treatment initially contained 48 nematode individuals, but at different species ratios (48:0; 32:16; 24:24; 16:32; 0:48). The populations were provided with three different bacterial densities (108, 109, and 1010cellsml-1) as food. The data were analyzed using a generalized linear mixed model. The best-fitting model revealed a significant decline in population growth rates with an increasing species ratio, but depending on the food density and species. These results provide strong evidence for positive interspecific interactions that vary with both species density and food-supply level. They also suggest important roles for positive interspecific interactions in habitat colonization and in maintaining the coexistence of species in the same trophic group.

The importance of species identity and interactions for multifunctionality depends on how ecosystem functions are valued.

Studies investigating how biodiversity affects ecosystem functioning increasingly focus on multiple functions measured simultaneously ("multifunctionality"). However, few such studies assess the role of species interactions, particularly under alternative environmental scenarios, despite interactions being key to ecosystem functioning. Here we address five questions of central importance to ecosystem multifunctionality using a terrestrial animal system. (1) Does the contribution of individual species differ for different ecosystem functions? (2) Do inter-species interactions affect the delivery of single functions and multiple functions? (3) Does the community composition that maximizes individual functions also maximize multifunctionality? (4) Is the functional role of individual species, and the effect of interspecific interactions, modified by changing environmental conditions? (5) How do these roles and interactions change under varying scenarios where ecosystem services are weighted to reflect different societal preferences? We manipulated species' relative abundance in dung beetle communities and measured 16 functions contributing to dung decomposition, plant productivity, nutrient recycling, reduction of greenhouse gases, and microbial activity. Using the multivariate diversity-interactions framework, we assessed how changes in species identity, composition, and interspecific interactions affected these functions in combination with an environmental driver (increased precipitation). This allowed us to identify key species and interactions across multiple functions. We then developed a desirability function approach to examine how individual species and species mixtures contribute to a desired state of overall ecosystem functioning. Species contributed unequally to individual functions, and to multifunctionality, and individual functions were maximized by different community compositions. Moreover, the species and interactions important for maintaining overall multifunctionality depended on the weight given to individual functions. Optimal multifunctionality was context-dependent, and sensitive to the valuation of services. This combination of methodological approaches allowed us to resolve the interactions and indirect effects among species that drive ecosystem functioning, revealing how multiple aspects of biodiversity can simultaneously drive ecosystem functioning. Our results highlight the importance of a multifunctionality perspective for a complete assessment of species' functional contributions.

Defensive tradeoffs are not prerequisites to plant diversity in a two species model

Trait‐based theories of biodiversity consider interspecific tradeoffs among species‐specific traits as prerequisites to maintaining community evenness, a component of species diversity. Such tradeoffs are commonly observed in plant communities, particularly in relation to traits associated with resistance to herbivory. Indeed, global experiments show that interspecific tradeoffs are common between plant defense and growth or competitive ability; however, the positive effects of herbivory on plant diversity predicted by theories with trait‐based tradeoffs are far less commonly observed. Moreover, both the overall and relative importance of these tradeoffs in promoting plant diversity are not well known. To disentangle the relationships among growth, competition, and defense in relation to plant community evenness, we built a model that describes the effects of a shared herbivore on two plant species with the potential to differ in each of these traits. While tradeoffs between plant defense and growth or competitive ability can increase plant diversity via evenness, this is not always the case nor is it a requirement for increased diversity. Herbivores may increase plant diversity even in the absence of defensive tradeoffs, preferentially consuming apparently maladapted species, by limiting the negative effects of interspecific interactions. Therefore, the importance of defensive tradeoffs in increasing diversity may not be as important, or as straightforward, as previously hypothesized.

Territoriality of Six Thamnophilidae Species In A Cloud Forest In Southeastern Brazil

ABSTRACT Territorial systems of Neotropical birds remain poorly understood, especially considering the effect of interspecific interactions. Studies on territorial behavior provide information about demography and life history, and are useful for the refinement of conservation strategies. We assessed territories of six species of antbirds (Thamnophilidae) from August 2010 to May 2011 at Pedra Azul State Park, a protected area in southeastern Brazil, in a 30-ha sampling grid. Birds were captured, marked, and followed through the study area. Territory sizes of Plain Antvireo (Dysithamnus mentalis), Ferruginous Antbird (Drymophila ferruginea), Ochre-rumped Antbird (Drymophila ochropyga), White-bibbed Antbird (Myrmeciza loricata), White-shouldered Fire-eye (Pyriglena leucoptera), and Variable Antshrike (Thamnophilus caerulescens) were estimated by the convex polygon method. We found 46 territories of the six species. We compared and evaluated the effect of body size on territories among the species. Males and...

Interspecific Interactions Affect Pests Differently

Spider mites, Tetranychus urticae Koch (Acari: Tetranychidae) and aphids, Myzus persicae (Sulzer) (Pterygota: Aphididae) share many host-plants, similar abiotic conditions and are world-wide distributed therefore, they often occur simultaneously in crops. However, the effects of interspecific interactions on the biology of these pests were poorly investigated. To test if they perform differently under intra- versus inter-specific interactions, host-plant acceptance, fecundity, survival, the total number of individuals and the rate of increase in the number of individuals were studied doing non-choice bioassays under laboratory conditions with leaf discs of tomato (Solanum lycopersicum L. ‘Ailsa Craig’), pak choi (Brassica rapa L. var. chinensis ‘Black Behi’) and bean (Phaseolus vulgaris L. ‘Saxa’). Alone, the pests differently accepted the host-plants. The acceptance of pak choi by spider mites was lower under interspecific interactions and higher on tomato for aphids. In general, spider mites’ performance decreased when aphids were present; the fecundity, the number of individuals and the rate of increase being significantly lower on pak choi and bean. In contrast, aphids produced more offspring in the presence of spider mites, leading to a higher rate of increase in aphids individuals on tomato and pak choi. Thus, pest’ responses to interspecific interactions is species-specific.

Growth depends on neighbours: experiments with three Sphagnum L. species

Our aim was to search for reasons why some peat mosses (Sphagnum), despite having wide distribution areas, consistently occur in small and distantly scattered populations. The effect of interspecific interactions was proposed as the main hypothesis. Three Sphagnum species exhibiting different distribution frequencies (S. wulfianum Girg., S. teres (Schimp.) Ångstr., and S. magellanicum Brid.) were selected, and two experiments in controlled conditions were established. In the first experiment, the peat mosses were grown in mono-species, two-species, and three-species mixtures. Only the growth of the species with the most restricted distribution (S. wulfianum) responded significantly to the presence of the other Sphagnum species. In the second experiment, shoots of S. wulfianum were watered with the exudates and extracts of the other two species. Significant effects were observed on the growth of S. wulfianum. We conclude that neighbour species can suppress the growth of some bryophyte species and possibly limit their natural distribution.