Testing for effects of climate change on competitive relationships and coexistence between two bird species

Climate change is expected to have profound ecological effects, yet shifts in competitive abilities among species are rarely studied in this context. Blue tits (Cyanistes caeruleus) and great tits (Parus major) compete for food and roosting sites, yet coexist across much of their range. Climate change might thus change the competitive relationships and coexistence between these two species. Analysing four of the highest-quality, long-term datasets available on these species across Europe, we extend the textbook example of coexistence between competing species to include the dynamic effects of long-term climate variation. Using threshold time-series statistical modelling, we demonstrate that long-term climate variation affects species demography through different influences on density-dependent and density-independent processes. The competitive interaction between blue tits and great tits has shifted in one of the studied sites, creating conditions that alter the relative equilibrium densities between the two species, potentially disrupting long-term coexistence. Our analyses show that long-term climate change can, but does not always, generate local differences in the equilibrium conditions of spatially structured species assemblages. We demonstrate how long-term data can be used to better understand whether (and how), for instance, climate change might change the relationships between coexisting species. However, the studied populations are rather robust against competitive exclusion.     

Interspecific competition in perennial sedentary organisms: An individual-based model

We investigated a mathematical model of the dynamics of the ecological system consisting of two competing perennial species, each of which leads a sedentary life. It is an individual-based model, in which the growth of each individual is described. The rate of this growth is weakened by competition from neighboring individuals. The strength of the competitors' influence depends on their size and distance to them. The conditions, in which the competitive exclusion of one of the competitors and the coexistence of both competitors take place are provided. The influence of the parameters responsible for the strength of competition, the degree of competitive asymmetry, and consideration of the importance of specific elements of the spatial structure of this ecological system on the results of the competition were analyzed. Both species co-exist when they are equal competitors. Permanent coexistence is possible only when interspecific competition is weaker than intraspecific. When interspecific competition is stronger, the coexistence of equal interspecific competitors is random. Both species have equal probability of extinction. If species are not equal competitors, the stronger one wins. This result can be modified by different strengths of intraspecific competition. The weaker interspecific competitor can permanently coexist with stronger one, when its individuals suffer stronger intraspecific competition.     

Competitive exclusion,beta diversity,and deterministic vs. stochastic drivers of community assembly

Species diversity has two components – number of species and spatial turnover in species composition (beta‐diversity). Using a field experiment focusing on a system of Mediterranean grasslands, we show that interspecific competition may influence the two components in the same direction or in opposite directions, depending on whether competitive exclusions are deterministic or stochastic. Deterministic exclusions reduce both patch‐scale richness and beta‐diversity, thereby homogenising the community. Stochastic extinctions reduce richness at the patch scale, but increase the differences in species composition among patches. These results indicate that studies of competitive effects on beta diversity may help to distinguish between deterministic and stochastic components of competitive exclusion. Such distinction is crucial for understanding the causal relationship between competition and species diversity, one of the oldest and most fundamental questions in ecology.     

Carrion fly community dynamics: patchiness, seasonality and coexistence

ABSTRACT. 1. An outdoor cage experiment was conducted to test the theory that localized interactions facilitate coexistence of species breeding in ephemeral habitats. The same amount of larval resource (50 g of liver) but divided into one, two, four, eight or sixteen pieces was placed into each of fifteen cages once a week from June to September for 4 years.
2. The cage populations were initially mixtures of thirteen species but after 4 years only Lucilia illustris (Meig.), Sarcophaga scoparia Pand. and S.aratrix Pand. remained. Lucilia illustris , by far the most abundant species in the field, predominated in every cage.
3. Sarcophaga went extinct in most cages, but they survived in five cages in which the larval resource was much divided, in agreement with the theoretical prediction.
4. Lucilia silvarum (Meig.) emerged about a week later than L.illustris in early summer; this phenological difference gave rise to a competitive asymmetry between the two species. This difference appears to explain why L.silvarum went extinct in the cages in 3 years, and it may explain why L.silvarum has consistently been less abundant than L.illustris in the natural community.
5. Other differences in phenology, voltinism and rate of development in the flies are described, and such differences are suggested to facilitate regional coexistence of many species in seasonal environments.     

Competitive exclusion through reproductive interference

A simple differential equation model was developed to describe the competitive interaction that may occur between species through reproductive interference. The model has the form comparable to Volterra's competition equations, and the graphical analysis of the outcome of the two-species interaction based on its zero-growth isoclines proved that: (1) The possible outcome in this model, as in usual models of resource competition, is either stable coexistence of both species or gradual exclusion of one species by the other, depending critically upon the values of the activity overlapping coefficient c_ij; (2) but, for the same c_ij-values, competitive exclusion is much more ready to occur here than in resource competition; (3) and moreover, the final result of the competition is always dependent on the initial-condition due to its non-linear isoclines, i.e., even under the parameter condition that generally allows both species to coexist, an extreme bias in intial density to one species can readily cause subsequent complete exclusion of its counterparts. Thus, it may follow that the reproductive interference is likely to be working in nature as an efficient mechanism to bring about habitat partitioning in either time or space between some closely related species in insect communities, even though they inhabit heterogeneous habitats where resource competition rarely occurs so that they could otherwise attain steady coexistence.     

生物竞争排斥对油藏微生物群落结构变化影响

【目的】海上S油田采用生物竞争排斥技术治理油藏硫化氢产出取得一定成效,本研究通过揭示该技术对油藏环境中微生物群落结构的影响,尝试研究硫化氢治理过程中产生效果差异的因素。【方法】采用高通量测序分析等方法对加入硝酸盐、亚硝酸盐等药剂后,治理效果低效井、高效井及未治理井中不同微生物群落结构变化进行分析。【结果】与低效井和未治理井相比,高效井中的反硝化菌和石油降解菌种类和丰度明显增加,其中石油降解菌增加24.14%,反硝化细菌增加5.23%;Fe²⁺、Zn²⁺等离子的存在对不同井间治理效果差异和微生物群落变化具有一定影响。【结论】海上油田硫化氢治理中,生物竞争排斥技术不仅可以明显降低硫化氢产出,同时对油藏微生物群落环境也影响显著,微生物群落结构分析可作为硫化氢治理效果评价的重要指标,为海上油田硫化氢治理工作提供技术支持。     

Phylogenetic limiting similarity and competitive exclusion

One of the oldest ecological hypotheses, proposed by Darwin, suggests that the struggle for existence is stronger between more closely related species. Despite its long history, the validity of this phylogenetic limiting similarity hypothesis has rarely been examined. Here we provided a formal experimental test of the hypothesis using pairs of bacterivorous protist species in a multigenerational experiment. Consistent with the hypothesis, both the frequency and tempo of competitive exclusion, and the reduction in the abundance of inferior competitors, increased with increasing phylogenetic relatedness of the competing species. These results were linked to protist mouth size, a trait potentially related to resource use, exhibiting a significant phylogenetic signal. The likelihood of coexistence, however, was better predicted by phylogenetic relatedness than trait similarity of the competing species. Our results support phylogenetic relatedness as a useful predictor of the outcomes of competitive interactions in ecological communities.     

外来物种入侵后的多物种竞争共存的集合种群模型

基于多物种竞争共存模型,提出外来物种与本地物种竞争共存途径的两种假想:外来物种通过插队竞争与本地物种实现共存;外来物种通过等位竞争与本地物种实现共存.并提出根据外来物种在两种竞争共存模式下占据生境斑块比例的稳定值大小来判断外来物种和本地物种的竞争共存途径.根据两种假想,分别建立了外来物种插队竞争共存模型和等位竞争共存模型.通过应用数学软件Mathematica 4.0对两个模型进行了模拟,得出以下结论:在外来物种与本地物种竞争共存状态下,如果外来物种通过插队竞争与本地物种实现共存,当本地物种竞争力差异较大时,外来物种极易对本地稀少物种构成危害.虽然外来物种不会直接造成本地稀少物种的灭绝,但是会使本地稀少物种的生境斑块急剧减少,增加本地稀少物种灭绝的可能性,而当本地物种竞争力差异较小时,外来物种对本地所有物种的影响都较小.如果外来物种通过等位竞争与本地物种实现共存,无论本地物种竞争力差异大小与否,外来物种只是影响到与其生态位相同的本地物种,影响程度取决于外来物种侵入时所占据生境斑块的比例大小.     

How do similarities in spatial distributions and interspecific associations affect the coexistence of Quercus species in the Baotianman National Nature Reserve,Henan, China

Congeneric species often have similar ecological characteristics and use similar resources. These similarities may make it easier for them to co‐occur in a similar habitat but may also lead to strong competitions that limit their coexistence. Hence, how do similarities in congeneric species affect their coexistence exactly? This study mainly used spatial point pattern analysis in two 1 hm² plots in the Baotianman National Nature Reserve, Henan, China, to compare the similarities in spatial distributions and interspecific associations of Quercus species. Results revealed that Quercus species were all aggregated under the complete spatial randomness null model, and aggregations were weaker under the heterogeneous Poisson process null model in each plot. The interspecific associations of Quercus species to non‐Quercus species were very similar in Plot 1. However, they can be either positive or negative in different plots between the co‐occurring Quercus species. The spatial distributions of congeneric species, interspecific associations with non‐Quercus species, neighborhood richness around species, and species diversity were all different between the two plots. We found that congeneric species did have some similarities, and the closely related congeneric species can positive or negative associate with each other in different plots. The co‐occurring congeneric species may have different survival strategies in different habitats. On the one hand, competition among congenerics may lead to differentiation in resource utilization. On the other hand, their similar interspecific associations can strengthen their competitive ability and promote local exclusion to noncongeneric species to obtain more living space. Our results provide new knowledge for us to better understand the coexistence mechanisms of species.     

Competitive strategies between Anastrepha fraterculus and Anastrepha obliqua (Diptera: Tephritidae) regulating the use of host fruits

Interspecific competition between individuals of different species can result in reductions in their fecundity, growth or survival, reflecting differential exploitation of resources that become intensified due to spatial co-occurrence, ecological similarity and increased population densities. As two species cannot occupy the same niche, coexistence is only possible if the available resources are used in non-overlapping manners such as niche partitioning or the use of refuges. Among agricultural insect pests, such as fruit flies of the family Tephritidae, competitive interactions can result in competitive displacement, host changes, or the expansion or restriction of the numbers of hosts utilized that can have negative consequences for human agricultural activities. We evaluated the competitive interactions between two fruit fly species of the genus Anastrepha, Anastrepha obliqua (Macquart, 1835) and Anastrepha fraterculus (Wiedmann, 1830), on their respective preferred hosts (mangoes and guava). Experiments of larval competition and competition for ovipositioning sites by adult females were performed to compare the parameters of larval development time, numbers of pupae and emerged adults and numbers of ovipositions in the presence or absence of interspecific competition. We observed that the interactions between those species were asymmetrical and hierarchical, and our results suggest a competitive displacement of A. fraterculus by A. obliqua when those two species are present on the same fruit, whether mangoes or guavas.     

Competitive exclusion and coexistence for pathogens in an epidemic model with variable population size

We study an SIR epidemic model with a variable host population size. We prove that if the model parameters satisfy certain inequalities then competition between n pathogens for a single host leads to exclusion of all pathogens except the one with the largest basic reproduction number. It is shown that a knowledge of the basic reproduction numbers is necessary but not sufficient for determining competitive exclusion. Numerical results illustrate that these inequalities are sufficient but not necessary for competitive exclusion to occur. In addition, an example is given which shows that if such inequalities are not satisfied then coexistence may occur.     

Temporal resource partitioning mitigates interspecific competition and promotes coexistence among insect parasites

A key to understanding life's great diversity is discerning how competing organisms divide limiting resources to coexist in diverse communities. While temporal resource partitioning has long been hypothesized to reduce the negative effects of interspecific competition, empirical evidence suggests that time may not often be an axis along which animal species routinely subdivide resources. Here, we present evidence to the contrary in the world's most biodiverse group of animals: insect parasites (parasitoids). Specifically, we conducted a meta-analysis of 64 studies from 41 publications to determine if temporal resource partitioning via variation in the timing of a key life-history trait, egg deposition (oviposition), mitigates interspecific competition between species pairs sharing the same insect host. When competing species were manipulated to oviposit at (or near) the same time in or on a single host in the laboratory, competition was common, and one species was typically inherently superior (i.e. survived to adulthood a greater proportion of the time). In most cases, however, the inferior competitor could gain a survivorship advantage by ovipositing earlier (or in a smaller number of cases later) into shared hosts. Moreover, this positive (or in a few cases negative) priority advantage gained by the inferior competitor increased as the interval between oviposition times became greater. The results from manipulative experiments were also correlated with patterns of life-history timing and demography in nature: the more inherently competitively inferior a species was in the laboratory, the greater the interval between oviposition times of taxa in co-occurring populations. Additionally, the larger the interval between oviposition times of competing taxa, the more abundant the inferior species was in populations where competitors were known to coexist. Overall, our findings suggest that temporal resource partitioning via variation in oviposition timing may help to facilitate species coexistence and structures diverse insect communities by altering demographic measures of species success. We argue that the lack of evidence for a more prominent role of temporal resource partitioning in promoting species coexistence may reflect taxonomic differences, with a bias towards larger-sized animals. For smaller species like parasitic insects that are specialized to attack one or a group of closely related hosts, have short adult lifespans and discrete generation times, compete directly for limited resources in small, closed arenas and have life histories constrained by host phenology, temporal resource subdivision via variation in life history may play a critical role in allowing species to coexist by alleviating the negative effects of interspecific competition.     

叶蜂总科生物地理研究IV东亚区特有属的分布式样及迁移路线(膜翅目)

本文分析归纳了东亚叶蜂总科特有属的分布式样及迁移路线。东亚区分布的１７９个叶蜂总科特有属可归纳为１个主要特化中心：川滇缅高原;５个小型次级特化中心：喜马拉雅中段小中心、浙闽山地小中心、秦巴山地小中心、燕山山地小中心和长白山地小中心;４条主要迁移演化路线：从主要中心沿喜马拉雅山脉走廊向西发展的西线,从主要中心沿缅－马走廊向南发展的南线,从主要中心沿南岭走廊向东发展的东线,从主要中心向北沿第二阶梯东缘走廊（大娄山－伏牛山－太行山－燕山）及西部走廊（第一阶梯东缘走廊）发展的北线,其中北线因四川盆地隔离可分为东西两支,但东西两支从秦岭山脉始重新部分融合;一个中心区域类型和３８种分布式样。     

陆生食肉动物竞争与共存研究概述

陆生食肉动物(食肉目哺乳动物, 以下简称食肉动物)作为食物链与营养级的高位物种对维持生态系统结构与功能稳定性起到重要作用。过度人类干扰已在全球范围内造成食肉动物种群数量剧烈下降和栖息地质量显著退化, 探究食肉动物的区域共存机制对理解生物群落构建、濒危物种保护与管理具有重要意义。本文通过梳理100余篇有关食肉动物在空间、时间和营养3个生态位维度上相互作用的研究, 分析了体型大小、猎物组成、种群结构、环境差异、人类干扰和气候变化等因素对食肉动物种间关系和区域共存的影响, 并对今后食肉动物区域共存研究中亟需解决的问题进行了展望。食肉动物通过生态位分离达到共存并没有单一的理论解释, 猎物、栖息地和人类干扰等因素可以调节食肉动物相互作用关系并直接或间接地影响共存, 共同适应在食肉动物区域共存中具重要作用。食肉动物区域共存是经过长期演化形成的相对稳定状态, 需要以动态的眼光去审视。要明晰生态位重叠与区域共存机制的区别与联系, 在理解生态位分离的基础上, 结合生活史、家域和行为等对食肉动物共存进行综合分析。     

Vertical community structure and resource utilization in neotropical forest cockroaches

ABSTRACT.

• 1 Patterns of vertical habitat use of ten species of cockroaches are examined. Three assemblages of cockroaches are recognized on the basis of morphology, foraging behaviour, foraging heights, and overlaps and breadths of vertical distributions.
• 2 Three apterous and brachypterous species occur near the ground and comprise one assemblage. They feed mainly on material in the leaf-litter.
• 3 Species that perch higher either migrate into the leaf-litter on a diel basis and feed on both leaf-litter and epiphyllic materials, or some are strictly arboreal and forage on algae, liverworts, lichens, spores, pollen and trichomes on the surfaces of leaves.
• 4 Trophic and behavioural correlations with perch height are described and the functions of perching are examined.
• 5 We conclude that studies of interactions among species are confounded by our lack of understanding of stage- and sex-specific interactions of coexisting species. A simplistic ‘species’approach to such interactions is inadequate because it does not recognize intraspecific variation.

     

集合种群模拟模型及其在竞争共存机制与物种多样性研究中的应用

以荒漠区人工植被的恢复与重建为背景,从宏观尺度研究了很集合种群的空间分布新模式,建立了基于Levins集合种群模型的数值模拟方法。对两物种的模拟结果表明：在适当选择参数下,模拟植被区的集合种群可以形成“海藻式”稳定的时空分布结构,在理论上表明相同生态特征的物种在空间生境中可以达成共存。为了达到物种丰富度和生产力最佳,实现持续发展,对多物种集合种群进行了模拟。模拟结果显示当物种的种数为5时,空间上随机播种的模拟种群覆盖率达到最大,因而可发挥最大的治沙作用。另外,模拟还显示在播种时应采取集聚式的空间播种模式,以使种群具有较高的防沙能力。该结果可为生物防沙治沙领域提供理论依据。     

Distance-limited dispersal promotes coexistence at habitat boundaries: reconsidering the competitive exclusion principle

Understanding the conditions for the stable coexistence of different alleles or species is a central topic in theoretical evolution and ecology. Different causes for stable polymorphism or species coexistence have already been identified but they can be grouped into a limited number of general processes. This article is devoted to the presentation and illustration of a new process, which we call 'habitat boundary polymorphism', and which relies on two key ingredients: habitat heterogeneity and distance-limited dispersal. Under direct competition and with fixed population densities, we show that this process allows for the equilibrium coexistence of more than n types in a n-habitat environment. Distance-limited dispersal indeed creates local maladaptation at habitat edges, which leaves room for the invasion of more generalist alleles or species. This mechanism provides a generic yet neglected process for the maintenance of polymorphism or species coexistence.     

Trophic resource partitioning drives fine‐scale coexistence in cryptic bat species

Understanding the processes that enable species coexistence has important implications for assessing how ecological systems will respond to global change. Morphology and functional similarity increase the potential for competition, and therefore, co‐occurring morphologically similar but genetically unique species are a good model system for testing coexistence mechanisms. We used DNA metabarcoding and high‐throughput sequencing to characterize for the first time the trophic ecology of two recently described cryptic bat species with parapatric ranges, Myotis escalerai and Myotis crypticus. We collected fecal samples from allopatric and sympatric regions and from syntopic and allotopic locations within the sympatric region to describe the diets both taxonomically and functionally and compare prey consumption with prey availability. The two bat species had highly similar diets characterized by high arthropod diversity, particularly Lepidoptera, Diptera and Araneae, and a high proportion of prey that is not volant at night, which points to extensive use of gleaning. Diet overlap at the prey item level was lower in syntopic populations, supporting trophic shift under fine‐scale co‐occurrence. Furthermore, the diet of M. escalerai had a marginally lower proportion of not nocturnally volant prey in syntopic populations, suggesting that the shift in diet may be driven by a change in foraging mode. Our findings suggest that fine‐scale coexistence mechanisms can have implications for maintaining broad‐scale diversity patterns. This study highlights the importance of including both allopatric and sympatric populations and choosing meaningful spatial scales for detecting ecological patterns. We conclude that a combination of high taxonomic resolution with a functional approach helps identify patterns of niche shift.