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1.
ISME J ; 13(5): 1133-1143, 2019 05.
Artigo em Inglês | MEDLINE | ID: mdl-30607028

RESUMO

Here we aim to incorporate trait-based information into the modern coexistence framework that comprises a balance between stabilizing (niche-based) and equalizing (fitness) mechanisms among interacting species. Taking the modern coexistence framework as our basis, we experimentally tested the effect of size differences among species on coexistence by using fifteen unique pairs of resident vs. invading cyanobacteria, resulting in thirty unique invasibility tests. The cyanobacteria covered two orders of magnitude differences in size. We found that both niche and fitness differences increased with size differences. Niche differences increased faster with size differences than relative fitness differences and whereas coexisting pairs showed larger size differences than non-coexisting pairs, ultimately species coexistence could not be predicted on basis of size differences only. Our findings suggest that size is more than a key trait controlling physiological and population-level aspects of phytoplankton, it is also relevant for community-level phenomena such as niche and fitness differences which influence coexistence and biodiversity.


Assuntos
Cianobactérias/fisiologia , Fitoplâncton/fisiologia , Biodiversidade , Cianobactérias/citologia , Ecossistema , Aptidão Genética , Fenótipo , Fitoplâncton/citologia
2.
Proc Biol Sci ; 282(1799): 20141745, 2015 Jan 22.
Artigo em Inglês | MEDLINE | ID: mdl-25473009

RESUMO

The competition-relatedness hypothesis (CRH) predicts that the strength of competition is the strongest among closely related species and decreases as species become less related. This hypothesis is based on the assumption that common ancestry causes close relatives to share biological traits that lead to greater ecological similarity. Although intuitively appealing, the extent to which phylogeny can predict competition and co-occurrence among species has only recently been rigorously tested, with mixed results. When studies have failed to support the CRH, critics have pointed out at least three limitations: (i) the use of data poor phylogenies that provide inaccurate estimates of species relatedness, (ii) the use of inappropriate statistical models that fail to detect relationships between relatedness and species interactions amidst nonlinearities and heteroskedastic variances, and (iii) overly simplified laboratory conditions that fail to allow eco-evolutionary relationships to emerge. Here, we address these limitations and find they do not explain why evolutionary relatedness fails to predict the strength of species interactions or probabilities of coexistence among freshwater green algae. First, we construct a new data-rich, transcriptome-based phylogeny of common freshwater green algae that are commonly cultured and used for laboratory experiments. Using this new phylogeny, we re-analyse ecological data from three previously published laboratory experiments. After accounting for the possibility of nonlinearities and heterogeneity of variances across levels of relatedness, we find no relationship between phylogenetic distance and ecological traits. In addition, we show that communities of North American green algae are randomly composed with respect to their evolutionary relationships in 99% of 1077 lakes spanning the continental United States. Together, these analyses result in one of the most comprehensive case studies of how evolutionary history influences species interactions and community assembly in both natural and experimental systems. Our results challenge the generality of the CRH and suggest it may be time to re-evaluate the validity and assumptions of this hypothesis.


Assuntos
Evolução Biológica , Clorófitas/fisiologia , Filogenia , Clorófitas/genética , Ecossistema , Dinâmica Populacional , Especificidade da Espécie , Transcriptoma
3.
PLoS One ; 8(9): e72561, 2013.
Artigo em Inglês | MEDLINE | ID: mdl-24023751

RESUMO

Despite their importance as ecosystem drivers, our understanding of the influence of bacterial diversity on ecosystem functioning is limited. After identifying twelve bacterial strains from two petroleum-contaminated sites, we experimentally explored the impact of biodiversity on total density by manipulating the number of strains in culture. Irrespective of the origin of the bacteria relative to the contaminant, biodiversity positively influenced total density. However, bacteria cultured in the crude oil of their origin (autochthonous) reached higher densities than bacteria from another origin (allochthonous) and the relationship between diversity and density was stronger for autochthonous bacteria. By measuring the relative contribution of each strain to total density we showed that the observed positive effect of increasing diversity on total density was mainly due to positive interactions among species and not the presence of a particular species. Our findings can be explained by the complex chemical composition of crude oil and the necessity of a diverse array of organisms with complementary enzymatic capacities to achieve its degradation. The long term exposure to a contaminant may have allowed different bacteria to become adapted to the use of different fractions of the crude, resulting in higher complementarity in resource use in autochthonous bacteria compared to allochthonous ones. Our results could help improve the success of bioaugmentation as a bioremediation technique by suggesting the use of a diversified set of autochthonous organisms.


Assuntos
Bactérias/metabolismo , Biodegradação Ambiental , Ecossistema , Bactérias/classificação , Biodiversidade
4.
Microb Ecol ; 66(4): 897-905, 2013 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-24013213

RESUMO

Bacterial infections are the second largest cause of mortality in shrimp hatcheries. Among them, bacteria from the genus Vibrio constitute a major threat. As the use of antibiotics may be ineffective and banned from the food sector, alternatives are required. Historically, phage therapy, which is the use of bacteriophages, is thought to be a promising option to fight against bacterial infections. However, as for antibiotics, resistance can be rapidly developed. Since the emergence of resistance is highly undesirable, a formal characterization of the dynamics of its acquisition is mandatory. Here, we explored the co-evolutionary dynamics of resistance between the bacteria Vibrio sp. CV1 and the phages V1G, V1P1, and V1P2. Single-phage treatments as well as a cocktail composed of the three phages were considered. We found that in the presence of a single phage, bacteria rapidly evolved resistance, and the phages decreased their infectivity, suggesting that monotherapy may be an inefficient treatment to fight against Vibrio infections in shrimp hatcheries. On the contrary, the use of a phage cocktail considerably delayed the evolution of resistance and sustained phage infectivity for periods in which shrimp larvae are most susceptible to bacterial infections, suggesting the simultaneous use of multiple phages as a serious strategy for the control of vibriosis. These findings are very promising in terms of their consequences to different industrial and medical scenarios where bacterial infections are present.


Assuntos
Infecções Bacterianas/veterinária , Bacteriófagos/fisiologia , Evolução Biológica , Terapia Biológica/veterinária , Penaeidae/microbiologia , Vibrio/genética , Vibrio/virologia , Animais , Aquicultura , Infecções Bacterianas/microbiologia , Infecções Bacterianas/terapia , Bacteriófagos/classificação , Bacteriófagos/genética , Humanos
5.
Proc Biol Sci ; 280(1768): 20131548, 2013 Oct 07.
Artigo em Inglês | MEDLINE | ID: mdl-23945692

RESUMO

The impact of biodiversity on the stability of ecological communities has been debated among biologists for more than a century. Recently summarized empirical evidence suggests that biodiversity tends to enhance the temporal stability of community-level properties such as biomass; however, the underlying mechanisms driving this relationship remain poorly understood. Here, we report the results of a microcosm study in which we used simplified systems of freshwater microalgae to explore how the phylogenetic relatedness of species influences the temporal stability of community biomass by altering the nature of their competitive interactions. We show that combinations of two species that are more evolutionarily divergent tend to have lower temporal stability of biomass. In part, this is due to negative 'selection effects' in which bicultures composed of distantly related species are more likely to contain strong competitors that achieve low biomass. In addition, bicultures of distantly related species had on average weaker competitive interactions, which reduced compensatory dynamics and decreased the stability of community biomass. Our results demonstrate that evolutionary history plays a key role in controlling the mechanisms, which give rise to diversity-stability relationships. As such, patterns of shared ancestry may help us predict the ecosystem-level consequences of biodiversity loss.


Assuntos
Clorófitas/fisiologia , Água Doce , Biodiversidade , Clorófitas/classificação , Clorófitas/genética , Ecossistema , Filogenia , Dinâmica Populacional , Especificidade da Espécie
6.
Ecology ; 94(11): 2529-36, 2013 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-24400504

RESUMO

Our understanding of how biodiversity influences ecosystem functioning is entering a new stage of its development through the incorporation of information about the evolutionary relatedness of species. Bacteria are prime providers of essential ecosystem services, representing an excellent model system to perform biodiversity-ecosystem function research. By using bacteria isolated from petroleum-contaminated sites, we show that communities composed of poorly related species were more productive than those containing highly related species. The nature of the forces controlling this positive effect of phylogenetic diversity on community productivity depended on the number of species in culture. In communities of two species the positive effect of phylogenetic diversity on productivity was driven by changes in the selection effect. Communities of two distantly related species were dominated by the most productive species in monoculture, whereas communities of two closely related species were dominated by the less productive species in monoculture. In communities of four species the positive effect of phylogenetic diversity on productivity was driven by changes in the complementarity effect. In communities composed of four distantly related species the influence of positive interactions such as facilitation, cross-feeding, and niche partitioning seemed to outweigh the influence of negative interactions such as interference. As a consequence the proportion of species favored by the presence of other species increased as they became less related. Multiple facets of biodiversity may influence ecosystem functioning. Here, we present evidence of an interaction between phylogenetic and taxonomic diversity on community productivity, underlining the importance of considering multiple aspects of biodiversity when studying its impact on ecosystem functioning.


Assuntos
Bactérias/genética , Biodiversidade , Filogenia
7.
Nature ; 486(7401): 59-67, 2012 Jun 06.
Artigo em Inglês | MEDLINE | ID: mdl-22678280

RESUMO

The most unique feature of Earth is the existence of life, and the most extraordinary feature of life is its diversity. Approximately 9 million types of plants, animals, protists and fungi inhabit the Earth. So, too, do 7 billion people. Two decades ago, at the first Earth Summit, the vast majority of the world's nations declared that human actions were dismantling the Earth's ecosystems, eliminating genes, species and biological traits at an alarming rate. This observation led to the question of how such loss of biological diversity will alter the functioning of ecosystems and their ability to provide society with the goods and services needed to prosper.


Assuntos
Biodiversidade , Extinção Biológica , Atividades Humanas , Animais , Mudança Climática/estatística & dados numéricos , Consenso , Ecologia/métodos , Ecologia/tendências , Humanos
8.
PLoS One ; 7(6): e37620, 2012.
Artigo em Inglês | MEDLINE | ID: mdl-22701572

RESUMO

The ecological insurance hypothesis predicts a positive effect of species richness on ecosystem functioning in a variable environment. This effect stems from temporal and spatial complementarity among species within metacommunities coupled with optimal levels of dispersal. Despite its importance in the context of global change by human activities, empirical evidence for ecological insurance remains scarce and controversial. Here we use natural aquatic bacterial communities to explore some of the predictions of the spatial and temporal aspects of the ecological insurance hypothesis. Addressing ecological insurance with bacterioplankton is of strong relevance given their central role in fundamental ecosystem processes. Our experimental set up consisted of water and bacterioplankton communities from two contrasting coastal lagoons. In order to mimic environmental fluctuations, the bacterioplankton community from one lagoon was successively transferred between tanks containing water from each of the two lagoons. We manipulated initial bacterial diversity for experimental communities and immigration during the experiment. We found that the abundance and production of bacterioplankton communities was higher and more stable (lower temporal variance) for treatments with high initial bacterial diversity. Immigration was only marginally beneficial to bacterial communities, probably because microbial communities operate at different time scales compared to the frequency of perturbation selected in this study, and of their intrinsic high physiologic plasticity. Such local "physiological insurance" may have a strong significance for the maintenance of bacterial abundance and production in the face of environmental perturbations.


Assuntos
Migração Animal/fisiologia , Bactérias , Biodiversidade , Biota , Modelos Biológicos , Plâncton/fisiologia , Análise de Variância , Eletroforese em Gel de Gradiente Desnaturante , Citometria de Fluxo , França , Biologia Marinha , Salinidade , Especificidade da Espécie
9.
Nature ; 469(7328): 89-92, 2011 Jan 06.
Artigo em Inglês | MEDLINE | ID: mdl-21131946

RESUMO

The relationship between biodiversity and ecosystem functioning (BEF) has become a cornerstone of community and ecosystem ecology and an essential criterion for making decisions in conservation biology and policy planning. It has recently been proposed that evolutionary history should influence the BEF relationship because it determines species traits and, thus, species' ability to exploit resources. Here we test this hypothesis by combining experimental evolution with a BEF experiment. We isolated 20 bacterial strains from a marine environment and evolved each to be generalists or specialists. We then tested the effect of evolutionary history on the strength of the BEF relationship with assemblages of 1 to 20 species constructed from the specialists, generalists and ancestors. Assemblages of generalists were more productive on average because of their superior ability to exploit the environmental heterogeneity. The slope of the BEF relationship was, however, stronger for the specialist assemblages because of enhanced niche complementarity. These results show how the BEF relationship depends critically on the legacy of past evolutionary events.


Assuntos
Fenômenos Fisiológicos Bacterianos , Biodiversidade , Evolução Biológica , Ecossistema , Organismos Aquáticos/classificação , Organismos Aquáticos/isolamento & purificação , Organismos Aquáticos/fisiologia , Bactérias/classificação , Bactérias/genética , Bactérias/isolamento & purificação , Bactérias/metabolismo , Conservação dos Recursos Naturais , Modelos Biológicos , Tipagem Molecular , RNA Ribossômico 16S/genética , Espanha , Especificidade da Espécie
10.
Proc Biol Sci ; 277(1692): 2339-45, 2010 Aug 07.
Artigo em Inglês | MEDLINE | ID: mdl-20335204

RESUMO

The influence of biodiversity on ecosystem functioning is a major concern of ecological research. However, the biodiversity-ecosystem functioning relationship has very often been studied independently from the mechanisms allowing coexistence. By considering the effects of dispersal and niche partitioning on diversity, the metacommunity perspective predicts a spatial scale-dependence of the shape of the relationship. Here, we present experimental evidence of such scale-dependent patterns. After approximately 500 generations of diversification in a spatially heterogeneous environment, we measured functional diversity (FD) and productivity at both local and regional scales in experimental source-sink metacommunities of the bacterium Pseudomonas fluorescens SBW25. At the regional scale, environmental heterogeneity yielded high levels of FD and we observed a positive correlation between diversity and productivity. At the local scale, intermediate dispersal increased local FD through a mass effect but there was no correlation between diversity and productivity. These experimental results underline the importance of considering the mechanisms maintaining biodiversity and the appropriate spatial scales in understanding its relationship with ecosystem functioning.


Assuntos
Biodiversidade , Ecossistema , Dinâmica Populacional , Pseudomonas fluorescens/crescimento & desenvolvimento , Animais , Ecologia/métodos , Pseudomonas fluorescens/genética
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