共查询到20条相似文献,搜索用时 0 毫秒
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Evgueny Kroll Scott Coyle Barbara Dunn Gregory Koniges Anthony Aragon Jeremy Edwards Frank Rosenzweig 《PloS one》2013,8(7)
Knowledge of the mechanisms that lead to reproductive isolation is essential for understanding population structure and speciation. While several models have been advanced to explain post-mating reproductive isolation, experimental data supporting most are indirect. Laboratory investigations of this phenomenon are typically carried out under benign conditions, which result in low rates of genetic change unlikely to initiate reproductive isolation. Previously, we described an experimental system using the yeast Saccharomyces cerevisiae where starvation served as a proxy to any stress that decreases reproduction and/or survivorship. We showed that novel lineages with restructured genomes quickly emerged in starved populations, and that these survivors were more fit than their ancestors when re-starved. Here we show that certain yeast lineages that survive starvation have become reproductively isolated from their ancestor. We further demonstrate that reproductive isolation arises from genomic rearrangements, whose frequency in starving yeast is several orders of magnitude greater than an unstarved control. By contrast, the frequency of point mutations is less than 2-fold greater. In a particular case, we observe that a starved lineage becomes reproductively isolated as a direct result of the stress-related accumulation of a single chromosome. We recapitulate this result by demonstrating that introducing an extra copy of one or several chromosomes into naïve, i.e. unstarved, yeast significantly diminishes their fertility. This type of reproductive barrier, whether arising spontaneously or via genetic manipulation, can be removed by making a lineage euploid for the altered chromosomes. Our model provides direct genetic evidence that reproductive isolation can arise frequently in stressed populations via genome restructuring without the precondition of geographic isolation. 相似文献
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New interactions with non-native species can alter selection pressures on native species. Here, we examined the effect of the spatial distribution of a non-native species, a factor that determines ecological and evolutionary outcomes but that is poorly understood, particularly on a fine scale. Specifically, we explored a native butterfly population and a non-native plant on which the butterfly oviposits despite the plant’s toxicity to larvae. We developed an individual-based model to describe movement and oviposition behaviors of each butterfly, which were determined by plant distribution and the butterfly''s host preference genotype. We estimated the parameter values of the model from rich field data. We simulated various patterns of plant distributions and compared the rates of butterfly population growth and changes in the allele frequency of oviposition preference. Neither the number nor mean area of patches of non-native species affected the butterfly population, whereas plant abundance, patch shape, and distance to the nearest native and non-native patches altered both the population dynamics and genetics. Furthermore, we found a dramatic decrease in population growth rates when we reduced the distance to the nearest native patch from 147 m to 136 m. Thus changes in the non-native resource distribution that are critical to the fate of the native herbivore could only be detected at a fine-grained scale that matched the scale of a female butterfly’s movement. In addition, we found that the native butterfly population was unlikely to be rescued by the exclusion of the allele for acceptance of the non-native plant as a host. This study thus highlights the importance of including both ecological and evolutionary dynamics in analyses of the outcome of species interactions and provides insights into habitat management for non-native species. 相似文献
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Wietse de Boer Maria P. J. Hundscheid Paulien J. A. Klein Gunnewiek Annelies S. de Ridder-Duine Cecile Thion Johannes A. van Veen Annemieke van der Wal 《PloS one》2015,10(9)
Knowledge on the factors that determine the composition of bacterial communities in the vicinity of roots (rhizosphere) is essential to understand plant-soil interactions. Plant species identity, plant growth stage and soil properties have been indicated as major determinants of rhizosphere bacterial community composition. Here we show that the presence of saprotrophic fungi can be an additional factor steering rhizosphere bacterial community composition and functioning. We studied the impact of presence of two common fungal rhizosphere inhabitants (Mucor hiemalis and Trichoderma harzianum) on the composition of cultivable bacterial communities developing in the rhizosphere of Carex arenaria (sand sedge) in sand microcosms. Identification and phenotypic characterization of bacterial isolates revealed clear shifts in the rhizosphere bacterial community composition by the presence of two fungal strains (M. hiemalis BHB1 and T. harzianum PvdG2), whereas another M. hiemalis strain did not show this effect. Presence of both M. hiemalis BHB1 and T. harzianum PvdG2 resulted in a significant increase of chitinolytic and (in vitro) antifungal bacteria. The latter was most pronounced for M. hiemalis BHB1, an isolate from Carex roots, which stimulated the development of the bacterial genera Achromobacter and Stenotrophomonas. In vitro tests showed that these genera were strongly antagonistic against M. hiemalis but also against the plant-pathogenic fungus Rhizoctonia solani. The most likely explanation for fungal-induced shifts in the composition of rhizosphere bacteria is that bacteria are being selected which are successful in competing with fungi for root exudates. Based on the results we propose that measures increasing saprotrophic fungi in agricultural soils should be explored as an alternative approach to enhance natural biocontrol against soil-borne plant-pathogenic fungi, namely by stimulating indigenous antifungal rhizosphere bacteria. 相似文献
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Changes in Individual Allometry Can Lead to Species Coexistence without Niche Separation 总被引:1,自引:0,他引:1
The principle of competitive exclusion is a fundamental tenet of ecology. Commonly used competition models predict that at
most only one species per limiting resource can coexist in the same environment at steady state; hence, the upper limit to
species diversity depends only on the number of limiting resources and not on the rates of resource supply. We demonstrate
that such model behavior is the result of both the growth and biomass turnover functions being proportional to the population
biomass. We argue that at least the growth function should be a nonlinear, concave downward function of biomass. This form
for the growth function should arise simply because of changes in the allometry of individuals in the population. With this
change in model structure, we show that any number of species can coexist at an asymptotically stable steady state, even where
there is only one limiting resource. Furthermore, if growth increases nonlinearly with biomass, the steady-state resource
concentration and hence the potential for biodiversity increases as the resource supply rate increases.
Received 31 August 2001; accepted 10 April 2002. 相似文献
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Mark W. Chynoweth Christopher A. Lepczyk Creighton M. Litton Steven C. Hess James R. Kellner Susan Cordell 《PloS one》2015,10(3)
Advances in wildlife telemetry and remote sensing technology facilitate studies of broad-scale movements of ungulates in relation to phenological shifts in vegetation. In tropical island dry landscapes, home range use and movements of non-native feral goats (Capra hircus) are largely unknown, yet this information is important to help guide the conservation and restoration of some of the world’s most critically endangered ecosystems. We hypothesized that feral goats would respond to resource pulses in vegetation by traveling to areas of recent green-up. To address this hypothesis, we fitted six male and seven female feral goats with Global Positioning System (GPS) collars equipped with an Argos satellite upload link to examine goat movements in relation to the plant phenology using the Normalized Difference Vegetation Index (NDVI). Movement patterns of 50% of males and 40% of females suggested conditional movement between non-overlapping home ranges throughout the year. A shift in NDVI values corresponded with movement between primary and secondary ranges of goats that exhibited long-distance movement, suggesting that vegetation phenology as captured by NDVI is a good indicator of the habitat and movement patterns of feral goats in tropical island dry landscapes. In the context of conservation and restoration of tropical island landscapes, the results of our study identify how non-native feral goats use resources across a broad landscape to sustain their populations and facilitate invasion of native plant communities. 相似文献
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Antonio Montresor David Addiss Marco Albonico Said Mohammed Ali Steven K. Ault Albis-Francesco Gabrielli Amadou Garba Elkhan Gasimov Theresa Gyorkos Mohamed Ahmed Jamsheed Bruno Levecke Pamela Mbabazi Denise Mupfasoni Lorenzo Savioli Jozef Vercruysse Aya Yajima 《PLoS neglected tropical diseases》2015,9(10)
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Dioecy is frequent in tropical forests. It has been suggested that small, unspecialized pollinators are among the factors responsible for gender separation in this habitat. The underlying assumption is that poor fliers and/or communal foragers frequently effect selfing which in turn, given sufficiently severe inbreeding depression, should favor the establishment of dioecy. At least 10% of the genera of the angiosperms includes dioecious species; in tropical flowering plants, however, pollinators are reliably known only in a few species. Whereas temperate dioecious species commonly are wind- or water-pollinated, anemophily is less important in tropical forests, but occurs in at least 30 dioecious genera. Our survey of tropical dioecious zoophilous species in 29 genera (in 21 families) for which detailed pollination information is available shows that these species have specialized flowers adapted to specific pollinators rather than generalized flowers suitable for diverse insects. Known pollinators include solitary and eusocial bees, beetles, moths, flies, wasps (including fig wasps), and rarely bats and birds, and cover a wide range in animal size and locomotive capabilities. Floral rewards comprise pollen, nectar, stylar mucilage, nutritious tissues, brood-places, and resins. About a third of the species offer no reward in the female morph, pollination by deceit apparently being common. Our data thus do not support the hypothesis that there is a broad correlation between a dioecious breeding system and unspecialized pollination, although such a correlation may be found in certain taxa. Specialized plant-pollinator relationships seem as critical in dioecious plants in tropical forests, where individuals often grow far apart, as they are in tropical plants with other breeding systems. 相似文献
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Daniel J. Salamango David A. Evans Mariju F. Baluyot Jackson N. Furlong Marc C. Johnson 《Journal of virology》2013,87(24):13900-13903
Fluorescent proteins are routinely employed as reporters in retroviral vectors. Here, we demonstrate that transduction with retroviral vectors carrying a tandem-dimer Tomato (TdTom) reporter produces two distinct fluorescent cell populations following template jumping due to a single nucleotide polymorphism between the first and second Tomato genes. Template jumping also occurs between repeated sequences in the Tomato and green fluorescent protein (GFP) genes. Thus, proper interpretation of the fluorescence intensity of transduced cells requires caution. 相似文献
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Mate Limitation in Fungal Plant Parasites Can Lead to Cyclic Epidemics in Perennial Host Populations
Virginie Ravigné Valérie Lemesle Alicia Walter Ludovic Mailleret Frédéric M. Hamelin 《Bulletin of mathematical biology》2017,79(3):430-447
Fungal plant parasites represent a growing concern for biodiversity and food security. Most ascomycete species are capable of producing different types of infectious spores both asexually and sexually. Yet the contributions of both types of spores to epidemiological dynamics have still to been fully researched. Here we studied the effect of mate limitation in parasites which perform both sexual and asexual reproduction in the same host. Since mate limitation implies positive density dependence at low population density, we modeled the dynamics of such species with both density-dependent (sexual) and density-independent (asexual) transmission rates. A first simple SIR model incorporating these two types of transmission from the infected compartment, suggested that combining sexual and asexual spore production can generate persistently cyclic epidemics in a significant part of the parameter space. It was then confirmed that cyclic persistence could occur in realistic situations by parameterizing a more detailed model fitting the biology of the Black Sigatoka disease of banana, for which literature data are available. We discuss the implications of these results for research on and management of Sigatoka diseases of banana. 相似文献
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Chang-Yong Choi Heung-Chul Kim Terry A. Klein Hyun-Young Nam Gi-Chang Bing 《The Korean journal of parasitology》2022,60(1):57
When free-ranging birds are accidentally killed or die, there may be greater potential for their associated ticks to detach, seek alternate hosts, and become established. We examined 711 carcasses of 95 avian species for ticks at a stopover island of migratory birds in the Republic of Korea where only Ixodes nipponensis and I. persulcatus were previously reported from local mammals and vegetation. A total of 16 ticks, I. turdus and Haemaphysalis flava, were collected from 8 fresh carcasses belonging to 5 avian species. Despite their known abundance on migratory birds and mainland Korea, these species had not colonized the isolated insular ecosystem possibly due to the low abundance and diversity of local hosts. The results imply that increasing human impact, such as the anthropogenic mortality of migratory birds and the introduction of non-native mammalian hosts, will increase the potential invasion and colonization risk of ticks. This finding also suggests that tick surveillance consisting of fresh carcasses of dead migratory birds may provide additional information, often ignored in surveillance of ticks on live birds, for the potential introduction of non-native ticks and associated pathogens affecting animal and human health. 相似文献
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Robert W. Pemberton 《The Botanical review》2010,76(2):275-292
Orchid pollinators have highly varied life histories with complex biotic resource requirements, about which we have limited
knowledge. Among the specialist orchid pollinators are insect predators and parasitoids with specific prey types such as aphids
and subterranean scarab larvae; oligolectic bees that collect pollen from limited sources such as bellflowers; euglossine
bees and butterflies that collect particular plant chemicals for reproduction and self defense; oil-collecting bees that provision
their brood cells with floral oils from a few plants; bees that collect rare floral resins to construct their nest and brood
cells; moths and butterflies that require specific larval host plants; mosquitos and horse flies that need blood; and fungus
gnats and carrion flies tied to fungi and dead animals. Loss of critical biotic resources and relationships can reduce the
abundance of orchid pollinators and/or their effectiveness. Protection of large, plant rich, pesticide-free orchid habitats
is key to conserving essential pollinator resources. 相似文献
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本文介绍了以液氮现场固定叶样,扫描电镜直接观察(照相)记录气孔形态、分布、日变化等的方法。从给出的实例可以看到该法能成功地记录气孔在一天的动态变化情况。这种方法特别适合于研究叶表皮密被绒毛的植物。 相似文献
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Avery E. Pearson Zeke Zelman Lauryn A. Hill Mia A. Stevens Evan X. Jackson Miyauna M. N. Incarnato Ren M. Johnson Stuart Wagenius Jennifer L. Ison 《American journal of botany》2023,110(6):e16190