Search

Large-scale tree planting with indigenous trees is one approach to combatting climate change and environmental degradation. However, a significant challenge with establishing planted indigenous forests at scale, particularly in New Zealand, is that our knowledge and capacity to achieve this in highly modified environments, covered by invasive species, is relatively poor. The purpose of our study was to quantify the survival and growth of five indigenous tree species (three gymnosperms, two angiosperms) planted either on their own (weed-free) or in association with an indigenous (Leptospermum scoparium J.R. Forst) or exotic (Cytisus scoparius (L.) Link) shrub species. We monitored survival and growth following planting for 2.5 years. Results showed that survival for the gymnosperms was > 90% for all treatments. In contrast, survival of the two angiosperms was poor, and, in general, not significantly related to the presence or absence of neighbouring vegetation. The response to vegetation management for tree height was similar across all species: weed-free treatment > L. scoparium treatment > C. scoparius treatment. Diameter growth was also highest for all tree species in the weed-free treatment, compared to the two other vegetation management treatments, but the extent of the increase varied by tree species. We found no direct evidence for neighbouring vegetation facilitating early survival and growth of the five indigenous tree species tested at our study site. However, the outcomes require testing at scale and across environments to underpin future forest restoration efforts. [ABSTRACT FROM AUTHOR]

Background and Aims: The deposition of atmospheric nitrogen has increased globally and interfered with plant growth and development. However, only a few studies have examined the influence of atmospheric nitrogen deposition on plant–herbivore interactions in the framework of plant invasion, and the underlying mechanisms remain unclear. Methods: In this study, we examined the changes in growth and herbivore resistance of the invasive weed Alternanthera philoxeroides and its native co-occurring congener Alternanthera sessilis in response to simulated nitrogen deposition. We further investigated the competitive ability of these two plant species grown in mono- and mix-culture conditions with or without herbivore pressures. Results: The results indicated that simulated nitrogen deposition largely increased the growth of both plant species, while A. philoxeroides produced more biomass than A. sessilis. The specialist and generalist herbivores showed contrasting preferences for the two plant species in the controls, whereas A. philoxeroides showed greater resistance to both herbivore species under simulated nitrogen deposition. Further investigation of host plant traits related to leaf structural and chemical defences suggested that such difference in herbivore resistance between the two plant species could be attributed to the increased levels of structural defense in A. philoxeroides and reduced levels of defensive metabolites in A. sessilis. The inter-specific competition test revealed that simulated nitrogen deposition largely increased the competitive advantage of A. philoxeroides over A. sessilis, regardless of the presence or absence of herbivores. Conclusion: Our study suggests that the invasiveness of A. philoxeroides may be enhanced by increased atmospheric nitrogen deposition. [ABSTRACT FROM AUTHOR]

Copyright of Xinjiang Agricultural Sciences is the property of Xinjiang Agricultural Sciences Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

With metamorphosis or not, creatures have varying ability in their different life stages to compete for resource, space or mating. Interaction of species with environment and competition between species are key factors in the evolution of ecological population. Taking these concerns into account, we study a model with two life stages, immature and mature, and incorporate both intra- and inter-specific competitions between two species in a two-patch environment. The structure of monotone dynamics in such a model leads us to explore its local and global dynamics. The investigation starts with the single-species model on which we establish the threshold dynamics that either the species eventually goes extinction or exists on both patches, which is determined by the parameters. Then we study the two-species model and formulate the threshold competition strength which monotonously but oppositely depends on the maturation times of two species, and indicates how the competitor invade an environment. Moreover, we demonstrate two mechanisms which give rise to dominance dynamics, under competition-dependent and -independent criteria respectively. Finally, we conduct numerical simulations to show that the proposed model admits multiple positive equilibria due to the consideration of two life stages. [ABSTRACT FROM AUTHOR]

Urban habitats differ from natural environments, however some predatory species have become established in cities across the globe. The aim of our study was to compare the occurrence of the red fox and the stone marten in Warsaw during three time periods (1976–1978, 2005–2008, 2015–2021) and in different habitats. Generalized linear models were used to show factors affecting the density indices of these two species (i.e., frequency of occurrence of tracks of each species recorded during snow tracking on linear transects). The frequency of occurrence of tracks of these two species on transects increased over time and was explained by habitat type and distance from the city centre. The frequency of fox tracks was higher in more‐natural habitats located far from the city centre. In the first period (1976–1978), this species was recorded only in forests and riparian areas. In the last period (2015–2021), its tracks were recorded frequently in built‐up areas and cemeteries. From the beginning of the first period, the stone marten was recorded in a wider range of habitats than the fox and it colonized all habitat types in the subsequent periods, but a statistically significant increase was observed only for cemeteries. The frequency of occurrence of stone marten tracks was lower than that of red fox tracks in most natural and seminatural habitats (forests, parks, riparian areas). No relationship between the occurrence of the red fox and the stone marten was found. We speculate that the growth of the urban red fox numbers was driven by an increase in the national population as a result of anti‐rabies vaccinations. In turn, the stone marten, being a synanthropic species, was present in the city centre from the beginning of the study, but it now occurs in a wider range of habitats. [ABSTRACT FROM AUTHOR]

The translocation of non-indigenous fishes into lowland rives can result in invasive populations establishing and dispersing. Because non-indigenous fishes can cause ecological harm, it is important to understand their trophic relationships and the effects they may have on native fishes. We assessed the trophic ecology of a translocated chub Squalius cephalus population in the River Frome, a lowland chalk stream in Southern England, using bulk stable isotope (δ13C, δ15N) metrics, and compared the results with those derived from indigenous chub populations. The isotopic niche sizes of all fishes in the River Frome were substantially larger in the tidal versus non-tidal site, with the δ13C values suggesting some fish were foraging further downstream of their sampling point in areas that had greater tidal and salinity influences. Inter-specific comparisons of isotopic niches revealed a consistent pattern of similar niche size and overlap between chub and the trophically analogous dace Leuciscus leuciscus. These isotopic relationships between chub and dace were then also apparent in the indigenous populations of these fishes. These results suggest that the colonisation of this lowland river by translocated chub is being facilitated by their isotopic relationships with other fishes that are similar to those observed in their native range. [ABSTRACT FROM AUTHOR]

Carnivore community dynamics are governed by a complex set of often interacting biotic, abiotic and anthropogenic factors that are increasingly volatile as a result of global change. Understanding how these changing conditions influence carnivore communities is urgent because of the important role carnivores play within ecosystems at multiple trophic levels, and the conservation threats that many carnivores face globally.While a great deal of research attention has historically been focused on large carnivores within ecosystems, the size‐mediated sensitivity hypothesis has recently been proposed where the smallest carnivore in a system is likely to be the most responsive to the diverse suite of ongoing environmental and anthropogenic changes within ecological communities.We deployed camera traps at 197 sites over 4 years to monitor a diverse suite of mammalian carnivores within the Blue Ridge Mountains of western North Carolina and then used a two‐step occupancy modelling–structural equation modelling framework to investigate the relative support for four primary hypothesized drivers (interspecific competition/predation, habitat complexity, food availability and anthropogenic disturbance) on carnivore occurrence.We found that each of the 10 carnivores in our system responded differently to conditions associated with each of these four hypothesized drivers, but that small and medium‐sized carnivores had a greater number of significant (p < 0.05) pathways by which these conditions were influencing occupancy relative to large carnivores. In particular, the smallest carnivore observed in our study was the only species for which we found support for each of the four hypothesized drivers influencing occupancy.Collectively, our study supports the size‐mediated sensitivity hypothesis and suggests that small carnivores are ideal sentinel species for global change. We echo recent calls for adopting a middle‐out approach to investigations into carnivore community dynamics by refocusing sustained monitoring and research efforts on smaller carnivores within systems. [ABSTRACT FROM AUTHOR]

Like humans, chimpanzees (Pan troglodytes) are well known for their vertebrate and invertebrate hunting, but they rarely scavenge. In contrast, while hunting and meat consumption became increasingly important during the evolution of the genus Homo, scavenging meat and marrow from carcasses of large mammals was also likely to be an important component of their subsistence strategies. Here, we describe a confrontational scavenging interaction between an adult male chimpanzee from the Issa Valley and a crowned eagle (Stephanoaetus coronatus), which resulted in the chimpanzee capturing and consuming the carcass of a juvenile bushbuck (Tragelaphus scriptus). We describe the interaction and contextualize this with previous scavenging observations from chimpanzees. [ABSTRACT FROM AUTHOR]

Background and Objectives: Non-native plant species have been introduced to provide various goods and services. Some species have not shown negative effects on the ecosystem, while others cause habitat disturbances. Considering this issue, it is necessary to know these species' positive and negative effects. Paulownia is an exotic industrial tree species, and there are debates on the positive and negative effects of its plantation in forests and non-forest areas among experts and scientists. Based on the literature review in Iran, there is a scarcity of studies examining the invasion behavior of Paulownia. Therefore, this study aims to investigate the competitive behavior of Paulownia in reforested mixed stands within the educational and research forest of Shast-Kalate, utilizing scientific methods. Materials and Methods: Data were collected in the educational and research forest of Dr. Bahram Nia (Shast Kalateh) in the two areas. An area of 2.5 ha of native species mixed with non-native species of Paulownia and another area of 2.5 ha that only had native species (as a control stand). All trees in the study area were inventoried. The measured variables for each tree include tree species, diameter at the breast height (DBH)> 5 cm, tree height, and crown diameter. The spatial coordinates of all trees were also recorded. The trees included the non-native species of Paulownia fortunei, and the native trees included Acer velutinum bioss, Acer cappadocicum Gled, and Carpinus betulus L. In order to investigate the interaction between species, bivariate O-Ring statistics and bivariate mark correlation functions were used based on distance. The independent T-statistic was used to compare the biometric variables of native species. Results: The graphs obtained from the O-Ring statistic between Paulownia species and native species indicate that the relationships are generally of the attraction or independent type. Also, the mark correlation function results indicate negative and independent interactions based on the DBH and crown diameter and negative for tree height between Paulownia and Acer cappadocicum. Interactions between Paulownia species and Carpinus betulus in all distances were independent based on DBH and negative and independent regarding crown diameter and tree height. Positive, negative and independent interactions were observed regarding tree height and crown diameter between Paulownia species and Acer velutinum and attraction and independent interactions were seen in terms of DBH. The independent t-test indicate that the average DBH and crown diameter of the Acer cappadocicum Gled in Paulownia mixed plantation is more than the control area, there is no significant difference in tree height. The average DBH and crown diameter of Acer velutinum bioss were higher, and tree height was less in Paulownia mixed plantation compared to the control area. The tree height of the Carpinus betulus L. was higher, and the crown diameter was less in the control than the Paulownia mixed plantation. No significant differences were seen in DBH between the two study areas. Conclusion: Considering Paulownia's growth nature, a higher tree height, DBH, and crown diameter can be expected, and the results confirmed this. In contrast, this growth rate does not exist in native species. On the other hand, the marks used in the mark correlation function include the variables of tree height, DBH and crown diameter, so the negative marked correlation function results can be attributed to this property. In order to introduce a species as invasive, comprehensive research is needed for its effects on the regeneration of native species, composition of vegetation, and soil properties. [ABSTRACT FROM AUTHOR]

Inter-specific competition among species in a mixed species plantation is inevitable, and the degree of competition for available resources determines the success of species co-existence. Different species compete and interact for resources at different physiological and developmental stages. However, most research has investigated inter-specific competition at the mature stage. We examined seed germination and seedling growth of two confamilial species, Albizia saman and Albizia lebbeck, and explored inter-specific competition at their early life stages, grown in a mixture of different proportions of seeds and seedlings through a series of replacement experiment. The experiment included germination and height growth tests for each species on its own, as well as three mixtures of species with ratios of 25:75, 50:50 and 75:25. We found that the germination speed and percentage, the probability of seedling emergence, and the seedling height were significantly higher in A. saman than in A. lebbeck. Moreover, in mixtures, we observed that A. saman exhibits higher germination speed and percentages compared to A. lebbeck. The increase in seedling height did not vary significantly among treatments when the seedlings of the studied species were mixed in different proportions. However, both species showed an apparent benefit when growing together, which was significantly influenced by A. saman in terms of inter-specific competition indexes. The knowledge of the early growth performance of these species and their inter-specific competition presented in this study may influence recruitment success and will be useful in understanding the population dynamics in the case of a mixed species plantation. Furthermore, our study suggests that there could be an impact of species mixture on the regeneration or recruitment process, even when the species are confamilial. Therefore, this information could be useful for selecting suitable species mixtures in any afforestation and reforestation activities. [ABSTRACT FROM AUTHOR]

Simple Summary: We aimed to investigate how an invasive cavity-breeding bird, the common (Indian) myna, and a native nest predator, the common brushtail possum, influence urban nest box use by native birds in Queensland and New South Wales, Australia. We quantified nest box use by invasive and native species, assessed nesting success and failure rates, and explored what environmental factors might influence nest box occupancy and nesting success. We found that the native possums were the most common nest box users and that possum occupancy of boxes was associated with higher rates of nesting failures by all bird species. More common myna nesting attempts were observed in areas where mynas have been established longer. We found no evidence of a significant negative impact by the common myna on other birds in our study locations, which may be partly due to the low rates of use of our nest boxes by native birds. Nevertheless, better nest box design and guidelines for setting them up are needed if we aim to provide more nesting opportunities for native birds to replace the decline in big old cavity trees. Many bird species in Australia require tree hollows for breeding. However, assessing the benefits of urban nest boxes to native birds requires frequent monitoring that allows to assess nesting success. To better understand the benefits of nest boxes for native birds, we examined the impact of local habitat characteristics, invasive species (common myna, Acridotheres tristis), and native mammalian predators on urban nest box use and nesting success of native birds. We installed 216 nest boxes across nine locations in southeastern Australia (S.E. Queensland and northern New South Wales) in both long-invaded sites (invaded before 1970) and more recently invaded sites (after 1990). We monitored all boxes weekly over two breeding seasons. We recorded seven bird species and three mammal species using the nest boxes. Weekly box occupancy by all species averaged 8% of all boxes, with the species most frequently recorded in the nest boxes being the common brushtail possum (Trichosurus vulpecula), a native cavity user and nest predator. We recorded 137 nesting attempts in the boxes across all bird species. The most frequent nesting species were the invasive alien common mynas (72 nesting attempts). We recorded an average nesting failure rate of 53.3% for all bird species. We did not record any common mynas evicting other nesting birds, and found that several native species used the same box after the common myna completed its nesting. We recorded native possums in 92% of the boxes, and possum occupancy of boxes per site was negatively correlated with bird nesting success (p = 0.021). These results suggest that when boxes are accessible to invasive species and native predators, they are unlikely to significantly improve nesting opportunities for native birds. To ensure efficient use of limited conservation resources, nest boxes should be designed to target species of high conservation importance and limit other species of both predators and competitors. [ABSTRACT FROM AUTHOR]

Nitrogen deposition has been proven to facilitate the establishment of alien plants. Previous studies have certified that nitrogen deposition enhances the resource availability of habitats and promotes the growth of alien invaders. Arbuscular mycorrhizal fungi (AMF) symbiose with vascular plants and assist plants in nutrient acquisition. AMF colonization has been proven to be another driving factor of plant invasion. However, few studies have integrated nitrogen deposition and AMF inoculation into the exploration on invasion mechanism. Based on a trait approach, the present study subjected the alien invader, Rhus typhina L., and its co-occurring native species, Acer truncatum Bunge, to nitrogen deposition and AMF inoculation and compared the phenotypic variation in aboveground and belowground traits in an inter-specific competition experiment. Through the effects of different nitrogen deposition and AMF infection on the functional traits of R. typhina and A. truncatum, the effects of mycorrhizal symbiosis between R. typhina and A. truncatum on abiotic factors and interspecific relationships were analyzed. We found that inter-specific competition stimulated the colonization of AMF in R. typhina, however, decreased the colonization rate of AMF in A. truncatum. Correspondingly, inter-specific competition significantly reduced the plant growth of A. truncatum as the aboveground morphological traits including plant height and crown area, and belowground traits including root length, root surface area, root volume, number of root tips, number of root tip branches and number of root cross decreased for A. truncatum. Nitrogen deposition promoted the shoot growth of R. typhina rather than that of A. truncatum. AMF inoculation significantly affected the belowground traits of A. truncatum as the root length and root surface area significantly decreased after AMF inoculation in the mixture planting of the two species. The chlorophyll content of A. truncatum decreased without AMF inoculation, while nitrogen deposition enhanced the net photosynthetic rate of R. typhina. The alien invader R. typhina outperforms its native competitor in the simulated scenario of resource fluctuation and facilitates its establishment. We speculate that AMF colonization promotes the extension of R. typhina rhizosphere and, thus, accelerates the growth and invasion of R. typhina. [ABSTRACT FROM AUTHOR]

Mangrove forests are reported to be invaded by invasive alien species (IAS). This study was therefore aimed at studying the level of distribution of the IAS, Acacia auriculiformis A. Cunn. ex Benth. in mangrove ecosystems in the southern coast of Sri Lanka and assessing the risk to periphery of mangrove forest by considering the Rekawa mangrove forest as a model site. Growth performances of two mangrove species; Rhizophora mucronata and Avicennia marina in the presence of Acacia plants were also tested under three different competition levels; low, moderate and high. According to the results, infestation of Acacia plants was significant in the southern coast of Sri Lanka, particularly in Matara and Hambantota districts (p < 0.05). Species diversity determined as the Simpson diversity index was high (0.77) in the periphery of the Rekawa mangrove forest. Four true mangroves and two associates co-occurring with A. auriculiformis in the periphery could be observed during the field validation experiment. The highest seedling (15.4 ± 2.2 m–2) and sapling (11.2 ± 2.8 m–2) densities were reported for A. auriculiformis plants. Dominance, calculated as the importance value index of different species in the mangrove periphery varied from 18.0–120.6 and the latter highest was recorded for Acacia which has the highest relative density (42.1%) and the relative dominance (52.5%). The total leaf area of the Rhizophora plants grown in the high-competition level was significantly lower than that of the control plants, while the dry weights at three different competition levels were significantly higher (p < 0.05) than the control. This could be due to the higher root biomass allocation. In Avicennia plants, cumulative shoot height, total leaf area and dry weight of the plants grown at the high-competition level were significantly lower than that of the control plants (p < 0.05). A. auriculiformis plants grown with these true mangrove species better performed and did not show any significant deviation from the respective control plants. The level of survival of Acacia was significantly reduced at 25 psu (p < 0.05). Early intervention and serious scrutiny are much needed to reverse the possible impacts of IAS on mangrove forests and the need for forest conservation is emphasized. [ABSTRACT FROM AUTHOR]

In the present study, we aimed to demonstrate that allelopathic compounds from the cyanobacterium Phormidium sp. can induce the collapse of large populations of the cyanobacteria Microcystis aeruginosa Kützing Kützing. We employed several strains of this toxic cyanobacteria, from six different locations, in order to test for adaptive variation in resistance to allelochemicals. As a preliminary test to detect allelopathic effect, we performed bioassays with Phormidium allelochemicals against the different strains of M. aeruginosa at low population abundances. Then, we combined long-term competition experiments and mechanistic modelling with two purposes: (a) demonstrate that the inhibitory effect of Phormidium sp. against M. aeruginosa was due to allelopathy and not resource competition; (b) test the effectiveness of these allelochemicals at inducing the collapse of large populations of M. aeruginosa. Our results showed a strong allelopathic effect of Phormidium, which induced the collapse of large populations of M. aeruginosa, without evidence of differences in sensitivity between strains. We demonstrated that allelopathy (interference competition) can reverse the outcome predicted by resource competition (exploitation competition). These results are encouraging in order to take further steps in the development of a bioremediation method, based in Phormidium allelopathy, against blooms of toxic cyanobacteria. [ABSTRACT FROM AUTHOR]

Invasive alien species could generate a multitude of impacts towards native species. The introduction and spread of Vespa velutina in Europe is raising concern for the conservation of insect's biodiversity, including wasps due to predation, competition or a combination of these two mechanisms. Nevertheless, most evidence for negative effects on other wasps are based on laboratory experiments, direct observations, and on considerations about the biology and ecology of Vespidae. No field study in Europe explored how the abundance of V. velutina could affect the population of native Vespidae, as expected in case of competition and predation. We analysed how the abundance of V. velutina influenced that of Vespa crabro, 4 years after the arrival and establishment of V. velutina in our study area, in Italy. Moreover, we compared the abundances of three native Vespidae (V. crabro, Vespula vulgaris, Vespula germanica), between our study area and an adjacent uninvaded area with similar environmental conditions. Bayesian Generalized Linear Models revealed that the abundance of V. velutina and V. crabro was positively associated, where V. velutina was scarce. Covariation disappeared only at those trapping sites where V. velutina was extremely abundant. Moreover, abundances of native wasps were similar between the invaded and the uninvaded areas. Implications for insect conservation: The wide-scale monitoring activity performed to investigate the effects of V. velutina on native wasps has not detected any negative effects in relation to the presence of the invasive species. More effort is however requested for understanding if V. velutina could really affect native Vespidae at the population-level. [ABSTRACT FROM AUTHOR]

Blooms of freshwater toxic cyanobacteria are a growing environmental health problem, enhanced by anthropogenic eutrophication and climate change. A variety of techniques were tested for their remediation, from physical methods using artificial mixing or flocculation, to chemical methods employing synthetic and natural compounds, as well as constructed wetlands. In this work, we conducted an evaluation at microcosm scale of the usefulness of the allelochemicals produced by a strain of the filamentous cyanobacteria Phormidium sp. for the bioremediation of proliferations of four strains of toxic freshwater cyanobacteria (Cylindrospermopsis raciborskii, Chrysosporum ovalisporum, Anabaena sp. and Nodularia sp.). Allelochemicals produced by this strain of Phormidium sp. belong to the portoamides compounds family. Their effect was tested in bioassays using cell-free filtrate, the results showing that all the four strains were sensitive. In addition, we performed phosphate-limited long-term competition experiments in continuous cultures, in which Phormidium sp. was co-cultured with each of the toxic cyanobacterial strains. The purpose of these later experiments was to demonstrate that allelopathy and not resource competition was responsible for the ecological exclusion of the toxic cyanobacteria strains, and also to employ higher population abundances to test the effectiveness of the allelochemicals. Before that, we needed to estimate the competitive ability of each species to limit the resource that we employed (phosphate). Phormidium sp. were clearly a better competitor for phosphate than Anabaena sp., worse than Nodularia sp., and very similar to C. raciborskii and C. ovalisporum. Only in the case of Nodularia sp. could we demonstrate that the ecological exclusion of the toxic cyanobacteria was caused by allelopathy. However, the rapid exclusion shown in our experiments suggests that allelopathy was the main cause in all cases. An inter-specific competition model including only competition for phosphate and an allelopathic interaction was able to accurately describe the patterns of population dynamics observed in our experiments. [ABSTRACT FROM AUTHOR]

In this paper, we consider a two-predator–one-prey population model that incorporates both the inter-specific competition between two predator populations and the intra-specific competition within each predator population. We investigate the dynamics of this model by addressing the existence, local and global stability of equilibria, uniform persistence as well as saddle-node and Hopf bifurcations. Numerical simulations are presented to explore the joint impacts of inter-specific and intra-specific competition on competition outcomes. Though inter-specific competition along does not admit a stable coexistence equilibrium, with intra-specific competition, the coexistence of the two competing predator species becomes possible and the two coexisting predator species may maintain at two different equilibrium populations. [ABSTRACT FROM AUTHOR]

Global environmental changes are believed to promote the invasion of many invasive plant species, especially under nitrogen enrichment conditions. However, it is unclear, how invasive plant species respond to nitrogen enrichment along with water deficit. In this study, competition of invasive plant (Wedelia trilobata, WT) was studied with its congener native (Wedelia chinensis, WC) under three levels of nitrogen (control, additional and double additional), two levels of water (normal and deficit) and three types of culture (single, mono and mixed). The result showed that under control treatment and additional nitrogen, the growth of WT was 30% higher than WC in all cultures but under additional nitrogen along with water deficit the growth of WT was 20% lower than WC within single plant and monoculture. Under competition, biomass, specific leaf area, root-to-shoot ratio, leaf chlorophyll content and leaf nitrogen of WT were 20–40% decreased as compared to WC under water deficit along with nitrogen addition treatments. These results indicated that competitive interaction between WT and WC was altered by additional nitrogen together with water deficit. It provides exceptional evidence that vigorous invasive species become weak competitor under additional nitrogen along with water deficit. [ABSTRACT FROM AUTHOR]

Study of foraging behaviour of Tricoloured Munia Lonchura malacca and its interaction in pearl millet crop fields was conducted in six villages of Tindivanam taluk, Villupuram district, Tamil Nadu from April to June 2020. A total of six flocks containing 1,640 birds of Tricoloured Munia were enumerated. The number of birds per flock varied from 60 to 800. They never split into small flocks and maintained the same flock size throughout the day. Tricoloured Munias used nine plant species for roosting. Twelve quadrats (0.3 ha) each of 5 m x 5 m size were laid in the pearl millet fields covering six villages. A total of 10,295 spikes were counted in these plots, and of these 3,785 spikes (36.7%) were found damaged by foraging munias. The maximum damage of 99.6% was observed in Thenputhur village. Along with Tricoloured Munia, five other granivorous birds, such as Baya Weaver Ploceus philippinus, Indian Silverbill Euodice malabarica, Common Babbler Turdoides caudata, Rose-ringed Parakeet Psittacula krameri, and White-rumped Munia Lonchura striata were also found foraging without any inter-specific competition. Farmers adopted various traditional bird repellent techniques such as beating utensils, throwing pebbles/soil on the crop, placing scarecrows, tying multi-coloured ribbons, and hanging bottles to chase the birds away. [ABSTRACT FROM AUTHOR]

Brood parasites such as the common cuckoo Cuculus canorus exploit the parental abilities of their hosts, hosts avoid brood parasitism and predation by showing specific behavior such as loss of feathers, emission of fear screams and contact calls, displaying wriggle behavior to avoid hosts or potential prey, pecking at hosts and prey, and expressing tonic immobility (showing behavior like feigning death or rapid escape from predators and brood parasites). These aspects of escape behavior are consistent for individuals but also among sites, seasons, and years. Escape behavior expressed in response to a broad range of cuckoo hosts and prey are consistently used against capture by humans, but also hosts and brood parasites and predators and their prey. An interspecific comparative phylogenetic analysis of escape behavior by hosts and their brood parasites and prey and their predators revealed evidence of consistent behavior when encountering potential parasites or predators. We hypothesize that personality axes such as those ranging from fearfulness to being bold, and from neophobic to curiosity response in brood parasites constitute important components of defense against brood parasitism that reduces the overall risk of parasitism. [ABSTRACT FROM AUTHOR]

Summary: Translocations to closed systems such as fenced reserves are commonly used for conservation of threatened fauna species worldwide; however, resources are limited in these areas, and natural processes that regulate populations in response to resource availability are unable to occur. This can result in overabundance followed by overuse of resources, potentially resulting in extreme declines or local extinctions. Resource exhaustion can negatively impact other fauna in the closed environment that exploit similar resources, through inter‐specific competition. This paper discusses the reintroduction of Boodie (Bettongia lesueur) and Mala (Lagorchestes hirsutus) to a fenced reserve on the Matuwa Indigenous Protected Area, Western Australia, and raises the concern of potential competition between the two threatened species. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Threatened Taxa is the property of Wildlife Information Liaison Development and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Variation in the foraging strategies used among species is a key factor in determining the trophic structure of ecological communities. Moreover, foraging niche differentiation could be driven by inter-specific competition and/or variation within species due to seasonal, age, sex and/or individual factors. Using stable isotope analysis, we assessed inter- and intra-specific differences in the foraging niches of female Southern Rockhopper penguin (Eudyptes chrysocome; SRP) and male and female Magellanic penguins (Spheniscus magellanicus; MP) at Isla de los Estados, Argentina. We sampled whole blood and feathers from breeding adults, representing the breeding and pre-moult periods over two consecutive years (2012 and 2013). We also compared stable isotope values between tissue to test for consistency in individuals foraging niches and the potential for foraging niche specialisation and segregation within breeding pairs. We observed clear foraging niche segregation between species that persisted during both breeding and pre-moult periods. SRP foraged in more oceanic/pelagic waters (lower δ13C values) while MP used coastal/benthic foraging habitats (higher δ13C values). In addition, SRP fed on lower trophic level prey (low δ15N values) relative to MP during both time periods. The isotopic foraging niches of MP highly overlapped between sexes at the population level and there was little to no evidence of niche segregation within breeding pairs or individual consistency in the seasonal foraging niche of both species. The results suggest that inter-specific foraging niche segregation is likely a more important factor influencing the trophic ecology and foraging behaviours of these species, relative to intra-specific factors. Even so, the persistence of inter-specific foraging niche segregation outside the breeding season suggests that either the potential for competition for food resource or foraging habitats remain high during this time or that the ultimate factors responsible for foraging niche segregation among these two species may be unrelated to these proximate factors. [ABSTRACT FROM AUTHOR]

مقدمه علف­ هرز گیاهی ناخواسته و مضر است که مزاحم و یا مانع عملیات زراعی بوده و باعث افزایش هزینه ‏‏های داشت و کاهش عملکرد محصولات زراعی می­شود (Diyanat et al, 2007).علف­های­ هرز اغلب برای منابع محدود از جمله آب خاک با گیاه­ زراعی رقابت می­کنند و قابلیت دسترسی به آب را در گیاه­ زراعی کاهش می­دهند (Asghari et al, 2001).یکی از اصول مهم مدیریت تلفیقی علف­های هرز، توسعه راهبردهای کنترل علف­های هرز بر پایه شناخت اثرات متقابل گیاه زراعی و علف­های هرز است و کمی کردن رقابت بین گیاه زراعی و علف­ هرز شرط لازم برای تصمیم گیری­های مدیریتی علف­ های هرز می­باشد (Swanton and Weise, 1991).یکی از مدل­های معتبر جهت برآورد میزان رقابت دو گونه در کشت مخلوط، روش عکس عملکرد تک بوته می­باشد (Beheshti and Soltaniyan, 2012). گندم از نظر تولید و سطح زیر کشت مهمترین محصول کشاورزی ایران و جهان است. تولید گندم در جهان در سال 2014 تا 2015 میلادی حدود 8/728 میلیون تن بود (IGC, 2016).مشکل علف­هرز در گندم یکی از مهمترین مسائل زراعی در نقاط گندم ­خیز جهان است و ترکیب جامعه گیاهی علف­هرز گندم، بازتابی از فصل کاشت، کنترل زراعی و شیمیایی علف­هرز، منطقه جغرافیایی و نوع خاک می­باشد (Kafi et al, 2005). بسیاری از مناطق ایران که در آن­ها گندم کشت می­شود، با مشکل چاودار روبرو هستند (Baghestani and Atri, 2003). توقعات کم این گیاه همراه با توانایی دگر­آسیبی و مورفولوژی و چرخه زندگی مشابه گندم، باعث پایداری و افزایش سطح آن در مزارع گندم پاییزه شده است (Pester et al, 2000). مواد و روش­ها به منظور ارزیابی شاخص­ های رقابتی گندم و چاودار در شرایط تنش خشکی با استفاده از مدل عکس عملکرد، مطالعه­ ای در سال 1391 در گلخانه تحقیقاتی دانشکده کشاورزی دانشگاه بیرجند به صورت فاکتوریل سه عاملی در قالب طرح کاملاً تصادفی با 3 تکرار اجرا شد. فاکتور­ های آزمایش شامل چهار تراکم گندم رقم روشن (0، 8، 16، 24 بوته در گلدان)، چهار تراکم چاودار (0، 2، 4، 6 بوته در گلدان) و دو سطح تنش خشکی شامل آبیاری در 20 و 60 درصد تخلیه رطوبت ظرفیت زراعی خاک بود. مدل عکس عملکرد براساس عملکرد بیولوژیک تک بوته گندم و چاودار در هر دو سطح رطوبتی برازش داده شد و رابطه عملکرد بیولوژیک تک بوته گندم و چاودار با تراکم این دو گیاه، با استفاده از رگرسیون خطی چند متغیره بدست آمد. قدرت رقابت نسبی و شاخص تمایز آشیان اکولوژیکی نیز با استفاده از ضرایب رقابت درون گونه­ای و برون گونه­ای محاسبه گردید. نتایج و بحث نتایج حاصل از مدل عکس عملکرد نشان داد، رقابت برون­ گونه­ ای در گندم بیشتر از رقابت درون گونه­ ای بود ولی در چاودار رقابت درون گونه­ای بیشتر از رقابت برون گونه ­ای بود. شاخص توانایی رقابت نسبی نشان داد که اثر یک بوته گندم در سطح رطوبتی 20 و 60 درصد تخلیه رطوبت خاک به ترتیب برابر با اثر 0.79 و 0.64 بوته چاودار بود و اثر یک بوته چاودار در همان سطوح رطوبتی به ترتیب معادل 1.85 و 2.43 بوته گندم بود. شاخص تمایز آشیان اکولوژیکی این دو گیاه در هر دو سطح رطوبتی بزرگتر از یک بدست آمد بطوری که شاخص تمایز نیچ اکولوژیک در سطح 20 درصد تخلیه رطوبت خاک حدود 1.46 و در سطح 60 درصد، حدود 1.55 برآورد شد. نتیجه گیری با افزایش تنش خشکی، قدرت رقابت نسبی چاودار، افزایش و قدرت رقابت نسبی گندم کاهش یافت. عملکرد بیولوژیک گندم بیشتر تحت تأثیر رقابت برون گونه ­ای قرار گرفت در نتیجه چاودار رقیب قوی­تری نسبت به گندم بود. اثر تنش خشکی و رقابت چاودار در تلفیق با یکدیگر باعث کاهش قابل توجهی در عملکرد بیولوژیک گندم شدند. به طور کلی در شرایط وجود تنش خشکی، شدت رقابت درون­ گونه ­ای و برون­ گونه ­ای بین بوته­ های گندم و چاودار افزایش یافت و باعث کاهش بیشتر عملکرد بیولوژیک این دو گیاه شد. در نتیجه کنترل علف­­ هرز چاودار در شرایط وجود تنش خشکی در مزارع گندم بسیار حائز اهمیت می­باشد.

Ｗｅ ｓｅｌｅｃｔｅｄ １ ｈｍ２ ｄｙｎａｍｉｃ ｍｏｎｉｔｏｒｉｎｇ ｐｌｏｔ ｏｆ ａ ｎａｔｕｒａｌ ｍｉｘｅｄ ｎｅｅｄｌｅ-ａｎｄ ｂｒｏａｄ-ｌｅａｖｅｄ ｆｏｒｅｓｔ ｃｏｍｍｕｎｉｔｙ ｉｎ Ｓｈｅｎｎｏｎｇｊｉａ Ｎａｔｉｏｎａｌ Ｐａｒｋ, ｖａｒｉａｎｃｅ ｒａｔｉｏ (ＶＲ), χ２ ｔｅｓｔ, ａｎｄ ａｓｓｏｃｉａｔｉｏｎ ｃｏｅｆｆｉｃｉｅｎｔ (ＡＣ) ｗｅｒｅ ｕｓｅｄ ｔｏ ｄｅｔｅｒｍｉｎｅ ｔｈｅ ｉｎｔｅｒｓｐｅｃｉｆｉｃ ａｓｓｏｃｉａｔｉｏｎ ｏｆ ｄｏｍｉｎａｎｔ ｓｐｅｃｉｅｓ ｏｆ ｔｒｅｅ, ｓｈｒｕｂ ａｎｄ ｈｅｒｂ ｉｎ ｔｈｅ ｃｏｍｍｕｎｉｔｙ. Ｔｈｅ ｒｅｓｕｌｔｓ ｗｅｒｅ ａｓ ｆｏｌｌｏｗｓ: (１) Ａｃｃｏｒｄｉｎｇ ｔｏ ｔｈｅ χ２ ｔｅｓｔ, ｔｈｅ ｐｏｓｉｔｉｖｅ-ｎｅｇａｔｉｖｅ ｃｏｒｒｅｌａｔｉｏｎ ｒａｔｉｏｓ ｏｆ ｔｈｅ ｄｏｍｉｎａｎｔ ｓｐｅｃｉｅｓ ｏｆ ｔｒｅｅ, ｓｈｒｕｂ ａｎｄ ｈｅｒｂ ｌａｙｅｒｓ ｗｅｒｅ ０.７０, ０.６１ ａｎｄ １.１４, ｒｅｓｐｅｃｔｉｖｅｌｙ. ＶＲ ｍｅａｓｕｒｅｄ ｔｈｅ ｏｖｅｒａｌｌ ａｓｓｏｃｉａｔｉｏｎ ｏｆ ｅａｃｈ ｌａｙｅｒ ｈａｄ ａ ｓｉｇｎｉｆｉｃａｎｔｌｙ ｐｏｓｉｔｉｖｅ ｃｏｒｒｅｌａｔｉｏｎ, ｔｈｅ ｃｏｍｍｕｎｉｔｙ ｗａｓ ｓｕｃｃｅｅｄｉｎｇ ｉｎ ａ ｓｔａｂｌｅ ｄｉｒｅｃｔｉｏｎ. (２) Ｆｒｏｍ ＡＣ, ｔｈｅｒｅ ｗｅｒｅ ３２.０５％ ｎｅｇａｔｉｖｅ ａｓｓｏｃｉａｔｉｏｎ ｐａｉｒｓ ｉｎ ｔｈｅ ｔｒｅｅ ｌａｙｅｒ, ｔｈｅ ｃｏｎｉｆｅｒｏｕｓ ａｎｄ ｂｒｏａｄ-ｌｅａｖｅｄ ｄｏｍｉｎａｎｔ ｓｐｅｃｉｅｓ ｈａｄ ａ ｈｉｇｈｌｙ ｃｏｍｐｅｔｉｔｉｏｎ, ａｎｄ ｔｈｅ ｐｏｓｉｔｉｖｅ ｃｏｒｒｅｌａｔｉｏｎ ｅｘｉｓｔｅｄ ｏｎｌｙ ｂｅｔｗｅｅｎ ｂｒｏａｄ-ｌｅａｖｅｄ ｓｐｅｃｉｅｓ. Ｔｈｅ ｓｈｒｕｂ ｌａｙｅｒ ａｎｄ ｔｈｅ ｈｅｒｂ ｌａｙｅｒ ｈａｄ ４８.８９％ ａｎｄ ３４.１７％ ｎｅｇａｔｉｖｅ ｃｏｒｒｅｌａｔｉｏｎ ｐａｉｒｓ, ｒｅｓｐｅｃｔｉｖｅｌｙ. Ｉｔ ｗａｓ ｄｕｅ ｔｏ ｔｈｅ ｃｏｍｐｅｔｉｔｉｏｎ ｏｆ ｌｉｍｉｔｅｄ ｒｅｓｏｕｒｃｅｓ ｂｙ ｓｐｅｃｉｅｓ ｗｉｔｈ ｓｉｍｉｌａｒ ｅｃｏｌｏｇｉｃａｌ ｃｈａｒａｃｔｅｒｉｓｔｉｃｓ. Ｔｈｅｒｅ ｗｅｒｅ ６５.３８％, ３５.５６％, ａｎｄ ４４.１７％ ｕｎｒｅｌａｔｅｄ ｓｐｅｃｉｅｓ ｐａｉｒｓ ｉｎ ｔｈｅ ａｒｂｏｒ, ｓｈｒｕｂ, ａｎｄ ｈｅｒｂ ｌａｙｅｒｓ, ｒｅｓｐｅｃｔｉｖｅｌｙ. Ｉｔ ｍａｙ ｂｅ ｔｈａｔ ｔｈｅ ｓｐｅｃｉｅｓ ｏｃｃｕｐｉｅｄ ａ ｓｕｉｔａｂｌｅ ｎｉｃｈｅ ａｎｄ ｔｈｅ ｄｅｐｅｎｄｅｎｃｅ ｂｅｔｗｅｅｎ ｓｐｅｃｉｅｓ ｗａｓ ｒｅｄｕｃｅｄ. Ｉｔ ｓｈｏｗｅｄ ｔｈａｔ ａ ｆｅｗ ｐａｉｒｓ ｔｅｎｄｅｄ ｔｏ ｔｈｅ ｓａｍｅ ｈａｂｉｔａｔ ａｎｄ ｓｐｅｃｉｅｓ ｈａｄ ａ ｐｏｓｉｔｉｖｅ ｃｏｒｒｅｌａｔｉｏｎ. Ｄｕｅ ｔｏ ｔｈｅ ｅｘｃｅｓｓｉｖｅ ｏｖｅｒｌａｐ ｏｆ ｎｉｃｈｅｓ, ｒｅｓｏｕｒｃｅ ｃｏｍｐｅｔｉｔｉｏｎ ｍａｄｅ ａ ｌａｒｇｅ ｎｕｍｂｅｒ ｏｆ ｐａｉｒｓ ｐｅｒｆｏｒｍ ｎｅｇａｔｉｖｅｌｙ. Ａｎｄ ｍｏｒｅ ｄｏｍｉｎａｎｔ ｓｐｅｃｉｅｓ ｈａｄ ｗｅａｋ ｃｏｎｎｅｃｔｉｏｎ ｄｕｅ ｔｏ ｏｃｃｕｐｙｉｎｇ ｔｈｅ ａｐｐｒｏｐｒｉａｔｅ ｎｉｃｈｅ. [ABSTRACT FROM AUTHOR]

Many animals produce acoustic signals for displaying their territoriality to other males and attracting mating partners. However, the acoustic signals are often eavesdropped on by other species. If a species with higher competitive ability eavesdrops on the acoustic signals of a species with lower competitive ability, the former can deprive the latter of their suitable calling sites. Therefore, the species with higher competitive ability exhibits a positive response to the acoustic signals of those with lower competitive abilities, whereas the species with lower competitive ability exhibits a negative response to the calling songs of those with higher competitive abilities. In the present study, male responses to conspecific and heterospecific song in two field cricket species Teleogryllus occipitalis (Audinet-Serville 1839) (Gryllidae) and Loxoblemmus equestris Saussure 1877 (Gryllidae) were investigated by playback experiments. T. occipitalis has larger body size than L. equestris. Both species did not exhibit precise negative or positive responses to conspecific and heterospecific songs. The results suggest that the cricket species do not utilize heterospecific song to acquire their calling sites. [ABSTRACT FROM AUTHOR]

Increasing atmospheric carbon dioxide (ab. CO2) and fertilizer‐nitrogen (ab. N) applications may have marked direct effects on the plant growth of agricultural crops, and in turn affect the higher trophic level of insect herbivores. In this study, the effects of elevated CO2 (i.e., 650 µl/L vs. ambient 400 µl/L) and fertilizer‐N (0, 50, 100, 200 kg/ha) on the population abundances and the inter‐specific competition among three co‐occurring species of wheat aphids, Sitobion avenae, Rhopalosiphum padi and Schizaphis graminum, were studied. The grain weight per ear and the 1,000‐grain weight were generally increased when grown under elevated CO2 and showed a significant effect at the 100 kg/ha (grain weight per ear) and 0, 50 and 100 kg/ha (1,000‐grain weight) N. These two yield indexes increased with increasing fertilizer‐N levels within reasonable limits and reached a maximum at 100 kg/ha. Elevated CO2 combined with fertilizer‐N levels formed complex indirect effects on the three wheat aphids through the wheat crops they fed on. Elevated CO2 significantly decreased the niche overlap index (ab. NOI) between S. avenae and R. padi under 0 and 100 kg/ha and that between R. padi and S. graminum under 0 kg/ha, while significantly increased the three NOIs under 50 kg/ha and that between R. padi and S. graminum under 100 and 200 kg/ha. S. avenae and R. padi had the larger population and stronger competition in low‐N condition (0 and 50 kg/ha), which was harmful to wheat yield and quality when combined with its own poor nutrition. Overall, the 100 kg/ha N level was the best option based on the aphid population, competition and wheat yields. Therefore, the balanced relationship formed among fertilizers, plants and insects under 100 kg/ha N was vital for the interactive ecosystem. [ABSTRACT FROM AUTHOR]

Increasing atmospheric carbon dioxide (ab. CO2) and fertilizer‐nitrogen (ab. N) applications may have marked direct effects on the plant growth of agricultural crops, and in turn affect the higher trophic level of insect herbivores. In this study, the effects of elevated CO2 (i.e., 650 µl/L vs. ambient 400 µl/L) and fertilizer‐N (0, 50, 100, 200 kg/ha) on the population abundances and the inter‐specific competition among three co‐occurring species of wheat aphids, Sitobion avenae, Rhopalosiphum padi and Schizaphis graminum, were studied. The grain weight per ear and the 1,000‐grain weight were generally increased when grown under elevated CO2 and showed a significant effect at the 100 kg/ha (grain weight per ear) and 0, 50 and 100 kg/ha (1,000‐grain weight) N. These two yield indexes increased with increasing fertilizer‐N levels within reasonable limits and reached a maximum at 100 kg/ha. Elevated CO2 combined with fertilizer‐N levels formed complex indirect effects on the three wheat aphids through the wheat crops they fed on. Elevated CO2 significantly decreased the niche overlap index (ab. NOI) between S. avenae and R. padi under 0 and 100 kg/ha and that between R. padi and S. graminum under 0 kg/ha, while significantly increased the three NOIs under 50 kg/ha and that between R. padi and S. graminum under 100 and 200 kg/ha. S. avenae and R. padi had the larger population and stronger competition in low‐N condition (0 and 50 kg/ha), which was harmful to wheat yield and quality when combined with its own poor nutrition. Overall, the 100 kg/ha N level was the best option based on the aphid population, competition and wheat yields. Therefore, the balanced relationship formed among fertilizers, plants and insects under 100 kg/ha N was vital for the interactive ecosystem. [ABSTRACT FROM AUTHOR]

Identifying and understanding ecological drivers that influence wildlife populations is challenging but critical for conservation. This typically requires integrating long‐term data on both the population and potential drivers within statistical models that are suitable for analysing these complex relationships. State‐space models offer one method for integrating such data. Once implemented within a Bayesian framework, these analyses can control for multifactorial influences on populations, allowing one to extract otherwise undetectable correlations between the environment and the underlying, inferred demography.In the Moray Firth, Scotland, harbour seals have been counted annually for 30 years (1988–2018). A Bayesian state‐space model was used to explore whether patterns in vital rates were correlated to changes in prey abundance, inter‐specific competition (grey seal abundance), environmental variables [the North Atlantic Oscillation (NAO) and sea‐surface temperature], or level of biotoxins (saxitoxin and domoic acid) in the Moray Firth waters.The credible interval of the posterior distributions of three of these covariate coefficients (sandeel proxy, NAO and grey seal abundance) suggested that there was a relationship between those covariates and vital rates. Both the sandeel proxy and NAO showed a positive correlation with fecundity, whereas grey seal abundance had a negative impact on pup survival.This work demonstrates how an integrated state‐space modelling approach can bring together diverse data sets and point to important interactions with prey, and with other predators in the system. This suggests that the wider‐scale management of UK harbour seal populations with their contrasting temporal trends needs to account for variation in the marine ecosystem at appropriate spatial scales, in line with current policy concerning spatial planning in the marine environment. [ABSTRACT FROM AUTHOR]

In intertidal sediments, bacteria attach to sand grains in mixed-species biofilms and inhabit the surrounding porewater as free-living communities. The large densities, high species diversity, and complex spatial distribution of sediment-attached bacteria implicate inter-specific competition as a likely force in structuring sediment communities. Both sediment-attached and free-living bacteria secrete antibiotics as a common means of competition. To establish the frequency of antibiotic production, bacteria isolated from intertidal sediments and porewater were screened using a disc-diffusion assay. Among sediment-attached bacteria, 39% displayed the ability to produce antibiotics, whereas significantly fewer of the porewater-associated bacteria (23.5%) produced inhibitory compounds. Denaturing gradient gel electrophoresis (DGGE) was used to identify a selection of isolated antibiotic-producing bacteria within wholecommunity environmental samples. Through sequencing a region of the 16S rRNA gene, the relative abundances of 4 antibiotic producers were established to be between 4.3-9.4% of the DGGE community profile. The high frequency of antibiotic-producing bacteria in sediments, and their significant quantitative contribution to the community composition, suggest that antibiosis likely plays a significant role in structuring benthic microbial communities. [ABSTRACT FROM AUTHOR]

A growing number of ecological studies suggest that animal distributions are not only influenced by classical ecological features such as habitat availability, but also by the motion capacity of the studied animal. Here we analyse the diversity and density of two wintering raptor communities from Crete and Sicily, two large Mediterranean islands located along migratory flyways. We performed 611 and 1030 km of transects in Crete and Sicily respectively, examining the spatial distribution of raptors in relation to land use, topography, raptor species diversity and abundance. Our results show that community diversity and specific abundance are strictly related in accordance with the 'More Individuals Hypothesis'. Comparing the two most common raptors, the density of the Eurasian kestrel was the highest in Sicily and that of the common buzzard in Crete. An overall positive effect of Eurasian kestrel density on that of the common buzzard was found in both islands, but higher in Crete. Our findings suggest that the distribution and density of the Eurasian kestrel, because of its higher movement ability, are less influenced by the presence of ecological barriers along potentially migratory flyways. We cannot exclude that higher inter specific competition with common buzzards in Crete might have pushed the smaller species to cross the Mediterranean Sea in order to overwinter in Africa. [ABSTRACT FROM AUTHOR]

Theory predicts that sympatric predators compete for food under conditions of limited resources. Competition would occur even within the same species, between neighboring populations, because of overlapping foraging habits. Thus, neighboring populations of the same species are hypothesized to face strong competition. To test the hypothesis that intra-specific competition is more intense than inter-specific competition owing to a lack of niche partitioning, we estimated the foraging area and diving depths of two colonial seabird species at two neighboring colonies. Using GPS and time-depth recorders, we tracked foraging space use of sympatric breeding Chinstrap and Gentoo penguins at Ardley Island (AI) and Narębski Point (NP) at King George Island, Antarctica. GPS tracks showed that there was a larger overlap in the foraging areas between the two species than within each species. In dive parameters, Gentoo penguins performed deeper and longer dives than Chinstrap penguins at the same colonies. At the colony level, Gentoo penguins from NP undertook deeper and longer dives than those at AI, whereas Chinstrap penguins did not show such intra-specific differences in dives. Stable isotope analysis of δ13C and δ15N isotopes in blood demonstrated both inter- and intra-specific differences. Both species of penguin at AI exhibited higher δ13C and δ15N values than those at NP, and in both locations, Gentoo penguins had higher δ13C and lower δ15N values than Chinstrap penguins. Isotopic niches showed that there were lower inter-specific overlaps than intra-specific overlaps. This suggests that, despite the low intra-specific spatial overlap, diets of conspecifics from different colonies remained more similar, resulting in the higher isotopic niche overlaps. Collectively, our results support the hypothesis that intra-specific competition is higher than inter-specific competition, leading to spatial segregation of the neighboring populations of the same species.

The effects of plant density and water stress on yield of Medicago sativa and Bromus tomentellus was studied. A greenhouse experiment was conducted at Isfahan University of Technology in 2013. The experiment included 18 treatments, three crop compositions (M.sativa, B. tomentellus or mixture of the two), two plant density levels, three watering regimes and four replicates, arranged in a completely randomized block design. Results showed that total yield of M. sativa mono-cropping was higher than mixed cropping and it was higher than B. tomentellus mono-cropping. Land Equivalent Ratio (LER) values were less than 1 for all mixed cropping treatments, indicated the interspecific competition in mixed cropping. The biomass production per plant decreased with increasing density, competition for resource utilization and water stress. Compare of above-ground and below-ground dry matter showed that M. sativa appeared to be more constrained by intraspecific than by interspecific competition, Conversely, B. tomentellus was more suppressed by interspecific competition exerted by M. sativa than by intraspecific competition. Relative competition intensity (RCI) values were positive for B. tomentellus and negative for M.sativa, implying that competitive ability of M.sativa was higher than B. tomentellus in mixed cropping .

Abstract In the paper we first propose a two-species Lotka–Volterra competition model with the stochastic terms related to the inter-specific competition rates and the coexistence equilibrium of the deterministic model. Then we establish the global asymptotic stability of the coexistence equilibrium. Finally, we provide some discussions and numerical examples to illustrate our mathematical results. [ABSTRACT FROM AUTHOR]

Abstract: Phenotypic plasticity in response to competition is a well‐described phenomenon in higher organisms. Here, we show that also bacteria have the ability to sense the presence of competitors and mount fine‐tuned responses to match prevailing levels of competition. In our experiments, we studied interspecific competition for iron between the bacterium Pseudomonas aeruginosa (PA) and its competitor Burkholderia cenocepacia (BC). We focused on the ability of PA to phenotypically adjust the production of pyoverdine, an iron‐scavenging siderophore. We found that PA upregulates pyoverdine production early on during competition under condition of low iron availability. This plastic upregulation was fine‐tuned in response to the level of competition imposed by BC, and seems to confer a relative fitness benefit to PA in the form of an earlier initiation of growth. At later time points, however, PA showed reduced growth in mixed compared to monoculture, suggesting that competitive responses are costly. Altogether, our results demonstrate that phenotypic plasticity in siderophore production plays an important role in interspecific competition for iron. Upregulating siderophore production may be a powerful strategy to lock iron away from competing species, and to reserve this nutrient for strain members possessing the compatible receptor for uptake. [ABSTRACT FROM AUTHOR]

Evaluation the plant density changes and weeding effects on yield and yield components of maize (KSC 704) in the research farm of Razi University, Kermanshah, Iran in the middle of the growing season were studied. The experimental design was split plot based on four replicated randomized complete block design. Main plot treatments were one and two steps weeding and sub plot levels were ten change plant densities included 88000 plants per hectare (pha-1), 106000 pha-1, change plant density from 106000 to 88000 pha-1 in the 8 and 14 leaf stage, 133000 pha-1, change plant density from 133000 to 106000 pha-1 in the 8 and 14 leaf stage, 177000 pha-1 and change plant density from 177000 to 133000 pha-1 in the 8 and 14 leaf stage. The results of ANOVA indicated the significant effects of plant density changes for ear length, cover weight of the ear, ear weight without cover, seed weight per ear, weight of ear wood, number of seeds per row (p= 0.01). The most seed yield per hectare was 16.7 tons that obtained from two steps weeding and change plant density from 106000 to 88000 pha-1in the 8 leaf stage. These results about seed yield indicated that cultivation of maize with plant density higher than plant density used by farmers increase the power of competition against weeds during sowing to 8 leaf stage and decrease plant density to conventional levels in this stage decrease the inter-specific competition. [ABSTRACT FROM AUTHOR]

Ozone (O) critical levels have been established under the Long-Range Transboundary Air Pollution Convention to assess the risk of O effects in European vegetation. A recent review study has led to the development of O critical levels for annual Mediterranean pasture species using plants growing in well-watered pots at a coastal site and under low levels of competition. However, uncertainties remain in the extrapolation of the O sensitivity of these species under natural conditions. The response of two O-sensitive annual Mediterranean pasture Trifolium species at the coastal site was compared with the response of the same species growing at a continental site, in natural soil and subject to water-stress and inter-specific competition, representing more closely their natural habitat. The slopes of exposure- and dose-response relationships derived for the two sites showed differences in the response to O between sites attributed to differences in environmental growing conditions, growing medium and the level of inter-specific competition, but the effect of the individual factors could not be assessed separately. Dose-based O indices partially explained differences due to environmental growing conditions between sites. The slopes showed that plants were more sensitive to O at the continental site, but homogeneity of slopes tests revealed that results from both experimental sites may be combined. Although more experimental data considering complex inter-specific competition situations and the effect of important interactive factors such as nitrogen would be needed, these results confirm the validity of applying the current flux-based O critical level under close to natural growing conditions. The AOT40-based O critical level derived at the coastal site was also considered a suitable risk indicator in close to natural growing conditions in the absence of soil moisture limitations on plant growth. [ABSTRACT FROM AUTHOR]

In intercropping systems (growing >1 species in a field), interactions between species affect the performance of plants and the overall yield. These interactions lead to plastic responses in plant traits due to the specific environmental conditions typical for intercrops, especially in agroforestry in which the understory crop is strongly shaded by the trees. To quantify the extent to how physiological plasticity is driven by inter-specific competition, field experiments with mixtures of cotton and jujube trees grown in strips were conducted in 2012 and 2013 in Hetian, Xinjiang, China. Cotton was grown at three levels of inter-specific competition, represented by the distance between the adjacent cotton and tree rows without change in plant density. The highest cotton yield was attained farthest away from the trees, i.e. at the lowest level of inter-specific competition, with a higher proportion of fiber in the bolls as well as a higher boll density compared to plants grown at higher inter-specific competition. Low inter-specific competition also increased maximum leaf area index (LAI), total light interception and dry matter accumulation. However, light-use efficiency was higher at high levels of inter-specific competition especially in the rows close to the tree line, associated with a higher fraction of diffuse radiation. These results aid in the optimization of the spatial pattern of crops in agroforestry system. [ABSTRACT FROM AUTHOR]

Copyright of Canadian Journal of Plant Science is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Primates and non-primates inhabiting tropical forests may interact with each other since they coexist in the same communities. Primates usually interact with their prey, predators, competitors and neutral species. Using 'all occurrence' sampling, we have studied inter-specific interactions of lion-tailed macaques with non-primate species found in their habitat. We observed that the percentage of total time spent on interactions with non-primates was less than 1. Also, the percentage of total time spent in interacting with competitors, predators and neutral species was less than 0.5. The lack of predation pressure and lack of opportunities for mixed-species associations for increasing foraging efficiency appear to be the major reasons for the absence of interactions with non-primates. By comparing with studies from other primate habitat regions, we observed that primates in South Asia interact much lesser with non-primates than those in South America and Africa. A previous study showed that the interactions of lion-tailed macaques even with other primate species in the Western Ghats are less than expected by chance. [ABSTRACT FROM AUTHOR]

Climate change accelerates biodiversity alterations in northern ecosystems. A prevalent example is that tundra regions are invaded by boreal species. This impacts negatively on native species through competition, predation and transmission of zoonoses. Scandinavian red foxes ( Vulpes vulpes) have emerged into the tundra and have altered the structure and function of the tundra community. For instance, they threaten persistence of the endangered Swedish Arctic fox ( Vulpes lagopus). County board administrations implement control of the tundra red foxes, but little is known about the underlying expansion dynamics. A broad-scale study revealed high connectivity where northern areas were supplemented with red foxes from surrounding population. However, red fox expansion is most prevalent in tundra regions and the fine-scaled expansion dynamics in these areas have not yet been disseminated. With the aim of identifying the invasive pathways of tundra red foxes, we present microsatellite data for 205 Swedish red foxes and mitochondrial sequence variation in 102 foxes sampled across the historical boreo-nemoral distribution and recently colonized tundra regions. Genetic structuring was low with high levels of ongoing, asymmetric dispersal from surrounding boreal zones into tundra habitats causing high genetic admixture. In both tundra and boreo-nemoral regions, inter-individual relatedness decreased with increasing geographic distance and data suggests male-biased dispersal patterns. Overall, fine-scaled expansion patterns were affected by multiple factors and we discuss its implications for future red fox management. [ABSTRACT FROM AUTHOR]

[Display omitted] • Potential tree growth is influenced by admixture suggesting species facilitation. • Competition reduction is species specific and mixture dependent. • Niche complementarity is present in pine/beech and pine/oak mixtures. • Site humidity modifies mixture effect on potential growth and competition reduction. Trees often show better growth in mixed as opposed to monospecific neighborhoods as consequence of competition reduction and facilitation between species. However, it can be challenging to discern the effect of these factors as they occur simultaneously, so often they are jointly refereed as complementarity. By using tree growth models based on potential tree growth reduced by a competition modifier and including species mixing effects on both components (potential tree growth and competition modifier), we aim to verify that tree potential growth is modified by admixture, which may provide further information on species interactions and complementarity. We used tree data from the Spanish National Forest Inventory, selecting plots located in two different mixtures, Scots pine – European beech and Scots pine – Oak mixtures, as well as in the corresponding monospecific stands of those species. To analyse whether the species mixture increases the potential basal area growth, we developed linear mixed quantile regressions to model the potential growth, while to analyse the competition reduction we developed linear mixed models. We include the Martonne aridity index as a measure of the site conditions in the models to explore whether climate conditions modify the effects of species mixture. Our results show a slight effect of the mixture on the potential basal area growth of pine while the potential growth of beech clearly benefited from the pine/beech mixtures. For the pine/oak mixtures the potential growth of both species was higher in mixtures than in monospecific stands. Moreover, we found a positive influence of humidity on potential growth for all the species and mixtures, although the magnitude of the effect was less important for beech and more notable in the case of the pine/oak mixtures. We also found that for the studied species, admixed species reduced competition, with lower inter-specific than intra-specific competition effects, and that these effects were mediated by climate conditions. We concluded that the potential tree basal area growth is influenced by the species admixture, which suggest that species mixing effects can be relevant also under low stand densities. Our results highlight the importance of integrating the effect of species interactions on both the potential growth of trees and the competition modifier when the aim of the research is to further our understanding of species interactions. [ABSTRACT FROM AUTHOR]

Background In mid hills of Western Himalayas, Himachal Pradesh India, growth, yield and economics of Solanum khasianum as a potential medicinal herb under Pinus roxburghii (Chir pine) plantation has been studied for two consecutive years to assess the performance of Solanum khasianum in undercanopy of Pinus roxburghii for developing Solanum khasianum and Pinus roxburghii based innovative silvi-medicinal system. Methods Growth parameters such as plant height, number of branches per plant and leaf area index followed by yield were estimated after Solanum khasianum was grown on three topographical aspects as; Northern, North - western and Western at a spacing of 45 cm × 45 cm, followed by three tillage depths as; minimum (0 cm), medium (up to 10 cm) and deep tillage (up to 15 cm), in open and below canopy conditions treatment. The study was conducted to explore the possibility of using Solanum khasianum based silvi-medicinal system to utilize the below canopy of Chir pine forest for enhancing the productivity of forests besides the conservation of the medicinal herb. Results The growth parameters such as plant height, number of branches per plant and leaf area index were non-significantly affected by topographical aspects and tillage practices, both below canopy and open conditions except fresh weight and dry weight of berries during harvesting stage. The maximum yield (0.61 t∙ha−1) was observed on Western aspect in open conditions as compared to below canopy of Chir pine. The highest gross returns were observed for the crop cultivated on Western aspect under deep tillage in open conditions than other aspect and tillage combinations. However the positive net returns from the crops raised in below canopy of Chir pine indicates its possible economic viability under agroforestry system as the gross returns was higher than the cost of cultivation. Conclusion Solanum khasianum when grown in below canopy of Pinus roxburghii, its growth and yield indicated positive net returns. Solanum khasianum and Pinus roxburghii based silvi-medicinal system has the potential to enhance the overall productivity of Chir pine forest. This silvi-medicinal system gives scope for utilizing floor Chir pine forests for growth and production of Solanum khasianum beside conservation of the medicinal herb.

Relationships between the volume growth of mixed stands and their species composition were analyzed in order to examine the so-called “mixture effect” on stand productivity. The influence of co-species was studied using multiple linear regression analysis. Stand level basal area and height growth models were constructed in order to find out which stand characteristics can be used to describe mixture-effects. The study material originates from the Estonian network of permanent forest growth plots, only stands consisting of mainly (≥ 50% of volume) Scots Pine with Norway spruce and/or Birch spp. as co-species were used. Sample size was 139 5-year measurement periods on 88 plots; stand ages range from 14 to 167 years. The study results indicate that an increasing proportion of birch in the stand causes a negative effect on both basal area and height growth. Spruce seems to be a weaker competitor than other pines as its trend in the model is positive. Also, height growth is more rapid when the mean diameter of spruce is smaller than that of pine. Species composition coefficients for co-species (calculated by standing volume) proved to be the most significant variables that describe stand composition in the models