Intense Intraspecific Competition Research Articles

Environmental colour pattern variation in Mediterranean Podarcis

BackgroundLizards of the genus Podarcis are widespread in the Mediterranean region, including islands and island archipelagos. These small-bodied lizards have a predominantly protective green-brown colouration. However, some populations display unusual patterns, in which the colouration is predominantly blue or uniformly black. This study explores the factors that influence this chromatic variation, whether environmental (climate and island conditions) or evolutionary (phylogenetic trait conservatism). The colouration of 1400 individuals (27 species) was analysed in the CIELAB colour space.ResultsPagel’s λ indicated that colouration is weakly conserved within phylogenetic lineages. Although the island surface plays a key role in the chromatic variability of these lacertids, geographic isolation and climate hold less influence. The colouration of some small island populations tends to be uniform and dark, possibly due to intense intraspecific competition and lower predatory pressure.ConclusionsThis study highlights the importance of island populations in understanding the processes that favour the emergence of extreme phenotypes in small ectothermic vertebrates.

Negative density‐regulated contest performance promotes conflict resolution in a tree lizard

Abstract Territoriality is a behavioural adaptation resulting from intraspecific competition and reflects the strategy of how individuals share limited resources in the environment. As a consequence, territorial contests and levels of aggressiveness are strongly influenced by population density. The positive relationship between population density and the intensity of intraspecific competition may appear straightforward. However, empirical evidence regarding this association remains inconclusive. This ambiguity may be attributed to studies that have predominantly focussed on specific fight‐associated traits while overlooking potential interactions between multiple phenotypic characteristics and population dynamics. To examine the effects of population density and other ecological factors on the variation in fight behaviour as well as fight‐associated morphology and performance. We conducted population surveys and behavioural experiments using the Swinhoe's tree lizard across eight populations. Our findings revealed that males from higher density populations tended to engage in less intense fights and exhibited a weaker resident advantage in fights, which coincided with our findings on lower rates of injuries, weaker bite forces and smaller body sizes (and vice versa). Male‐specific variation in fight behaviour, morphology and performance along a density gradient suggests different evolutionary equilibria in territoriality influenced by local costs and benefits. Our study supports the significant role of negative density dependence as a fundamental regulator of eco‐evolutionary dynamics. The observed phenotypic variation emphasizes the importance of ecological and social factors in shaping ontogenetic growth and life‐history strategies. Our findings provide a basis for future investigations into pace‐of‐life syndromes and shed light on how phenotypic adaptation may shape population structure. Read the free Plain Language Summary for this article on the Journal blog.

Models of the bed structure dynamics of mass marine bivalves of the White Sea

The present paper is a synthesis of all the results of long-term (for almost 35 years) observations of beds of nine widespread bivalve species, carried out at the Marine Biological Station of St. Petersburg State University in the White Sea (Chupa Inlet mouth, Kandalaksha Bay). The purpose of the investigations is to identify the patterns of the spatial-temporal organization of bivalve beds. As a result, a generalized analysis of the reasons for the spatial and temporal heterogeneity of the bed structure of widespread long-lived bivalve species in an undisturbed environment is presented, and attempts are made to develop models of the dynamics of the age structure of bivalve beds in the White Sea. An integrated approach to identifying the patterns in the organization of bivalve beds: the study of changes in the size-age structure of beds as a reflection of the recruitment, growth and mortality features, made it possible to identify intraspecific relationships as determining long-term trends in the structure changes of mollusk beds in the White Sea. Studies have shown that long-term stability of size-age structure is not a typical feature of the bivalve beds in the White Sea, and substantial fluctuations in their structure take place even under relatively undisturbed environmental conditions. The main reasons for the fluctuations of the bed structure appear to be connected to inter-annual variation in recruitment rates. These variations are mainly caused by the intensity of mollusks intraspecific interactions, and by the conditions of mollusk survival in the early stages of the life cycle. As a result of interannual fluctuations in the bed bivalve recruitment rates, specimens of only 1 or 2 generations dominated for several years. A periodic change of the dominant generations could be considered as a recurrence in the bed development. However, the recurrence of the bed structure dynamics can be easily disrupted under unfavorable conditions for the mollusk survival in the early stages of the life cycle. The bivalve stationary beds in the White Sea are likely the exception from the general rule. They can be formed in case of a relatively stable level of annual recruitment with a decrease in intensity of intraspecific competition. The latter in the White Sea beds of Bivalvia was observed either when the ecological needs of individuals of different ages were differentiated, or in the case of a relatively poor bed density.

Density regulation amplifies environmentally induced population fluctuations.

Density-dependent regulation is ubiquitous in population dynamics, and its potential interaction with environmental stochasticity complicates the characterization of the random component of population dynamics. Yet, this issue has not received attention commensurate with its relevance for descriptive and predictive modeling of population dynamics. Here we use a Bayesian modeling approach to investigate the contribution of density regulation to population variability in stochastic environments. We analytically derive a formula linking the stationary variance of population abundance/density under Gompertz regulation in a stochastic environment with constant variance to the environmental variance and the strength of density feedback, to investigate whether and how density regulation affects the stationary variance. We examine through simulations whether the relationship between stationary variance and density regulation inferred analytically under the Gompertz model carries over to the Ricker model, widely used in population dynamics modeling. The analytical decomposition of the stationary variance under stochastic Gompertz dynamics implies higher variability for strongly regulated populations. Simulation results demonstrate that the pattern of increasing population variability with increasing density feedback found under the Gompertz model holds for the Ricker model as well, and is expected to be a general phenomenon with stochastic population models. We also analytically established and empirically validated that the square of the autoregressive parameter of the Gompertz model in AR(1) form represents the proportion of stationary variance due to density dependence. Our results suggest that neither environmental stochasticity nor density regulation can alone explain the patterns of population variability in stochastic environments, as these two components of temporal variation interact, with a tendency for density regulation to amplify the magnitude of environmentally induced population fluctuations. This finding has far-reaching implications for population viability. It implies that intense intra-specific resource competition increases the risk of environment-driven population collapse at high density, making opportune harvesting a sensible practice for improving the resistance of managed populations such as fish stocks to environmental perturbations. The separation of density-dependent and density-independent processes will help improve population dynamics modeling, while providing a basis for evaluating the relative importance of these two categories of processes that remains a topic of long-standing controversy among ecologists.

高寒条件下根际环境对极小种群大理白前竞争能力的影响

PDF HTML阅读 XML下载 导出引用 引用提醒 高寒条件下根际环境对极小种群大理白前竞争能力的影响 DOI: 10.5846/stxb202203270754 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: 第四次全国中药资源普查(2019PC001) Effects of rhizosphere environment on the competitive ability of extremely small population of Cynanchum forrestii Schltr under alpine conditions Author: Affiliation: Fund Project: the fourth national survey of traditional Chinese medicine resources (Grant No. 2019PC001) 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:大理白前(Cynanchum forrestii Schltr)是中国无危极小种群野生植物,研究高寒环境下大理白前-根际土壤系统的化学计量特征及其元素吸收,有助于解析极小种群的生存策略及其对环境的适应能力。以川西九龙县高寒草甸中的大理白前为对象,研究了其种群特征、光合色素特性、植物体和土壤的化学元素、根际土/非根际土的养分和细菌多样性。结果表明:与非根际土相比,根际土P、C/P和N/P较高而C/N较低,有机质(SOM)、全磷(TP)、全氮(TN)、速效氮(AN)、速效磷(AP)、速效钾(AK)增加;大理白前根际土P与茎的N、C/P、N/P呈正相关,而与P、C/N呈负相关。高通量测序表明,根际土/非根际土的优势细菌包括6个类群。根际土的变形菌门、芽单胞菌门相对丰度较高,而酸杆菌门、拟杆菌门、放线菌门、厚壁菌门的相对丰度较低,拟杆菌门相对丰度降低了45.53%,变形菌门相对丰度增加了32.89%。RDA分析结果显示,变形菌门相对丰度与土壤C、N、P呈正相关。在高寒草甸中,大理白前株丛呈均匀分布,平均株高(27 cm)高于群落其他植物的平均水平,地上生物量占比高达41.24%,种群密度和生态位宽度较大;随着株高增加,叶面积增大,光合色素含量和Chla/Chlb先增加后下降,但比叶质量变化不大;根茎叶对土壤元素均具有富集作用,其中对Ca、Mn、Na、K、P富集能力和对P、Ca、K转移能力较强。叶的C/N、C/P和N/P高于根、茎,各器官的N/P均小于14,表明养分主要分配到根、茎且受N限制。上述结果表明,大理白前富集有益的土壤微生物以改善根际土壤养分状况,提高植物体对Ca、Mn、Na、K、P等元素的吸收和转移能力,增强抗冻和抗辐射能力,并借助株高和叶面积的优势,弥补了光合色素含量较低的缺陷,从而提高了大理白前在高寒环境中的种间竞争能力和适合度,但却加剧种内竞争,导致其株丛呈均匀分布。推测种内竞争激烈是大理白前局限分布的原因之一。 Abstract:Cynanchum forrestii Schltr, an erect perennial herb of Asclepiadaceae, is a wild plant with extremely small population(WPESP) in China. This unique plant grows in a variety of habitats such as plateau and mountain at altitudes of 1000-3500 m. The root of C. forrestii is often used as a substitute for the traditional Chinese medicine "Baiwei". In Jiulong County, Ganzi Tibetan Autonomous Prefecture, western Sichuan Province, China, this plant is confined to alpine meadows in valleys at the altitude of 3100-3500 m. The rhizosphere is a part of the soil ecosystem where plant roots, soil and the soil microorganisms interact with each other. Soil microorganisms actively participate in soil material transformation and play a leading role in nutrient cycling by influencing the transformation of mineral elements. Most of the nutrients needed of plants come from soil and enter plants through rhizosphere interaction. The chemical element characteristics of plants can reflect the supply of nutrients to the soil. The study of plant and soil stoichiometric characteristics helps to understand the growth strategies of plants and their adaptability to the environment. Investigating the stoichiometric characteristics and element enrichment of the C. forrestii-rhizosphere soil system under the alpine environment will help to analyze the survival strategies of the extremely small populations and their adaptability to the environment. In this study, we investigated the effects of rhizosphere soil nutrients and bacterial community on population characteristics and photosynthetic characteristics of C. forrestii in the alpine meadow of Jiulong County by using plot and line transect sampling methods, physiological and biochemical analysis and Illumina-MiSeq high-throughput sequencing technology. The results showed that compared with the non-rhizosphere soil, the rhizosphere soil had higher P, C/P and N/P and lower C/N, and increased soil organic matter (SOM), total phosphorus (TP), total nitrogen (TN), available nitrogen (AN), available phosphorus (AP), and available potassium (AK). The Pearson correlation analysis showed that the value of N, C/P, N/P in C. forrestii stem were significantly positively correlated with the rhizosphere soil P, while the value of P and C/N were significantly negatively correlated with the rhizosphere P. High-throughput sequencing showed that the dominant bacteria in rhizosphere soil/non-rhizosphere soil included 6 groups. Compared with non-rhizosphere soil, the relative abundance of Proteobacteria and Gemmatimonadetes in rhizosphere soil was higher, while the relative abundance of Acidobacteria, Bacteroidetes, Actinobacteria and Firmicutes was lower. The relative abundance of Bacteroidetes decreased by 45.53%, and the relative abundance of Proteobacteria increased by 32.89%. Redundancy analysis (RDA) results showed that the relative abundance of Proteobacteria was positively correlated with soil C, N and P contents. The average plant height of C. forrestii was 27 cm, which was higher than the average height of other plants in the community. The proportion of above ground biomass reached 41.24%, and the population density and niche width also were larger than those of other plants. With the increase of plant height and leaf area, the photosynthetic pigment contents and Chla/Chlb raised first and then decreased, but leaf mass per area (LMA) had little change. Plants had enrichment effect on soil elements, the relatively high enrichment capacity for Ca, Mn, Na, K and P, and high transfer capacity for P, Ca, and K. Analysis of C, N, P stoichiometry showed that the C/N, C/P and N/P in C. forrestii leaves were higher than those of roots and stems, and the N/P of each organ was less than 14, indicating that N was the limit factor. In general, C. forrestii enriched beneficial soil microorganisms to improve the nutrient status of the rhizosphere soil, enhanced the absorption and transfer of elements such as Ca, Mn, Na, K, and P in plants, and promoted the ability to resist freezing and radiation. With the advantages of plant height and leaf area, it made up for the defect of low photosynthetic pigment content, thereby improving the interspecific competition ability and fitness of C. forrestii in the alpine environment, but intraspecific competition was intensified, which resulted in uniform distribution of plant clusters. It was speculated that the intense intraspecific competition was one of the reasons for the limited distribution of C. forrestii. 参考文献 相似文献 引证文献

Non-genetic resistance facilitates survival while hindering the evolution of drug resistance due to intraspecific competition

Rising rates of resistance to antimicrobial drugs threaten the effective treatment of infections across the globe. Drug resistance has been established to emerge from non-genetic mechanisms as well as from genetic mechanisms. However, it is still unclear how non-genetic resistance affects the evolution of genetic drug resistance. We develop deterministic and stochastic population models that incorporate resource competition to quantitatively investigate the transition from non-genetic to genetic resistance during the exposure to static and cidal drugs. We find that non-genetic resistance facilitates the survival of cell populations during drug treatment while hindering the development of genetic resistance due to competition between the non-genetically and genetically resistant subpopulations. Non-genetic resistance in the presence of subpopulation competition increases the fixation times of drug resistance mutations, while increasing the probability of mutation before population extinction during cidal drug treatment. Intense intraspecific competition during drug treatment leads to extinction of susceptible and non-genetically resistant subpopulations. Alternating between drug and no drug conditions results in oscillatory population dynamics, increased resistance mutation fixation timescales, and reduced population survival. These findings advance our fundamental understanding of the evolution of resistance and may guide novel treatment strategies for patients with drug-resistant infections.

Analysis of inter-nodal properties of two industrial hemp cultivars (Fasamo and Ferimon 12) and their relationships with plant density and row spacing

Research and development of an efficient production system for industrial hemp (Cannabis sativa L.) fiber needs to integrate multidisciplinary knowledge from cultivation to processing of plant materials. This study investigated two industrial hemp cultivars (Fasamo and Ferimon 12) for their inter-nodal properties, i.e., length and diameter. The relationship of the inter-nodal properties with agronomic factors such as planting density (40, 80, 120, 160 plants/m2) and row spacing (15 and 30 cm) was examined in a field experiment. The findings suggested that plants cultivated at higher plant densities (e.g., 80 and 160 plants/m2) had a smaller inter-nodal diameter and longer inter-nodal length. Row spacing did not show a significant effect on the Fasamo cultivar. However, row spacing had a significant effect on the Ferimon 12 cultivar that might imply more intense intra-specific competition of the taller plants for sunlight. The inter-nodal length pattern resembling a bimodal distribution might indicate crop maturity. However, further research into the inter-nodal length pattern is recommended. When the inter-nodal properties and other crop parameters (e.g., bast fiber yield) were interpreted together, they could convey important information, including the extent of crop maturity and a suitable harvesting period for more bast or hurd fiber production. Although the study generated interesting and promising results from the inter-nodal property analysis, further research into the internodal properties in relation to other influential agronomic factors is recommended.

Does recruitment trigger negative density-dependent feedback loops in stream-dwelling salmonids?

I explored the hypothesis that recruitment may stabilize the numerical dynamics of stream-dwelling salmonids by triggering density-dependent feedback loops through the operation of recruitment dependence on individual growth, mortality, life span and maximum size and their effects on fecundity. I examined 98 cohorts of two Salmo trutta populations of northern Spain and a population of Jutland (Denmark) located 2400 km apart. Recruitment, growth, mortality, life span and maximum size were inter-related, were recruitment-dependent and described negative power trajectories. In the Spanish populations, faster-growing individuals of weakly recruited cohorts with lower mortality attain longer life span and larger size. Hence, larger females spawning more abundant, larger eggs that, in turn, induce stronger cohorts of higher spawners’ abundance, recruitment and mortality. The mortality patterns match the self-thinning patterns, an ultimate expression of competition. Significant relationships among self-thinning slopes and mortalities rates with increasing recruitment demonstrate that the rate at which density-driven mortality is higher, the stronger the intensity of intraspecific competition. Space-limited habitat and size-dependent resource availability underpinning site-specific carrying capacities suggest that interference competition is the primary mechanism underpinning population regulation.

不同坡向川西亚高山林木竞争与叶片表型可塑性的关系研究

PDF HTML阅读 XML下载 导出引用 引用提醒 不同坡向川西亚高山林木竞争与叶片表型可塑性的关系研究 DOI: 10.5846/stxb202009172425 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: 国家重点研发计划项目（2017YFC0505003） Relationships between competition intensity and leaf phenotypic plasticity of woody plants in subalpine forests on different slope directions Author: Affiliation: Fund Project: 2017YFC0505003 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:表型可塑性是植物生长响应外界环境变化的重要表现形式，体现了植物个体在环境胁迫下的适合度。但是关于植物表型可塑性的驱动机制仍然存在很多争议。为了探讨植物表型可塑性的影响因素，以四川省阿坝藏族羌族自治州位于同一海拔梯度但坡向相反的天然次生林为研究对象，分析了不同坡向竞争强度与10种树木叶片功能性状表型可塑性的关系的差异。研究发现：（1）研究样地中阴坡水分和养分资源优于阳坡；（2）阴坡上林木平均种内和种间竞争强度高于阳坡，阴坡上林木种内竞争强度随着树木个体大小的增加而显著性减少，阳坡上林木种内竞争强度却随着个体大小的增加而增加；（3）阴坡上叶片表型可塑性高于阳坡，表型可塑性随着个体大小的增加而增加，在阳坡上却随着个体大小增加而降低。这些结果表明阴坡上水分等资源环境条件优于阳坡，林木生长受到环境资源限制较少。在林木生长过程中，较高的竞争强度引起的资源重叠加剧，尤其是种内竞争强度的变化，从而导致了阴坡上较高的叶片表型可塑性。因为较高的竞争强度，随着林木个体大小的增加，树木需要更高的可塑性赢得竞争优势来获取更多的资源支持生长。但是在阳坡上，资源相对缺乏，环境资源对树木生长的限制降低了叶片表型的可塑性，因为环境资源的限制，随着树木个体大小的增加越容易受到资源限制的影响，因此阳坡上表型可塑性随着个体大小的增加而降低。研究说明，阴坡上叶片表型可塑性主要受到竞争强度的影响，而阳坡上则主要受环境资源的限制。 Abstract:Phenotypic plasticity is an indicator of the responses of plant growth and development to environmental changes, which reflects the fitness of plant individuals under environmental stress. However, the driving mechanism of plant phenotypic plasticity is still controversial. To explore the impacts of environmental conditions and competition on the phenotypic plasticity of leaf traits in trees, we surveyed two secondary forests with different slope directions in the Ngawa (Aba) Tibetan and Qiang Autonomous Prefecture in western Sichuan, China and analyzed the difference in the relationship between competition intensity and phenotypic plasticity of 10 tree species leaf functional traits between shade and sunny slopes. Results show that:(1) water and nutrient availabilities were greater on shade slope than those on sunny slope. (2) Mean intraspecific and interspecific competitions of tree species on shade slope were higher than those on sunny slope; intraspecific competition intensity decreased with the increases of individual tree size on shade slope, but it increased along with the increase of individual size on sunny slope. (3) The leaf traits include specific leaf area (SLA), leaf carbon content (C), leaf nitrogen content (N), leaf phosphorus content (P), leaf kalium content (K), leaf carbon-phosphorus ratio (CPR), leaf carbon-nitrogen ratio (CNR), and leaf nitrogen-phosphorus ratio (NPR). Phenotypic plasticity of all eight measured leaf traits on shade slope was higher than on sunny slope. Phenotypic plasticity of leaf traits increased with the increase of individual tree size on shade slope, but decreased with the increase of individual size on sunny slope. These findings suggest that the environmental resources of community on shade slope were greater than on sunny slope. The growth of forest trees was less restricted by the availability of environmental resources on shade slope, where higher competition intensity led to the intensification of resource overlap, especially the high intraspecific competition intensity, ultimately resulted in the higher phenotypic plasticity of leaf traits on shade slope. Because of higher competition intensity, with the increase of individual size, trees need higher phenotypic plasticity to gain competitive advantage and obtain more resources to support growth. However, because resources were relatively poor, the limitation of the availability of environmental resources reduced to the lower phenotypic plasticity of leave traits on sunny slope. Due to the limitation of the availability of environmental resources, with the increase of individual size, trees were more likely to suffer resource constraints. Therefore, phenotypic plasticity of leaf traits on sunny slope decreased with the increase of tree individual size. To summary, our study demonstrated that leaf phenotypic plasticity was mainly affected by competition intensity on the shade slope, while it was mainly limited by the availability of environmental resources on the sunny slope. 参考文献 相似文献 引证文献

Stereoscopic Planting in Ridge and Furrow Increases Grain Yield of Maize (Zea mays L.) by Reducing the Plant’s Competition for Water and Light Resources

Increasing planting density is an important ways to increase maize yield. A hot topic of conversation in the current research is how to improve crop light efficiency and yield potential by optimizing the cultivation mode under high density planting is a hot topic in current research. Thus, in this study, a field experiment was conducted to explore the effects of stereo-planting patterns on water and the utilization light resource and maize yields. Planting patterns included the conventional flat planting pattern (as the control, CK) and the stereo-planting in ridge and furrow (T). Each planting pattern had three planting densities, i.e., 60,000 plants ha−1 (D1), 75,000 plants ha−1 (D2) and 90,000 plants ha−1 (D3). The results showed that stereo-planting affected the physiological characteristics of plants by changing the spatial distribution of soil moisture. At the silking stage (R1), photosynthetic rate (Pn) of plants on the ridge was similar to CK, and transpiration rate (Tr) was significantly lower than that of CK. Pn of maize in the furrow was significantly higher than that of CK, and Tr was similar to CK. Stereoscopic planting had different effects on intraspecific competition intensity in maize population in different growing stages. In the six-leaf stage (V6), stereo-planting increased competition intensity of maize on the ridge, but lowered that of maize in the furrow by affecting the spatial distribution of soil moisture. During the R1 stage, stereo-planting increased the light transmittance rate within the canopy and eased the plant’s competition for light by reducing plant height and leaf area of maize under three density conditions. Stereo-planting had no effect on grain yield and dry matter accumulation of ridge-planted maize in the later growing stage, but it did increased the dry matter accumulation and grain yield of furrow-planted maize due to the improvement of the light environment and photosynthetic characteristics of the population. In two test years, stereo-planting increased 5.0–11.0% average yield of maize compared to CK under three density conditions. These results indicate that stereo-planting can reduce the plant’s competition for light and water resources and improve its physiological traits of plant by optimizing its spatial distribution of soil moisture and canopy structure, thus further increasing grain yield of maize under high-density planting conditions.

Fluid Nest Membership Drives Variable Relatedness in Groups of a Facultatively Social Bee

Kin selection theory has dominated our understanding of the evolution of group living. However, many animal groups form among non-relatives, which gain no indirect fitness benefits from cooperating with nestmates. In this study, we characterized the relatedness and inter-nest migration behavior of the facultatively social carpenter bee, Xylocopa sonorina. Nesting constraints due to costly nest construction in this species give rise to intense intraspecific competition over access to existing nests. We used mark-recapture techniques to characterize patterns of dispersal and nest relocation within a nesting aggregation of spatially clustered nests. Two-thirds of bees relocated at least once during the reproductive season, likely to seek reproductive opportunities in another nest. This fluid nest membership creates opportunities for association among non-relatives. To assess the effects of this dynamic nesting behavior on group relatedness, we used microsatellite analysis to estimate relative relatedness within and between nests in the aggregation. We found that relatedness was variable across sampling years, but that in many cases nestmates were no more related to one another than they were to non-nestmate bees in the population. Together, these results suggest that group composition in X. sonorina may result from strategies to maximize direct fitness. This study supports the hypothesis that factors beyond kinship, such as ecological constraints, are likely to drive group formation in this species.

The early evolution of cranial appendages in Bovoidea revealed by new species of Amphimoschus (Mammalia: Ruminantia) from China

Abstract The cranial appendage (headgear) is an iconic structure of modern ruminants, and four of the five extant pecoran families display morphological and physiological specialties. They probably share one origin from the same genetic basis, whereas the evolution of the cranial appendages is still debatable, especially in consideration of fossil taxa lacking headgear. Amphimoschus is an enigmatic pecoran that comprises no more than two species, mainly known from the late early/early middle Miocene of Western and Central Europe and considered not to possess any cranial appendages. Here, we present Amphimoschus xishuiensis sp. nov., discovered in the Tabenbuluk area, Gansu Province, China. The new species reveals the first evidence of cranial ornamentations in the genus, including a supraorbital bump, an antorbital protuberance and frontal thickening. In our phylogenetic analysis the genus was inferred as a basal member of the Bovoidea, and thus the cranial ornamentations of A. xishuiensis might provide insight into the early evolution of cranial appendages in Bovoidea. They could be interpreted as weapons to defend territories in intense intraspecific or interspecific competition during the late early Miocene.

Annual Growth Progression, Nutrient Transformation, and Carbon Storage in Tissues of Cunninghamia lanceolata Monoculture in Relation to Soil Quality Indicators Influenced by Intraspecific Competition Intensity

Annual Growth Progression, Nutrient Transformation, and Carbon Storage in Tissues of Cunninghamia lanceolata Monoculture in Relation to Soil Quality Indicators Influenced by Intraspecific Competition Intensity

Age and growth of Palaeoloxodon huaihoensis from Penghu Channel, Taiwan: significance of their age distribution based on fossils.

Dental material attributed to Palaeoloxodon huaihoensis from the Middle to Late Pleistocene were recovered over decades from the Penghu Channel during commercial fisheries activities. The National Museum of Nature Science (NMNS) has a collection of such dental material, which differs in size and morphology and likely represents ontogenetic variation and growth trajectory of various age groups of P. huaihoensis. However, little is known regarding age determination. By using length of dental material, enamel thickness (ET), and plate counts, we established the method to distinguish the age of the species, which is directly derived from the extant African forest elephant Loxodonta africana. When measuring signs of allometric growth, we found that in both the upper and lower jaws, tooth width was correlated negatively with lamellar frequency but positively with ET. In the same age group, the number of lamellae was higher in P. huaihoensis than in L. africana. The reconstructed age distribution indicated no difference in the upper or lower jaw. Notably, within our sample, P. huaihoensis is skewed towards adult and older individuals with median age between 33–34.5 years and differed significantly from that of Mammuthus primigenius in the European Kraków Spadzista site. This age distribution pattern is speculated to be related to the harsh environmental conditions and intense intraspecific competition among P. huaihoensis during the last ice age.

Structural stability of coexistence in evolutionary dynamics of cyclic competition

One of the common assumptions in previous spatial dynamics of cyclic competition is that, regardless of competing structure and strength among species, the spatial size of a network is considered as large as possible to avoid finite size effect for species biodiversity. In real ecosystems, however, species richness, which can be defined by spatial size and competition strength, can sensitively affect species coexistence as a competition among individuals becomes complicated. In this paper, we investigate the structural stability of coexistence of mobile species in three cyclic competition games due to network complexity in which imposes a size of a square lattice and competition strength among species. By exploiting the coexistence probability, our computations quantitatively reveal that the network complexity due to changes in the competition rate and lattice size can strongly affect the structural stability of coexistence in each model. In particular, intense intraspecific competition can yield the robust coexistence at small-sized lattices regardless of mobility, and strengthening interspecific competition simultaneously induces changes in critical mobility that hampers coexistence and in spatial size for stable coexistence. Qualitatively, we find that such structural stability of coexistence relates to the degree of stability of fixed points in deterministic systems. Our finding can be useful to gain insights into species coexistence on spatially extended systems with respect to network complexity.

The Intraspecific competition as a driver for true production potential of soybean

Phenotypic plasticity of agricultural plants is considered to be one of the main means by which plants cope with the variability of environmental factors. A major contributor to plant plasticity is sowing density, which has a relevant impact on competitive intensity concerning plant density in different environments (CI) and absolute severity of competition (ASC) concerning plant-plant responses to each other in canopy. A field experiment with soybean was set up at the Experimental Station in Prusy, Krakow, to determine the impact of intraspecific competition on growth, plant architecture, nitrogen accumulation, and yield of soybean as an effect of seven different plant densities and weather conditions. The study showed that intraspecific competition in soybean was conditioned by sowing density and access to water, thus revealing the true plant productive potential. Low intraspecific competition increased with plant density causing an increase in the yield of plants. In the wet year of 2014, strong intraspecific competition resulted in high yield and nitrogen accumulation only up to a density of 42 plants m–2, compared to dry years when nitrogen uptake of soybean increased with plant density in full range. The CI and ASC competition indices were sensitive to the varying amount of rainfall. Greater rainfall during crop vegetation increased the intensity of competition as well as the absolute severity of competition and decreased the relative yield with increasing density. In contrast, drought reduced intraspecific competition, eliminating it entirely at over 52 plants m–2.
 Highlights - It is recommended to increase the sowing density in areas with less rainfall to compensate number of pods and number of seeds. - Low intraspecific competition increased yield and nitrogen accumulation in the seeds as the plant density increased.- In the wet year, strong intraspecific competition resulted in high yield and nitrogen accumulation only up to a density of 42 plants m–2. - At very low crop density, the intensity of intraspecific competition is very low and blocked the manifestation of the plants’ true production potential. - In the dry year, nitrogen uptake of soybean increased with plant density in the canopy up to the maximum density.

Plasticity of Root Traits under Competition for a Nutrient-Rich Patch Depends on Tree Species and Possesses a Large Congruency between Intra- and Interspecific Situations

Belowground competition is an important structuring force in terrestrial plant communities. Uncertainties remain about the plasticity of functional root traits under competition, especially comparing interspecific vs. intraspecific situations. This study addresses the plasticity of fine root traits of competing Acer pseudoplatanus L. and Fagus sylvatica L. seedlings in nutrient-rich soil patches. Seedlings’ roots were grown in a competition chamber experiment in which root growth (biomass), morphological and architectural fine roots traits, and potential activities of four extracellular enzymes were analyzed. Competition chambers with one, two conspecific, or two allospecific roots were established, and fertilized to create a nutrient ‘hotspot’. Interspecific competition significantly reduced fine root growth in Fagus only, while intraspecific competition had no significant effect on the fine root biomass of either species. Competition reduced root nitrogen concentration and specific root respiration of both species. Potential extracellular enzymatic activities of β-glucosidase (BG) and N-acetyl-glucosaminidase (NAG) were lower in ectomycorrhizal Fagus roots competing with Acer. Acer fine roots had greater diameter and tip densities under intraspecific competition. Fagus root traits were generally more plastic than those of Acer, but no differences in trait plasticity were found between competitive situations. Compared to Acer, Fagus roots possessed a greater plasticity of all studied traits but coarse root biomass. However, this high plasticity did not result in directed trait value changes under interspecific competition, but Fagus roots grew less and realized lower N concentrations in comparison to competing Acer roots. The plasticity of root traits of both species was thus found to be highly species- but not competitor-specific. By showing that both con- and allospecific roots had similar effects on target root growth and most trait values, our data sheds light on the paradigm that the intensity of intraspecific competition is greater than those of interspecific competition belowground.

Competition and facilitation co-regulate the spatial patterns of boreal tree species in Kanas of Xinjiang, northwest China

Competition and facilitation are the primary mechanisms structuring communities and driving spatial distribution patterns of trees. However, we still know relatively little about the underlying effects of these two processes on natural forest ecosystems and this is particularly true in boreal forest ecosystems. Our lack of understanding regarding the factors regulating spatial patterns of boreal forest ecosystems is important given their role in carbon sequestration and timber products. Using data from a 12-ha boreal forest dynamic plot in the Kanas Nature Reserve of Northwest China, we assessed the population distribution and diameter at breast height (DBH) structure, as well as intra- and interspecific interactions, of the four most abundant tree species (Larix sibirica, Picea obovata, Pinus sibirica, and Betula pendula). Our results indicate that the spatial distribution patterns of these species were aggregated at small spatial scales because of dispersal limitation, and that the degree of aggregation decreased with increasing spatial scale. Aggregation was the highest for the less common species (i.e., B. pendula pendula). Saplings (1 cm ≤ DBH < 5 cm) and juveniles (5 cm ≤ DBH < 15 cm) were more aggregated than larger individuals (DBH ≥ 15 cm). Only P. obovata adults (DBH ≥ 15 cm) showed a regular (i.e., hyperdispersed) distribution because of the intense intraspecific competition at small scales (i.e., <5 m). Intraspecific interactions between individuals were either positive or not significant. In terms of interspecific competition, there were significant negative associations among large (DBH ≥ 15 cm) and small adults (5 cm ≤ DBH < 15 cm) for the two shade tolerant species (P. obovata and P. sibirica). In contrast, we observed positive interspecific interactions between individuals of different DBH classes and different shade tolerance species. Thus, most of the intra- and interspecific interactions showed positive or no significant correlations. Negative associations were generally less common than positive associations both within and between species. Our results show that competition and facilitation simultaneously influence the spatial patterns of plants in this community. Moreover, positive interactions between tree individuals in this temperate region are likely to be more common than competitions for survival and growth of tree stems.

Population-level performance of Arabidopsis thaliana (L.) Heynh in dense monocultures

Abstract Aims Very little is known about the performance of non-agricultural plant species in monocultures, even though nearly all agricultural species have experienced the transition from multi-species environments to dense monospecific stands during the breeding process. In the light of recent work that highlighted the possibility that the weedy species Arabidopsis thaliana can offer novel insight into crop breeding, we aimed to test the effect of sowing density on group and individual performance in different photoperiod environments in A. thaliana. Methods We studied the performance of A. thaliana Cvi-0 ecotype. The choice of Cvi-0 was based on a preliminary experiment in which plants of Cvi-0 ecotype exhibited high competitive performance. Sowing densities used were 17.6, 8.8, 4.4, 2.2 and 1.1 cm2 per plant and photoperiod environments 12 or 16 h of day light. Important Findings In this experiment, populations attained constant total seed yield for all densities. Some interaction effect occurred, as at high sowing density and at longer day length plants produced heavier seeds, whereas at shorter day length seed weight was negatively related to plant density. These results shed light on different strategies that annual plants can adopt when they face intense intraspecific competition, and could help to offer new perspectives for breeding crops with enhanced group performance.

Global stability of the boundary solution of a nonautonomous predator-prey system with Beddington-DeAngelis functional response

ABSTRACT In this paper, we consider a nonautonomous predator-prey system with Beddington-DeAngelis functional response and explore the global stability of boundary solution. Based on the dynamics of logistic equation, some new sufficient conditions on the global asymptotic stability of boundary solution are presented for general time-dependence case. Our main results indicate that (i) the long-term ineffective predation behaviour or high mortality of predator species will lead the predator species to extinction, even if the intraspecies competition of predator species is weak or no intraspecies competition; (ii) the long-term intense intraspecific competition may lead the predator species to extinction, even though the long-term accumulative predation benefit is higher than the death lose. When all parameters are periodic functions with common period, a necessary and sufficient condition on the global stability of boundary periodic solution is obtained. In addition, some numerical simulations are performed to illustrate the theoretical results.