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Pierre-olivier Cheptou - One of the best experts on this subject based on the ideXlab platform.

  • CSR ecological strategies and plant mating systems: outcrossing increases with competitiveness but stress-tolerance is related to mixed mating
    Oikos, 2016
    Co-Authors: François Munoz, Cyrille Violle, Pierre-olivier Cheptou
    Abstract:

    A number of plant traits influence the success of fertilization and reproduction in plants. Collectively these traits represent ecological syndromes that are of evolutionary significance. However, while an association between mating system and Colonizing Ability has been proposed, the existence of a broader relationship between mating system and a species’ position in ecological succession has not been extensively investigated. Grime’s CSR theory stresses that an ecological succession can involve changes from Colonizing to either competitive or stress-tolerant strategies. How distinct dimensions of competitiveness and stress tolerance covary with mating systems has still not been considered. We designed a comparative approach to evaluate the link between mating system, life form and CSR strategies for 1996 herbaceous and woody species. We found that CSR strategies are significantly related to mating systems. Ruderal species – colonizers in early succession – were mostly selfers while more competitive species were more often outcrossers. On the other hand, greater physiological stress tolerance was associated with mixed mating systems. Outcrossing is classically expected to be advantageous for most life history strategies other than colonizers, but we suggest that reproductive assurance can counterbalance this effect in stressful environments where populations are sparse and pollinators are rare. Therefore, our results emphasize that competition and abiotic stresses are not equivalent selective pressures on the evolution of mating systems. Finally, we found plant life span to convey additional information on mating system variation, supporting its role for mating system evolution. These findings encourage further investigation of the evolutionary role of ecological strategies as syndromes of traits and suggest that the emergence of large databases of plant traits will help address the major evolutionary hypotheses on such syndromes.

  • pollination fluctuations drive evolutionary syndromes linking dispersal and mating system
    The American Naturalist, 2009
    Co-Authors: Pierre-olivier Cheptou, François Massol
    Abstract:

    Abstract: The existence of a syndrome linking dispersal rate and mating system has long been debated in evolutionary ecology, especially in plants. Some verbal models hypothesize that the Ability to self‐fertilize may be associated with high dispersal, since completely outcrossing species cannot reproduce when they disperse to an empty destination site. However, empirical observations fail to support a clear trend, and an association of high Colonizing Ability with high outcrossing has been reported. Here we develop a general metapopulation model for the joint evolution of seed dispersal and self‐fertilization when local pollen limitation varies stochastically over time. Under these assumptions, we study how dispersal and mating system influence each other through selection. We predict the existence of two consistent syndromes of traits: dispersing outcrossers and nondispersing (partial) selfers. These theoretical expectations contradict the classical view and shed new light on an old problem, allowing us...

  • Pollination fluctuations drive evolutionary syndromes linking dispersal and mating system
    American Naturalist, 2009
    Co-Authors: Pierre-olivier Cheptou, François Massol
    Abstract:

    The existence of a syndrome linking dispersal rate and mating system has long been debated in evolutionary ecology, especially in plants. Some verbal models hypothesize that the Ability to self-fertilize may be associated with high dispersal, since completely outcrossing species cannot reproduce when they disperse to an empty destination site. However, empirical observations fail to support a clear trend, and an association of high Colonizing Ability with high outcrossing has been reported. Here we develop a general metapopulation model for the joint evolution of seed dispersal and self-fertilization when local pollen limitation varies stochastically over time. Under these assumptions, we study how dispersal and mating system influence each other through selection. We predict the existence of two consistent syndromes of traits: dispersing outcrossers and nondispersing (partial) selfers. These theoretical expectations contradict the classical view and shed new light on an old problem, allowing us to reinterpret empirical data. Finally, our predictions are discussed in light of empirical data concerning the association of seed dispersal mechanism and breeding system.

Ben Lugtenberg - One of the best experts on this subject based on the ideXlab platform.

  • flagella driven chemotaxis towards exudate components is an important trait for tomato root colonization by pseudomonas fluorescens
    Molecular Plant-microbe Interactions, 2002
    Co-Authors: Sandra De Weert, Hans Vermeiren, Irene Kuiper, Nico Hendrickx, Ine H M Mulders, Guido V Bloemberg, Ben Lugtenberg
    Abstract:

    Motility is a major trait for competitive tomato root-tip colonization by Pseudomonas fluorescens. To test the hypothesis that this role of motility is based on chemotaxis toward exudate components, cheA mutants that were defective in flagella-driven chemotaxis but retained motility were constructed in four P. fluorescens strains. After inoculation of seedlings with a 1:1 mixture of wild-type and nonmotile mutants all mutants had a strongly reduced competitive root Colonizing Ability after 7 days of plant growth, both in a gnotobiotic sand system as well as in nonsterile potting soil. The differences were significant on all root parts and increased from root base to root tip. Significant differences at the root tip could already be detected after 2 to 3 days. These experiments show that chemotaxis is an important competitive colonization trait. The best competitive root-tip colonizer, strain WCS365, was tested for chemotaxis toward tomato root exudate and its major identified components. A chemotactic response was detected toward root exudate, some organic acids, and some amino acids from this exudate but not toward its sugars. Comparison of the minimal concentrations required for a chemotactic response with concentrations estimated for exudates suggested that malic acid and citric acid are among major chemo-attractants for P. fluorescens WCS365 cells in the tomato rhizosphere.

  • tomato seed and root exudate sugars composition utilization by pseudomonas biocontrol strains and role in rhizosphere colonization
    Environmental Microbiology, 1999
    Co-Authors: Ben Lugtenberg, L V Kravchenko, Marco Simons
    Abstract:

    The role of tomato seed and root exudate sugars as nutrients for Pseudomonas biocontrol bacteria was studied. To this end, the major exudate sugars of tomato seeds, seedlings and roots were identified and quantified using high-performance liquid chromatographic (HPLC) analysis. Glucose, fructose and maltose were present in all studied growth stages of the plant, but the ratios of these sugars were strongly dependent on the developmental stage. In order to study the putative role of exudate sugar utilization in rhizosphere colonization, two approaches were adopted. First, after co-inoculation on germinated tomato seeds, the root-Colonizing Ability of the efficient root-Colonizing P. fluorescens strain WCS365 in a gnotobiotic quartz sand-plant nutrient solution system was compared with that of other Pseudomonas biocontrol strains. No correlation was observed between the Colonizing Ability of a strain and its Ability to use the major exudate sugars as the only carbon and energy source. Secondly, a Tn5lacZ mutant of P. fluorescens strain WCS365, strain PCL1083, was isolated, which is impaired in its Ability to grow on simple sugars, including those found in exudate. The mutation appeared to reside in zwf, which encodes glucose-6-phosphate dehydrogenase. The mutant grows as well as the parental strain on other media, including tomato root exudate. After inoculation of germinated sterile tomato seeds, the mutant cells reached the same population levels at the root tip as the wild-type strain, both alone and in competition, indicating that the Ability to use exudate sugars does not play a major role in tomato root colonization, despite the fact that sugars have often been reported to represent the major exudate carbon source. This conclusion is supported by the observation that the growth of mutant PCL1083 in vitro is inhibited by glucose, a major exudate sugar, at a concentration of 0.001%, which indicates that the glucose concentration in the tomato rhizosphere is very low.

  • a two component system plays an important role in the root Colonizing Ability of pseudomonas fluorescens strain wcs365
    Molecular Plant-microbe Interactions, 1998
    Co-Authors: Linda C Dekkers, C J P Bloemendaal, L A De Weger, C A Wijffelman, Herman P Spaink, Ben Lugtenberg
    Abstract:

    We describe the characterization of a novel Tn5lacZ colonization mutant of the efficiently Colonizing Pseudomonas fluorescens strain WCS365, mutant strain PCL1210, which is at least 300- to 1,000-fold impaired in colonization of the potato root tip after co-inoculation of potato stem cuttings with a 1:1 mixture of mutant and parental cells. Similarly, the mutant is also impaired in colonization of tomato, wheat, and radish, indicating that the gene involved plays a role in the Ability of P. fluorescens WCS365 to colonize a wide range of plant species. A 3.1-kb DNA fragment was found to be able to complement the observed mutation. The nucleotide sequence of the region around the Tn5lacZ insertion showed three open reading frames (ORFs). The transcriptional start site was determined. The operon is preceded by an integration host factor (IHF) binding site consensus sequence whereas no clear ‐10 and ‐35 sequences are present. The deduced amino acid sequences of the first two genes of the operon, designated as colR and colS, show strong similarity with known members of two-component regulatory systems. ColR has homology with the response regulators of the OmpR-PhoB subclass whereas ColS, the product of the gene in which the mutation resides, shows similarity to the sensor kinase members of these two-component systems. Hydrophobicity plots show that this hypothetical sensor kinase has two transmembrane domains, as is also known for other sensor kinases. The product of the third ORF, Orf222, shows no homology with known proteins. Only part of the orf222 gene is present in the colonizationcomplementing, 3.1-kb region, and it therefore does not play a role in complementation. No experimental evidence for a role of the ColR/ ColS two-component system in the suspected colonization traits chemotaxis and transport of exudate compounds could be obtained. The function of this novel two-component system therefore remains to be elucidated. We conclude that colonization is an active process in which an environmental stimulus,

K W Buck - One of the best experts on this subject based on the ideXlab platform.

  • rare interspecific hybrids in natural populations of the dutch elm disease pathogens ophiostoma ulmi and o novo ulmi
    Fungal Biology, 1998
    Co-Authors: C M Brasier, Susan Kirk, N D Pipe, K W Buck
    Abstract:

    Ophiostoma ulmi and O. novo-ulmi are partly reproductively isolated, morphologically, behaviourally and molecularly distinct species responsible for the first and current pandemics of Dutch elm disease, respectively. Among >11000 isolates sampled from Dutch elm disease sites across Eurasia and North America since 1973, nine could not be assigned to O. ulmi or O. novo-ulmi . Of these isolates one (P129) was from Poland and eight (d10, d11, e12, e27, e28, e37, f30 and g3) were from a single bark sample in Portugal. These nine isolates were termed ‘fast-waxy’ isolates because of their unusual cultural characteristics. The possibility that they were interspecific hybrids was investigated. When compared with O. ulmi and O. novo-ulmi for colony pattern, growth-rate, optimum temperature for growth, vascular wilt Ability, elm bark Colonizing Ability, cerato-ulmin toxin production, Ability to fertilize (as ♂) O. novo-ulmi , and Ability to be fertilized (as ♀) by O. ulmi , they exhibited a combination of O. ulmi -like, O. novo-ulmi -like, intermediate or novel characters (female sterility) consistent with their being hybrids. P129 and representative Portuguese isolates d10 and e27 each exhibited a different combination of characters, indicating each was a different hybrid genotype. When d10 and e27 were independently crossed to the same O. novo-ulmi isolate, differences in their F 1 progeny sets for growth-rate and pathogenicity distributions were consistent with their being different recombinant genotypes. A molecular analysis of P129, d10 and e27 using RAPDs of genomic DNA, rDNA RFLPs and cerato-ulmin gene sequences confirmed that each was a unique interspecific hybrid. The mechanism of origin of these hybrids and their evolutionary significance are discussed. Combined experimental and circumstantial evidence indicates that they are relatively unfit, rare and probably transient, and that they arise when O. novo-ulmi invades territory occupied by O. ulmi and replaces it. Nonetheless, the possibility that the hybrids act as a genetic bridge, facilitating transfer of novel vegetative compatibility loci and other loci form O. ulmi to O. novo-ulmi at recent epidemic fronts, requires investigation.

Lamson Phan Tran - One of the best experts on this subject based on the ideXlab platform.

  • improvement of growth fruit weight and early blight disease protection of tomato plants by rhizosphere bacteria is correlated with their beneficial traits and induced biosynthesis of antioxidant peroxidase and polyphenol oxidase
    Plant Science, 2015
    Co-Authors: Anupama Narendra Babu, Sudisha Jogaiah, Amruthesh Kestur Nagaraj, Lamson Phan Tran
    Abstract:

    Five plant growth promoting rhizobacteria (PGPRs) of different genera, newly isolated from healthy tomato rhizosphere, were characterized with phosphate solubilizing and root Colonizing Ability. Treatment with these isolates recorded a significant increase in seed germination and seedling vigor as well as tomato growth and fruit weight which might be partly attributed to the Ability of the PGPRs to produce IAA and enhance nutrient uptake and chlorophyll content in treated plants. More importantly, a strong protection against early blight disease was observed in PGPR-pretreated tomato plants infected with Alternaria solani which is in accordance with the presence of siderophores, HCN, chitinase and glucanase in the isolated PGPRs. Additionally, a significantly enhanced accumulation of antioxidant peroxidase (POX) and polyphenol oxidase (PPO) enzymes was observed in the PGPR-pretreated plants with or without pathogen infection in comparison with water or pathogen control. Notably, the highest increase in POX and PPO accumulations was recorded in tomato plants raised from seeds primed with TN_Vel-35 strain. A significant upregulation of POX and PPO in tomato plants subjected to similar treatment with TN_Vel-35 versus respective control was also noticed, further strengthening that the PGPR-induced POX and PPO biosyntheses also contribute to PGPR-mediated protection against early blight disease in tomato plants.

Ricardo E Gurtler - One of the best experts on this subject based on the ideXlab platform.

  • habitat specific occupancy and a metapopulation model of triatoma sordida hemiptera reduviidae a secondary vector of chagas disease in northeastern argentina
    Journal of Medical Entomology, 2018
    Co-Authors: Lucia I Rodriguezplanes, Sol M Gaspe, Gustavo F Enriquez, Ricardo E Gurtler
    Abstract:

    : Triatoma sordida Stal (Hemiptera: Reduviidae), a secondary vector of Trypanosoma cruzi Chagas (Kinetoplastida: Trypanosomatidae), occasionally colonizes human sleeping quarters in Paraguay, Bolivia, and Brazil, whereas only sylvatic and peridomestic populations are found in Argentina. We carried out a cross-sectional survey of house infestation in a well-defined rural area of northeastern Argentina to identify the key habitats of T. sordida; describe its spatial distribution in an apparently undisturbed setting under no recent insecticide treatment and use metapopulation theory to investigate these spatially structured populations. Timed-manual searches in 2,177 georeferenced sites from 368 houses yielded T. sordida in 78 sites (house infestation prevalence, 19.9%). Most triatomines occurred in chicken nests, chicken coops, and trees where chickens roosted (prime habitats). Goat or sheep corrals and pig corrals had a lower fraction of occupied sites (occupancies) and abundance. Both occupancy and catch increased with increasing refuge availAbility according to multimodel inference with model averaging. The majority of suitable habitats were unoccupied despite their proximity to occupied sites. The site-specific occurrence of T. sordida and Triatoma infestans Klug (Hemiptera: Reduviidae) was positively and homogeneously associated over ecotopes, showing no evidence of interspecific interference. An incidence function metapopulation model (including intersite distances and vector carrying capacity) predicted a fivefold greater occupancy relative to the observed pattern, suggesting the latter represented a transient state. T. sordida failed to colonize human sleeping quarters, thrived in peridomestic habitats occupied by chickens, and had a limited occupancy likely related to a poor Colonizing Ability and the relative instAbility of its prime habitats.