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The relative importance of competition and predation in environment characterized by resource pulses – an experimental test with a microbial community
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Resource availability and predation are believed to affect community dynamics and composition. Although the effects of resource availability and predation on prey communities are usually studied in isolation, these factors can also have interactive effects, especially since the outcome of competition under shared predation is expected to depend on resource availability. However, there are few experimental studies that test the interactive roles of resources and predation on dynamics of more complex multispecies communities. Here, we examine the importance of competition and predation on microbial community dynamics in a resource pulse environment.
We manipulated resource availability and predation simultaneously in a microbial microcosm experiment, where a bacterial community was exposed to the protozoan predator Tetrahymena thermophila in three different resource concentrations (low, intermediate and high). The prey community consisted of three heterotrophic bacterial species: Bacillus cereus, Serratia marcescens and Novosphingobium capsulatum, all feeding on a shared plant detritus medium. In fresh culture media, all species grew in all resource concentrations used. However, during experiments without any addition of extra resources, the existing resources were soon depleted to very low levels, slowing growth of the three bacterial species. Prior to the microcosm experiment, we measured the competitive ability and grazing resistance, i.e. reduced vulnerability to predation, of each prey species. The three species differed in allocation patterns: in general, N. capsulatum had the best competitive abilities and B. cereus had good grazing resistance abilities. In the long-term microcosm experiment, N. capsulatum dominated the community without predation and, with predation, B. cereus was the dominant species in the intermediate and high resource environments.
Short-term, single-species assays revealed significant differences in the allocation of competitive and defensive traits among the prey species. Based on these differences, we were, to some extent, able to predict how the long-term community structure, e.g. species dominance, is modified by the resource availability and predation interaction in pulsed resource environments. Our results are consistent with theoretical predictions and also highlight the importance of interactive effects of resource competition and predation, suggesting that these factors should not be studied in isolation.
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... Dispersal, an ecological process involving the movement of individual/multiple species, is one of the main determinants shaping the structure of ecological communities and maintaining the biodiversity [13,22,23]. The causes and consequences as well as the selection and evolution of dispersal strategies have been central questions in ecology extensively investigated in the literature (cf. ...
This paper is concerned with existence, non-existence and uniqueness of positive (coexistence) steady states to a predator-prey system with density-dependent dispersal. To overcome the analytical obstacle caused by the cross-diffusion structure embedded in the density-dependent dispersal, we use a variable transformation to convert the problem into an elliptic system without cross-diffusion structure. The transformed system and pre-transformed system are equivalent in terms of the existence or non-existence of positive solutions. Then we employ the index theory alongside the method of the principle eigenvalue to give a nearly complete classification for the existence and non-existence of positive solutions. Furthermore we show the uniqueness of positive solutions and characterize the asymptotic profile of solutions for small or large diffusion rates of species. Our results pinpoint the positive role of density-dependent dispersal on the population dynamics for the first time by showing that the density-dependent dispersal is a beneficial strategy promoting the coexistence of species in the predator-prey system by increasing the chance of predator's survival.
... Several studies have evaluated the functional responses of coccinellids, both individually (Bayoumy 2011a;Osman and Bayoumy 2011;Gupta et al. 2012) and within guilds (Snyder and Ives 2003;Snyder 2009;Grez et al. 2011Grez et al. , 2012Omkar and Pervez 2011;Jamour and Shishehbor 2012;Vanaclocha et al. 2013;Kumar et al. 2014a), and report either a type II or a modified type II functional response. Despite the important role of predation in shaping community structure, comparisons of functional responses of coccinellids under fluctuating-prey conditions are rarely investigated (Hiltunen and Laakso 2013). In addition, the role of learning in modulating the functional response curves of coccinellid beetles has rarely been studied. ...
In the present study, we assessed functional response curves of two generalist coccinellid beetles (Coleoptera: Coccinellidae), specifically Menochilus sexmaculatus and Propylea dissecta, using fluctuating densities of aphid prey as a stimulus. In what may be the first such study, we investigated how the prey density experienced during the early larval development of these two predatory beetle species shaped the functional response curves of the late instar–larval and adult stages. The predators were switched from their rearing prey-density environments of scarce, optimal, or abundant prey to five testing density environments of extremely scarce, scarce, suboptimal, optimal, or abundant prey. The individuals of M. sexmaculatus that were reared on either scarce- and optimal- or abundant-prey densities exhibited type II functional response curves as both larvae and adults. However, individuals of P. dissecta that were reared on scarce- and abundant-prey densities displayed modified type II functional response curves as larvae and type II functional response curves as adults. In contrast, individuals of P. dissecta reared on the optimal-prey density displayed type II functional response curves as larvae and modified type II functional response curves as adults. The fourth-instar larvae and adult females of M. sexmaculatus and P. dissecta also exhibited highest prey consumption (T/Th) and shortest prey-handling time (Th) on the scarce-prey rearing density. Thus, under fluctuating-prey conditions, M. sexmaculatus is a better biological control agent of aphids than P. dissecta is.
... In general, negative interactions between species have traditionally dominated theory in community organization (Weiher and Keddy, 1999). Competition (Cody, 1974;Kelt et al., 1995;Koeppel and Wu, 2014;Letten et al., 2017) and predation (Forsman et al., 2001) have been most commonly invoked as drivers of community assembly (Sinclair, 1985;Weiher et al., 2011;Hiltunen and Laakso, 2013). Competitive interactions are known to influence species distribution and coexistence (MacArthur, 1958;Connell, 1961; also reviewed in Schoener, 1974Schoener, , 1983Rusterholz, 1981) although evidence for this is not unequivocal (Park and Lloyd, 1955). ...
Animals that live in groups may experience positive interactions such as cooperative behavior or negative interactions such as competition from group members depending on group size and similarity between individuals. The effect of group size and phenotypic and ecological similarity on group assembly has not been well-studied. Mixed-species flocks are important subsets of bird communities worldwide. We examined associations within these in relation to flock size, to understand rules of flock assembly, in the Western Ghats of India. We examined the relationship between phenotypic clumping and flock richness using four variables—body size, foraging behavior, foraging height and taxonomic relatedness. Using a null model approach, we found that small flocks were more phenotypically clumped for body size than expected by chance; however, phenotypic clumping decreased as flocks increased in size and approached expected phenotypic variation in large flocks. This pattern was not as clear for foraging height and foraging behavior. We then examined a dataset of 55 flock matrices from 24 sites across the world. We found that sites with smaller flocks had higher values of phenotypic clumping for body size and sites with larger flocks were less phenotypically clumped. This relationship was weakly negative for foraging behavior and not statistically significant for taxonomic relatedness. Unlike most single-species groups, participants in mixed-species flocks appear to be able to separate on different axes of trait similarity. They can gain benefits from similarity on one axis while mitigating competition by dissimilarity on others. Consistent with our results, we speculate that flock assembly was deterministic up to a certain point with participants being similar in body size, but larger flocks tended to approach random phenotypic assemblages of species.
... The species can be maintained either under settings of recurrent sexual reproduction, or as asexual lineages only. The Tetrahymena strain used in our pre-/post-ingestion defence: toxin release [12] Sphingomonas capsulata HAMBI 103 model prey [27] Brevundimonas diminuta HAMBI 18 ...
Predator–prey interactions heavily influence the dynamics of many ecosystems. An increasing body of evidence suggests that rapid evolution and coevolution can alter these interactions, with important ecological implications, by acting on traits determining fitness, including reproduction, anti-predatory defence and foraging efficiency. However, most studies to date have focused only on evolution in the prey species, and the predator traits in (co)evolving systems remain poorly understood. Here, we investigated changes in predator traits after approximately 600 generations in a predator–prey (ciliate–bacteria) evolutionary experiment. Predators independently evolved on seven different prey species, allowing generalization of the predator's evolutionary response. We used highly resolved automated image analysis to quantify changes in predator life history, morphology and behaviour. Consistent with previous studies, we found that prey evolution impaired growth of the predator, although the effect depended on the prey species. By contrast, predator evolution did not cause a clear increase in predator growth when feeding on ancestral prey. However, predator evolution affected morphology and behaviour, increasing size, speed and directionality of movement, which have all been linked to higher prey search efficiency. These results show that in (co)evolving systems, predator adaptation can occur in traits relevant to foraging efficiency without translating into an increased ability of the predator to grow on the ancestral prey type.
... Animal feeding behaviour i.e., to locate, acquire, and consume food resources shaped their characteristics, community interactions, and the development of their complex behaviour to efficiently obtain food and survive (Roberts, 1942;McFarland, 1981). While, the availability of resources and predation are among the most important biotic drivers that shape interactions across wildlife communities (Talbot, 1978;Hiltunen & Laakso, 2013;Glen & Dickman, 2014). Within an ecosystem, when the predator populations decline or are absent, the prey population may dramatically increase (Gese & Knowlton, 2001;Ritchie et al., 2013). ...
Predation of bats in their roosts has previously only been attributed to a limited number of species such as various raptors, owls, and snakes. However, in situations where due to over-crowding and limited roost space, some individuals may be forced to roost in suboptimal conditions, such as around the entrances of caves and may thus be vulnerable to predation by species which would normally be unlikely to predate bats whilst roosting inside caves. Here, we describe the first documented cooperative hunting of the Large-billed Crow, Corvus macrorhynchos Wagler, 1827 (Passeriformes: Corvidae) and opportunistic predation by the Yellow-headed water monitor, Varanus cumingi Martin, 1839 (Squamata: Varanidae) in the world's largest colony of Geoffroy's Rousette, Rousettus amplexicaudatus (É. Geoffroy Saint-Hilaire, 1810) (Chiroptera: Pteropidae) in the Island of Samal, Mindanao, Philippines.
... Likewise, community structure is also massively influenced by the various biotic interactions, which mainly involve food availability and interconnections between species (Woodin & Jackson, 1979; (Fig. 1.1.). Within a community, organisms can interact with each other in varieties of ways, in which competition and predation are believed to strongly affect community dynamics and composition (Coneil, 1961a;Wilson, 1991;Hiltunen & Laakso, 2013). Competition occurs when the interactions between organisms result in a reduction of growth, survival or reproduction for both partners of the interactions (each species affected negatively). ...
Locating between the Amazon and Orinoco Rivers, the 1500 km-long Atlantic coastline of South America are considered as the muddiest areas in the world due to the large discharge of suspended sediment from the Amazon. Despite the extreme morphodynamics of these ecosystems, the Guianas mudflats are important feeding zones for many shorebirds and fish. However, the state of knowledge on benthic organisms associated with these highly unstable environments is still at an exploratory stage. This study, therefore, aims to describe the structure and dynamics of the intertidal benthic infauna in the Guianas mudflats and to define its functioning in such highly unstable tropical muddy environments. As expected, the high instability of the sediment resulted in very low diversity of both macrofauna and meiofauna assemblages. Nonetheless, the infauna communities of the Guianas mudflats showed remarkably high abundance with the predominance of small-sized opportunistic species. A total of 39 operational taxonomic units of macrofauna was recorded while meiofauna was less diverse with the occurrence of 34 taxa. The tanaid Halmyrapseudes spaansi and the polychaeta Sigambra grubii are the two most abundant macrofauna species, which widely distributed along the Guianas coast. Likewise, the nematodes epistrate feeder Pseudochromadora spp. and non-deposit feeders Halomonhystera sp. 1 were the principal components of meiofauna communities in every station. The distribution patterns of the infauna were both site-specific and seasonal variation. The assemblages in estuarine habitat were more diverse than in the bare mudflat habitat, while infauna abundances in the WS were always higher than in the DS. Both abiotic and biotic factors significantly influenced the benthic communities. Nevertheless, the changes in benthic community structure induced by food source availability (chl a) and predation pressure were more prominent than the assemblage variations imposed by abiotic parameters (mud content, salinity…). Particularly, the tight coupling between meiofauna and MPB was observed in both distribution patterns and trophic structures. The isotopic measurements of different intertidal compartments not only revealed the pivotal role of MPB on structuring meiofaunal coummunities, but also indicated the ecological importance of meiofauna as the main food source for the small shorebirds and coastal fish. Meiofauna and MPB entered the diet of three coastal fish in great proportion, whereas the migrating shorebirds showed a wider diet breadth. The isotopic ratios were perfectly matched with the feeding guilds assigned by morphological features. However, the relative contribution of tanaids to the top epibenthic predators were surprisingly lower than expected. The thesis has increased our understanding of the Guianas infauna communities, and revealed for the first time a conceptual food web model of these unique intertidal mudflats.
... lions, and for this reason, their diel movement behaviour pattern is not affected by these natural predators (Tambling et al. 2015). When the risk of predation is always present at a low level, strong responses are not expected, but if the risk fluctuates, prey species exhibit strong behavioural adjustments (Creel and Christianson, 2008, Sheriff et al., 2011, Hiltunen and Laakso, 2013. Human beings are the most important predators of elephants by way of illegal hunting, a practice that is the most significant immediate threat to elephants beside the albeit longer-term habitat loss (Nellemann et al., 2013). ...
The illegal killing of elephants, i.e. poaching and human-elephant related mortality, is the greatest immediate threats to elephants. They have led to declining of many populations of elephants in Africa. The Monitoring of Illegal Killing of Elephants (MIKE) program of the Convention on International Trade in Endangered Species (CITES) was set up in the year 2002 as a framework of monitoring trends in illegal killing in 57 African sites. MIKE program seeks to establish the relationships between the levels of illegal killing of elephants and various possible explanatory variables within and beyond the monitoring sites. The effort in implementing MIKE program vary from site to site, and to make the results comparable; a metric referred to as the Proportion of Illegally Killed Elephants (PIKE) out of all recorded deaths in a site has been adopted as the standard measure of severity of illegal killing.
Loss of habitat due to the expansion of agriculture and infrastructural developments are the largest long-term threats to elephants. The migratory corridors of elephants and other wildlife in many landscapes have been cut off. The majority of wildlife resides outside formally protected areas on private and community lands. In the landscapes shared by wildlife and humans, competition for resources influences the spatial-temporal distributions of wildlife. Efforts to win the goodwill of private and community landowners regarding hosting of wildlife on their lands are ongoing in many sites across the elephant range. Despite the numerous studies on the nature of risk faced by elephants, fewer studies have focused on the behavioural adaptations of elephants living in those risky landscapes.
This thesis sought to understand the site level drivers of illegal killing and how elephants adapt to the threat in Africa’s most intensively monitored site, the Laikipia-Samburu MIKE in northern Kenya. Using field verified records of causes of elephant mortality, the distribution of live elephants, and, the cadastral attributes of land parcels in the ecosystem, the thesis established that land use type is the most important correlate of levels of illegal killing and not its ownership. The study analyses the movement of elephants at hourly, day and night, and overall 24 hr activity cycle in relation to the spatial and temporal variation of the levels of illegal killing. Past studies have given a lot of attention to movement behaviour along corridors. The research in this thesis focusses on movement within core areas. At the hourly time interval, the research showed that elephants walk with lower tortuosity when they are in core areas with higher levels of illegal killing, i.e., higher risk. The study found that elephants move more at night when they are in core areas with higher risk, than when they are in safer core areas. Based on this finding, the research presents a new metric for inferring the levels of risk, i.e., night-day sped ratio. When elephants move from a core area to another one with a different level of risk, they alter their daily activity pattern to include a longer resting phase during the mid-day hours, and this is even more pronounced in core areas closest to permanent human settlements. The study found that as a result of the alteration of activity cycle within 24-hour periods, elephants loose approximately one hour of activity time.
The results have the potential use as a remote means of assessing the spatial and temporal variation of risk by analysing elephant movement behaviour remotely thus complimenting patrol based anti-poaching efforts. The study provides new insight into the ecology of elephants living in fear. The confirmed increase of night-time movement potentially predisposes calves to the savannah predators, who are more active at night.
... This cost of resistance adds to the higher impact of predation on bacterial communities under high nutrient concentrations compared to low nutrient concentrations. The interplay of resource availability, competition, and predation on overall community composition and diversity has been studied especially for aquatic systems (Corno et al. 2008, Hiltunen andLaakso 2013). Nevertheless, very few if any studies have experimentally tested if competitiveness and resistance to predation are correlated with lifehistory traits such as growth rate and if these factors in turn are related to species rarity or abundance in the field. ...
While dam construction supports social and economic development, changes in hydraulic conditions can also affect natural aquatic ecosystems, especially microbial ecosystems. The compositional and functional traits of multi-trophic microbiota can be altered by dam construction, which may result in changes in aquatic predator-prey interactions. To understand this process, we performed a large-scale sampling campaign in the urban reaches of the dam-impacted Yangtze River (1 995 km) and obtained 211 metagenomic datasets and water quality data. We first compared the compositional traits of planktonic microbial communities upstream, downstream, and in a dam reservoir. Results showed that Bacteroidetes (R-strategy) bacteria were more likely to survive upstream, whilst the reservoir and downstream regions were more conducive to the survival of K-strategy bacteria such as Actinobacteria. Eukaryotic predators tended to be enriched upstream, whilst phototrophs tended to be enriched in the reservoir and downstream regions. Based on bipartite networks, we inferred that the potential microbial predator-prey interactions gradually and significantly decreased from upstream to the downstream and dam regions, affecting 56% of keystone microbial species. Remarkably, functional analysis showed that the abundance of the photosynthetic gene psbO was higher in the reservoir and downstream regions, whilst the abundance of the KEGG carbohydrate metabolic pathway was higher upstream. These results indicate that dam construction in the Yangtze River induced planktonic microbial ecosystem transformation from detritus-based food webs to autotroph-based food webs.
Predator-prey interactions are key for the dynamics of many ecosystems. An increasing body of evidence suggests that rapid evolution and coevolution can alter these interactions, with important ecological implications by acting on traits determining fitness, including reproduction, anti-predatory defense and foraging efficiency. However, most studies to date have focused only on evolution in the prey species, and the predator traits in coevolving systems remain poorly understood. Here we investigated changes in predator traits after ~600 generations in a predator-prey (ciliate-bacteria) coevolutionary experiment. Predators independently evolved on seven different prey species, allowing generalization of the predator's evolutionary response. We used highly resolved automated image analysis to quantify changes in predator life history, morphology and behavior. Consistent with previous studies, we found that prey evolution impaired growth of the predator. In contrast, predator evolution did not cause a clear increase in fitness when feeding on ancestral prey. However, predator evolution affected morphology and behavior, increasing size, speed and directionality of movement, which have all been linked to higher prey search efficiency. These results show that in coevolving systems, predator adaptation can occur in traits relevant to offense level without translating into an increased ability of the predator to grow on the ancestral prey type.
The question "Why are there so many species?" has puzzled ecologist for a long time. Initially, an academic question, it has gained practical interest by the recent awareness of global biodiversity loss. Species diversity in local ecosystems has always been discussed in relation to the problem of competi tive exclusion and the apparent contradiction between the competitive exclu sion principle and the overwhelming richness of species found in nature. Competition as a mechanism structuring ecological communities has never been uncontroversial. Not only its importance but even its existence have been debated. On the one extreme, some ecologists have taken competi tion for granted and have used it as an explanation by default if the distribu tion of a species was more restricted than could be explained by physiology and dispersal history. For decades, competition has been a core mechanism behind popular concepts like ecological niche, succession, limiting similarity, and character displacement, among others. For some, competition has almost become synonymous with the Darwinian "struggle for existence", although simple plausibility should tell us that organisms have to struggle against much more than competitors, e.g. predators, parasites, pathogens, and envi ronmental harshness.
Background: Organisms may experience alternating periods of feast and famine determined by variation in both resource supply and community composition. Environments with rare and large resource pulses may select for rapid growth during resource abundance and survival during resource scarcity. However, trade-offs may prevent individuals from investing in both traits equally. Questions: Does the selective response of rapid-growth ability, or the ability to endure resource deprivation, dominate in an environment with rare resource pulses? Does the response depend on pulse amplitude? Does it also depend on whether a species faces only intra-specific competition or both intra- and inter-specific competition? Study organisms: Two heterotrophic bacterial species - a gleaner (Novosphingobium capsulatum) and an opportunist (Serratia marcescens). Methods: We imposed 7-day resource renewal cycles with either high- or low-amplitude fluctuations in resource availability. We cultured the bacteria in one-species monocultures or in two-species communities. We measured the fitness of ancestor strains and evolved strains in 7-day assays that mimicked the environments of the selection experiment. Results: Both species rapidly evolved a prudent strategy: descendents had both larger populations and better survival than ancestors. In addition, when growing with S. marcescens, N. capsulatum had an increased growth rate in environments with larger resource fluctuations. Otherwise, the maximum growth rate of neither species responded to the experiments. Conclusion: Survival during low-resource conditions can be a key community contextdependent trait in fluctuating environments. We found no trade-off between growth rate during feast and survival during famine.
The impact of community complexity on pairwise coevolutionary dynamics is theoretically dependent on the extent to which species evolve generalised or specialised adaptations to the multiple species they interact with. Here, we show that the bacteria Pseudomonas fluorescens diversifies into defence specialists, when coevolved simultaneously with a virus and a predatory protist, as a result of fitness trade-offs between defences against the two enemies. Strong bacteria-virus pairwise coevolution persisted, despite strong protist-imposed selection. However, the arms race dynamic (escalation of host resistance and parasite infectivity ranges) associated with bacteria-virus coevolution broke down to a greater extent in the presence of the protist, presumably through the elevated genetic and demographic costs of increased bacteria resistance ranges. These findings suggest that strong pairwise coevolution can persist even in complex communities, when conflicting selection leads to evolutionary diversification of different defence strategies.
As one of the most quantitative of ecological subdisciplines, resource competition is an important, central area of ecology. Recently research into this area has increased dramatically and resource competition models have become more complex. The characterisation of this phenomenon is therefore the aim of this book. Resource Competition seeks to identify the unifying principles emerging from experimental and theoretical approaches as well as the differences between organisms, illustrating that greater knowledge of resource competition will benefit human and environmental welfare. This book will serve as an indispensable guide to ecologists, evolutionary biologists and environmental managers, and all those interested in resource competition as an emerging discipline.
Discussed several models of frequency-dependent predation, which can be categorized as either mechanistic or descriptive. Mechanistic models are based on explicit assumptions about the behavioral components of prey choice, and how these components respond to relative or absolute prey density. The author considers 2 commonly used descriptive models of frequency-dependent predation and proposes a new one. These models are evaluated on the basis of how well they describe several empirical and theoretical examples of frequency-dependent predation and in terms of their potential usefulness in elucidating the mechanisms of prey choice.-from Author
Because mechanistic models of interspecific interactions are often complex, one should deliberately seek simple unifying principles that transcend system-specific details. Earlier work on resource competition has led to the ''R* rule,'' which states that a dominant competitor suppresses resources to a lower level than any other competing species. This rule describes the outcome of even ornate models of competition. Here we show that analogous simple rules can characterize systems with predation. We first demonstrate, for a simple two-prey, one-predator model without resource competition but with a predator numerical response leading to apparent competition, that the winning prey supports (and withstands) the higher predator density; that is, the outcome is described by a ''P* rule.'' We then develop a general model in which predation is inflicted evenhandedly on two prey species competing for a single resource and show that the R* and P* rules hold: the winning prey both depresses resources to the lowest level and sustains the higher predator density. We next examine a more complex model with differential predation. Assuming a closed system (i.e., a fixed nutrient pool), we portray the four-dimensional system dynamics in a two-dimensional graphical model, and we assess the domain of applicability of simple dominance rules in more complex systems. We address the generality of our conclusions and end by examining the implications of different, reasonable biological constraints for community structure.
Early experimental and modelling work in community ecology1 led to the principle of competitive exclusion. This states that, among two or more species of primary producer — that is, plants — competing for a shared resource, only the best competitor will survive2. The apparent contradiction between competitive exclusion and the species richness found in nature has been a long-standing enigma. Explanations of why strong competitors do not inevitably have a stranglehold have invoked environmental disturbance and the differing resource requirements of different species. On page 407 of this issue, however, Huisman and Weissing3 present a way to reconcile the persistence of diversity with competitive exclusion in undisturbed ecosystems with few limiting resources.
Competition theory generally predicts that diversity is maintained by temporal environmental fluctuations. One of the many suggested mechanisms for maintaining diversity in fluctuating environments is the gleaner-opportunist trade-off, whereby gleaner species have low threshold resource levels and low maximum growth rates in high resource concentration while opportunist species show opposite characteristics. We measured the growth rates of eight heterotrophic aquatic bacteria under different concentrations of chemically complex plant detritus resource. The growth rates revealed gleaner-opportunist trade-offs. The role of environmental variability in maintaining diversity was tested in a 28-day experiment with three different resource fluctuation regimes imposed on two four-species bacterial communities in microcosms. We recorded population densities with serial dilution plating and total biomass as turbidity. Changes in resource availability were measured from filter-sterilised medium by re-introducing the consumer species and recording short-term growth rates. The type of environmental variation had no effect on resource availability, which declined slowly during the experiment and differed in level between the communities. However, the slowly fluctuating environment had the highest Shannon diversity index, biomass, and coefficient of variation of biomass in both communities. We did not find a clear link between the gleaner-opportunist trade-off and diversity in fluctuating environments. Nevertheless, our results do not exclude this explanation and support the general view that temporal environmental variation maintains species diversity also in communities feeding chemically complex resource.