Allelopathy (i.e. chemical interactions between plants) is known to affect individual performance, community structure and plant invasions. Yet, a quantitative synthesis is lacking. Here, we ...performed a meta‐analysis of 384 studies that measured allelopathic effects of one species (allelopathy plant) on another species or itself (test plant). Overall, allelopathy reduced plant performance by 25%, but the variation in allelopathy was high. The type of method affected the allelopathic effect: compared to leachates, allelopathy was more negative when residues of allelopathy plants were applied, and less negative when soil conditioned by allelopathy plants was applied. The negative effects of allelopathy diminished with study duration, and increased with concentrations of leachates or residues. Although allelopathy was not significantly related to lifespan, life form or domestication of the interacting plants, it became more negative with increasing phylogenetic distance. Moreover, native plants suffered more from leachates of naturalised alien plants than from leachates of other native plants. Our synthesis reveals that allelopathy could contribute to success of alien plants. The negative relationship between phylogenetic distance and allelopathy indicates that allelopathy might contribute to coexistence of closely related species (i.e. convergence) or dominance of single species.
Our meta‐analysis showed that allelopathy reduced plant performance by 25%, but the variation was high. The allelopathic effect was related to evolutionary history, indicating the role of allelopathy in species coexistence and plant invasion. We also reveal some major caveats in our current knowledge and provide suggestions for future studies.
Microbes are typically surrounded by different strains and species with whom they compete for scarce nutrients and limited space. Given such challenging living conditions, microbes have evolved many ...phenotypes with which they can outcompete and displace their neighbours: secretions to harvest resources, loss of costly genes whose products can be obtained from others, stabbing and poisoning neighbouring cells, or colonising spaces while preventing others from doing so. These competitive phenotypes appear to be common, although evidence suggests that, over time, competition dies down locally, often leading to stable coexistence of genetically distinct lineages. Nevertheless, the selective forces acting on competition and the resulting evolutionary fates of the different players depend on ecological conditions in a way that is not yet well understood. Here, we highlight open questions and theoretical predictions of the long-term dynamics of competition that remain to be tested. Establishing a clearer understanding of microbial competition will allow us to better predict the behaviour of microbes, and to control and manipulate microbial communities for industrial, environmental, and medical purposes.
Behavioral interference between species, such as territorial aggression, courtship, and mating, is widespread in animals. While aggressive and reproductive forms of interspecific interference have ...generally been studied separately, their many parallels and connections warrant a unified conceptual approach. Substantial evidence exists that aggressive and reproductive interference have pervasive effects on species coexistence, range limits, and evolutionary processes, including divergent and convergent forms of character displacement. Alien species invasions and climate change-induced range shifts result in novel interspecific interactions, heightening the importance of predicting the consequences of species interactions, and behavioral interference is a fundamental but neglected part of the equation. Here, we outline priorities for further theoretical and empirical research on the ecological and evolutionary consequences of behavioral interference.
Aggressive and reproductive forms of behavioral interference between species are widespread in animals and share many parallels in their underlying causes and their ecological and evolutionary effects.
Behavioral interference can determine whether species coexist and, thus, affects species ranges, the persistence of native species, and the spread of invasive species.
As species ranges shift under environmental change and new interspecific interactions arise, it will be important to incorporate knowledge of behavioral interference into ecological forecasts and conservation planning.
Behavioral interference can drive both divergent and convergent character displacement processes and thereby contribute to phenotypic diversity and speciation.
Evidence is accumulating that behavioral interference has shaped large-scale ecological and evolutionary patterns.
The diverse ecology of parasitoids is shaped by extrinsic competition, i.e., exploitative or interference competition among adult females and males for hosts and mates. Adult females use an array of ...morphological, chemical, and behavioral mechanisms to engage in competition that may be either intra- or interspecific. Weaker competitors are often excluded or, if they persist, use alternate host habitats, host developmental stages, or host species. Competition among adult males for mates is almost exclusively intraspecific and involves visual displays, chemical signals, and even physical combat. Extrinsic competition influences community structure through its role in competitive displacement and apparent competition. Finally, anthropogenic changes such as habitat loss and fragmentation, invasive species, pollutants, and climate change result in phenological mismatches and range expansions within host-parasitoid communities with consequent changes to the strength of competitive interactions. Such changes have important ramifications not only for the success of managed agroecosystems, but also for natural ecosystem functioning.
Killer toxins are proteins that are often glycosylated and bind to specific receptors on the surface of their target microorganism, which is then killed through a target-specific mode of action. The ...killer phenotype is widespread among yeast and about 100 yeast killer species have been described to date. The spectrum of action of the killer toxins they produce targets spoilage and pathogenic microorganisms. Thus, they have potential as natural antimicrobials in food and for biological control of plant pathogens, as well as therapeutic agents against animal and human infections. In spite of this wide range of possible applications, their exploitation on the industrial level is still in its infancy. Here, we initially briefly report on the biodiversity of killer toxins and the ecological significance of their production. Their actual and possible applications in the agro-food industry are discussed, together with recent advances in their heterologous production and the manipulation for development of peptide-based therapeutic agents.
One of the most important ways that bacteria compete for resources and space is by producing antibiotics that inhibit competitors. Because antibiotic production is costly, the biosynthetic gene ...clusters coordinating their synthesis are under strict regulatory control and often require "elicitors" to induce expression, including cues from competing strains. Although these cues are common, they are not produced by all competitors, and so the phenotypes causing induction remain unknown. By studying interactions between 24 antibiotic-producing strains of streptomycetes, we show that strains commonly inhibit each other's growth and that this occurs more frequently if strains are closely related. Next, we show that antibiotic production is more likely to be induced by cues from strains that are closely related or that share secondary metabolite biosynthetic gene clusters (BGCs). Unexpectedly, antibiotic production is less likely to be induced by competitors that inhibit the growth of a focal strain, indicating that cell damage is not a general cue for induction. In addition to induction, antibiotic production often decreases in the presence of a competitor, although this response was not associated with genetic relatedness or overlap in BGCs. Finally, we show that resource limitation increases the chance that antibiotic production declines during competition. Our results reveal the importance of social cues and resource availability in the dynamics of interference competition in streptomycetes.
Bacteria secrete antibiotics to inhibit their competitors, but the presence of competitors can determine whether these toxins are produced. Here, we study the role of the competitive and resource environment on antibiotic production in
, bacteria renowned for their production of antibiotics. We show that
cells are more likely to produce antibiotics when grown with competitors that are closely related or that share biosynthetic pathways for secondary metabolites, but not when they are threatened by competitor's toxins, in contrast to predictions of the competition sensing hypothesis.
cells also often reduce their output of antibiotics when grown with competitors, especially under nutrient limitation. Our findings highlight that interactions between the social and resource environments strongly regulate antibiotic production in these medicinally important bacteria.
Abstract
Interspecific competition from introduced and naturally colonizing species has potential to affect resident populations, but demographic consequences for vertebrates have rarely been tested. ...We tested hypotheses of interspecific and intraspecific competition for density, body mass, and fertility of adult female Roe Deer (Capreolus capreolus) across a heterogeneous forest landscape occupied by two introduced deer species: Mediterranean Fallow Deer (Dama dama); and subtropical Reeve’s Muntjac (Muntiacus reevesi). Species-specific deer densities in buffers around culling locations of 492 adult female Roe Deer, sampled over seven years, were extracted from spatially explicit models calibrated through annual nocturnal distance sampling. Roe Deer fertility and body mass were related to species-specific deer densities and extent of arable lands using piecewise structural equation models. Reeve’s Muntjac density was lower at higher Fallow Deer densities, suggesting interspecific avoidance via interference competition, but greater when buffers included more arable land. Roe Deer body mass was marginally greater when buffers included more arable land and was independent of deer densities. However, Roe Deer fertility was unrelated to female body mass, suggesting that fertility benefits exceeded an asymptotic threshold of body condition in this low-density population. However, Roe Deer fertility was slightly greater rather than reduced in areas with greater local Roe Deer density, suggesting negligible intraspecific competition. In contrast, Roe Deer was less fertile in areas with greater Reeve’s Muntjac densities; thus, interspecific exceeded intraspecific competition in this assemblage. In contrast, we found no support for any effects of Fallow Deer density on Roe Deer density, body mass, or fertility. Complex networks of interspecific competition operating in this deer assemblage include: interspecific interference from Fallow Deer exceeded habitat effects for Reeve’s Muntjac; and interspecific competition from introduced, smaller sedentary Reeve’s Muntjac reduced fertility, unlike intraspecific, or potential competition with larger, more mobile, Fallow Deer for native Roe Deer. Mechanisms driving Roe Deer fertility may include interspecific behavioral interference or stress–resource depletion is considered less likely because Roe Deer fertility was independent of body mass. Findings emphasize the importance of ensuring appropriate management strategies for controlling invasive species.
Costly interactions between species that arise as a by-product of ancestral similarities in communication signals are expected to persist only under specific evolutionary circumstances. Territorial ...aggression between species, for instance, is widely assumed to persist only when extrinsic barriers prevent niche divergence or selection in sympatry is too weak to overcome gene flow from allopatry. However, recent theoretical and comparative studies have challenged this view. Here we present a large-scale, phylogenetic analysis of the distribution and determinants of interspecific territoriality. We find that interspecific territoriality is widespread in birds and strongly associated with hybridization and resource overlap during the breeding season. Contrary to the view that territoriality only persists between species that rarely breed in the same areas or where niche divergence is constrained by habitat structure, we find that interspecific territoriality is positively associated with breeding habitat overlap and unrelated to habitat structure. Furthermore, our results provide compelling evidence that ancestral similarities in territorial signals are maintained and reinforced by selection when interspecific territoriality is adaptive. The territorial signals linked to interspecific territoriality in birds depend on the evolutionary age of interacting species, plumage at shallow (within-family) timescales, and song at deeper (between-family) timescales. Evidently, territorial interactions between species have persisted and shaped phenotypic diversity on a macroevolutionary timescale.
Red or purple coloration of abaxial (lower) leaf surfaces is a taxonomically-widespread phenomenon that has evolved independently in multiple plant lineages. The trait has long been associated with ...deeply-shaded forest understory habitats, but also occurs in many taxa adapted to high light, including aquatic plants with floating leaves, and herbs that thrive in sun-exposed meadows, rocks, or cliff faces. We surveyed the literature for information related to the taxonomic and environmental distribution of plants displaying abaxial leaf reddening, the chemical structures and anatomical locations of pigments associated with abaxial leaf reddening (if known), and the physiological and ecological (e.g., defensive– anti-herbivory and anti-pathogenic) hypotheses proposed to explain their occurrence. We report examples of abaxial leaf reddening in more than 50 angiosperm families and 100 genera, as well as analogous coloration in some basal plant lineages (e.g., selaginellins in ventral surfaces of Selaginella microphylls, auronidins in ventral surfaces of liverwort thalli). Leaf-warming was one of the first hypotheses proposed for abaxial leaf reddening (19th century); while slight (1–2 °C) warming effects were reported, few studies have since successfully corroborated these early results. Lee et al. (1979) proposed that abaxial red pigments back-scatter red-photons, maximizing light capture efficiency of the leaf in light-limited environments. This hypothesis was largely refuted by later studies. The photoprotection hypothesis is currently the most well-supported explanation for abaxial leaf reddening, whereby red pigments function to attenuate excess photons either directly incident on the abaxial surface of inclined/inverted leaves, or transmitted through adaxial cell layers. This function is beneficial in understory environments exposed to frequent high-light events (e.g., sunflecks, sungaps), as well as in high light environments or seasons. However, this case is far from “closed”, as photoprotective effects have only been shown for a few select species, and many ecological hypotheses (e.g., aposematism, leaf camouflage, undermining insect camouflage, defense from fungi, interference competition) have not been fully tested.
•Abaxial leaf reddening evolved many times, occurring in >50 angiosperm families.•Structure (and color) of abaxial red pigments is largely influenced by phylogeny.•Photoprotection is the most well-supported hypothesis for this leaf trait.•Warming and interference competition hypotheses need more experimental support.•Hypotheses not tested fully include aposematism, camouflage, anti-fungal defense.
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