Seed release by invasive thistles: the impact of plant and environmental factors

Jongejans, Eelke; Pedatella, N. M.; Shea, Katriona; Skarpaas, Olav; Auhl, Richard

doi:10.1098/rspb.2007.0190

Cited by 45 publications

(114 citation statements)

References 20 publications

(27 reference statements)

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“…If water supply to capitula is negligible during this period of active drying, then all of the components are available to incorporate with our results and weather data to mechanistically model the effects of evaporative conditions on seed release in the field -with the caveat that in order to know how many seeds release some biological data may be required. The addition of this information to our current knowledge of the effects of wind speed and turbulence on seed release (Greene 2005;Skarpaas et al 2006;Jongejans et al 2007;Wright et al 2008) will greatly improve the predictive power of mechanistic seed release and dispersal models.…”

Section: Discussionmentioning

confidence: 99%

“…Mechanistic seed release models are a key component necessary to understand under which conditions seeds disperse and how far they travel (Jongejans et al 2007;Soons and Bullock 2008;Wright et al 2008;Nathan et al 2011). Seeds that disperse long distances are more likely to have an appreciable impact on migration and gene flow.…”

Section: Discussionmentioning

confidence: 99%

“…Turbulence was created by the insertion of a threaded rod of 1.5 cm diameter held by a wooden frame at capitulum height 30 cm from capitula, because both species have been shown to release more seeds under turbulent conditions than in laminar air flow and because truly laminar flow is rare in nature (Skarpaas et al 2006;Jongejans et al 2007). The turbulence intensity, which is equal to the standard deviation of the downstream wind speed divided by the mean downstream wind speed, was less than 0.036 (Jongejans et al 2007). These wind conditions were chosen so that if a capitulum did not release seeds in the wind tunnel, it would be very unlikely to release seeds in the field under the same physiological conditions.…”

Section: Wind Tunnel Trialsmentioning

confidence: 99%

“…Seed release trials were conducted in a closed-circuit wind tunnel of the Pennsylvania State University's Aerospace Engineering Department with a 0.9 m high, 0.6 m wide and 6 m long test section (see also Dauer et al 2006;Skarpaas et al 2006;Jongejans et al 2007;Marchetto et al 2010b). Turbulence was created by the insertion of a threaded rod of 1.5 cm diameter held by a wooden frame at capitulum height 30 cm from capitula, because both species have been shown to release more seeds under turbulent conditions than in laminar air flow and because truly laminar flow is rare in nature (Skarpaas et al 2006;Jongejans et al 2007).…”

Section: Wind Tunnel Trialsmentioning

confidence: 99%

“…Therefore, calls have been made for more research on this important topic (Schippers and Jongejans 2005;Kuparinen 2006;Nathan 2006). As more and more researchers investigate the mechanisms underlying seed release, it is becoming increasingly clear that seed release is not a random process, but occurs under certain predictable conditions (Greene and Johnson 1992;Tackenberg et al 2003;Greene 2005;Skarpaas et al 2006;Jongejans et al 2007;Soons and Bullock 2008;Hamilton-Brown et al 2009;Marchetto et al 2010b;Greene and Quesada 2011), which may vary by species (Wright et al 2008).…”

Section: Introductionmentioning

confidence: 99%

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Water loss from flower heads predicts seed release in two invasive thistles

Marchetto

Jongejans

Shea

et al. 2012

Plant Ecology & Diversity

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Background: Non-random seed release caused by plant responses to weather conditions is important for seed dispersal. Much is known about the effects of wind speed and turbulence, but our understanding of the effects of water loss on seed release is either qualitative, or indirect and phenomenological. Aims: To quantify the empirical relationship between water loss and seed release. Methods: Capitula of the invasive thistles Carduus acanthoides and C. nutans were collected from the field and treated for either 0, 1, or 2 days in the laboratory at three different vapour pressure deficit levels (3.4, 9.5, and 17.0 hPa) to cause a range of water loss values. Total seed release was quantified before and during wind tunnel trials. Results: Water loss was the only significant predictor of whether or not capitula released any seeds. The number of seeds released was predicted by water loss, capitulum diameter, and herbivore damage, with the same amount of water loss having less effect on larger capitula. Conclusions: These results represent an important step towards using weather data to predict seed release for many xerochastic species. Incorporating the effects of water loss on seed release into mechanistic seed dispersal models will greatly improve predictions of when and how far seeds disperse. While initiation of dispersal in some species is more likely during precipitation events (Pufal and Garnock-Jones 2010), a majority of wind dispersed angiosperms and gymnosperms are xerochastic, meaning that drying enhances seed abscission and release (Greene et al. 2008). For many Asteraceae species, including the invasive thistles Carduus nutans L. and Carduus acanthoides L. (Figure 1), drying causes cohesion tissues located on the outer side of the involucral bracts to lose turgidity and buckle, causing the bracts to be lowered away from the seeds and thus exposing seeds to the wind (Fahn 1990). Drying may also cause contraction of the receptacle away from seeds (Smith and Kok 1984).The ubiquity of xerochastic plant species suggests that seed dispersal models could be made more realistic and accurate for a wide range of species if weather data describing potential evaporation could be used to mechanistically predict seed release. Two important pieces of information need to be re-examined to accomplish this goal. First, we must predict water loss from inflorescences using weather data. A number of models already exist that use weather data to predict water loss from entire plants (de Bruin and Holtslag 1982;Sumner and Jacobs 2005), and even from capitula separately from vegetative structures (Guilioni and Lhomme 2006). The second necessary piece of information, the relationship between water loss and seed release, must still be documented and is the focus of this paper.Currently, our understanding of the effects of water loss and weather on seed release is either qualitative or phenomenological. Physiologically, we understand what effects dry conditions have on capitula (Smith and Kok 1984;Fahn 1990) and seed attachm...

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Wind Tunnel Trialsmentioning

confidence: 99%

Section: Wind Tunnel Trialsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Water loss from flower heads predicts seed release in two invasive thistles

Marchetto

Jongejans

Shea

et al. 2012

Plant Ecology & Diversity

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Caught in transit: offshore interception of seafaring propagules from seven mangrove species

et al. 2018

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Many organisms are transported passively and make use of the energy of natural phenomena or other organisms to disperse. However, not all species are equally likely to disperse over long distances. In mangroves, which possess seafaring propagules, it is largely unknown which species are more likely to reach the ocean and contribute to long-distance dispersal. This is because dispersal has been mainly studied under reductionist laboratory conditions and via localized release-recapture experiments. Direct interceptions of propagules at sea have hardly been attempted because of the high labor intensity. Here, we set up a local citizen-science network and engaged local fishermen to collect floating mangrove propagules over a period of 27 months. By comparing the dispersing community of propagules from the local stands in which they were produced, the open water of the bay, and the open ocean beyond the coral reef barrier, we could study the transition between local and long-distance dispersal. The composition of the dispersing community changed from the local stands toward the ocean, suggesting that this transition imposes an important selective filter for leaving the local system. With the exception of three rare species (Lumnitzera racemosa, Pemphis acidula, and Xylocarpus moluccensis), we intercepted dispersing propagules of every mangrove species occurring in the East African region. Most intercepted propagules were produced by Rhizophora mucronata and Ceriops tagal, followed by Bruguiera gymnorrhiza and Avicennia marina, which also represent the most abundant species in the nearby mangrove forest. A larger number of propagules were intercepted during the wet season, with fewer propagules recovered during the dry season. Overall, our study indicates that differences in the dispersal capacity of mangrove propagules are not straightforward and that some species may better disperse at local scales within an estuary or embayment, while others might be more suitable for dispersal over longer distances. The presence of such trade-offs may help explain why current attempts to use mangrove traits to predict mangrove species distributions at different scales have remained only moderately successful.

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