High Intraspecific Competition Research Articles

Особенности роста и структуры древесины сосны на вырубке и под пологом древостоя в условиях Республики Карелии

The intraspecific variability of the anatomical and hydraulic characteristics of xylem in the undergrowth in Scots pine (Pinus sylvestris L.) has been assessed during natural regeneration in the felling areas and under the canopy of a middle taiga blueberry pine forest in the conditions of the European North (Republic of Karelia). The influence of habitat conditions on the formation of structural elements of wood cells has been revealed. In felling areas under conditions of higher illumination, air and soil temperatures, the transition of pine undergrowth to the category of large with a height of more than 1.5 m occurs at the age of 6 years, whereas under the canopy of a mature stand the undergrowth reaches this category no earlier than 15 years. At the same time, in the 1st decade of growth under felling conditions, the growth of pine in diameter has been 4 times higher than that of pine under the canopy of a mature stand due to the formation of a larger number of rows of tracheids in the early and late zones. In addition, the pine undergrowth in the felling area has the highest potential hydraulic conductivity of the xylem, and, on the contrary, the lowest specific density of tracheids, the basic wood density and late wood content relative to the pine undergrowth under the canopy of the stand. The latter exhibited a significant decrease in the structural and functional characteristics of wood, with the exception of the thickness of the cell membranes of late tracheids. In the interanual dynamics, more stringent linear regression dependencies between the indices of early and late tracheids have been observed in pine undergrowth under the forest canopy. The results obtained indicate a greater correspondence of the environmental conditions in the felling area to the optimum for the growth and formation of wood of young pine trees relative to the conditions under the canopy of a mature blueberry pine forest. Inhibition of the growth activity of undergrowth under the canopy occurs due to high intraspecific competition from the dominant pine stand for light, moisture and soil nutrition.

Resource diversity mitigates the effects of intraspecific competition in co-occurring cryptic nematode species

Intraspecific competition and resource diversity are considered major drivers of niche differentiation, which are expected to promote population niche expansion by driving individuals to feed on alternative resources and/or by enhancing individual diet specialization. Nevertheless, experimental studies on the interaction effects of both factors on animal behavior and population dynamics remain scant. Here, we investigate how resource diversity alters the impact of intraspecific competition on resource preference and fitness of three co-occurring cryptic species of the marine nematode complex Litoditis marina (Pm I, Pm III and Pm IV). For each cryptic species, two competition regimes (‘low nematode density’ and ‘high nematode density’) were established in microcosms with varying resource diversity (E. coli, low-, medium- and high-diversity food). Our results show differences in resource preference and population fitness depending on intraspecific competition and resource diversity, but the response also varied considerably between cryptic species. Pm III did not exhibit resource preference under low intraspecific competition, but preferred the two most diverse food sources under high intraspecific competition. Pm IV also showed preference for medium-diversity food under high competition, whereas no resource preference was observed in Pm I regardless of competition regimes and resource diversity. Nevertheless, all cryptic species exhibited enhanced adult population growth on a more diverse food source under stronger intraspecific competition. These results indicate that resource diversity can alleviate intraspecific competition and affect niche diversification, which may impact diversity maintenance in ecological communities.

The impact of sward height, forage quality and competitive conditions on foraging behaviour of free-ranging rabbits (Oryctolagus cuniculus L.)

The habitat choice of the small hindgut fermenter, the European rabbit (Oryctolagus cuniculus L.), was studied in relation to sward height, forage quality, population size fluctuations and spatial distribution of burrows in a temperate grassland. In a multi-phase differential clipping experiment with alternating short and tall vegetation strips, rabbits tended to graze near the closest burrows in situations of equal vegetation heights, while a clear preference for short swards was found during summer (July). In this period, general crude protein content was significantly lower than in spring (April) and autumn (September), apparently leading to a potential forage quality deficit. The summer behavioural pattern with short sward preference coincided with the relatively higher crude protein content of short swards as compared to tall swards in this period, and with higher intraspecific competition, due to significantly larger numbers of animals present in summer. In autumn, rabbit densities decreased, while crude protein content of both short and tall vegetation increased to a higher, though not significantly different level, comparable with spring crude protein content. In those conditions, significant preference for low vegetation height could no longer be detected. Data suggest that selection for nutritive quality appears when intraspecific competition is high and nutritive quality remains under a certain threshold value. When, in autumn, competition decreases and nutritive quality increases again, short sward preference disappears. We conclude that short sward preference is primarily caused by the better forage quality of re-growth in periods of forage quality limitation, while this preference disappears when forage quality limitation no longer occurs.

Intraspecific competition hinders drought recovery in a resident but not in its range-expanding congener plant independent of mycorrhizal symbiosis

Background and aimsUnderstanding biotic interactions within plant populations and with their symbiotic partners is crucial for elucidating plant responses to drought. While many studies have highlighted the importance of intraspecific plant or mutualistic fungal interactions in predicting drought responses, we know little about the combined effects of these two interactions on the recovery of plants after drought.MethodsWe conducted an experiment to study the recovery after an extreme drought event of a native European plant species (Centaurea jacea) and its range-expanding congener (Centaurea stoebe), across a gradient of plant density and in association with an AM fungal species (Rhizophagus irregularis).ResultsOur results showed strong intraspecific competition in C. jacea, which constrained their post-drought recovery. We further found that AM fungi constrained root biomass recovery of C. jacea after drought under high intraspecific competition. The post-drought recovery in C. stoebe was high potentially due to its greater plasticity in the root diameter under drought conditions.ConclusionStrong intraspecific competition can constrain recovery in plants like C. jacea with lesser root trait plasticity after drought, independent of mycorrhizal symbiosis.

Competitive interactions between invasive fall armyworm and Asian corn borer at intraspecific and interspecific level on the same feeding guild.

Interspecific competition is an important factor in the population dynamics and geographical distribution of insect populations. Fall armyworm (FAW), Spodoptera frugiperda, an invasive species, and the Asian corn borer (ACB), Ostrinia furnacalis, a native pest species are major pests on maize in China, posing a threat to maize yield and grain quality. A series of laboratory, greenhouse, and field experiments were conducted to elucidate the competitive interactions between FAW and ACB. In the laboratory experiments, FAW exhibited aggressive behaviors more frequently when compared with ACB, while the latter species exhibited defense behaviors more frequently. Higher intraspecific competition was recorded in the FAW conspecific rather than in ACB, particularly in the 6th larval stage. FAW had a higher interspecific competitive advantage through intraguild predation over ACB, resulting in partial or complete displacement ACB when initially the ratio of the 2 species was 1 : 1. The interspecific competition also had significantly influenced on the population parameters, defensive enzymes, and nutrient of these 2 species. Competitive interaction proved that the response of superoxide, catalase, and soluble protein in FAW were significantly increased, whereas the total sugar content in both species was substantially decreased. Survival rate, and the plant damage that co-infested by both species varied significantly among the sequential combinations under greenhouse and field conditions. FAW consistently exhibited stronger intraspecific aggression than ACB under laboratory and field conditions when co-existing on the same feeding guild. These findings contribute to efforts toward the improvement of integrated pest management programs for FAW, in decision making for invasive and native pests' management strategies to reduce the high risks of FAW and ACB outbreaks.

Spatial, temporal and trophic resource partitioning among the four egret species (Aves: Pelecaniformes: Ardeidae) in a tropical wetland ecosystem, India

The diversity of micro-habitats in tropical wetlands allows the coexistence of several species. These sympatric species interact with each other, either directly or indirectly, to optimally use the available resources. They achieve this through niche separation or minimal overlap to avoid competition. India’s wetland ecosystems are home to various sympatric species, such as the Great Egret Ardea alba (GE), Median Egret Ardea intermedia (IE), Little Egret Egretta garzetta (LE) and Cattle Egret Bubulcus ibis (CE). These egret species are closely related, and as a result, have similar niche requirements, which could lead to high intra-specific competition. However, there have been few studies on how these species utilize resources. This study aims to understand the possible mechanisms that enable the coexistence of these species in a tropical wetland. We have examined habitat characteristics, feeding behaviour, timings of seasonal and daily activities, and spacing patterns to evaluate possible models of species coexistence. We discovered that these four sympatric egret species have differences in microhabitat selection, activity patterns, both daily and seasonally, and feeding preferences. The study further indicates that there is a relationship between the niche dimensions, but it is only partially dependent on each other.

Long‐term analysis of body condition reveals species coupling and the impacts of an invasion

AbstractPredator–prey coupling can result in oscillations of predator–prey densities. These oscillations in predator–prey densities correspond to oscillations in intraspecific competition where a high population density causes high intraspecific competition. Strong coupling of native species can however be disrupted by the introduction of invasive species into food webs. Here, we investigated how the body condition (body mass relative to body length) of a predator, lake trout, and its primary prey, cisco, changed as their respective population densities shifted. We found that the body condition of lake trout and cisco was strongly influenced by their respective population densities, that is, density dependence. The body conditions of lake trout and cisco were also inversely related, which highlights strong predator–prey coupling. Further, we were able to detect the impacts of a recent invasive species, Bythotrephes, as we saw size‐specific shifts in the body condition of prey following the invasion. Overall, this study highlights how the long‐term study of a simple measure, body condition, can reveal predator–prey coupling and yield new insights into the impacts of an invasive species.

Body Condition and Breeding of Urban Red Squirrels: Comparison of Two Populations Affected by Different Levels of Urbanization

The red squirrel is among the mammals that have adjusted well to urban habitats. Here, we focused on the two populations inhabiting Warsaw: in a park (with year-round supplemental feeding) and in an urban forest. We hypothesised that park squirrels would have higher body mass (and better body condition), being more stable over the year, and would have a higher breeding rate (i.e., the share of breeding females). Contrary to our hypothesis, forest squirrels were heavier and had better body condition than park squirrels. The body masses of squirrels from both areas were quite stable (with the highest values obtained in spring). Females in better body conditions were more likely to breed. More breeding females and sub-adults were trapped in the park. Regardless of the study site, the highest share of breeding females was in spring, but they also bred in winter and in the remaining seasons. The lower body mass/condition of park squirrels may be possibly explained by high intraspecific competition, or by stable food (and thermal as typical for the city) conditions, in which accumulating fat was not crucial. Mild winter conditions may have also enabled squirrels to breed early. This study showed the high plasticity of red squirrels living in human-transformed habitats.

Does natural root grafting make trees better competitors?

Natural root grafts (anastomoses) are morphological unions formed between roots of different trees. Common root systems allow translocation of water, nutrients and photosynthesis products between grafted trees, affecting their growth and their physiology. As carbohydrates are redistributed among grafted trees, the formation of a common root system could reduce the negative effect of intraspecific competition for light or soil resources within stands. The aim of this study was to investigate the role of root grafting on intraspecific competition and growth of balsam fir Abies balsamea. We studied inter‐tree relationships in three natural balsam fir stands of the boreal forest of Quebec (Canada) that contained an average 36% of grafted trees. At each stand, ring width and basal area of trees were measured using dendrochronology techniques. We used mixed linear models to test the effect of root grafting and intraspecific competition on annual basal area increment of trees. Trees before grafting had higher growth rates than trees once grafted. Thus, root grafting did not improve tree growth. Growth of grafted trees was more negatively affected by intraspecific competition than growth of non‐grafted trees. Thus, grafted trees cannot be considered as better competitors than non‐grafted trees. Under high intraspecific competition, growth of larger grafted trees was less affected than that of smaller trees suggesting that they were able to divert resources at their advantage within a union. Our study demonstrated that grafted trees acted on each other's growth and provides support for the idea that grafted trees respond to competition for resources more as a community rather than as individual trees.

Greater tree species diversity and lower intraspecific competition attenuate impacts from temperature increases and insect epidemics in boreal forests of western Quebec, Canada

We investigated how the surrounding environment influences the growth of dominant trees and their responses to temperature and insect epidemics in boreal forests of eastern Canada. We focused on 82 black spruce and jack pine focal trees in stands spanning a double gradient of species diversity and soil texture within a 36 km2 area of western Quebec. For these trees, we compared their diameter at breast height, growth rates, temperature–growth relations, and growth during insect defoliator epidemics. We used linear models to study how surrounding tree attributes and soil properties affected the growth of focal trees. Models showed that tree growth responses and responses to temperature and insect epidemics were generally negative with higher intraspecific competition and positive with greater tree species diversity. Growth of both species benefitted from lower soil sand content. Our research offers novel insights on the potential role of the surrounding environment, notably tree competition and species diversity, in mitigating the vulnerability of eastern Canada's boreal trees to anthropogenic climate change and insect epidemics.

Body Size and Symmetry Properties of Termite Soldiers Under Two Intraspecific Competition Scenarios

Single-piece nesting termites live and forage in the same piece of wood throughout their life, which limit their colony size. In certain species, more than one colony thrive in a given piece of wood (multicolonial substrate) and intraspecific competition become important in this limited resource, as has been reported in Zootermopsis nevadensis (Hagen, 1858) and Neotermes chilensis (Blattodea: Kalotermitidae) (Blanchard, 1851). The effects of such competition have been described mainly at population and colony levels rather than at the individual level. In eusocial insects such as termites, intraspecific competition constitutes a stress factor imposed to a colony as a whole and should also cause developmental instability in soldiers produced under such conditions. Investment in the production of soldiers involves a trade-off between colony maintenance costs and defense benefits. Hence, we hypothesize that body size and fluctuating asymmetry, two indicators of developmental instability, will increase when two or more colonies of N. chilensis share a piece of wood (high intraspecific competition scenario). Our results showed that soldiers developing in multicolonial substrates were indeed larger and more asymmetric than soldiers developing in unicolonial substrates. The large body size in a soldier could improve its chance to win a physical contest with a non-nestmate opponent; thus, despite the high cost to produce large soldiers in small colonies, larger soldier production could be an adaptative strategy to avoid being outcompeted. However, the effects of deviations from perfect symmetry on soldier performance are not clear.

Vultures feeding on the dark side: current sanitary regulations may not be enough

SummaryIt is widely acknowledged that the conservation of vultures, a group of birds threatened worldwide, requires the management of safe, high-quality human subsidies, free of potentially harmful toxic compounds. Additionally, in Europe, the supply of livestock carcasses is subject to current sanitary regulations. It is largely unknown how vultures use sources of food of different abundance, predictability, or different legal status and how individual features shape these preferences. To answer these questions, we took advantage of information yielded by 35 GPS-tagged adult Eurasian Griffon Vultures Gyps fulvus living in a region of northern Spain, which hosts one of the most important European populations. Our results indicated that vultures preferably used predictable feeding sites, such as carcass dumping sites, intensive farms and landfills which together account for the 62% of the observed feeding sites. Less than 10% of all observed sites had permission of authorities for the disposal of the carcasses. Interestingly, sites with large accumulations of carcasses were less used that those with intermediate amounts of food probably because of high intraspecific competition. In addition, sex and breeding status also played a role with males and breeding birds being more prone to visit the studied intensively managed feeding places. This vulture population is heavily dependent on food sources which are not under legal control where the birds could be at risk of intoxication and pathogen acquisition. Hence, current legal scenario allowing farmers to abandon carcasses in their exploitations seems insufficient. The future of vultures in highly anthropized regions is uncertain if interdictory regulations on the abandonment of carcasses of intensive livestock are applied. Additionally, conservation scenarios based on food subsidization must consider the effects of environmental and individual variability. We need science-based strategies ensuring the long-term viability of avian scavenger populations within a scenario of anthropized landscapes and livestock farming intensification.

Density-by-Diet Interactions during Larval Development Shape Adult Life History Trait Expression and Fitness in a Polyphagous Fly.

AbstractHabitat quality early in life determines individual fitness, with possible long-term evolutionary effects on groups and populations. In holometabolous insects, larval ecology plays a major role in determining the expression of traits in adulthood, but how ecological conditions during the larval stage interact to shape adult life history and fitness, particularly in nonmodel organisms, remains subject to scrutiny. Consequently, our knowledge of the interactive effects of ecological factors on insect development is limited. Here, using the polyphagous fly Bactrocera tryoni, we conducted a fully factorial design where we manipulated larval density and larval diet (protein rich, standard, and sugar rich) to gain insights into how these ecological factors interact to modulate adult fitness. As expected, a protein-rich diet resulted in faster larval development and heavier and leaner adults that were more fecund compared with the standard and sugar-rich diets, irrespective of larval density. Females from the protein-rich larval diet had overall higher reproductive rate (i.e., eggs per day) than females from other diets, and reproductive rate decreased linearly with density for females from the protein-rich diet but nonlinearly for females from the standard and sugar-rich diets over time. Surprisingly, adult lipid reserve increased with larval density for adults from the sugar-rich diet (as opposed to decreasing as in other diets), possibly because of a stress response to an extremely adverse condition during development (i.e., high intraspecific competition and poor nutrition). Together, our results provide insights into how ecological factors early in life interact and shape the fate of individuals through life stages in holometabolous insects.

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

The effect of inter‐ and intraspecific competition on individual and population niche widths: a four‐decade study on two interacting salmonids

Competition is assumed to shape niche widths, affecting species survival and coexistence. Expectedly, high interspecific competition will reduce population niche widths, whereas high intraspecific competition will do the opposite. Here we test in situ how intra‐ and interspecific competition affects trophic resource use and the individual and population niche widths of two lacustrine fish species, Arctic charr and brown trout, covering a 40 year study period with highly contrasting competitive impacts prior to and following a large‐scale fish culling experiment. Initially, an overcrowded Arctic charr population dominated the study system, with brown trout being nearly absent. The culling experiment reduced the littoral Arctic charr density by 80%, whereupon brown trout gradually increased its density in the system. Thus, over the study period, the Arctic charr population went from high to low intraspecific competition, followed by increasing interspecific competition with brown trout. As hypothesized, the relaxed intraspecific competition following the experimental culling reduced individual diet specialization and compressed population niche width of Arctic charr. During the initial increase of the brown trout population, there was a large dietary overlap between the two species. Over the subsequent intensified interspecific competition from the population build‐up of brown trout, their trophic niche overlap chiefly declined due to a dietary shift of Arctic charr towards enhanced zooplankton consumption. Contrary to theoretical expectations, the individual and population niche widths of Arctic charr increased with intensified interspecific competition. In contrast, the diet and niche width of brown trout remained stable over time, confirming its competitive superiority. The large‐scale culling experiment and associated long‐term research revealed pronounced temporal dynamics in trophic niche and resource use of the inferior competitor, substantiating that intra‐ and interspecific competition have large and contrasting impacts on individual and population niches.

Evolutionary loss of thermal acclimation accompanied by periodic monocarpic mass flowering in Strobilanthes flexicaulis

While life history, physiology and molecular phylogeny in plants have been widely studied, understanding how physiology changes with the evolution of life history change remains largely unknown. In two closely related understory Strobilanthes plants, the molecular phylogeny has previously shown that the monocarpic 6-year masting S. flexicaulis have evolved from a polycarpic perennial, represented by the basal clade S. tashiroi. The polycarpic S. tashiroi exhibited seasonal thermal acclimation with increased leaf respiratory and photosynthetic metabolism in winter, whereas the monocarpic S. flexicaulis showed no thermal acclimation. The monocarpic S. flexicaulis required rapid height growth after germination under high intraspecific competition, and the respiration and N allocation were biased toward nonphotosynthetic tissues. By contrast, in the long-lived polycarpic S. tashiroi, these allocations were biased toward photosynthetic tissues. The life-history differences between the monocarpic S. flexicaulis and the polycarpic S. tashiroi are represented by the “height growth” and “assimilation” paradigms, respectively, which are controlled by different patterns of respiration and nitrogen regulation in leaves. The obtained data indicate that the monocarpic S. flexicaulis with the evolutionary loss of thermal acclimation may exhibit increased vulnerability to global warming.

First small-sized Dinofelis: Evidence from the Plio-Pleistocene of North Africa

We describe small-sized specimens of the metailurine felid Dinofelis from a new Plio-Pleistocene site in North Africa. Dinofelis is a genus of saber-toothed cats mainly recorded from East and South Africa with numerous leopard to jaguar-sized species. The described specimens, clearly smaller than all the other African Dinofelis, resemble isolated remains from the Late Pliocene of France and the Early Pleistocene of Africa. Present evidence suggests that our form represents a new species and/or new lineage of Dinofelis, smaller and probably occupying a different ecological niche compared to the previously known members of the genus, and thus it adds complexity to the high intraspecific competition among large carnivorans in the Plio-Pleistocene of Africa.

Individual behavioural traits not social context affects learning about novel objects in archerfish

Learning can enable rapid behavioural responses to changing conditions but can depend on the social context and behavioural phenotype of the individual. Learning rates have been linked to consistent individual differences in behavioural traits, especially in situations which require engaging with novelty, but the social environment can also play an important role. The presence of others can modulate the effects of individual behavioural traits and afford access to social information that can reduce the need for ‘risky’ asocial learning. Most studies of social effects on learning are focused on more social species; however, such factors can be important even for less-social animals, including non-grouping or facultatively social species which may still derive benefit from social conditions. Using archerfish, Toxotes chatareus, which exhibit high levels of intra-specific competition and do not show a strong preference for grouping, we explored the effect of social contexts on learning. Individually housed fish were assayed in an ‘open-field’ test and then trained to criterion in a task where fish learnt to shoot a novel cue for a food reward—with a conspecific neighbour visible either during training, outside of training or never (full, partial or no visible presence). Time to learn to shoot the novel cue differed across individuals but not across social context. This suggests that social context does not have a strong effect on learning in this non-obligatory social species; instead, it further highlights the importance that inter-individual variation in behavioural traits can have on learning.Significance statementSome individuals learn faster than others. Many factors can affect an animal’s learning rate—for example, its behavioural phenotype may make it more or less likely to engage with novel objects. The social environment can play a big role too—affecting learning directly and modifying the effects of an individual’s traits. Effects of social context on learning mostly come from highly social species, but recent research has focused on less-social animals. Archerfish display high intra-specific competition, and our study suggests that social context has no strong effect on their learning to shoot novel objects for rewards. Our results may have some relevance for social enrichment and welfare of this increasingly studied species, suggesting there are no negative effects of short- to medium-term isolation of this species—at least with regards to behavioural performance and learning tasks.

Arbuscular mycorrhizal colonization rate of an exotic plant, Galinsoga quadriradiata, in mountain ranges changes with altitude.

Arbuscular mycorrhizal fungi (AMF) are suggested to be important for invasions by many exotic plants. However, it is not yet known how associations between AMF and invasive plant populations change in mountains ranges and how changed associations affect further expansion of different populations in new habitats. We conducted a field survey to detect AMF colonization rate of the invasive Galinsoga quadriradiata along an elevational gradient ranging from 223 to 1947masl in the Qinling and Bashan Mountains, China. Additionally, a greenhouse experiment was conducted to compare plant growth performance among five elevational populations. In the field, total plant mass and seed production, as well as root AMF colonization rate, significantly decreased with elevation. When populations were grown in a novel soil environment in the greenhouse, the high-altitude populations achieved higher seed and total mass at lower AMF colonization rate than the low-altitude populations. Moreover, high AMF association was related to high intraspecific competition within low-altitude populations and limited seed production. Our results revealed that the associations between AMF and G. quadriradiata decrease with altitude in mountain ranges, and this may indicate that differentiation of association between AMF and elevational populations occurs during range expansion of G. quadriradiata. The results of the greenhouse experiment suggest that the high-altitude populations are more aggressive than the low-altitude populations in a non-stressful environment.

Intraspecific sexual competition in the clonal gynodioecious herb Glechoma hederacea in response to patchy nutrient distribution

Plants have developed numerous strategies to maximise resource uptake in response to the highly heterogeneous resource distribution in soils. Clonal growth enables plants to scavenge larger surfaces, potentially maximising nutrient acquisition by selectively growing in nutrient-rich patches. However, the production of clonal units put plants into higher intraspecific competition. In gynodioecious clonal plants, genders usually exhibit sexual dimorphism in several growth and life history traits, but whether the genders have different competitive abilities and whether these are affected by nutrient distribution is underexplored. Here, we investigated whether the genders of Glechoma hederacea have different competitive abilities and whether these are affected by soil nutrient distribution using a greenhouse pot experiment. Female and hermaphrodite ramets were grown either alone or in competition with the same or the opposite gender in two different soil nutrient distributions for four months. Our results show that competition was the strongest factor affecting biomass accumulation and allocation. Females and hermaphrodites showed little sexual dimorphism in total biomass accumulation, but they differed in how they allocated this biomass between roots and shoots and in their clonal growth strategies in response to soil nutrient distribution. Taken together, our results indicate that soil nutrient distribution affects the competitive abilities of G. hederacea in a gender-specific manner. In the field, these differences would determine the structure and the dynamics of the two genders within the populations.