Morphologic and Aerodynamic Considerations Regarding the Plumed Seeds of Tragopogon pratensis and Their Implications for Seed Dispersal

Casseau, Vincent; Croon, Guido de; Izzo, Dario; Pandolfi, Camilla

doi:10.1371/journal.pone.0125040

Cited by 49 publications

(33 citation statements)

References 28 publications

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“…We have assumed that rain destroys all seeds, which may be a crude assumption. For some wind-dispersed species, rain makes the pappi of different seeds stick together, as in Sonchus asper among our study species, but other species have mechanisms that cause the pappus to close and wait for reopening until all water has disappeared (Casseau et al 2015). Our computed optimal wind speed thresholds were highly similar to the measured bias in wind speeds sampled by released seeds in the field study which indicates the presence of a disturbance with similar magnitude.…”

Section: Discussionsupporting

confidence: 62%

Costs and benefits of non‐random seed release for long‐distance dispersal in wind‐dispersed plant species

Treep

Jager

Kuiper

et al. 2018

Oikos

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The dispersal ability of plants is a major factor driving ecological responses to global change. In wind‐dispersed plant species, non‐random seed release in relation to wind speeds has been identified as a major determinant of dispersal distances. However, little information is available about the costs and benefits of non‐random abscission and the consequences of timing for dispersal distances. We asked: 1) to what extent is non‐random abscission able to promote long‐distance dispersal and what is the effect of potentially increased pre‐dispersal risk costs? 2) Which meteorological factors and respective timescales are important for maximizing dispersal? These questions were addressed by combining a mechanistic modelling approach and field data collection for herbaceous wind‐dispersed species. Model optimization with a dynamic dispersal approach using measured hourly wind speed showed that plants can increase long‐distance dispersal by developing a hard wind speed threshold below which no seeds are released. At the same time, increased risk costs limit the possibilities for dispersal distance gain and reduce the optimum level of the wind speed threshold, in our case (under representative Dutch meteorological conditions) to a threshold of 5–6 m s–1. The frequency and predictability (auto‐correlation in time) of pre‐dispersal seed‐loss had a major impact on optimal non‐random abscission functions and resulting dispersal distances. We observed a similar, but more gradual, bias towards higher wind speeds in six out of seven wind‐dispersed species under natural conditions. This confirmed that non‐random abscission exists in many species and that, under local Dutch meteorological conditions, abscission was biased towards winds exceeding 5–6 m s–1. We conclude that timing of seed release can vastly enhance dispersal distances in wind‐dispersed species, but increased risk costs may greatly limit the benefits of selecting wind conditions for long‐distance dispersal, leading to moderate seed abscission thresholds, depending on local meteorological conditions and disturbances.

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Section: Discussionsupporting

confidence: 62%

Costs and benefits of non‐random seed release for long‐distance dispersal in wind‐dispersed plant species

Treep

Jager

Kuiper

et al. 2018

Oikos

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“…(4), (5), and (7), along with their boundary conditions, was computed using the finite-element-based commercial code COMSOL Multiphysics. The half section of the permeable circular disk of diameter D and aspect ratio χ = 10 was modeled by a rectangular box (0.5D × 0.1D) in a 2D-axisymmetric computational domain, Fig.…”

Section: Computational Domain and Gridmentioning

confidence: 99%

“…5 For very low permeabilities, permeable bodies interact with the surrounding fluid as though they were impervious to it; hence, many of the results for impervious bodies hold for highly impermeable bodies. As a body's permeability is increased, some interesting features emerge, which distinguish the flow around a permeable body from its impervious counterpart.…”

Section: Introductionmentioning

confidence: 99%

The effect of permeability on the flow past permeable disks at low Reynolds numbers

et al. 2017

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The viscous flow over a thick permeable circular disk in the Reynolds number (Re) range of 10 to 130 and in the Darcy number (Da) range of 10−9 to 1 is examined. Direct numerical simulations are performed on a 2D grid with axisymmetric boundary conditions. Three flow regimes are observed: I, II, and III. In regime I (effectively impervious; Da<10−6), the wake is characterized by the presence of a toroidal vortex whose length is approximately equal to that of an impervious disk. In regime II (transition; 10−6<Da<10−3), the increase in Da causes the vortex to shorten and move downstream and eventually vanishes at a critical Darcy number Dac. Regime III (Da>10−3) is the highly permeable regime, in which there is no recirculation. In I, good agreement with existing experimental data for impervious disks is found. In III, an analytical expression for the drag force on the disk is derived, showing good agreement with the numerical results. A global upper limit of Dac=Damax above which the disk is unable to maintain a recirculating wake for any Re is identified. Finally, in regime II, it is demonstrated that increasing the permeability can lead to large variations in the length of the recirculating wake but with minimal effect on the drag coefficient even when Da>Damax. This has important implications in our understanding of the locomotive strategies adopted by organisms that use porous bodies for movement.

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“…Even though biomass allocation to dispersal (pappus mass) in G. hybridus is tightly correlated with biomass investment in defense and seed reserve (Chen and Giladi, ), there is still much flexibility in how the biomass allocated to the pappus is distributed and affects terminal velocity. Plants have evolved complex structures of pappus, where a nearly optimal construction of pappus may provide aerodynamics properties with little investment in biomass, thus decoupling the link between dispersal investment and dispersal performance (Casseau et al., ; Tabassum and Bonser, ). For example, the weaving of the filamentous structure of pappus in Asteraceae species constructs an efficient dispersal device, where porosity provides stability while boundary layers between filaments enhance flight stability and generate drag four times more efficient than what a simple disk membrane of a comparable surface area would do (Casseau et al., ; Cummins et al., ).…”

Section: Discussionmentioning

confidence: 99%

“…Plants have evolved complex structures of pappus, where a nearly optimal construction of pappus may provide aerodynamics properties with little investment in biomass, thus decoupling the link between dispersal investment and dispersal performance (Casseau et al., ; Tabassum and Bonser, ). For example, the weaving of the filamentous structure of pappus in Asteraceae species constructs an efficient dispersal device, where porosity provides stability while boundary layers between filaments enhance flight stability and generate drag four times more efficient than what a simple disk membrane of a comparable surface area would do (Casseau et al., ; Cummins et al., ). In accordance with an interspecific study (Thomson et al., ), our intraspecific data also show that the absolute biomass investment in dispersal device (i.e., pappi or wings) contributed little to diaspore dispersal ability for wind‐dispersed species.…”

Section: Discussionmentioning

confidence: 99%

Variation in morphological traits affects dispersal and seedling emergence in dispersive diaspores of Geropogon hybridus

Chen

Giladi

2020

American J of Botany

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Premise Intraspecific variation in diaspore characteristics could affect various aspects of plant performance at the population, individual plant, and seed levels. We quantified variation in dispersal traits in a wind‐dispersed annual, Geropogon hybridus (Asteraceae), focusing on continuous morphological traits of dispersive diaspores and their relationships to dispersal ability and seedling emergence. Methods We measured the morphological traits, terminal velocity, and seedling emergence of 1140 seeds from 10 populations in two successive years. We assessed the variation in traits among three hierarchical levels of organization and between years, and quantified their effects on diaspore terminal velocity and seedling emergence. Results Diaspore morphological traits varied substantially at the population, plant, and diaspore levels. Variables of pappus geometry, especially pappus width and pappus opening angle, were consistent between years and were found to be the best predictors of diaspore terminal velocity and seedling emergence. There was a significant negative relationship between diaspore terminal velocity and seedling emergence. Conclusions The intraspecific variation in diaspore traits is sufficiently large to substantially allow a dispersal–dormancy trade‐off of individual diaspores. Our results support the hypothesis that traits of dispersive diaspores evolve in concert to select for increased dispersal potential, and provide an avenue to predict plant offspring performance through simply measured traits.

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Morphologic and Aerodynamic Considerations Regarding the Plumed Seeds of Tragopogon pratensis and Their Implications for Seed Dispersal

Cited by 49 publications

References 28 publications

Costs and benefits of non‐random seed release for long‐distance dispersal in wind‐dispersed plant species

Costs and benefits of non‐random seed release for long‐distance dispersal in wind‐dispersed plant species

The effect of permeability on the flow past permeable disks at low Reynolds numbers

Variation in morphological traits affects dispersal and seedling emergence in dispersive diaspores of Geropogon hybridus

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