Category Archives: AoB PLANTS

Spatial and temporal functional changes in alpine summit vegetation are driven by increases in shrubs and graminoids

13080-TR1Classical approaches to investigating temporal and spatial changes in community composition offer only partial insight into the ecology that drives species distribution, community patterns and processes, whereas a functional approach can help to determine many of the underlying mechanisms that drive such patterns. In order to determine the mechanisms that drive changes in plant community composition across spatial and temporal scales, a new study published in AoB PLANTS by Venn et al. used plant functional traits to interpret the results of a repeat species survey across a gradient of five alpine summits in south-east Australia. Vegetation changes were strongly affected by the high and increasing proportion of tall shrubs and graminoids, especially at the lower elevation summits. Several significant relationships between the community trait-weighted mean of different traits and elevation suggest that processes such as competition are influencing vegetation preferentially across the elevation gradient, with shrubs and graminoids driving these patterns.

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Network epidemiology and plant trade networks

13113R1Epidemic models in complex networks are helping us better understand infectious disease outbreaks. A review by Pautasso and Jeger published in AoB PLANTS focuses on the application of new developments in network epidemiology to the study and management of plant diseases. The main aspects covered are: 1) surveys of social networks, 2) models and data about human mobility, 3) epidemic models in directed and hierarchical networks, 4) studies of dynamic networks, and 5) spatial epidemic simulations integrating network data. Because of the increasing amounts of traded plant commodities and the associated rise in introduced plant pests and pathogens, network theory has a great potential in plant science.

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Live cell imaging reveals extensive intracellular cytoplasmic colonization of banana by normally non-cultivable endophytic bacteria

13072R1It is generally believed that endophytic microorganisms are intercellular inhabitants present in either cultivable or non-cultivable form primarily as root colonizers. In a new study in AoB PLANTS, Thomas and Sekhar report extensive cytoplasmic colonization by endophytic bacteria in banana shoot-tissue which prima-facie displayed ‘Brownian movement’. Live cell imaging on tissue sections, callus, cell suspensions and protoplasts directly and after vital / SYTO-9 staining revealed two intracellular niches, namely cytoplasmic and periplasmic. Designated as ‘Cytobacts’ and ‘Peribacts’, these organisms were rarely amenable to cultivation and thus may have escaped the attention of biologists. This article, supported largely by live cell video-imaging, opens the way to studying these intracellular entities.

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How environmental stress from transplanting into foreign habitats influences inbreeding depression

Inbreeding depression can lower individual fitness and cause the extinction of populations. As a result, it is of interest to evolutionary biologists and conservationists alike. Studies have shown that inbreeding depression can increase in stressful environments. However, most of these studies do not utilize natural environmental stress. In a recent article published in AoB PLANTS, Hereford tested how natural environmental stress from transplanting into foreign habitats influences inbreeding depression. While there was significant inbreeding depression, there was no difference in inbreeding depression between plants in their native environment versus foreign habitats. These results imply that inbreeding depression does not increase when environmental stress reflects natural variation.

The image shows a flower of Diodia teres along with Inland (left) and Dunes (right) habitats.

The image shows a flower of Diodia teres along with Inland (left) and Dunes (right) habitats.

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Phragmites australis management in the United States: 40 years of methods and outcomes

13046S1R1Studies on invasive plant management are often short in duration, are limited in the methods tested, and lack an adequate description of plant communities that replace the invader following removal. In a recent review published in AoB PLANTS, Hazelton et al. reviewed all available studies on Phragmites australis management in the United States in an effort to elucidate future directions for research in invasive plant management.  Their results show that there is a heavy emphasis on herbicides to manage Phragmites, relative to other methods, and a lack of information on what types of plant communities establish once Phragmites is removed.  Their model of Phragmites establishment and reproduction describes the invasion as a symptom of watershed-scale land use and disturbance.  They advocate more holistic approaches to control and management that focus on improving water quality and minimizing human disturbance to deter future invasion and improve resilience of native plant communities.

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Floral specialization and angiosperm diversity: Phenotypic divergence, fitness trade-offs, and realized pollination accuracy

13092R1Plant reproduction by means of flowers has long been thought to promote the success and diversification of angiosperms. It remains unclear, however, how this success has been come about. A recent review by Scott Armbruster published in AoB PLANTS considers the role of reproductive factors in the evolutionary success of flowering plants, with emphasis on flowers and pollination. Flowers are complex structures that have varying degrees of integration of parts and surprising evolutionary lability. Diversification of floral form usually accompanies plant diversification by speciation. This correlation has traditionally been interpreted as the result of floral specialization increasing speciation rates. However, another possibility is that species diversity generates selection for divergent specialized flowers when related species occur together, thereby reducing extinction rates.

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Identifying the genes underlying quantitative traits: A rationale for the QTN programme

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Photo credit: Sonke Johnson, Duke University

Identifying quantitative trait nucleotides (QTNs), the genetic polymorphisms linked to phenotypic variation, has become a goal for many plant ecologists and evolutionary biologists in recent years. But what is the true value of this potentially expensive and labor intensive programme of research? In a review published in AoB PLANTS, Lee et al. discuss the ways by which the QTN programme can offer unique insight into the ecology and evolution of adaptation in plants. They cite recent noteworthy examples of QTN work and provide recommendations for refocusing efforts to identify and study the genes underlying ecologically important traits.

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Impact of nitrogen availability and soil communities on biomass accumulation of an invasive species

inderjitExotic plant species impact belowground processes by influencing resource availability through enhanced microbial activity as a consequence of litter inputs. We have little understanding of the impact of microbe-driven nutrient fluctuations on biomass accumulation of invasive species. In a recent article in AoB PLANTS, Bajpai and Inderjit attempt to determine whether soil community-driven nitrogen availability influences invader biomass. They discovered that soil communities cultured by Ageratina adenophora, a neotropical invader in Asia, retain available nitrogen that influences the biomass of the invader. Through soil manipulation experiments they found that A. adenophora grows better in soil with higher available nitrogen content. Ageratina adenophora-invaded soil had higher microbial activity and available nitrogen due to higher inputs of terpene-rich litter compared to soil not yet invaded by it. Their results provide evidence that microbe-linked nitrogen availability exerts a positive impact on A. adenophora biomass accumulation, emphasizing the importance of soil community-driven nitrogen availability in invasion success.

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Direct and reverse pollen-mediated gene flow between GM rice and red rice weed

13042-TR3The potential risks of genetically modified crops must be identified before their commercialization. In this context, several studies have reported the transfer of transgenes from transgenic rice to red rice weed. However, gene flow also occurs in the opposite direction, resulting in transgenic seeds that have incorporated the traits of wild red rice. In a new study in AoB PLANTS, Serrat et al. found that this reverse flow was higher than direct gene flow, but that transgenic seeds carrying wild genes remained in the spike and were thus mostly removed at harvesting. Nevertheless, this phenomenon must be considered in fields used for elite seed production and in developing countries where there is a risk of increasing GM red rice weed infestation.

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Contrasting physiological responses to excess heat and irradiance in two tropical savanna sedges

13049R1Trinidad’s Aripo Savanna is a rare example of an intact tropical grassland. It is a living laboratory in which to explore the mechanisms used by plants to survive the stress of life in the full glare of the equatorial sun. In a new study in AoB PLANTS, John-Bejai et al. found that the dominant species, Lagenocarpus rigidus, avoids overheating not through higher transpiration or more reflective leaf surfaces (as expected), but by altering the size and shape of its leaves to suit each location. This plasticity in leaf morphology is combined with plasticity in cell membrane properties, which allows the leaves to tolerate periods of extreme heat. In the absence of these traits a closely related species Lagenocarpus guianensis, finds its range restricted to the shaded savanna edges where heat and light are less overbearing.  The results highlight the importance of trait-plasticity to the survival of plants in the face of climate change.

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